U.S. patent application number 09/785144 was filed with the patent office on 2001-10-04 for optical wavelength division multiplexer/demultiplexer having adhesive overflow channels with dams to achieve tight adhesive bond.
Invention is credited to Kim, Peter K., Prouteau, Sophie.
Application Number | 20010026663 09/785144 |
Document ID | / |
Family ID | 23363910 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010026663 |
Kind Code |
A1 |
Kim, Peter K. ; et
al. |
October 4, 2001 |
Optical wavelength division multiplexer/demultiplexer having
adhesive overflow channels with dams to achieve tight adhesive
bond
Abstract
An optical wavelength division multiplexer and demultiplexer is
provided wherein the optical couplings and alignment of the device
are achieved by forming and adhesively joining a prefabricated
optical block to a molded coupling module to avoid post-fabrication
alignment and adjustment of the optical pathway otherwise required.
One or more adhesive overflow channels are formed in said upper
surface of the molded coupling module to receive excess adhesive
used to join the optical block to the molded coupling module. Dams
are formed adjacent each of said adhesive overflow channels to
contain adhesive used to join the optical block to the molded
coupling module, and to facilitate the use of low viscosity
adhesive which in turn achieves a tighter, more parallel bond
between the adhesively bonded parts.
Inventors: |
Kim, Peter K.; (Alamo,
CA) ; Prouteau, Sophie; (Berkeley, CA) |
Correspondence
Address: |
Bruce H. Johnsonbaugh
Eckhoff, Hoppe, Slick, Mitchell & Anderson
Suite 760
Four Embarcadero Center
San Francisco
CA
94111
US
|
Family ID: |
23363910 |
Appl. No.: |
09/785144 |
Filed: |
February 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
09785144 |
Feb 16, 2001 |
|
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09347490 |
Jul 2, 1999 |
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6201908 |
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Current U.S.
Class: |
385/76 ;
385/24 |
Current CPC
Class: |
Y10S 439/931 20130101;
H05K 3/361 20130101; G02B 6/4292 20130101; G02B 6/4246 20130101;
G02B 6/3865 20130101; H05K 1/0237 20130101; G02B 6/29358 20130101;
G02B 6/2938 20130101; G02B 6/29367 20130101; H05K 2201/10121
20130101; G02B 6/4214 20130101 |
Class at
Publication: |
385/76 ;
385/24 |
International
Class: |
G02B 006/36; G02B
006/28 |
Claims
What is claimed is:
1. In an optical wavelength division multiplexer and demultiplexer
for single-mode or multi-mode fiber optic communication systems,
wherein n channels are transmitted through a single fiber optic
cable having n different wavelengths and wherein the optical
couplings and alignment of the device are achieved by forming and
adhesively joining a prefabricated optical block to a molded
coupling module to avoid post-fabrication alignment and adjustment
of the optical pathway otherwise required, having an optical block
with a flat lower surface, said molded coupling module having a
flat upper surface on which said flat lower surface of said optical
block is mounted, the improvement comprising: one or more adhesive
overflow channels formed in said upper surface of said molded
coupling module, said channels being adapted to receive excess
adhesive used to join said optical block to said molded coupling
module, and dam means formed adjacent each of said adhesive
overflow channels to contain adhesive used to join said optical
block to said molded coupling module.
2. The apparatus of claim 1 wherein said adhesive overflow channel
or channels facilitates the use of lower viscosity adhesive which
in turn achieves a tighter and more parallel bond between said
optical block and said molded coupling module.
3. The apparatus of claim 1 wherein said dam means comprises a
single, continuous dam formed along the periphery of the upper
surface of said molded coupling module.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation-in-part of U.S. patent application
Ser. No. 09/347,490 filed Jul. 2, 1999.
BACKGROUND AND BRIEF SUMMARY OF THE INVENTION
[0002] The present invention relates generally to optical
wavelength division multiplexers/demultiplexers (WDM). More
specifically, the present invention relates to optical
multiplexers/demultiplexers wherein the device incorporates two
primary components which are adhesively bonded to form an optic
module. The present invention provides specially designed adhesive
overflow channels with dams formed on the upper surface of a molded
coupling module to which an optical block is adhesively mounted.
The invention facilitates the use of low viscosity adhesive which
in turn reduces the thickness of the adhesive bond between the
major pieces, thereby achieving a tighter bond and better alignment
of the optics.
[0003] The present invention is particularly effective in achieving
a tighter and more parallel bond between the optical block and
molded coupling module components in the multiplexer/demultiplexer
design shown and described in U.S. application Ser. No. 09/347,490,
which is incorporated by reference herein as though set forth in
full. The design shown in Ser. No 09/347,490 incorporates a pattern
of relief cuts wherein each relief cut extends through the exterior
side wall of the molded coupling module. Those relief cuts did not
allow the use of relatively low viscosity adhesive being used to
join the primary two components of the device together, because the
low viscosity adhesive would drip down the sides of the module,
potentially contaminating the optical pathway extending through the
lower surface of the module. Using a high viscosity adhesive limits
the closeness of the adhesive bond between the two components and
limits the degree of parallelism between those components
achievable by the adhesive bond.
[0004] The present invention provides a new modified form of
adhesive overflow channel which allows the use of a much lower
viscosity adhesive. The use of the low viscosity adhesive reduces
the thickness of the adhesive joint, increasing the degree of
parallelism between the lower surface of the optical block and the
upper surface of the molded coupling module. Increasing the
parallelism between those components significantly enhances the
optical alignment and operational characteristics of the assembled
multiplexer/demultiplexer.
[0005] A primary object of the invention is to provide an improved
design for achieving a very thin adhesive bond between the two
primary components of an optical multiplexer/demultiplexer,
enhancing the optical alignment characteristics of the assembled
device.
[0006] A further object of the invention is to provide one or more
adhesive overflow channels between an upper and lower optical
component wherein the performance of the assembled device is
enhanced by achieving the thinnest possible adhesive bond between
components.
[0007] Another object of the invention is to provide adhesive
overflow channels wherein each channel has a dam formed near the
outermost edge of the lower optical component to facilitate the use
of low viscosity adhesive and to prevent the adhesive from spilling
over the outermost edges of the optical component and potentially
contaminating the optical pathway of the WDM.
[0008] Other objects and advantages will become apparent from the
following description and the drawings wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows a cross section side view of a WDM optical
multiplexer/demultiplexer using the present invention;
[0010] FIG. 2 is a perspective view showing the molded coupling
module having the pattern of adhesive overflow channels formed in
its upper surface according to the present invention;
[0011] FIG. 3 is a perspective view showing the optical coupling
module with the optical block shown in phantom in its ultimate
position adhesively bonded to the molded coupling module;
[0012] FIG. 4 is a perspective view showing an alternate embodiment
of the present invention wherein a continuous dam is formed around
the periphery of the upper surface of the molded coupling
module;
[0013] FIG. 5 is a schematic illustration showing in exaggerated
form how the optical block may become misaligned on top of the
molded coupling module when using relatively high viscosity
adhesive; and
[0014] FIG. 6 is a schematic illustration showing in exaggerated
form the tighter and more parallel alignment of the optical block
on top of the molded coupling module when using low viscosity
adhesive.
DETAILED DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 shows the assembled wavelength division
multiplexer/demultiplexer 10 which utilizes the present invention.
A complete description of the device shown in FIG. 1 is contained
in application Ser. No. 09/347,490. A portion of that description
is repeated here for convenience. The device shown in FIG. 1 has
the ability to combine individual light signals into a single
optical path which can be directed towards an optical fiber, and/or
demultiplex such signals into individual channels. For simplicity
of explanation, the demultiplexing functionality is described,
since those skilled in the art will readily understand the
correlative multiplexing functionality.
[0016] FIG. 1 shows the assembled primary components and
illustrates the optical pathway 90-96 wherein an incoming signal
includes eight separate wavelengths (n wavelengths in the general
case), which are separated into eight separate channels to be read
by photodetectors (not shown). An optical block 20 formed of glass
or molded of plastic is shown with a plurality of filters 40
carried on its lower surface 22. The optical block 20 has an upper
flat surface 21 which is coated with a reflective material 85.
[0017] A molded coupling module 60 has a flat upper surface 61
which is adhesively connected to the flat lower surface 22 of
optical block 20. The present invention facilitates the use of low
viscosity adhesive to achieve a thinner and tighter bond between
module 60 and optical block 20.
[0018] The molded coupling module 60 in the embodiment illustrated
in FIG. 1 includes a fiber optic cable receptacle 80 integrally
molded therein for receiving the end of a fiber optic cable (not
shown) so that the end of the cable engages receptacle seat 81.
[0019] As illustrated in FIG. 1, a multiplexed optical beam moves
along optical pathway 90, exits the end of the fiber optic cable
(not shown) and begins to diverge as shown at 91. An integrally
molded collimating lens 65 collimates the diverging light beam 91
and forms a collimated beam 92. The collimated light beam 92 is
reflected off integrally formed reflective surface 66 of the molded
coupling module 60 and is directed upwardly toward the reflective
coating 85 carried by the flat upper surface 21 of the optical
block 20. As the light beam moves through that section 93 of the
optical pathway, it impinges against the reflective coating 85 at a
predetermined angle of incidence as known in the art. The reflected
beam 94 is reflected in a zigzag pattern in optical block 20
between the plurality of n filters 40 and the reflective surface 85
as is known in the art. As the reflected beam enters each of the n
filters, one of the n different wavelengths of light is transmitted
through each filter and the separated wavelengths move along the
optical pathways 95a through 95h toward the plurality of molded
aspheric surfaces 70 formed on the lower surface 62 of the molded
coupling module 60. Each of the n aspheric molded surfaces focuses
the separated wavelength bands or channels 96a-96h onto separate
photodetectors (not shown), as known in the art.
[0020] As shown in FIG. 1, the optical block 20 is generally
rectangular in shape having flat upper and lower surfaces 21 and
22, a flat proximal end wall 23 and a flat distal wall 24. The
optical block in the preferred embodiment of the invention is
formed from a high quality optical glass. Alternately, the optical
block 20 may be injection molded using high quality optical
plastic. The reflective coating 85 is applied to the upper surface
21 of block 20. The reflective coating may be formed of materials
conventionally used in this art, such as dielectric interference
coatings or metallic coatings.
[0021] The optical block 20 has a reflective coating on one side
and an array 40 of discrete multiwavelength Fabry-Perot
transmission filters on the other side. The precision optical block
20 can be formed of any transparent optical material capable of
transmitting light over the desired spectral region and being
formed or polished to the correct thickness. The reflective surface
85 can be placed on the optical block by a number of techniques, to
include; dielectric interference coatings, metallic coatings,
etc.
[0022] The plurality of n filters 40 includes eight discrete
Fabry-Perot filters mounted on the flat bottom surface 22 of
optical block 20.
[0023] The assembly of the filter array onto the optical block and
then the adhesive bonding of the optical block 20 to the molded
coupling module 60 achieves a passive optical alignment of the
critical optical elements of the device. When assembled as
described above, the output beam 91 of the fiber optic cable is
directly coupled to the wavelength division
multiplexer/demultiplexer 10 and is automatically and passively
aligned with the internal optics of the device, including the
collimating lens 65, the beam reflection means, the reflective
coating 85 on the top surface of optical block 20 as well as with
the plurality of filters 40 and the plurality of aspheric surfaces
70. No postfabrication alignment or tuning or adjustment of these
optical elements is required.
[0024] FIG. 2 illustrates the molded coupling module 60 before it
is adhesively bonded to optical block 20. A series of adhesive
overflow channels 64 are formed in the upper flat surface 61 of
module 60. The channels 64 are adapted to receive excess adhesive
used to join the optical block 20 to the molded coupling module 60.
According to the present invention, each channel 64 has a dam 101
formed between the channel 64 and the outer edge surface 105 of the
molded coupling module 60. The purpose of dams 101 is to prevent
adhesive from running outwardly along channel 64 and downwardly
along the edge surface 105 where it can possibly contaminate the
optical pathway by reaching the aspherical lens surface 70 (FIG.
1). By forming a dam at the end of each adhesive overflow channel
64, the use of low viscosity adhesive is facilitated.
[0025] FIG. 3 illustrates the optical block 20 shown in phantom in
the position in which it is adhesively bonded to the optical
coupling module 60. The outer ends of channels 64 extend outwardly
beyond the lateral side walls 25 and 26 of optical block 20.
[0026] FIG. 4 illustrates an alternate form of the invention
wherein the molded coupling module 160 has a continuous dam 201
extending around the periphery of its upper surface. The purpose of
the continuous dam 201 is to prevent excess adhesive from running
downwardly over the outside edges of molded coupling module 160.
One or more adhesive overflow channels 164 are formed in the upper
surface of molded coupling module 160 to receive excess bonding
adhesive.
[0027] FIG. 5 illustrates in exaggerated form how the optical block
20 may become somewhat misaligned on molded coupling module 60 when
using a high viscosity adhesive 110 having a thickness t.sub.1.
Optical block 20 may become somewhat misaligned with respect to
molded coupling module 60. Any rotation of optical block 20
relative to molded coupling module 60, as illustrated in FIG. 5,
can seriously affect the alignment of the optical pathway and the
overall performance of the assembled device.
[0028] FIG. 6 illustrates how the use of a low viscosity adhesive
210 adhieves a much thinner adhesive layer having a thickness
t.sub.2 substantially less than t.sub.1. The reduced thickness of
the adhesive bond increases the parallelism between optical block
20 and molded coupling module 60. The increased degree of
parallelism between the optical block 20 and molded coupling module
60 is particularly important in the present invention wherein the
devices are capable of high speed automatic assembly and wherein
bonding of the optical block 20 to the molded coupling module 60
achieves passive alignment of the optical elements and no post
assembly optical alignment is required.
[0029] The foregoing description of the invention has been
presented for purposes of illustration and description and is not
intended to be exhaustive or to limit the invention to the precise
form disclosed. Modifications and variations are possible in light
of the above teaching. The embodiments were chosen and described to
best explain the principles of the invention and its practical
application to thereby enable others skilled in the art to best use
the invention in various embodiments and with various modifications
suited to the particular use contemplated. The scope of the
invention is to be defined by the following claims.
* * * * *