U.S. patent application number 12/457922 was filed with the patent office on 2009-12-24 for optical module,optical transmission system, and fabrication method for optical module.
This patent application is currently assigned to Fujitsu Limited. Invention is credited to Shigenori AOKI, Masayuki KATO.
Application Number | 20090317035 12/457922 |
Document ID | / |
Family ID | 38575362 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090317035 |
Kind Code |
A1 |
AOKI; Shigenori ; et
al. |
December 24, 2009 |
Optical module,optical transmission system, and fabrication method
for optical module
Abstract
An optical module includes a substrate, one or a plurality of
planar optical devices mounted on the substrate, and a waveguide
block including one or a plurality of curved waveguides formed on a
plane. The waveguide block is mounted on the substrate such that
the plane on which the curved waveguides are formed is
perpendicular to the substrate and the curved waveguides and an
incidence face or an emitting face of the planar optical device are
opposed to each other on one end face of the waveguide block.
Further, the waveguide block is configured so that an optical fiber
can be connected to the other end face of the waveguide block which
is orthogonal to the one end face.
Inventors: |
AOKI; Shigenori; (Kawasaki,
JP) ; KATO; Masayuki; (Kawasaki, JP) |
Correspondence
Address: |
KRATZ, QUINTOS & HANSON, LLP
1420 K Street, N.W., Suite 400
WASHINGTON
DC
20005
US
|
Assignee: |
Fujitsu Limited
Kawasaki
JP
|
Family ID: |
38575362 |
Appl. No.: |
12/457922 |
Filed: |
June 25, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11475970 |
Jun 28, 2006 |
7609922 |
|
|
12457922 |
|
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Current U.S.
Class: |
385/49 ;
385/32 |
Current CPC
Class: |
G02B 6/4292 20130101;
G02B 6/3897 20130101; G02B 6/4284 20130101 |
Class at
Publication: |
385/49 ;
385/32 |
International
Class: |
G02B 6/30 20060101
G02B006/30 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 2006 |
JP |
2006-085255 |
Claims
1-11. (canceled)
12. An optical module comprising: a substrate; one or a plurality
of planar optical devices mounted on said substrate; and a
waveguide block including one or a plurality of curved waveguides
formed on a plane; said waveguide block being mounted on said
substrate such that the plane on which said curved waveguides are
formed is perpendicular to said substrate and said curved
waveguides and an incidence face or an emitting face of said planar
optical device are opposed to each other on one end face of said
waveguide block and being configured so that an optical fiber can
be connected to the other end face of said waveguide block which is
orthogonal to the one end face, wherein said plural planar optical
devices are a plurality of planar light emitting devices having
light emission wavelengths different from each other and arranged
in series along an end face of said waveguide block, and said
waveguide block includes a waveguide type multiplexer formed by
overlapping said curved waveguides on a one-end side thereof.
13. The optical module as claimed in claim 12, wherein said
waveguide block is formed by laminating a plurality of film
waveguides including said waveguide type multiplexer, and said film
waveguides are laminated such that end faces of said curved
waveguides on the side on which said curved waveguides are
overlapped line up in series along the surface of said substrate so
that an optical fiber array formed from a plurality of optical
fibers can be connected to the end faces.
14. An optical module, comprising: a substrate; one or a plurality
of planar optical devices mounted on said substrate; and a
waveguide block including one or a plurality of curved waveguides
formed on a plane; said waveguide block being mounted on said
substrate such that the plane on which said curved waveguides are
formed is perpendicular to said substrate and said curved
waveguides and an incidence face or an emitting face of said planar
optical device are opposed to each other on one end face of said
waveguide block, and being configured so that an optical fiber can
be connected to the other end face of said waveguide block which is
orthogonal to the one end face, wherein said planar optical devices
are a plurality of planar photo-detectors arranged in series along
an end face of said waveguide block, and said waveguide block
includes a waveguide type demultiplexer connected to each of said
plural curved waveguides, said waveguide type demultiplexer
including a plurality of wavelength filters connected to said
plural curved waveguides, a mirror provided on the end face of said
waveguide block, and a channel optical waveguide formed between
said wavelength filters and said mirror.
15. The optical module as claimed in claim 14, wherein said
waveguide block is formed by laminating a plurality of film
waveguides including said waveguide type demultiplexer, and said
film waveguides are laminated such that incidence side end faces of
the channel optical waveguides line up in series on end faces of
said film waveguides so that an optical fiber array formed from a
plurality of optical fibers can be connected to said film
waveguides.
16. The optical module as claimed in claim 12, further comprising a
plurality of planar light emitting device arrays each formed from a
plurality of planar light emitting devices which have an equal
light emission wavelength, said planar light emitting device arrays
having light emission wavelengths different from each other, said
plural planar light emitting device arrays being arranged such that
the planar light emitting devices which have an equal light
emission wavelength are arranged in series along a lamination
direction of said film waveguides and the plural planar light
emitting devices which have light emission wavelengths different
from each other are arranged in series along end faces of said film
waveguides.
17. The optical module as claimed in claim 14, further comprising a
plurality of planar photo-detector arrays each formed from a
plurality of planar photo-detectors, said planar photo-detector
arrays being arranged such that a plurality of said planar
photo-detectors which form the same planar photo-detector array
line up in series along a lamination direction of said film
waveguides and a plurality of said planar photo-detectors which
form different ones of said planar photo-detector arrays line up in
series along end faces of said film waveguides.
18-19. (canceled)
20. An optical transceiver, comprising: a first optical module,
comprising: a first substrate; one or a plurality of first planar
optical devices mounted on said first substrate; and a first
waveguide block including one or a plurality of first curved
waveguides formed on a first plane; said first waveguide block
being mounted on said first substrate such that the first plane on
which said first curved waveguides are formed is perpendicular to
said first substrate and said first curved waveguides and an
incidence face or an emitting face of said first planar optical
device are opposed to each other on one end face of said first
waveguide block, and being configured so that a first optical fiber
can be connected to the other end face of said first waveguide
block which is orthogonal to the one end face of said first
waveguide block, wherein said plural first planar optical devices
are a plurality of planar light emitting devices having light
emission wavelengths different from each other and arranged in
series along an end face of said first waveguide block, and said
first waveguide block includes a waveguide type multiplexer formed
by overlapping said first curved waveguides on a one-end side
thereof; and a second optical module, comprising: a second
substrate; one or a plurality of second planar optical devices
mounted on said second substrate; and a second waveguide block
including one or a plurality of second curved waveguides formed on
a second plane; said second waveguide block being mounted on said
second substrate such that the second plane on which said second
curved waveguides are formed is perpendicular to said second
substrate and said second curved waveguides and an incidence face
or an emitting face of said second planar optical device are
opposed to each other on one end face of said second waveguide
block, and being configured so that a second optical fiber can be
connected to the other end face of said second waveguide block
which is orthogonal to the one end face of said second waveguide
block, wherein said second planar optical devices are a plurality
of planar photo-detectors arranged in series along an end face of
said second waveguide block, and said second waveguide block
includes a waveguide type demultiplexer connected to each of said
plural second curved waveguides, said second waveguide type
demultiplexer including a plurality of wavelength filters connected
to said plural second curved waveguides, a mirror provided on the
end face of said second waveguide block, and a channel optical
waveguide formed between said wavelength filters and said mirror;
wherein said first optical module and said second optical module
are stuck integrally to each other on a back face side of said
first substrate and a back face side of said second substrate.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and hereby claims priority to
Japanese Application No. 2006-085255 filed on Mar. 27, 2006 in
Japan, the contents of which are hereby incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] (1) Field of the Invention
[0003] This invention relates to an optical module, an optical
transceiver, an optical transmission system and a fabrication
method for an optical module, suitable for use with a multi-channel
optical transceiver (for example, a wavelength division
multiplexing multi-channel optical transceiver) which includes a
planar optical device such as, for example, a planar light emitting
laser or a photo-diode (photo-detector).
[0004] (2) Description of the Related Art
[0005] In a case wherein an optical module such as, for example, a
multi-channel optical transceiver uses a planar optical device such
as a planar light emitting laser or photo-diode, since a light
incidence face or a light emitting face of the planar optical
element extends in parallel to a mounting board, light is incident
or emitted perpendicularly upon or from the mounting board.
[0006] Meanwhile, in such an optical module as mentioned above, it
is necessary to achieve reduction in size and thickness.
[0007] In order to achieve reduction in size and thickness,
preferably optical fibers (optical fiber array) are disposed in
parallel to a mounting board. In this instance, end faces of the
optical fiber and the light incidence face or light emitting face
of the planar optical device have a relationship of the
substantially right angle to each other. Therefore, such various
proposals as described below have been made in order to curve the
paths (light paths) of incidence or emitting light perpendicularly
to the light incidence face or light emitting face of a planar
optical device mounted on a board by approximately 90 degrees to
optically connect the optical fibers and the planar optical device
to each other.
[0008] For example, Japanese Patent laid-Open No. 2005-115346
discloses a technique which uses an optical waveguide structure of
a three-dimensional configuration wherein optical waveguides are
formed on a curved plane for curving the advancing direction of
light such that light to be incident to or emitted from a planar
optical device is guided along the curved plane and coupled to an
optical fiber array (refer to, for example, FIGS. 27 and 28).
[0009] Meanwhile, Japanese Patent Laid-Open No. 2003-322740
discloses that, in order to optically couple optical waveguides
provided along a mounting face and a planar light emitting laser to
each other, it is necessary to convert the direction of light by
90.degree. and, as a method therefor, a 45.degree. mirror is formed
as a direction converter on a waveguide film which connects devices
to each other.
[0010] Incidentally, as one of methods of making it possible to
expand the transmission band width, an attempt to introduce a
wavelength division multiplexing technique to increase the
transmission capacity per one channel is available, and it is
disclosed that a multiplexer or a demultiplexer which uses spatial
propagation of light and a reflecting optical system is provided
between a planar light emitting laser or a photo-diode and optical
fibers (for example, refer to Brian E. Lemoff et al., "MAUI:
Enabling Fiber-to-the-Processor with Parallel Multiwavelength
Optical Interconnects,", JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 22,
NO. 9, SEPTEMBER, 2004).
[0011] Incidentally, in an optical module such as a multi-channel
optical transceiver as described above, it is a subject to reduce
the cost for a portion (optical coupling portion) which optically
interconnects a planar optical device [planar optical device array;
for example, a VCSEL (Vertical-Cavity Surface-Emitting Laser) array
or a PD (Photo Detector) array] and optical fibers (optical fiber
array).
[0012] Therefore, also common use of parts has been and is
proceeding gradually. At present, both of the pitch (array pitch)
between a plurality of planar optical devices which form a planar
optical device array and the pitch (array pitch) between a
plurality of optical fibers which form an optical fiber array have
been standardized to 0.25 mm. Further, both of the number (array
number) of planar optical devices which form a planar optical
device array and the number (array number) of optical fibers which
form an optical fiber array have been standardized to 4, 8, 12 and
24.
[0013] Meanwhile, for example, in the case of a multi-channel
optical transceiver, a VCSEL array and a PD array are mounted in a
juxtaposed relationship with each other on a board. However, a
mounting gap (gap between chips) of, for example, approximately 1
mm is essentially required between the arrays.
[0014] In this instance, also between optical fibers (VCSEL fibers)
optically connected to the VCSEL array and optical fibers (PD
fibers) optically connected to the PD array, a gap corresponding to
the mounting gap is required.
[0015] Once the pitch is standardized to 0.25 mm between a VCSEL
array or a PD array and an optical fiber array and also the array
number is standardized to 4, 8, 12 or 24 in such a manner as
described above, in order, for example, for a multi-channel optical
transceiver of 8 channels (4-channel input+4-channel output) to be
ready for the standardization, such a countermeasure is taken as to
adopt a standardized optical fiber array for 12 channels by adding
4 channels corresponding to the gap (for example, 1 mm) between the
chips to 8 channels originally required for the input and the
output.
[0016] In this instance, optical fibers for the four channels
corresponding to the gap between the chips are useless because they
are not used for the input or the output. Further, since an optical
fiber array for 12 channels is inferior in all aspects such as the
performance and the price to an optical fiber array for 8 channels,
preferably an optical fiber array for 8 channels is used.
[0017] Therefore, it is desired to implement a simple and
convenient structure which can optically connect planar optical
devices (planar optical device array) such as planar light emitting
devices or planar photo-detectors and optical fibers (optical fiber
array) to each other without providing a gap, which corresponds to
a gap (mounting gap) between the chips, between optical fibers
optically connected to the planar light emitting devices (VCSEL
array) and optical fibers optically connected to the planar
photo-detectors (PD array).
[0018] It is to be noted that this problem is solved in principle
if it is possible to produce a part which connects to an optical
fiber array for 8 channels with the waveguide distance reduced
midway from the planar optical devices to the optical fibers.
[0019] However, where an optical waveguide structure of a
three-dimensional configuration wherein optical waveguides are
formed on a curved plane for curving the advancing direction of
light is used as disclosed, for example, in Japanese Patent
Laid-Open 2005-115346, it is necessary to form optical waveguides
of a high degree of accuracy for optically connecting optical
devices and optical fibers to each other on a curved plane.
However, at present, a countermeasure which can implement such a
complicated highly accurate three-dimensional structure as
described above simply and conveniently is not available and has
not been placed into practical use. Further, it is difficult from
restrictions in a fabrication method to implement a structure which
can simultaneously achieve also pitch conversion.
[0020] Meanwhile, another countermeasure wherein a mirror
(90.degree. deflecting mirror) is used to achieve high-density
optical connection between chips and pitch conversion as disclosed,
for example, in Japanese Patent Laid-Open No. 2003-322740, is
disadvantageous in that the loss at the mirror (that is, the
absorption loss on the surface of the mirror) is significant and
the optical connection and the pitch conversion are liable to be
influenced by the accuracy in alignment and the accuracy in
working. Further, crosstalk at an intersecting location between
waveguides cannot be avoided, and the optical performance is not
high.
[0021] Incidentally, although the aforementioned thesis "MAUI:
Enabling Fiber-to-the-Processor with Parallel Multiwavelength
Optical Interconnects" discloses a high-grade module which
introduces a wavelength division multiplexing technique and uses
spatial propagation of light and a reflecting optical system, the
module has the following problems.
[0022] First, since a spatial propagation system is used, the beam
diameter cannot be made very small (for example, a diameter of 250
.mu.m), there is a limitation to miniaturization of the module.
Further, since a spatial multiple reflecting optical system is
adopted, alignment is difficult. Furthermore, it is difficult to
assure a high impact resistance of the product. As a result, also
reduction in cost is difficult.
SUMMARY OF THE INVENTION
[0023] Aspect of the present invention can provide an optical
module, an optical transceiver, an optical transmission system and
a fabrication method for an optical module wherein optical
connection between planar optical devices [for example, planar
light emitting lasers or photo-diodes (photo-detectors)] mounted on
a board and optical fibers attached in parallel to the board can be
implemented simply and readily.
[0024] According to one aspect of the present invention, an optical
module includes a substrate, one or a plurality of planar optical
devices mounted on the substrate, and a waveguide block including
one or a plurality of curved waveguides formed on a plane, the
waveguide block being mounted on the substrate such that the plane
on which the curved waveguides are formed is perpendicular to the
substrate and the curved waveguides and an incidence face or an
emitting face of the planar optical device are opposed to each
other on one end face of the waveguide block, and being configured
so that an optical fiber can be connected to the other end face of
the waveguide block which is orthogonal to the one end face.
[0025] According to another aspect of the present invention, an
optical transmission system includes two such optical modules as
described above which are optically connected to each other by an
optical fiber array formed from a plurality of optical fibers, the
optical fiber array being connected to the two optical modules
while twisted by 180 degrees between the two optical modules such
that the longest one of the curved waveguides of one of the optical
modules and the shortest one of the curved waveguides of the other
one of the optical modules are connected to each other.
[0026] According to a further aspect of the present invention,
there is provided an optical transceiver including, as the optical
modules described above, an optical transmitter (the module
described above wherein the plural planar optical devices are a
plurality of planar light emitting devices having light emission
wavelengths different from each other and arranged in series along
an end face of the waveguide block, and the waveguide block
includes a waveguide type multiplexer formed by overlapping the
curved waveguides on a one-end side thereof) and an optical
receiver (the optical module described above wherein the planar
optical devices are a plurality of planar photo-detectors arranged
in series along an end face of the waveguide block, and the
waveguide block includes a waveguide type demultiplexer connected
to each of the plural curved waveguides, the waveguide type
demultiplexer including a plurality of wavelength filters connected
to the plural curved waveguides, a mirror provided on the end face
of the waveguide block, and a channel optical waveguide formed
between the wavelength filters and the mirror), the optical
transmitter and the optical receiver being stuck integrally to each
other on the back face side of the substrates.
[0027] According to a still further aspect of the present
invention, a fabrication method for an optical module includes the
steps of producing a waveguide block including one or a plurality
of curved waveguides on a plane, mounting one or a plurality of
planar optical devices on a substrate, and mounting the waveguide
block on the substrate such that the plane on which the curved
waveguide is formed is perpendicular to the substrate and the
curved waveguide and an incidence face or an emitting face of the
planar optical device are opposed to each other on one end face of
the waveguide block.
[0028] With the optical module, optical transceiver, optical
transmission system and fabrication method for an optical module of
the above aspects of the present invention, there is an advantage
that optical connection between planar optical devices [for
example, face light emitting lasers, photo-diodes (photo-detectors)
and so forth] mounted on a board and optical fibers attached in
parallel to the board can be implemented simply and readily.
[0029] The above and other aspects and advantages of the present
invention will become apparent from the following description and
the appended claims, taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a schematic view showing a configuration of an
optical module according to a first embodiment of the present
invention;
[0031] FIG. 2 is a schematic view showing a configuration of a
waveguide block provided in the optical module according to the
first embodiment of the present invention;
[0032] FIG. 3 is a schematic view showing a modification to the
waveguide block provided in the optical module according to the
first embodiment of the present invention;
[0033] FIG. 4 is a schematic view showing a configuration of the
waveguide block provided in the optical module according to the
first embodiment of the present invention and is an enlarged front
elevational view showing a portion denoted by A in FIG. 1 in an
enlarged scale;
[0034] FIG. 5 is a schematic view showing a configuration of the
waveguide block provided in the optical module according to the
first embodiment of the present invention and is a sectional view
taken along line A-A of FIG. 4;
[0035] FIG. 6 is a schematic view showing a configuration of the
waveguide block provided in the optical module according to the
first embodiment of the present invention and is an enlarged front
elevational view showing a portion denoted by B in FIG. 1 in an
enlarged scale;
[0036] FIG. 7 is a schematic view showing a configuration of the
waveguide block provided in the optical module according to the
first embodiment of the present invention and is an enlarged right
side elevational view showing the portion B in FIG. 1 in an
enlarged scale;
[0037] FIGS. 8(A) to 8(D) are schematic views illustrating a
fabrication method of the waveguide block provided in the optical
module according to the first embodiment of the present
invention;
[0038] FIGS. 9(A) to 9(D) are schematic views illustrating a
fabrication method of the optical module according to the first
embodiment of the present invention;
[0039] FIG. 10 is a schematic view showing a configuration of an
optical transmitter as an optical module according to a second
embodiment of the present invention;
[0040] FIG. 11 is a schematic view showing a configuration of a
transmitter film waveguide provided in the optical transmitter as
an optical module according to the second embodiment of the present
invention;
[0041] FIG. 12 is a schematic view showing a configuration of a
transmitter waveguide block and a planar light emitting device
array provided in the optical transmitter as an optical module
according to the second embodiment of the present invention;
[0042] FIGS. 13(A) to 13(C) are schematic views illustrating a
fabrication method of a transmitter film waveguide (transmitter
waveguide block) provided in the optical transmitter as an optical
module according to the second embodiment of the present
invention;
[0043] FIGS. 14(A) to 14(C) are schematic views illustrating a
fabrication method of the optical module (optical transmitter)
according to the second embodiment of the present invention;
[0044] FIG. 15 is a schematic view showing a configuration of an
optical receiver as an optical module according to the second
embodiment of the present invention;
[0045] FIG. 16 is a schematic view showing a configuration of a
receiver film waveguide provided in the optical receiver as an
optical module according to the second embodiment of the present
invention;
[0046] FIG. 17 is a schematic view showing a configuration of a
receiver waveguide block and a planar photo-detector array provided
in the optical receiver as an optical module according to the
second embodiment of the present invention;
[0047] FIGS. 18(A) to 18(E) are schematic views illustrating a
fabrication method of a receiver film waveguide (receiver waveguide
block) provided in the optical receiver as an optical module
according to the second embodiment of the present invention;
and
[0048] FIGS. 19(A) to 19(C) are schematic views illustrating a
fabrication method of the optical module (optical receiver)
according to the second embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] In the following, an optical module, an optical transceiver,
an optical transmission system and a fabrication method for an
optical module according to embodiments of the present invention
are described.
First Embodiment
[0050] First, an optical module, an optical transceiver, an optical
transmission system and a fabrication method for an optical module
according to a first embodiment of the present invention are
described with reference to FIGS. 1 to 7, 8(A) to 8(D) and 9(A) to
9(D).
[0051] The optical module according to the present embodiment is,
for example, a multi-channel optical transceiver which includes a
function (optical transmitter) for converting electric signals
inputted thereto into optical signals and transmitting the optical
signals through optical fibers in the form of an array, and a
function (optical receiver) for converting optical signals inputted
thereto through an optical fiber array into electric signals and
receiving the electric signal.
[0052] The present multi-channel optical transceiver includes, for
example as shown in FIG. 1, a printed board (circuit board) 1, a
planar photo-detector array (PD array chip) 3 formed from a
plurality of planar photo-detectors [here, photo-diodes; PDs] each
having an incidence face on the surface thereof, and a planar light
emitting device array (VCSEL array chip) 2 formed from a plurality
of planar light emitting devices [here, planar light emitting
lasers; VCSELs (Vertical-Cavity Surface-Emitting Lasers)] each
having an emitting face on the surface thereof, and a waveguide
block (waveguide array) 5 including a plurality of curved
waveguides 4 having a function for converting the pitch. In the
following, the planar photo-detectors and the planar light emitting
devices are sometimes referred to collectively as planar optical
devices.
[0053] The planar photo-detector array 3 and the planar light
emitting device array 2 are mounted on the printed board 1 in such
a manner that a plurality of planar light emitting devices and a
plurality of planar photo-detectors line up along a single straight
line as seen in FIG. 1.
[0054] Here, the multi-channel optical transceiver includes a
single planar photo-detector array 3 and a single planar light
emitting device array 2, and therefore, it includes a plurality of
planar optical device arrays. It is to be noted that the
multi-channel optical transceiver may otherwise be formed as a
multi-channel optical receiver which includes only one planar
photo-detector array 2 or a multi-channel optical transmitter which
includes only one planar light emitting device array 2. Or, the
multi-channel optical transceiver may otherwise be formed as an
optical transceiver which includes a single planar photo-detector
and a single planar light emitting device. Further, the
multi-channel optical transceiver may otherwise be formed as an
optical module which includes only one planar optical device such
as an optical receiver which includes only one planar light
emitting device or an optical transmitter which includes only one
planar light emitting device. In this instance, the waveguide block
5 may include a single curved waveguide formed on a plane.
[0055] In the present embodiment, the curved waveguides 4 provided
on the waveguide block 5 are formed on a plane as seen in FIG. 2.
Therefore, the degree of freedom in the method of fabrication is
high and the curved waveguides 4 can be fabricated readily, for
example, by a molding method based on a planar metal mold
fabricated with an electro formed replica. It is to be noted that a
particular method of formation of the curved waveguides 4 is
hereinafter described.
[0056] Further, in the present embodiment, the curved waveguides 4
include a plurality light emitting device curved waveguides 4A
individually optically connected to the planar light emitting
devices, and a plurality of photo-detector curved waveguides 4B
individually optically connected to the planar photo-detectors as
seen in FIGS. 1 and 2.
[0057] The light emitting device curved waveguides 4A are formed
such that, as shown in FIGS. 1 and 2, they have a distance (pitch)
corresponding to the distance (pitch) of the planar light emitting
devices on an end face 5A of the waveguide block 5 but have a
distance (pitch) corresponding to the distance (pitch) of optical
fibers, which form an optical fiber array (ribbon fiber) 6, on the
other end face 5B of the waveguide block 5.
[0058] Meanwhile, the photo-detector curved waveguides 4B are
formed such that, as shown in FIGS. 1 and 2, they have a distance
(pitch) corresponding to the distance (pitch) of the planar
photo-detectors on the end face 5A of the waveguide block 5 but
have a distance (pitch) corresponding to the distance (pitch) of
the optical fibers, which form the optical fiber array 6, on the
other end face 5B of the waveguide block 5.
[0059] Further, in the present embodiment, as seen in FIGS. 1 and
2, the distance between the light emitting device curved waveguides
4A and the photo-detector curved waveguides 4B is a distance
(pitch) corresponding to the distance (pitch) between the planar
light emitting device array 2 and the planar photo-detector array 3
on the end face 5A but is a distance (pitch) corresponding to the
distance (pitch) of the optical fibers, which form the optical
fiber array 6, on the other end face 5B.
[0060] By forming the curved waveguides 4 so as to be compatible
with the array pitch of the optical fiber array 6 in this manner,
the curved waveguides 4 can convert the mounting gap (chip
distance) between the planar light emitting device array 2 and the
planar photo-detector array 3 into an arbitrary optical fiber pitch
irrespective of the mounting gap (even if the planar light emitting
device array 2 and the planar photo-detector array 3 are disposed
in a spaced relationship by an arbitrary distance from each other).
Consequently, such a situation that part of the optical fiber array
becomes wasteful depending upon the mounting gap between the planar
light emitting device array 2 and the planar photo-detector array 3
as in the conventional apparatus described hereinabove can be
prevented. Therefore, for example, in an optical transceiver for 8
channels, the necessity to use an optical fiber array for 12
channels is eliminated, and a high cost reduction effect can be
anticipated.
[0061] In the present embodiment, the curved waveguides 4 extend
from the end face 5A of the waveguide block 5 to the other end face
5B which extends orthogonally to the end face 5A as seen in FIG. 2.
In other words, the curved waveguides 4 are formed as curved
waveguides curved substantially to the right angle in a plane.
[0062] The waveguide block 5 having the configuration described
above is mounted on the printed board 1 such that the plane on
which the curved waveguides 4 are formed extends perpendicularly to
the printed board 1 and besides the curved waveguides 4 and the
incidence faces or the emitting faces of the planar optical devices
mounted on the printed board 1 are opposed to each other on the end
face 5A as seen in FIG. 1. Consequently, the curved waveguides 4
provided on the waveguide block 5 and the planar optical devices
which form the planar optical device arrays 2 and 3 are optically
connected to each other. It is to be noted that the printed board 1
is electrically connected to an external apparatus such that an
electric signal is inputted to or outputted from the external
apparatus (electric I/O).
[0063] Here, the end face 5A of the waveguide block 5 is opposed to
the surface of the board. Meanwhile, the optical fiber array 6
formed from the optical fibers is optically connected to the other
end face 5B of the waveguide block 5 which extends orthogonally to
the end face 5A.
[0064] In this instance, the optical fiber array 6 is mounted in
parallel to the printed board 1, and the end faces of the optical
fibers and the incidence faces or the emitting faces of the planar
optical device arrays 2 and 3 have a substantially right-angled
positional relationship. However, the planar optical device arrays
2 and 3 and the optical fiber array 6 are optically connected to
each other through the waveguide block 5 (that is, the plural
curved waveguides 4 provided on the waveguide block 5) such that
the paths (light paths) of light which comes in or goes out
perpendicularly to the incidence faces or the emitting faces of the
planar optical devices mounted on the printed board 1 are curved by
approximately 90 degrees.
[0065] Incidentally, where such a waveguide block 5 as described
above is fabricated actually, it is preferably configured such that
not only it has such a structure that the light paths are curved
substantially to the right angle but also a lens and positioning
elements (for example, positioning convex/concave elements and so
forth) are integrated with the waveguide block 5. In this instance,
a transparent polymer material which can use a mold is effectively
used as a material of the waveguide block 5. This makes it possible
to produce a complicated planar waveguide configuration simply and
conveniently.
[0066] Therefore, in the present embodiment, a lens 7 is provided
at each of positions of the end face 5A of the waveguide block 5
corresponding to end faces of waveguide cores 14 which individually
form the curved waveguides 4 as seen in FIGS. 4 and 5. Meanwhile,
another lens 7 is provided at each of positions of the other end
face 5B of the waveguide block 5 corresponding to end faces of the
waveguide cores 14 which form the curved waveguides 4 as seen in
FIGS. 6 and 7. It is to be noted that, in FIGS. 5 and 7, reference
numeral 15 denotes a cladding film which forms the curved
waveguides 4.
[0067] Further, the waveguide block 5 includes a board side
positioning section (here, a positioning pin 8) provided on the end
face 5A side for positioning the waveguide block 5 with respect to
the printed board 1 as seen in FIGS. 4 and 5. Further, the
waveguide block 5 includes an optical fiber side (optical connector
side) positioning section (here, a positioning pin insertion hole
9) provided on the other end face 5B side for positioning the
waveguide block 5 with respect to the optical fiber array 6 formed
from a plurality of optical fibers.
[0068] It is to be noted that, in order to facilitate assembly, the
end faces of the optical fiber array (ribbon fiber) 6 are
preferably terminated by an optical connector 10 compatible with an
array such as, for example, an MT (mechanically transferable) type
optical connector.
[0069] In this instance, positioning pins (optical connector side
positioning sections) 11 are provided on the outer side on an
extension line of the optical fiber array 6 as seen in FIG. 1.
Since the optical fiber array 6 and the curved waveguides 4 are
disposed on the same plane, a positioning pin insertion hole 9 for
inserting one of the positioning pins 11 is provided above the
curved waveguides 4, and this increases the height of the waveguide
block 5. Therefore, when it is intended to minimize the thickness,
as seen in FIG. 3, the curved waveguides 4 should be curved
substantially to the right angle once and then curved back so that
the curved waveguides 4 may be positioned at a position as low as
possible on the other end face 5B (end face on the optical fiber
connection side) of the waveguide block 5 (that is, the curved
waveguides 4 are formed so as to be shifted to the printed board 1
side on the other end face 5B) thereby to lower the position of the
positioning pin insertion hole 9 provided above the curved
waveguides 4. By the configuration just described, reduction in
thickness of the optical module can be implemented. Further, since
also the optical fiber array 6 is mounted at a position as low as
possible, also the height of the entire module (thickness of the
module) including the optical fiber array can be reduced, and
consequently, reduction in thickness can be anticipated. Such a
configuration as just described is effective particularly where the
number of channels is great.
[0070] It is to be noted that two optical modules configured in
such a manner as described above (having the same configuration)
are prepared and optically connected to each other by the optical
fiber array 6 formed from a plurality of optical fibers to
configure an optical transmission system, as seen in FIG. 1.
[0071] However, in the present optical module, since the curved
waveguides 4 have lengths different from each other (since length
of the optical path differs among different channels), where it is
necessary for the optical wirings (optical paths) to be equal to
each other, the optical fiber array 6 is connected while twisted by
180 degrees between the two optical modules such that the longest
one of the curved waveguides 4 of one of the optical modules and
the shortest one of the curved waveguides 4 of the other one of the
optical modules are connected to each other.
[0072] Now, a fabrication method for the optical module
(multi-channel optical transceiver) according to the present
embodiment is described with reference to FIGS. 8(A) to 8(D) and
9(A) to 9(D).
[0073] First, the waveguide block 5 which includes the plural
curved waveguides (in-plane curved waveguides) 4 formed on a plane
can be fabricated, for example, in such a manner as described
below.
[0074] A metal mold (molding metal mold) 12 having a waveguide
pattern of a convex shape (here, a pattern for forming a plurality
of curved waveguides) as shown in FIG. 8(A) is fabricated.
[0075] Then, olefin resin 13 (for example, a refractive index
n=1.52 after cured) to be used for formation of a lower cladding
material is poured into the metal mold 12 to perform molding.
[0076] Then, epoxy resin 14 (for example, a refractive index n=1.54
after cured) of the ultraviolet curing type to be used for
formation of waveguide cores is dropped (applied) into grooves 13A
(waveguide grooves) of the molded member 13 in the form of a plate
made of the transparent olefin resin as seen in FIG. 8(B). Then, a
film 15 (cladding film; refractive index n=1.52; for example, 0.1
mm thick) of olefin resin prepared separately is stuck as seen in
FIG. 8(C).
[0077] Then, ultraviolet rays are irradiated while a load is
applied to cure the epoxy resin 14 as seen in FIG. 8(D).
[0078] Thereafter, the end faces are mirror polished to fabricate a
waveguide block 5 (waveguide block formed from a molded member in
the form of a flat plate) having curved waveguides 4 (here, eight
curved waveguides) formed on a plane as seen in FIG. 9(B).
[0079] Here, the outside dimension of the waveguide block 5 is 10
mm.times.10 mm.times.5 mm. The dimension of the waveguide cores
which form the curved waveguides 4 is 0.05 mm.times.0.05 mm. Of the
eight curved waveguides 4, the left side four curved waveguides 4
in FIG. 9(B) are the light emitting device curved waveguides
(transmission curved waveguides) 4A to be optically connected to
the planar light-emitting device array (VCSEL array) 2, and the
pitch of the waveguide cores which form the light emitting device
curved waveguides 4A is 0.25 mm. Meanwhile, of the eight curved
waveguides 4, the right side four curved waveguides 4 in FIG. 9(B)
are photo-detector curved waveguides (reception curved waveguides)
4B to be optically connected to the photo-detector array (PD array)
3, and the pitch of the waveguide cores which form the reception
curved waveguides 4B is 0.25 mm. Further, the pitch between the
waveguide cores which form the transmission curved waveguides 4A
and the waveguide cores which form the reception curved waveguides
4B is 1.00 mm on the end face 5A of the waveguide block 5 (on the
end face on the side of the waveguide block 5 to be optically
connected to the VCSEL array 2 and the PD array 3), but is 0.25 mm
on the other end face 5B orthogonal to the end face 5A (on the end
face on the side of the waveguide block 5 to be optically connected
to the optical fiber array 6). Thus, the pitch is converted.
[0080] Meanwhile, the planar light emitting device array (VCSEL
array) 2 and the photo-detector array (PD array) 3 are mounted in
advance on the printed board 1 (device mounting board) as seen in
FIG. 9(A). In particular, the planar light emitting device array 2
and the planar photo-detector array 3 are stuck to the printed
board 1 using conductive paste with a heat radiating block 16 (heat
spreader: for example, 0.25 mm thick), for example, of a copper
tungsten alloy interposed therebetween such that the light emitting
faces of a plurality of planar light emitting lasers which form the
planar light emitting laser array 2 and the light receiving faces
(incidence faces) of a plurality of photo-detectors which form the
planar photo-detector array 3 are directed upwardly in a direction
perpendicular to the printed board 1 and the planar light emitting
lasers and the photo-detectors line up on a straight line.
[0081] It is to be noted that the distance between the planar light
emitting laser array 2 and the photo-detector array 3 (gap between
the two chips) is set to 1 mm although it may be an arbitrary one.
Further, though not shown, electrodes on the surface of the chips
and wirings on the printed board may be connected to each other by
wire bonding so that they may serve as feeder lines.
[0082] Here, a multi-mode 4-channel array of a wavelength of, for
example, 850 nm is used as the planar light emitting laser array 2.
The array pitch is 0.25 mm, and the outside dimension is 1.0
mm.times.0.25 mm.times.0.25 mm.
[0083] Further, a 4-channel array of a wavelength of, for example,
850 nm is used as the photo-detector array 3. The array pitch is
0.25 mm, and the outside dimension is 1.0 mm.times.0.25
mm.times.0.25 mm.
[0084] On the printed board 1 fabricated in this manner and having
the chips mounted thereon, the waveguide block 5 fabricated in such
a manner as described above is mounted with spacers 17 (for
example, 0.6 mm thick) interposed therebetween. For example, the
waveguide block 5 may be fixed to the printed board 1 using
ultraviolet curing resin.
[0085] Thereupon, for example, a flip chip bonder having a vertical
visual field camera may be used to perform positioning so that the
centers of the waveguide cores which form the curved waveguides 4
provided on the waveguide block 5 may be aligned with the centers
of the light receiving faces of the photo-detectors and the centers
of the light emitting faces of the planar light emitting
lasers.
[0086] After the waveguide block 5 including the curved waveguides
4 (in-plane curved waveguides) curved in a plane was fabricated
using polymer and was mounted on the printed board 1 together with
the planar light emitting laser array 2 and the planar
photo-detector array 3 to fabricate a multi-channel optical
transceiver as an optical module in this manner, the optical fiber
array 6 was assembled and the insertion loss of the curved
waveguides 4 which form the waveguide block 5 was measured in order
to evaluate the transmission and reception performances as seen in
FIG. 9(C). According to a result of the measurement, the insertion
loss was 2.0.+-.0.3 dB including the coupling loss by coupling to
the chips 2 and 3, and the variation in insertion loss among
channels is little. Thus, it was confirmed successfully that the
pitch conversion by the waveguide block 5 fabricated in such a
manner as described above is effective.
[0087] It is to be noted that the optical fiber array 6 was
connected to the end face of the waveguide block 5 mounted on the
printed board 1 through the optical connector (fiber connector) 10
as shown in FIG. 9(C). Thereupon, electric current was supplied to
the face light emitting lasers to perform positioning by active
alignment.
[0088] Accordingly, with the optical module, optical transceiver,
optical transmission system and fabrication method for an optical
module according to the present embodiment, there is an advantage
that optical connection between the planar optical devices [for
example, face light emitting lasers, photo-diodes (photo-detectors)
and so forth] mounted on the printed board 1 and the optical fibers
attached in parallel to the printed board 1 can be implemented
simply and readily.
[0089] It is to be noted that, while, in the present embodiment,
the optical module of the present invention is described taking a
multi-channel optical transceiver as an example, the optical module
of the present invention is not limited to this, but the present
invention can be applied widely to any optical module only if it
requires optical connection between a planar optical device [for
example, a planar light emitting laser, a photo-diode
(photo-detector) or the like] mounted on a board and an optical
fiber attached in parallel to the board.
Second Embodiment
[0090] Now, an optical module, an optical transceiver and a
fabrication method for an optical module according to the second
embodiment of the present invention is described with reference to
FIGS. 10 to 17, 18(A) to 18(E) and 19(A) to 19(C).
[0091] The optical module according to the present embodiment is
different from the multi-channel optical transceiver of the first
embodiment described hereinabove in the structure for making
wavelength division multiplexing transmission possible. In
particular, the optical module according to the present embodiment
is different in that it is a wavelength division multiplexing
multi-channel optical transceiver (optical transmitter, optical
receiver) which is based on a thin film channel waveguide and has a
structure (CWDM structure) which permits wavelength division
multiplexing transmission which makes use of a demultiplexing and
multiplexing technique.
[0092] In the following, an optical transmitter which can be used
to form a wavelength division multiplexing multi-channel optical
transceiver is described with reference to FIGS. 10 to 12, 13(A) to
13(C) and 14(A) to 14(C). Thereafter, an optical receiver which can
be used to form a wavelength division multiplexing multi-channel
optical receiver is described with reference to FIGS. 15 to 17,
18(A) to 18(E) and 19(A) to 19(C). Finally, a wavelength division
multiplexing optical transceiver is described. It is to be noted
that, in FIGS. 10 to 17, 18(A) to 18(E) and 19(A) to 19(C), like
elements to those of the first embodiment (refer to FIG. 1)
described hereinabove are denoted by like reference characters.
[Optical Transmitter]
[0093] First, the optical transmitter according to the present
embodiment includes, for example, as shown in FIG. 10, planar light
emitting device arrays 2A to 2D (VCSEL array chips) each formed
from a plurality of planar light emitting devices [here, planar
light emitting lasers; VCSELs (Vertical-Cavity Surface-Emitting
lasers)] having an emitting face on the surface thereof, and a
transmitter waveguide block 20 (waveguide array) formed from a
plurality of transmitter film waveguides 21 laminated with each
other and each including a waveguide type multiplexer 22 which in
turn includes a plurality of curved waveguides 24A to 24D.
[0094] The waveguide type multiplexer 22 is formed such that a
plurality of curved waveguides 24A to 24D are overlapped with each
other on one end side thereof such that lights having propagated
along the curved waveguides 24A to 24D are multiplexed on the one
end side. Here, a multi-channel multiplexer is formed by a
plurality of film waveguides 21 laminated with each other.
[0095] Meanwhile, the transmitter waveguide block 20 is formed such
that a plurality of film waveguides 21 are laminated with each
other in such a manner that end faces 24X of the curved waveguides
24A to 24D on the side on which the curved waveguides 24A to 24D
are overlapped with each other line up individually in series and
in parallel to each other along the surface of the printed board 1
as seen in FIG. 10. The multi-channel waveguide block 20 is
configured by disposing the film waveguides 21 in multiple layers
in this manner, and a multi-channel optical transmitter is
implemented thereby. Then, to the end faces 24X on the side on
which the curved waveguides 24A to 24D are overlapped, an optical
fiber array (ribbon fiber) 6 formed from a plurality of optical
fibers is connected through the optical connector 10, as seen in
FIG. 10.
[0096] Therefore, by setting the thickness of the transmitter film
waveguides 21 (that is, the distance between the waveguide cores
which form the curved waveguides of the transmitter film waveguides
21) to a thickness (distance) corresponding to the fiber pitch of
the optical fiber array 6, conversion of the pitch into an
arbitrary optical fiber pitch can be implemented irrespective of
the mounting gap (chip distance) between the planar light emitting
device arrays (even if the plural planar light emitting device
arrays are disposed at an arbitrary distance) similarly as in the
first embodiment described hereinabove. Consequently, the degree of
freedom in design is enhanced, and it can be prevented that part of
an optical fiber array becomes wasteful.
[0097] Further, the planar light emitting device arrays 2A to 2D
include a plurality of planar light emitting devices having same
light emitting wavelengths as each other. The planar light emitting
device arrays 2A to 2D are disposed in parallel to each other on
the printed board 1 such that the emitting faces of the planar
light emitting devices are directed upwardly and perpendicularly to
the printed board 1 and besides the planar light emitting devices
line up in series along the lamination direction of the transmitter
film waveguides 21.
[0098] In the present embodiment, a plurality of planar light
emitting devices having different light emitting wavelengths from
each other are mounted on the printed board 1 such that they line
up in series along an end face of the transmitter waveguide block
20 (laminated transmitter film waveguides 21) as seen in FIG.
11.
[0099] In particular, as seen in FIG. 12, a first planar light
emitting device array 2A formed from a plurality of first planar
light emitting devices of a light emitting wavelength .lamda.1, a
second planar light emitting device array 2B formed from a
plurality of second planar light emitting devices of a light
emitting wavelength .lamda.2, a third planar light emitting device
array 2C formed from a plurality of third planar light emitting
devices of a light emitting wavelength .lamda.3, and a fourth
planar light emitting device array 2D formed from a plurality of
fourth planar light emitting devices of a light emitting wavelength
.lamda.4 are mounted on the printed board 1 such that they line up
individually in series along an end face of the transmitter
waveguide block 20 (laminated transmitter film waveguides 21) and
in parallel to each other.
[0100] In the present embodiment, the curved waveguides 24A to 24D
are formed as a transmitter film waveguide 21 and are channel
waveguides formed on a plane. Therefore, the degree of freedom in
fabrication method is high, and the curved waveguides 24A to 24D
can be fabricated readily by a molding method which is based on a
plane metal mold formed, for example, by an electroformed replica.
Further, since the channel waveguides are adopted, a beam can be
confined to a width of, for example, approximately 50 .mu.m, and
therefore, miniaturization of the module can be anticipated.
Furthermore, since the optical paths are produced in a
two-dimensional plane first, the curved waveguides 24A to 24D are
superior in terms of positioning and reliability (impact
resistance) when compared with an alternative case wherein spatial
light is used. Further, since the curved waveguides 24A to 24D are
formed on a plane, they can be molded using a simple embossing
technique, and therefore, the cost is low. It is to be noted that a
particular formation method of the curved waveguides 24A to 24D is
hereinafter described.
[0101] Further, in the present embodiment, the curved waveguides
24A to 24D which form the waveguide type multiplexer 22 are
optically connected to respective ones of a plurality of planar
light emitting devices on an end face 20A of the transmitter
waveguide block 20, and are optically connected to optical fibers
on the other end face 20B of the transmitter waveguide block 20
orthogonal to the end face 20A as seen in FIG. 10.
[0102] Consequently, as seen in FIG. 10, lights of different
wavelengths emitted from the emitting faces of a plurality of
planar light emitting devices of different light emitting devices
are optically coupled to the curved waveguides 24A to 24D provide
on the transmitter waveguide block 20, and the optical paths of the
lights are curved substantially to the right angle in the plane.
Then, the lights are multiplexed into wavelength division
multiplexed light, which is optically coupled to the optical fibers
through the optical connector 10.
[0103] In the present embodiment, since the optical transmitter
includes a plurality of planar light emitting devices having same
light emitting wavelengths as each other and the transmitter
waveguide block 20 is structured such that a plurality of
transmitter film waveguides 21 having the same configuration are
laminated and besides the optical fiber array 6 formed from a
plurality of optical fibers is connected to the transmitter
waveguide block 20, wavelength division multiplexed lights
(multi-channel wavelength division multiplexed lights) multiplexed
by the plurality of the waveguide type multiplexer 22 of the same
configuration are emitted to respective ones of the plural optical
fibers.
[0104] Now, a fabrication method for the optical transmitter
(optical module) which form the wavelength division multiplexing
multi-channel optical transceiver according to the present
embodiment is described with reference to FIGS. 13(A) to 13(C) and
14(A) to 14(C).
[0105] First, the transmitter waveguide block 20 which includes the
curved waveguides 24A to 24D (in-plane curved waveguides) formed in
planes can be fabricated, for example, in such a manner as
described below. It is to be noted that, in FIGS. 13(A) to 13(C),
only two curved waveguides are shown for the convenience of
illustration.
[0106] A metal mold for a transmitter (molding metal mold) having a
convex-shaped transmitter waveguide pattern (here, a pattern for
formation of a plurality of curved waveguides) is fabricated.
[0107] Then, olefin resin (for example, a refractive index n=1.52
after cured) used to form a lower cladding material is poured into
the metal mold to perform molding. Consequently, a film-like molded
body 25 made of the transparent olefin resin is formed as seen in
FIG. 13(A).
[0108] Then, epoxy resin 26 (for example, a refractive index n=1.54
after cured) of the ultraviolet curing type used to form a
waveguide core is filled (applied) into grooves (waveguide grooves)
25A of the film-like molded body 25 as seen in FIG. 13(B). Then, a
film 27 (cladding film; refractive index n=1.52; 0.1 mm thick) of
olefin resin prepared separately is stuck as seen in FIG.
13(C).
[0109] Then, ultraviolet rays are irradiated while a load is
applied to cure the epoxy resin 26.
[0110] Thereafter, the end faces are mirror polished to produce a
transmitter film waveguide 21 having curved waveguides 24A to 24D
formed on a plane as seen in FIG. 11. Then, a plurality of such
transmitter film waveguides 21 of the same configuration fabricated
in such a manner as described above are laminated to fabricate a
transmitter waveguide block 20 as seen in FIG. 12.
[0111] Here, the outside dimension of the transmitter waveguide
block 20 is 10 mm.times.5 mm.times.5 mm. The dimension of the
waveguide cores 26 which form the curved waveguides 24A to 24D is
0.05 mm.times.0.05 mm.
[0112] Then, an optical transmitter (transmission module) which
includes the transmitter waveguide block 20 fabricated in such a
manner as described above can be fabricated, for example, in the
following manner.
[0113] A plurality of (here, two) planar light emitting laser
arrays 2A and 2B are mounted in advance on the printed board 1 as
seen in FIG. 14(A). In particular, the planar light emitting laser
arrays 2A and 2B are stuck to the printed board 1 using conductive
paste with heat radiating blocks 16 (for example, a thickness of
0.25 mm) of copper tungsten alloy interposed therebetween such that
the light emitting faces (emitting faces) of a plurality of planar
light emitting lasers which form the planar light emitting laser
arrays 2A and 2B are directed upwardly in a direction perpendicular
to the printed board 1 and the planar light emitting laser arrays
2A and 2B line up in parallel to each other.
[0114] It is to be noted that the distance between the planar light
emitting laser array 2A and the planar light emitting laser array
2B (gap between the two chips) may be an arbitrary distance and may
be, for example, 1 mm. Further, the electrodes on the surface of
the chips and the wirings on the printed board are coupled to each
other by wire bonding so that they may serve as feeder lines.
[0115] Here, two different multi-mode planar light emitting laser
arrays 2A and 2B of wavelengths 850 nm and 980 nm are used. The
outside dimension of the planar light emitting laser arrays 2A and
2B is 0.25 mm.times.0.25 mm.times.0.25 mm.
[0116] The transmitter waveguide block (transmission side waveguide
block) 20 fabricated in such a manner as described above is mounted
on the printed board 1 fabricated in such a manner as described
above and having the chips mounted thereon with the spacers 17 (for
example, a thickness of 0.6 mm) interposed therebetween as seen in
FIG. 14(B). For example, the transmitter waveguide block 20 may be
fixed to the printed board 1 using ultraviolet curing resin.
[0117] Thereupon, for example, a flip chip bonder having a vertical
visual field camera may be used to perform positioning so that the
centers of the waveguide cores which form the curved waveguides 24A
to 24D provided on the transmitter waveguide block 20 may
individually be aligned with the centers of the light emitting
faces of the planar light emitting lasers.
[Optical Receiver]
[0118] Now, the optical receiver according to the present
embodiment includes, for example, as shown in FIG. 15, planar
photo-detector arrays (PD array chips) 3A to 3D each formed from a
plurality of planar photo-detectors [here, photo-diodes
(photo-detectors; PDs)]; having an incidence face on the surface
thereof, and a receiver waveguide block (waveguide array) 30 formed
from a plurality of receiver film waveguides 31 laminated with each
other and each including a plurality of (here, four) curved
waveguides 34A to 34D and a waveguide type demultiplexer 32.
[0119] Referring to FIG. 16, the waveguide type demultiplexer 32
includes a plurality of (here, four) wavelength filters 35A to 35D
connected to the plural curved waveguides 34A to 34D, a mirror 36
provided at an end face of the receiver waveguide block 30
(laminated receiver film waveguides 31), and channel waveguides 37
formed between the wavelength filters 35A to 35D and the mirror 36.
The waveguide type demultiplexer 32 demultiplexes wavelength
division multiplexed light incoming through an incidence side end
face 37X of the channel waveguides 37 into lights of different
wavelengths and emits the lights to the curved waveguides 34A to
34D. Here, a plurality of film waveguides 31 are laminated to form
a multi-channel demultiplexer.
[0120] In the present embodiment, a thin film filter formed as a
horizontally elongated chip part is used for the wavelength filters
35A to 35D. Here, an n-channel common use chip is used for the
wavelength filters 35A to 35D, and the wavelength filters 35A to
35D are mounted in such a manner as to extend through a plurality
of laminated receiver film waveguides 31 to share the parts among
the different channels. Further, each of the wavelength filters 35A
to 35D is configured so as to transmit light of only one wavelength
therethrough but reflect lights of the other wavelengths. Here, the
wavelength filters 35A to 35D transmit lights of different
wavelengths from one another.
[0121] The waveguide type demultiplexer 32 configured in such a
manner as described above demultiplexes lights of different
wavelengths included in wavelength division multiplexed light in
the following manner.
[0122] In particular, as seen in FIG. 16, only light having the
first wavelength .lamda.1 included in wavelength division
multiplexed light incoming through the incidence side end face 37X
of the channel waveguides 37 passes through and is demultiplexed by
the first wavelength filter 35D and is then introduced to the first
curved waveguide 34D.
[0123] On the other hand, the remaining wavelength division
multiplexed light is reflected by the first wavelength filter 35D,
guided by a channel waveguide 37 and then reflected by the mirror
36, whereafter it is guided by another channel waveguide 37. Thus,
only light having the second wavelength .lamda.2 passes through and
is demultiplexed by the second wavelength filter 35C and is
introduced to the second curved waveguide 34C.
[0124] Further, the remaining wavelength division multiplexed light
is reflected by the second wavelength filter 35C, guided by a
channel waveguide 37, reflected by the mirror 36 and then
introduced by another channel waveguide 37. Thus, only light having
the third wavelength .lamda.3 passes through and is demultiplexed
by the third wavelength filter 35B and is introduced to the third
curved waveguide 34B.
[0125] Then, the remaining light having the fourth wavelength
.lamda.4 is reflected by the third wavelength filter 35B, guided by
a channel waveguide 37, reflected by the mirror 36 and further
guided by another channel waveguide 37. Thus, the light passes
through and is demultiplexed by the fourth wavelength filter 35A
and is introduced to the fourth curved waveguide 34A.
[0126] It is to be noted that, although, in the waveguide type
demultiplexer 32 configured in such a manner as described above, an
optical path length difference appears between different
wavelengths, the optical path length difference can be eliminated
by the design of the curved waveguides 34A to 34D, and it is
possible to achieve equalization of the optical path lengths for
the individual wavelengths. Further, where the waveguide type
demultiplexer 32 is connected to the optical transmitter which
includes the curved waveguides 24A to 24D described hereinabove,
the optical path length difference can be eliminated also by the
design of the curved waveguides 24A to 24D of the optical
transmitter.
[0127] Meanwhile, the receiver waveguide block 30 is formed from a
plurality of receiver film waveguides 31 laminated such that, as
shown in FIG. 17, incidence side end faces 37X of the channel
waveguides 37 line up individually in series along the surface of
the printed board 1 and in parallel to each other. The receiver
waveguide block 30 is configured to implement a multi-channel
optical receiver by laminating the receiver film waveguides 31 in
this manner. Further, an optical fiber array 6 (ribbon fiber)
formed from a plurality of optical fibers is connected to the
incidence side end faces 37X of the plural channel waveguides 37
through the optical connector 10 as seen in FIG. 15.
[0128] By setting the thickness of the film waveguides 31 (that is,
the distance between the waveguide cores which form the curved
waveguides of the receiver film waveguides 31) so as to be equal to
a thickness (distance) corresponding to the fiber pitch of the
optical fiber array 6, the block 30 can convert the mounting gap
(chip distance) between the planar light emitting device arrays
into an arbitrary optical fiber pitch irrespective of the mounting
gap (even if the plural planar light emitting device arrays are
disposed in a spaced relationship by an arbitrary distance from
each other) similarly as in the first embodiment described
hereinabove. Consequently, the degree of freedom in design is
enhanced, and such a situation that part of an optical fiber array
becomes wasteful can be prevented.
[0129] Further, each of the planar photo-detector arrays 3A to 3D
includes a plurality of planar light photo-detectors as seen in
FIG. 17. The planar photo-detector arrays 3A to 3D are disposed in
parallel to each other on the printed board 1 such that the
incidence faces of the planar photo-detectors are directed upwardly
in a direction perpendicular to the printed board 1 and besides the
planar photo-detectors line up in series along the lamination
direction of the receiver film waveguides 31.
[0130] In the present embodiment, a plurality of planar
photo-detectors which form the different planar photo-detector
arrays 3A to 3D are mounted on the printed board 1 in such a manner
as to line up in series along an end face of the receiver waveguide
block 30 (laminated receiver film waveguides 31) as seen in FIG.
17.
[0131] In particular, as seen in FIG. 17, a first planar
photo-detector array 3A formed from a plurality of first planar
photo-detectors, a second planar photo-detector array 3B formed
from a plurality of second planar photo-detectors, a third planar
photo-detector array 3C formed from a plurality of third planar
photo-detectors, and a fourth planar photo-detector array 3D formed
from a plurality of fourth planar photo-detectors are mounted on
the printed board 1 such that they line up individually in series
along an end face of the receiver waveguide block 30 (laminated
receiver film waveguides 31) and in parallel to each other.
[0132] In the present embodiment, the plural curved waveguides 34A
to 34D are formed individually as the film waveguides 31 and are
channel waveguides formed on a plane. Therefore, the degree of
freedom in fabrication method is high, and the curved waveguides
34A to 34D can be fabricated readily by a molding method which is
based on a plane metal mold fabricated, for example, using an
electroformed replica. Further, since the channel waveguides are
adopted, a beam can be confined to a width of, for example,
approximately 50 .mu.m, and therefore, miniaturization of the
module can be anticipated. Furthermore, since the optical paths are
produced in a two-dimensional plane first, the curved waveguides
34A to 34D are superior in terms of positioning and reliability
(impact resistance) when compared with an alternative case wherein
spatial light is used. Further, since the curved waveguides 34A to
34D are formed on a plane, they can be molded with a simple
embossing technique, and therefore, the cost is low. It is to be
noted that a particular formation method of the curved waveguides
34A to 34D is hereinafter described.
[0133] Further, as seen in FIG. 15, in the present embodiment, the
curved waveguides 34A to 34D are optically connected to respective
ones of a plurality of planar photo-detectors on an end face 30A of
the receiver waveguide block 30. Meanwhile, the curved waveguides
34A to 34D are connected at the other ends thereof to a waveguide
type demultiplexer 32. Further, on the other end face 30B of the
receiver waveguide block 30 orthogonal to the end face 30A, an
optical fiber is connected to the incidence side end face 37X of
the channel waveguides 37 which form the waveguide type
demultiplexer 32.
[0134] Consequently, as seen in FIG. 15, wavelength division
multiplexed light introduced along the optical fiber is optically
coupled to the incidence side end face 37X of the channel
waveguides 37 which form the waveguide type demultiplexer 32. Then,
when the wavelength division multiplexed light is guided by the
channel waveguides 37, it is filtered and demultiplexed into lights
of different wavelengths by the wavelength filters 35A to 35D. The
lights of the different wavelengths are guided by the curved
waveguides 34A to 34D, which curve the optical paths substantially
to the right angle in a plane until they are optically coupled to
the respective planar photo-detectors.
[0135] In the present embodiment, since the optical transmitter
includes a plurality of planar photo-detectors and the receiver
waveguide block 30 is structured such that a plurality of receiver
film waveguides 31 having the same configuration are laminated and
besides the optical fiber array 6 formed from a plurality of
optical fibers is connected to the receiver waveguide block 30,
wavelength division multiplexed lights (multi-channel wavelength
division multiplexed lights) introduced from the plural optical
fibers are demultiplexed by the plural waveguide type demultiplexer
32 of the same configuration and emitted to respective ones of the
plural planar photo-detectors through the plural curved waveguides
34A to 34D.
[0136] Now, a fabrication method for the optical receiver (optical
module) which forms the wavelength division multiplexing
multi-channel optical transceiver according to the present
embodiment is described with reference to FIGS. 18(A) to 18(E) and
19(A) to 19(C).
[0137] First, the receiver waveguide block 30 which includes the
curved waveguides (in-plane curved waveguides) 34A to 34D formed in
planes can be fabricated, for example, in such a manner as
described below. It is to be noted that, in FIGS. 18(A) to 18(E),
only two curved waveguides are shown for the convenience of
illustration.
[0138] A metal mold for a receiver (molding metal mold) having a
convex-shaped receiver waveguide pattern (here, a pattern for
formation of a plurality of curved waveguides) is fabricated.
[0139] Then, olefin resin (for example, a refractive index n==1.52
after cured) used to form a lower cladding material is poured into
the metal mold to perform molding. Consequently, a film-like molded
body 38 made of the transparent olefin resin is formed as seen in
FIG. 18(A).
[0140] Then, epoxy resin 39 (for example, a refractive index n=1.54
after cured) of the ultraviolet curing type used to form a
waveguide core is filled (applied) into grooves (waveguide grooves)
38A of the film-like molded body 38 as seen in FIG. 18(B). Then, a
film 40 (cladding film; refractive index n=1.52; 0.1 mm thick) of
olefin resin prepared separately is stuck as seen in FIG.
18(C).
[0141] Then, ultraviolet rays are irradiated while a load is
applied to cure the epoxy resin.
[0142] Thereafter, thin film filter inserting grooves are formed,
and then narrow bandwidth wavelength filters 35 (35A to 35D), for
example, for 980 nm are inserted into the grooves and fixed using a
transparent adhesive as seen in FIG. 18(D).
[0143] Then, a mirror 36 is stuck to the end face, to which optical
fibers are to be connected, for example, using a transparent
adhesive as seen in FIG. 18(E).
[0144] Finally, the end faces are mirror polished to produce a film
waveguide 31 having curved waveguides 34A to 34D formed on a plane
as seen in FIG. 16. Then, a plurality of such receiver film
waveguides 31 of the same configuration fabricated in such a manner
as described above are laminated to fabricate a receiver waveguide
block 30 as seen in FIG. 17.
[0145] Here, the outside dimension of the receiver waveguide block
30 is 10 mm.times.5 mm.times.5 mm. The dimension of the waveguide
cores 39 which form the curved waveguides 34A to 34D is 0.05
mm.times.0.05 mm.
[0146] Then, an optical receiver (reception module) which includes
the receiver waveguide block 30 fabricated in such a manner as
described above can be fabricated, for example, in the following
manner.
[0147] A plurality of (here, two) photo-detector arrays 3A and 3B
are mounted in advance on the printed board 1 as seen in FIG.
19(A). In particular, the photo-detector arrays 3A and 3B are stuck
to the printed board 1 by conductive paste with heat radiating
blocks 16 (for example, a thickness of 0.25 mm), for example, of
copper tungsten alloy interposed therebetween such that the light
receiving faces (incidence faces) of a plurality of photo-detectors
which form the photo-detector arrays 3A and 3B are directed
upwardly in a direction perpendicular to the printed board 1 and
the photo-detector arrays 3A and 3B line up in parallel to each
other.
[0148] It is to be noted that the distance between the planar
photo-detector array 3A and the planar photo-detector array 3B (gap
between the two chips) may be an arbitrary distance and may be, for
example, 1 mm. Further, the electrodes on the surface of the chips
and the wirings on the printed board are coupled to each other by
wire bonding so that they may be used as feeder lines.
[0149] Here, two different photo-detector arrays 3A and 3B having a
sensitivity, for example, to wavelengths 850 to 980 nm are used.
The outside dimension of the photo-detector arrays 3A and 3B is
0.25 mm.times.0.25 mm.times.0.25 mm.
[0150] The receiver waveguide block (reception side waveguide
block) 30 fabricated in such a manner as described above is mounted
on the printed board 1 fabricated in such a manner as described
above and having the chips mounted thereon with spacers 17 (for
example, a thickness of 0.6 mm) interposed therebetween as seen in
FIG. 19(B). For example, the receiver waveguide block 30 may be
fixed to the printed board 1 using ultraviolet curing resin.
[0151] Thereupon, for example, a flip chip bonder having a vertical
visual field camera may be used to perform positioning so that the
centers of the waveguide cores which form the curved waveguides 34A
to 34D provided on the receiver waveguide block 30 may individually
be aligned with the centers of the light receiving faces of the
photo-detectors.
[Evaluation]
[0152] A transmitter waveguide block 20 and a receiver waveguide
block 30 which include curved waveguides (in-plane curved
waveguides) which are curved in a plane were fabricated using
polymer, and the transmitter waveguide block 20 was mounted on a
printed board 1 together with a planar light emitting device array
2 to fabricate a multi-channel optical transmitter while the
receiver waveguide block 30 was mounted on the printed board 1
together with a planar photo-detector array 3 to produce a
multi-channel optical receiver in such a manner as described
hereinabove, whereafter an optical fiber array 6 was assembled in
such a manner as seen in FIGS. 14(C) and 19(C) and the insertion
loss of the curved waveguides which form the waveguide blocks 20
and 30 was measured in order to evaluate the transmission and
reception performances. As a result of the measurement, the
insertion loss including the coupling loss to each chip was 5.0 dB
(980 nm) and 4.8 dB (850 nm) with regard to the optical transmitter
(transmission side optical module) and 2.5 dB (980 nm) and 3.2 dB
(850 nm) with regard to the optical receiver (reception side
optical module). Thus, it was confirmed successfully that the
waveguide blocks 20 and 30 fabricated in such a manner as described
above are effective.
[0153] It is to be noted that the optical fiber array 6 was
connected to the end face of the transmitter waveguide block 20
mounted on the printed board 1 and the end face of the receiver
waveguide block 30 mounted on the printed board 1 through
individual optical connectors (not shown) as seen in FIGS. 14(C)
and 19(C). Thereupon, the planar light emitting lasers were
energized to perform positioning by active alignment.
[Optical Transceiver]
[0154] The wavelength division multiplexing multi-channel optical
transceiver according to the present embodiment can be configured
by sticking the optical transmitter configured in such a manner as
described above and the optical receiver configured in such a
manner as described above to each other on the rear face side of a
printed board to integrate the optical transmitter and the optical
receiver with each other.
[Operation and Effects]
[0155] Accordingly, with the optical module, optical transceiver
and fabrication method for an optical module according to the
present embodiment, there is an advantage that optical connection
between the planar optical devices [for example, face light
emitting lasers, photo-diodes (photo-detectors) and so forth]
mounted on the printed board 1 and the optical fibers attached in
parallel to the printed board 1 can be implemented simply and
readily similarly to those of the first embodiment described
hereinabove.
[0156] Particularly, where such a configuration as described above
is adopted, a wavelength division multiplexing multi-channel
optical transceiver of a small size can be implemented simply and
conveniently, and remarkable enhancement of the transmission band
can be achieved.
[Others]
[0157] The present invention is not limited to the embodiments
specifically described above, and variations and modifications can
be made without departing from the scope of the present
invention.
* * * * *