U.S. patent application number 16/427748 was filed with the patent office on 2020-12-03 for precision tff posa and wdm systems using parallel fiber interface devices.
The applicant listed for this patent is ALLIANCE FIBER OPTIC PRODUCTS, INC.. Invention is credited to Dong Gui, Qijun Xiao.
Application Number | 20200379182 16/427748 |
Document ID | / |
Family ID | 1000005218639 |
Filed Date | 2020-12-03 |
![](/patent/app/20200379182/US20200379182A1-20201203-D00000.png)
![](/patent/app/20200379182/US20200379182A1-20201203-D00001.png)
![](/patent/app/20200379182/US20200379182A1-20201203-D00002.png)
![](/patent/app/20200379182/US20200379182A1-20201203-D00003.png)
![](/patent/app/20200379182/US20200379182A1-20201203-D00004.png)
![](/patent/app/20200379182/US20200379182A1-20201203-D00005.png)
![](/patent/app/20200379182/US20200379182A1-20201203-D00006.png)
![](/patent/app/20200379182/US20200379182A1-20201203-D00007.png)
![](/patent/app/20200379182/US20200379182A1-20201203-D00008.png)
![](/patent/app/20200379182/US20200379182A1-20201203-D00009.png)
![](/patent/app/20200379182/US20200379182A1-20201203-D00010.png)
View All Diagrams
United States Patent
Application |
20200379182 |
Kind Code |
A1 |
Gui; Dong ; et al. |
December 3, 2020 |
PRECISION TFF POSA AND WDM SYSTEMS USING PARALLEL FIBER INTERFACE
DEVICES
Abstract
The precision TFF POSA is formed by pressing a TFF glass rod
array into a top surface of a master glass block to flatten the
otherwise curved TFFs formed using conventional TFF deposition
processes on glass. The TFF glass rod array is secured to the
master glass block with a securing material to form a fabrication
structure, which is singulated to form precision TFF POSAs having
TFF members with flat TFFs and long TFF member long axes. A fiber
interface device is arranged at a back surface of the TFF POSA.
Other fiber interface devices having device axes are arranged
proximate the TFF members. The device axes are parallel to the TFF
member long axes to form a WDM system with a parallel
configuration. In this configuration, there is one positionally
adjustable fiber interface device for each wavelength channel,
which allows for optimizing WDM optical communication in Mux and
DeMux directions.
Inventors: |
Gui; Dong; (San Jose,
CA) ; Xiao; Qijun; (Fremont, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALLIANCE FIBER OPTIC PRODUCTS, INC. |
Sunnyvale |
CA |
US |
|
|
Family ID: |
1000005218639 |
Appl. No.: |
16/427748 |
Filed: |
May 31, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/29367 20130101;
G02B 6/29382 20130101; H04J 14/02 20130101; C03C 27/048 20130101;
H04B 10/2581 20130101 |
International
Class: |
G02B 6/293 20060101
G02B006/293; C03C 27/04 20060101 C03C027/04; H04J 14/02 20060101
H04J014/02; H04B 10/2581 20060101 H04B010/2581 |
Claims
1. A method of forming a precision passive optical structure
assembly (POSA) for wavelength-division multiplexing (WDM)
applications, comprising: forming respective thin film filters on
respective first surfaces of two or more glass rods using a
thin-film deposition process, wherein: each of the two or more
glass rods also has a second surface substantially parallel to the
first surface, each of the thin film filters has a thickness
variation due to curvature of an optical surface of the thin film
filter that is opposite the first surface of the corresponding
glass rod, and the thin film filters have different non-overlapping
wavelength transmissions; forming a glass rod assembly comprising
the two or more glass rods arranged side-by-side so that the thin
film filters reside in a common plane; arranging the glass rod
assembly on a top surface of a master glass block with the thin
film filters confronting the top surface, wherein the master glass
block is elongate in a first direction; pressing the glass rod
assembly and the master glass block together with a securing
material therebetween to substantially reduce the amounts of
curvature of the optical surfaces of the thin film filters; curing
the securing material during said pressing to fix the glass rod
assembly in place on the master glass block with the thin film
filters having the substantially reduced amounts of curvature; and
singulating the glass rod assembly and the master glass block after
said curing, in a plane transverse to the first direction, to form
the precision POSA.
2. (canceled)
3. The method according to claim 1, wherein said curing comprises
exposing the securing material to actinic radiation transmitted
through at least a portion of the master glass block while said
pressing is performed using a top plate disposed atop the glass rod
assembly.
4. The method according to claim 3, wherein the actinic radiation
comprises infrared light or ultraviolet light.
5. The method according to claim 1, wherein the master glass block
has opposite sides and a bottom surface opposite the top surface
such that the top surface, the bottom surface, and the opposite
sides define a parallelepiped shape, the method further comprising:
forming on a first portion of the bottom surface an antireflection
coating and on a second portion of the bottom surface a reflection
coating.
6. The method according to claim 1, wherein said pressing is
performed through a top plate disposed atop the glass rod
assembly.
7. The method according to claim 1, wherein said pressing is
performed using a squeezing device.
8. The method according to claim 1, wherein as a result of said
singulating, the precision POSA includes respective glass rod
sections of the two or more glass rods with each of the glass rod
sections having a long axis, the method further comprising forming
a wavelength-division multiplexing (WDM) system by: operably
disposing a first multi-fiber interface device adjacent an
antireflection coating on a bottom surface of the master glass
block that is opposite the top surface; and operably disposing two
or more second multi-fiber interface devices adjacent the two or
more glass rod sections respectively, wherein each second
multi-fiber interface device has a device axis that runs in
substantially the same direction as the long axes of the glass rod
sections.
9. The method according to claim 8, wherein the first and second
multi-fiber interface devices each comprises a fiber array unit
(FAU) and a collimating lens array.
10. The method according to claim 9, further comprising: adjustably
supporting one or more of the second multi-fiber interface devices;
and independently positionally adjusting one or more of the second
multi-fiber interface devices to optimize optical communication
between the first multi-fiber interface device and the second
multi-fiber interface devices.
11. The method according to claim 10, wherein the positionally
adjusting comprises at least one of a translation and a
rotation.
12-20. (canceled)
21. A precision passive optical structure assembly (POSA) formed by
the process comprising: forming respective thin film filters on
respective first surfaces of two or more glass rods using a
thin-film deposition process, wherein: each of the two or more
glass rods also has a second surface substantially parallel to the
first surface, each of the thin film filters has a thickness
variation due to curvature of an optical surface of the thin film
filter that is opposite the first surface of the corresponding
glass rod, and the thin film filters have different non-overlapping
wavelength transmissions; forming a glass rod assembly comprising
the two or more glass rods arranged side-by-side so that the thin
film filters reside in a common plane; arranging the glass rod
assembly on a top surface of a master glass block with the thin
film filters confronting the top surface; pressing the glass rod
assembly and the master glass block together with a securing
material therebetween to substantially reduce the amounts of
curvature of the optical surfaces of the thin film filters;
securing the glass rod assembly to the master glass block with the
securing material while the thin film filters have said
substantially reduced amounts of curvature; and singulating the
glass rod assembly and the master glass block after said securing,
in a plane transverse to the first direction, to form the precision
POSA.
22. The precision POSA according to claim 21, wherein said securing
comprises irradiating the securing material with actinic radiation
through the master glass block.
23. The method according to claim 1, wherein said pressing reduces
the thickness variation in thickness of the thin film filters over
their respective optical surfaces by at least 50%.
24. A method of forming multiple precision passive optical
structure assemblies (POSAs) for wavelength-division multiplexing
(WDM) applications, comprising: forming respective thin film
filters on respective first surfaces of at least four glass rods
using a thin-film deposition process, wherein: each of at least
four glass rods also has a second surface substantially parallel to
the first surface, each of the thin film filters has a thickness
variation due to curvature of an optical surface of the thin film
filter that is opposite the first surface of the corresponding
glass rod, and the thin film filters of the at least four glass
rods have different non-overlapping wavelength transmissions;
forming a glass rod assembly comprising the at least four glass
rods arranged side-by-side so that the thin film filters reside in
a common plane; arranging the glass rod assembly on a top surface
of a master glass block with the thin film filters confronting the
top surface, wherein the master glass block is elongate in a first
direction; pressing the glass rod assembly and the master glass
block together with a securing material therebetween to
substantially reduce the amounts of curvature of the optical
surfaces of the thin film filters; curing the securing material
during said pressing to fix the glass rod assembly in place on the
master glass block with the thin film filters having the
substantially reduced amounts of curvature; and after said curing,
singulating the glass rod assembly and the master glass block into
multiple sections to form the multiple precision POSAs, wherein
said singulating is along planes transverse to the first
direction.
25. The method according to claim 24, wherein the master glass
block has opposite sides and a bottom surface opposite the top
surface such that the top surface, the bottom surface, and the
opposite sides define a parallelepiped shape, the method further
comprising: forming on a first portion of the bottom surface an
antireflection coating and on a second portion of the bottom
surface a reflection coating.
26. The method according to claim 25, wherein as a result of said
singulating, each of the multiple precision POSAs includes
respective glass rod sections of the at least four glass rods with
each of the glass rod sections having a long axis, the method
further comprising forming a wavelength-division multiplexing (WDM)
system with a first precision POSA of the multiple precision POSAs
by: operably disposing a first multi-fiber interface device
adjacent the antireflection coating on the bottom surface of master
glass block of the first precision POSA; and operably disposing at
least four multi-fiber interface devices adjacent the at least four
glass rod sections respectively, wherein each second multi-fiber
interface device has a device axis that runs in substantially the
same direction as the long axes of the glass rod sections.
27. The method according to claim 26, wherein the first and second
multi-fiber interface devices each comprises a fiber array unit
(FAU) and a collimating lens array.
28. The method according to claim 27, further comprising:
adjustably supporting one or more of the second multi-fiber
interface devices; and independently positionally adjusting one or
more of the second multi-fiber interface devices to optimize
optical communication between the first multi-fiber interface
device and the second multi-fiber interface devices.
29. The method according to claim 28, wherein the positionally
adjusting comprises at least one of a translation and a
rotation.
30. The method according to claim 24, wherein said pressing reduces
the thickness variation in thickness of the thin film filters over
their respective optical surfaces by at least 50%.
Description
FIELD
[0001] The present disclosure relates to thin-film filter (TFF)
passive optical system assemblies (POSAs) used in
wavelength-division multiplexing (WDM) applications, and in
particular to precision TFF POSAs and WDM systems using parallel
fiber interface devices.
BACKGROUND
[0002] Modern-day optical telecommunications systems provide
high-speed (large data rates) in part by combining (multiplexing or
Mux) and de-combining (demultiplexing or DeMux) optical data
signals encoded onto different wavelengths of light.
[0003] There are two common types of WDM platforms. The first type
is based on an arrayed waveguide grating (AWG) planer lightwave
circuit (PLC) assembly ("AWG-PLC assembly") and the second type is
based on an optical thin-film filter (TFF) free-space passive
optical system assembly ("TFF POSA"). TFF POSAs are superior
regarding loss, passband ripple, passband width, isolation, and
thermal stability as compared to AWG-PLC assemblies and so are
preferred for many WDM applications.
[0004] FIG. 1A is an elevated view of a conventional TFF POSA 10 as
described in U.S. Pat. No. 8,488,244, which is incorporated by
reference herein. The TFF POSA 10 comprises a glass block 20 having
a parallelogram y-z cross-sectional shape (i.e., has the form of a
parallelepiped) in the local Cartesian coordinates shown. The glass
block 20 has a body 21 that defines a front surface 22, a back
surface 24 and sides 26. The back surface 24 includes a reflection
coating 25 and an antireflection coating 27 arranged as shown on
different portions of the back surface 24. The front surface 22
includes TFF members 30 arranged generally along the
y-direction.
[0005] FIG. 1B is a top-down view of the TFF POSA 10 of FIG. 1A
used to form a conventional WDM system 50. The WDM system 50
includes a lens array 60 that includes lens elements 62, with the
lens elements 62 operably disposed proximate respective TFF members
30 and thus the lens array 60 running in the y-direction, which is
taken as being "vertical" for ease of discussion. Thus, the lens
array 60 is referred to as the vertical lens array 60. The TFF
elements 30 are each configured to transmit a select wavelength and
reflect other wavelengths. Four example TFF elements 30, denoted
30a, 30b, 30c and 30d are shown, respectively configured to
transmit wavelengths .lamda..sub.a, .lamda..sub.b, .lamda..sub.c
and .lamda..sub.d.
[0006] The WDM system 50 also includes a vertical photonic device
array 70 proximate the vertical lens array 60. The vertical
photonic device array 70 comprises a support member 71 that
operably supports first photonic devices 72 in the vertical
direction. The vertical photonic device array 70 has a device axis
Ad. The lens array 60 is disposed so that the lens elements 62
reside opposite the TFF members 30 and optically aligned therewith.
Thus, the vertical photonic device array 70 follows the same
orientation of the array of TFF members 30, i.e., the device axis
Ad runs in the same direction as the stacking of the TFF members
30.
[0007] In example, the photonic devices 72 can be light emitters
(e.g., LEDs, laser diodes, waveguides, fibers, etc.) or can be
light detectors (e.g., photodiodes, waveguides, fibers, etc.). Four
example photonic devices 72a through 72d are shown and represent
four different channel ports for four different channels.
[0008] The WDM system 50 also includes a multi-wavelength photonic
device 80, which in an example can be multi-wavelength light
emitter or multi-wavelength light receiver. In an example, the
multi-wavelength photonic device 80 can be an optical fiber that
supports optical waveguide modes at different (multiple)
wavelengths, such the four wavelengths .lamda..sub.a,
.lamda..sub.b, .lamda..sub.c and .lamda..sub.d.
[0009] For the sake of discussion in describing the general
operation of the TFF POSA 10 and the WDM device 50 formed thereby,
assume that a multi-wavelength light beam 90 is emitted from the
multi-wavelength photonic device 80 and collimated by a collimating
lens 82. The multi-wavelength light beam 90 includes by way of
example the four wavelengths .lamda..sub.a, .lamda..sub.b,
.lamda..sub.c and .lamda..sub.d that define four different light
beams 90a, 90b, 90c and 90d. This direction of light travel can be
referred to as the "DeMux" direction since the multi-wavelength
light beam 90 is later divided into its wavelength-component beams
90a, 90b, 90c and 90d, representing the four different example
communication channels.
[0010] The multi-wavelength light beam 90 enters the glass block 20
at the anti-reflection coating 27 on the back surface 24. As noted
above, each TFF member 30 is configured to transmit one of the
wavelength components and reflect the others. Thus, for example,
the TFF member 30a transmits the light beam 90a of wavelength Aa
and reflects the remaining portion 90' of the light beam 90 at an
angle towards the back surface 24. The reflective coating 25
thereon reflects the light beam 90' toward the next TFF member 30b,
which transmits the light beam 90b and reflects the remaining
portion 90'' of the light beam 90' at an angle toward the back
surface 24 and the reflective coating 25 thereon. The light beam
90'' is then reflected by the reflective coating 25 to the TFF
member 30c, which transmits the light beam 90c and reflects the
remaining light beam 90''' at an angle toward the reflective
coating. The remaining light beam 90''' travels to the TFF filter
30d, which transmits the light beam 90d. The transmitted light
beams 90a through 90d are respectively incident upon the photonic
devices 72a through 72d, which in the present example can be
considered photodetectors or receiving fibers.
[0011] The WDM system 50 works well if the optical surfaces of the
TFF POSA 10 are precision optical surfaces and if the vertical lens
array 60 is properly aligned and has properly formed and aligned
lens elements 62. As it turns out, forming sufficiently flat TFFs
on the TFF members 30 is problematic. FIG. 2A includes two
cross-sectional x-y views (using local (x,y,z) Cartesian
coordinates) an example idealized TFF member 30 (left side) and an
actual TFF member 30 (right side). The TFF member 30 includes a
glass substrate 31 having a front surface 32 and a back surface 34.
A TFF 40 resides on the front surface 32. The TFF 40 has thickness
TH as measured in the direction of the local x-coordinate shown.
The TFF 40 is formed using conventional thin-film deposition
techniques known in the art and is initially deposited as a flat
film with a uniform thickness TH.
[0012] Unfortunately, the TFF deposition process is performed at an
elevated temperature. Upon cooling, the mismatch in the
coefficients of thermal expansion (CTEs) between each deposition
layer of the TTF 40, and between the glass substrate 31, cause the
whole finished structure to accumulate enormous internal stress and
have a thickness that varies across the filter after dicing. This
variation is illustrated in the right-side TFF 30 and in FIG. 2B,
which is a plot of the TFF thickness TH (.mu.m) versus y-position
(.mu.m) based on measurements of an example TFF member 30. The plot
of FIG. 2B shows that over a 350 .mu.m distance, the thickness TH
varies by about 200 nm. The overall variation in the thickness TH
is about 0.5 .mu.m. Thus, rather having the idealized form on the
left side of FIG. 2A, the TFF member 30 actually has a curved
surface due to the varying thickness TH of the TFF 40 as shown on
the right side of FIG. 2A.
[0013] FIG. 3A is similar to FIG. 1B and shows a more realistic
version of the TFF POSA 10 using the more realistic TFF members 30
as shown on the right side of FIG. 2B. FIG. 3A also illustrates how
the reflected and transmitted light beams deviate from their ideal
or reference optical paths (denoted by REF) in the y-direction due
to reflecting from the curved TFF members 30, with increasing
numbers of reflection resulting in an increasing amount of optical
path deviation. FIG. 3B is a top-down view of the convention TFF
POSA 10 of FIG. 3A and showing the deviation of the optical paths
of the reflected light beams 90a through 90d as projected onto the
y-z plane. The curved TFF members 30 act like convex mirrors rather
than precision flat mirrors at the reflective wavelengths, thereby
causing x and y deviations in the optical path at each reflection.
Note also how the light path deviation increases with each
reflection from a TFF 40 so that light path deviation is not a
simple fixed offset but varies as a function of position and angle
at the vertical photonic device array 70.
[0014] The x and y deviations of the optical paths of the reflected
light beams can result in the transmitted light beams 92a through
92d not being ideally coupled with the photonic devices 72a through
72d of the vertical photonic device array 70. When the light beams
92a through 92d travel in the other direction (the Mux direction),
then the x and y deviations of the light beams 92a through 92d
originating from the vertical photonic device array 70 cause the
light beams to miss being multiplexed at the multi-wavelength
photonic device 80.
[0015] Thus, the optical path variations caused by the TFF members
30 having curved TFFs 40 can adversely impact WDM optically
coupling to fibers, detectors, emitters, waveguides, etc. at the
optical inputs/output ends. The problem is particularly acute for
conventional WDM systems using vertical photonic device arrays with
fixed-position photonic devices since there is no efficient way to
obtain optical alignment of the photonic devices for each
wavelength (channel). This complicates the formation of reliable,
highly parallel WDM systems using conventional TFF POSAs.
SUMMARY
[0016] Aspects of the disclosure are directed to forming a
precision TFF POSA. The precision TFF POSA is formed by pressing a
TFF glass rod array into a top surface of a master glass block to
flatten the otherwise curved TFFs formed using conventional TFF
deposition processes on glass. The TFF glass rod array is secured
to the master glass block with a securing material to form a
fabrication structure, which is singulated to form precision TFF
POSAs having TFF members with flat TFFs and TFF member long
axes.
[0017] Another aspect of the disclosure includes operably arranging
a first fiber interface device at a back surface of the TFF POSA.
Second fiber interface devices having device axes are arranged
proximate the TFF members. The device axes are parallel to the TFF
member long axes to form a WDM system with a parallel
configuration. In this configuration, there is one positionally
adjustable fiber interface device for each wavelength channel,
which allows for optimizing WDM optical communication in Mux and
DeMux directions.
[0018] An aspect of the disclosure is directed to a method of
forming a precision TFF POSA for WDM applications, comprising:
forming a TFF glass rod assembly comprising two or more glass rods
each having substantially parallel first and second surfaces, with
the first surfaces supporting respective TFFs having different
non-overlapping wavelength transmissions; arranging the TFF glass
rod assembly on a top surface of a master glass block with the TFFs
confronting the top surface; pressing the TFF glass rod assembly
and master glass block together with a securing material
therebetween to substantially reduce the amounts of curvature of
the TFFs to form a fabrication structure wherein the TFFs have said
substantially reduced amounts of curvature; and singulating the
fabrication structure to form the precision TFF POSA.
[0019] Another aspect of the disclosure is directed to a method of
forming a WDM system, comprising: forming a precision TFF POSA
having a glass block section with first surface that supports two
or more TFF members each having a TFF member long axis and a second
surface having an antireflection coating and a reflective coating;
operably disposing a first multi-fiber interface device adjacent
the antireflection coating; operably disposing two or more second
multi-fiber interface devices adjacent the two or more TFF members
respectively, wherein each second multi-fiber interface device has
a device axis that runs in substantially the same direction as the
TFF member long axis; and positionally adjusting one or more of the
second multi-fiber interface devices to optimize optical
communication between the first multi-fiber interface device and
the second multi-fiber interface devices.
[0020] Another aspect of the disclosure is directed to a WDM
system, comprising: a precision thin-film filter (TFF) passive
optical structure assembly (POSA) having a first surface with two
or more TFF members having different non-overlapping wavelength
transmissions and each having a TFF member long axis, and a second
surface having an antireflection coating and a reflective coating;
a first multi-fiber interface device operably disposed adjacent the
antireflection coating; and two or more second multi-fiber
interface devices operably disposed the two or more TFF members
respectively, wherein each second multi-fiber interface device has
a device axis that runs in substantially the same direction as the
TFF member long axis, and wherein one or more of the second
multi-fiber interface devices are operably supported by respective
one or more positionally adjustable mounts.
[0021] Another aspect of the disclosure is directed to a precision
TFF POSA formed by the process comprising: forming a TFF glass rod
assembly comprising two or more glass rods each having
substantially parallel first and second surfaces, with the first
surfaces supporting respective TFFs having different
non-overlapping wavelength transmissions; arranging the TFF glass
rod assembly on a top surface of a master glass block with the TFFs
confronting the top surface; pressing the TFF glass rod assembly
and master glass block together with a securing material
therebetween to substantially reduce the amounts of curvature of
the TFFs; securing the TFF glass rod assembly to the master glass
block with the securing material to form a fabrication structure
wherein the TFFs have said substantially reduced amounts of
curvature; and singulating the fabrication structure to form the
precision TFF POSA.
[0022] Additional features and advantages are set forth in the
Detailed Description that follows, and in part will be apparent to
those skilled in the art from the description or recognized by
practicing the embodiments as described in the written description
and claims hereof, as well as the appended drawings. It is to be
understood that both the foregoing general description and the
following Detailed Description are merely exemplary, and are
intended to provide an overview or framework to understand the
nature and character of the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The accompanying drawings are included to provide a further
understanding, and are incorporated in and constitute a part of
this specification. The drawings illustrate one or more
embodiment(s), and together with the Detailed Description explain
the principles and operation of the various embodiments. As such,
the disclosure will become more fully understood from the following
Detailed Description, taken in conjunction with the accompanying
Figures, in which:
[0024] FIG. 1A is an elevated view of a conventional TFF POSA;
[0025] FIG. 1B is a top-down view of an example WDM system that
utilizes the conventional TFF POSA of FIG. 1A along with a vertical
photonic device array with fixed photonic devices.
[0026] FIG. 2A shows two x-y cross-sectional views (in local
(x,y,z) Cartesian coordinates) of a TFF member of the TFF POSA,
wherein the left-side TFF is an idealized view that shows the TFF
having a uniform thickness and the right-side TFF represents a more
realistic view wherein the TFF has a varying thickness profile that
defines a curved TFF.
[0027] FIG. 2B is a plot of the thickness (microns, .mu.m) versus
y-position (.mu.m) showing an example measurement of the TFF of a
TFF member wherein the TFF has a thickness variation of 200
nanometers (nm) over a 350 .mu.m section of the TFF.
[0028] FIG. 3A is a top-down view of the conventional TFF POSA with
the more realistic TFF members shown in the right-hand side of FIG.
2B, and showing the deviation of the optical paths of the reflected
light beams as projected onto the y-z plane relative to an ideal or
reference optical path.
[0029] FIG. 3B is a side view of the conventional TFF POSA of FIG.
3A, showing the optical path deviations of the light beams as
projected onto the x-z plane.
[0030] FIG. 4A is an elevated view of an example glass rod having a
rectangular cross section.
[0031] FIG. 4B is similar to FIG. 4A and shows the glass rod having
a TFF formed on its top surface to define a TFF glass rod.
[0032] FIG. 4C is an elevated view showing a TFF glass rod assembly
formed by placing and securing the TFF glass rods side by side with
the TFFs facing upward.
[0033] FIG. 4D is an exploded view of an example fabrication
structure used to form the precision TFF assemblies disclosed
herein.
[0034] FIG. 4E is an elevated view showing the initially assembled
example fabrication structure of FIG. 4D, along with a top plate
used in finalizing the fabrication structure.
[0035] FIG. 5A is and elevated view similar to FIG. 4E and shows
the application of a pressing force on the top plate to press the
TFFs and the securing material into the top surface of the master
glass block, which flattens the TFFs.
[0036] FIGS. 5B and 5C are cross-sectional views of the fabrication
structure of FIG. 5A showing two different examples of the
application of the pressing force, and also showing an example of
curing of the securing material through the master glass block,
with the close-up inset of FIG. 5B showing micro-recesses on the
TFF surface of one of the TFFs and securing material residing
within the micro-recesses.
[0037] FIG. 6A is an elevated view of the finalized fabrication
structure showing example singulation lines for singulating the
fabrication structure to form precision TFF POSAs as disclosed
herein.
[0038] FIG. 6B is an elevated view similar to FIG. 6A and shows an
example precision TFF POSA singulated (separated) from the
fabrication structure.
[0039] FIG. 6C is a close-up elevated view of an example precision
TFF POSA.
[0040] FIGS. 7A and 7B are front and back elevated views of an
example multiple-optical-fiber interface device ("multi-fiber
interface device" or "fiber interface device") comprising an array
of optical fibers supported by a fiber array unit (FAU) and
including an integrated collimator lens array.
[0041] FIG. 7C is a side view of the fiber interface device of
FIGS. 7A and 7B, showing a close-up view of one of the optical
fibers and also showing example grooves in the support substrate of
the FAU sized to accommodate the optical fibers.
[0042] FIG. 7D is a side view similar to FIG. 7C and shows an
example configuration of the support substrate as having a raised
front-end section that includes grooves.
[0043] FIG. 7E is a close-up view of the front end of the fiber
interface device showing an example of how guided light traveling
in one of the optical fibers is collimated by one of the lenses in
the collimator lens array.
[0044] FIG. 7F is an elevated view similar to FIG. 7A and shows
multi-wavelength light being transmitted on each of the four
example fibers.
[0045] FIG. 8A is an elevated view showing a fiber interface device
operably disposed adjacent the back surface of the precision TFF
POSA, and showing how one of the multi-wavelength collimated light
beams is divided by the TFF POSA into four separate
single-wavelength light beams that respectively exit the four TFF
members to define four separate channels.
[0046] FIG. 8B is an elevated view of four stacked fiber interface
devices and illustrating two example WDM light beams (510a of
wavelength Aa and 510d of wavelength .lamda..sub.d) and their
respective sub-channels (510a-1 through 510a-4; 510d-1 through
510d-4) as received by or transmitted from the fiber interface
devices.
[0047] FIG. 8C is an elevated view similar to FIG. 8A and further
includes the stacked fiber interface devices of FIG. 8B operably
arranged at the front end of a precision TFF POSA to form a WDM
system.
[0048] FIG. 8D is a side view of the WDM system of FIG. 8C.
DETAILED DESCRIPTION
[0049] Reference is now made in detail to various embodiments of
the disclosure, examples of which are illustrated in the
accompanying drawings. Whenever possible, the same or like
reference numbers and symbols are used throughout the drawings to
refer to the same or like parts. The drawings are not necessarily
to scale, and one skilled in the art will recognize where the
drawings have been simplified to illustrate the key aspects of the
disclosure.
[0050] The claims as set forth below are incorporated into and
constitute part of this Detailed Description.
[0051] Cartesian coordinates are shown in some of the Figures for
the sake of reference and are not intended to be limiting as to
direction or orientation. Different Cartesian coordinates are also
used in different Figures and can be considered as local Cartesian
coordinates for the item, component, part, assembly, etc. being
described.
[0052] Relative terms like front, back, top, bottom, etc. are used
for ease of description and are not intended to be limited as to
direction or orientation.
[0053] In the discussion below, the TFFs are said to have different
non-overlapping wavelength transmissions, meaning that the TFFs
have different wavelength transmission bandwidths centered on
different wavelengths (center wavelengths), wherein the center
wavelengths and the transmission bandwidths are such that there is
either no overlap or no substantial overlap (e.g., less than 10%
overlap) of the transmission bandwidths for adjacent center
wavelengths. The transmission wavelengths discussed below (e.g.,
.lamda..sub.a, .lamda..sub.b, . . . ) are center wavelengths unless
otherwise noted.
Fabrication Structure for Forming Precision TFF POSAs
[0054] An aspect of the disclosure is directed to a method of
fabricating a precision TFF POSA. The method includes forming a
fabrication structure that can be divided up into multiple
precision TFF POSAs.
[0055] A first step in the fabrication method utilizes multiple
optical-quality glass rods. FIG. 4A is an elevated view of an
example optical quality glass rod 100 having a rectangular (e.g.,
square) cross-sectional shape. The glass rod has body 101 that
defines opposed first and second surfaces 102 and 104 (which may be
referred to as top and bottom surfaces), opposite sides 106, a
front end 113 and a back end 114. In an example, at least the first
and second surfaces 102 and 104 are precision surfaces, i.e., have
a high degree of optical flatness.
[0056] FIG. 4B is similar to FIG. 4A and illustrates the next step
in the fabrication method wherein a TFF 120 is formed on the first
surface 102 of the glass rod 100 to form a TFF glass rod 110. The
TFF 120 is formed using conventional thin-film deposition processes
known in the art. It is noted here that at this stage, the TFF 120
is curved due to the aforementioned difference in the CTEs of the
TFF and the glass rod (see FIG. 2A). The TFF 120 has a surface
122.
[0057] FIG. 4C is similar to FIG. 4B and shows the next step in the
fabrication method, which involves forming an array ("TFF glass rod
array" or "TFF glass rod assembly") 112 of
[0058] TFF glass rods 110. The example TFF glass rod array 112
includes four TFF glass rods 110, which are denoted as 110a through
110d and which are arranged side-by-side so that the TFFs 120 (120a
through 120d) reside in a common plane. The first surfaces 102 of
the TFF glass rods 110 are parallel or substantially parallel (the
latter referring to an intention to be parallel, but accounting for
manufacturing tolerances). The front ends 113 also reside in a
common plane. The TFF glass rods 110a through 110d have respective
TFFs 120a through 120d corresponding to four different wavelength
transmissions, i.e., four different transmission wavelengths
.lamda..sub.a, .lamda..sub.b, .lamda..sub.c and .lamda..sub.d. The
four TFF glass rods 110 can be secured to each other at their
respective sides 106 using a securing material (not shown), such as
an ultraviolet (UV) curable adhesive, or other conventional
glass-securing means known in the art. In an example of the method,
the glass rods 100 can be arranged and secured side-by-side and
then the TFF formed on the first surfaces 102 of the collected
glass rods. While four example TFF glass rods 110 are shown, in
general the TFF glass rod array 112 can be formed from two or more
TFF glass rods.
[0059] FIG. 4D is an elevated and exploded view of example
fabrication structure 150 formed by the next steps in the
fabrication method. The fabrication structure 150 includes the TFF
glass rod assembly 112 as described above and a master glass block
160. In an example, the master glass block 160 has a parallelogram
cross-sectional shape in the y-z plane while being elongate in the
x-direction (e.g., has a parallelepiped shape). The master glass
block 160 has a body 161, a top surface 162, a bottom surface 164,
opposite sides 166, a front end 172 and a back end 174. In an
example, the master glass block is made of an optical-quality
glass, such as fused quartz.
[0060] The TFF glass rod assembly 112 is arranged above the top
surface 162 of the master glass block 160 with the TFFs 120 facing
the top surface of the master glass block 160. A transparent
securing material 177 is used to secure the TFF glass rod assembly
112 to the top surface 162 of the master glass block 160 and so is
shown residing between the TFF glass rod assembly 112 and the
master glass block 160. As examples, the securing material 177 may
comprise an ultra-violet (UV) curable adhesive, a thermally
activated adhesive, epoxy, or a dual-activated adhesive or epoxy.
In some example embodiments, the securing material is index-matched
to the refractive index of the material making up the body 161 of
the master glass block 160. In an example, the securing material
177 cures by chemical reaction over time, i.e., does not require
outside activation to cause curing.
[0061] FIG. 4D also shows a plate 180 arranged above the TFF glass
rod assembly 112 facing the second surfaces 104 of the glass rods
100. The plate 180 has a top surface 182 and a bottom surface 184.
The plate 180 is optional and is not a component of the fabrication
structure 150 and is shown because it is used in an example of
making the fabrication structure, as seen below. In an example, the
plate 180 is transparent, and further in the example is made of
glass. Because the plate resides atop the TFF glass rod assembly
112, it is also referred to below as the top plate 180.
[0062] The next fabrication step can include adding an
anti-reflection coating 192 and a reflective coating 194 to
respective sections of the bottom surface 164 of the master glass
block 160 (see also FIGS. 5B and 5C, introduced and discussed
below). This step can also be performed earlier or later in the
fabrication process.
[0063] FIG. 4E is similar to FIG. 4D and shows the next step in the
fabrication wherein the fabrication structure 150 is assembled by
placing the TFF glass rod assembly 112 on top surface 162 of the
master glass block 160 with the securing material 177 between. At
this time, the securing material 177 remains substantially uncured.
The top plate 180 is placed on the TFF glass rod assembly 112 on
the second surfaces 104 of the glass rods 100, which are now facing
upwards.
[0064] FIGS. 5A and 5B show the next step in the fabrication
process of applying a downward of pressing force FP on the top
plate 180 while the fabrication structure 150 rests upon a solid
(firm) support structure 200. FIG. 5C shows a similar alternative
method step of applying a pressing force FP to both sides to the
fabrication structure 150, which can include using a second
(bottom) plate 180 at the bottom surface 164 of the master glass
block 160. In an example, the pressing force FP can be generated by
a heavy object or by placing the fabrication structure 150 in a
squeezing device 186, such as a vice or clamp (FIG. 5B).
[0065] The application of a pressing force FP presses the TFF 120
of each TFF glass rod 110 against the securing material 177 and the
top surface 162 of the master glass block 160. This flattens out
the curved TFFs 120, i.e., substantially reduces the amount of
curvature in the TFFs. In examples, the substantial reduction in
curvature is at least 5% or at least 10% or at least 20% or at
least 30% or at least 40% or at least 50% or at least 75% or at
least 100% of the variation in the thickness variation of the TFF
over its surface or a portion of its surface that is used in the
reflection and transmission of light. The phrase "at least X%"
refers to a range from X% to 100%.
[0066] As the pressing force FP is being applied, the securing
material 177 can be cured, e.g., by transmitting actinic radiation
210 (e.g., UV light or infrared light (heat)) through the master
glass block to the securing material, as shown in FIGS. 5A through
5C, or simply by allowing the securing material 177 to cure on its
own. This fixes the TFF glass rod assembly 112 in place on the
master glass block 160 and also fixes the now substantially flat
(i.e., substantially reduced curvature) TFFs 120 (e.g., 120a
through 120d). Once the securing material 177 is cured, the
pressing force(s) FP can be removed, along with one or both plates
180.
[0067] The close-up inset of FIG. 5B (which is not to scale) shows
a close up of the surface ("TFF surface") 122 of the TFF 120
pressed up against the top surface 162 of the master glass block
160 as part of the process to flatten the TFFs 120. In practice the
TFF surface 122 is not perfectly smooth and includes micro-recesses
123 into which the securing material 177 can flow and reside when
the TFF glass rod assembly 112 is pressed into the master glass
block 160.
[0068] At least a portion of the micro-recess 123 are substantially
smaller than the wavelengths of light used in WDM applications.
Since the securing material 177 is preferably index matched to the
master glass block 160, the filling of the micro-recess 123 with
securing material renders them anodyne with respect to optical
performance. On the other hand, the securing material 177 residing
in the micro-recesses 123 (when cured) acts to secure the TFF glass
rod assembly 112 to the master glass block 160 while allowing for
the TFF surface 122 to be substantially flattened by pressing the
TFF surface into the top surface 162 of the master glass block 160
prior to curing.
[0069] In an example, the micro-recess 123 can be used to conduct
the securing material 177 from the edges of the TFF glass rod
assembly 112 and the master glass block 160 into the center of the
interface between the TFF glass rod assembly and the master glass
block via capillary action.
[0070] Any excess securing material 177 squeezed out of the
interface between the TFF glass rod assembly 112 and the master
glass block 160 during the pressing process can be removed prior to
or after curing. Note that in FIGS. 5B and 5C, the securing
material 177 is shown as a layer between the top surface 162 of the
master glass block 160 and the TFFs 120. This is for ease of
illustration and explanation, and as described above the TFFs 120
press into the top surface 162 of the master glass block 160, with
the securing material residing in the micro-recesses 123.
[0071] FIG. 6A shows the resulting fabrication structure 150. The
layer of securing material 177, having accomplished its goal, is
now omitted for ease of illustration. FIG. 6A shows example
separation lines SL that indicate where the fabrication structure
150 can be separated into multiple sections to define individual
TFF POSAs 350, as shown in FIG. 6B. In an example, the fabrication
structure 150 can be separated (singulated) using a mechanical
cutting process (e.g., sawing) or laser-based cutting process. In
an example, the fabrication structure 150 can itself serve as the
TFF POSA 350.
[0072] FIG. 6C is a close-up elevated view of the TFF POSA 350 of
FIG. 6B. The TFF POSA 350 comprises a glass block section 160S,
which as described above is a section of the master glass block
160. The glass block section 160S comprises the same body 161 of
the master glass block and thus the same top surface 162, bottom
surface 164, and sides 166, and in an example has the same
parallelepiped shape. The glass block section 160S also comprises
front and back ends 172 and 174, at least one of which is "new"
front and/or back end formed by singulation process. The TFF POSA
350 has a front end 352 and a back end 354.
[0073] The TFF POSA 350 also has TFF members 110S defined by
respective sections of the TFF glass rods 110 of the fabrication
structure 150. Each TFF member 110S includes its corresponding TFF
120 formed on the first surface 102 of the glass rod 100. Each TFF
member 110S has a central (long) axis AM that runs in the
x-direction. This central (long) axis AM is also referred to as the
TFF member axis AM.
[0074] The securing material 177 is also shown in representative
form as layer residing between the top surface 162 of the glass
block section 160S and the TFFs 120 of the TFF members 110S. The
four example TFF members 110S are denoted 110Sa, 110Sb, 110Sc and
110Sd and are configured to respectively transmit the four example
wavelengths .lamda..sub.a, .lamda..sub.b, .lamda..sub.c and
.lamda..sub.d. Because the fabrication structure 150 is made using
the method described above, the TFFs 120 of the TFF members 110S of
the TFF POSA 350 are substantially flat.
Multi-Fiber Optical Interface Device
[0075] The TFF POSA 350 can be used to form a WDM system, as
described below. This can be accomplished by employing a photonic
device array, which can be, for example here, multi-fiber optical
interface devices, or just "multi-fiber interface devices" or
"fiber interface devices" for short. As already stated, these
design structures are merely exemplary, and are intended to provide
an overview or framework to understand the nature and character of
the claims. FIGS. 7A and 7B are elevated views and FIG. 7C is a
side view of an example fiber interface device 400 having a central
(long) axis Al that runs in the z-direction and a device axis AD
that runs in the x-direction. The device axis AD and the long axis
Al define a device plane, which in FIGS. 7A and 7B is the x-z
plane.
[0076] The fiber interface device 400 includes a support substrate
410 having a top surface 412, a bottom surface 414, a front end 416
and a back end 418. The fiber interface device also includes a
cover 420 having a top surface 422, a bottom surface 424, a front
end 426 and a back end 428. In an example shown in the close-up
inset, the bottom surface 424 of the cover 420 can have grooves
425, such as V-grooves, that run in the direction of the central
axis Al. In an example, the top surface 412 can have grooves 425,
such as shown in FIG. 7C. FIG. 7D is similar to FIG. 7C and shows
an example where the support substrate 410 includes a raised
front-end section 417 in which the grooves 425 are formed.
[0077] The fiber interface device 400 also includes an array
("fiber array") 450 of optical fibers 452. Each optical fiber 452
has a coated section 454 and a bare section 456, with at least a
portion of the bare section 456 supported by the support substrate
410. The cover 420 acts to hold the fiber bare sections 456 in
place on the support substrate. The grooves 425 in one or both of
the support substrate 410 and cover 420 serve to maintain alignment
of the fiber bare sections 456. As best seen in FIG. 7C, each
optical fiber 452 has an end face 460 that resides at or near the
front end 416 of the support substrate 410. Each optical fiber 452
also has a fiber axis AF.
[0078] The fiber interface device 400 also includes a lens array
unit 480 that includes lens elements 482 each having a lens axis
AL. The lens array unit 480 (also referred to as "collimating lens
array") includes a front end 492 and a back end 494. In an example,
the lens elements 482 comprise gradient-index (GRIN) lenses, which
do not a curved surface. In another example, the lens elements 482
are conventional lens elements (microlenses) having at least one
curved surface. The lens elements 482 are arranged in a row that
runs in the x-direction, i.e., along the device axis AD. The
optical fibers 452 reside in the device plane or in a plane
parallel to the device plane as defined by axes Al and AD.
[0079] The lens array unit 480 resides at the front end 416 of the
support substrate 410 and is disposed such that the fiber axes AF
of the optical fibers 452 in the fiber array 450 are aligned with
(i.e., coaxial with) respective lens axes AL of the lens elements
482 of the lens array unit 480. In this regard, the grooves 425 in
one or both of the support substrate 410 and the cover 420
facilitate this alignment. In an example, the front end 426 of the
cover 420 is in contact with the back end 494 of the lens array
unit 480. In an example, a securing material (not shown) is used to
secure the optical fibers 452, the support substrate 410, the cover
420 and the lens array unit 480. In an example, the support
substrate 410, the cover 420 and the optical fibers 452 constitute
a fiber array unit (FAU). The combination of the FAU and the lens
array unit 480 (and thus the fiber interface device 400 itself) can
be referred to as a collimated FAU.
[0080] FIG. 7E is a close-up side view of the fiber interface
device 400 showing how guided light 510G traveling in the optical
fiber 452 as a guided wave exits the end face 460 of the optical
fiber and diverges as unguided light 510. The unguided light 510
initially diverges based on numerical aperture (NA) of the optical
fiber. The lens element 82, which is shown as a GRIN lens, acts as
a collimating lens by bending the otherwise diverging unguided
light 510 until it travels as a light beam with light rays
substantially parallel to the lens axis AL, thereby defining
collimated light (collimated light beam) 510.
[0081] FIG. 7F is similar to FIG. 7A and illustrates an example
fiber interface device 400 used at the back end 354 of the
precision TFF POSA 350 emits multi-wavelength light 510 (e.g.,
having four wavelengths .lamda..sub.a, .lamda..sub.b, .lamda..sub.c
and .lamda..sub.d that respectively define four channels) over each
optical fiber 452. If there were only one optical fiber 452, then
the four wavelengths would define four channels for the one
multi-wavelength light beam 510. Since the fiber interface device
400 supports multiple optical fibers 452, the fiber interface
device supports a corresponding number of sub-channels as carried
by multiple multi-wavelength light beams 510, denoted 510-1 through
510-4 for the four example sub-channels, thereby defining a total
of 16 optical communication lanes.
WDM System With Parallel Fiber Interface Devices
[0082] FIG. 8A is an elevated view showing an example fiber
interface device 400 operably disposed adjacent the back end 354 of
the precision TFF POSA 350. The example fiber interface device 400
emits four collimated multi-wavelength light beams 510, such as
shown in FIG. 7F, but only one collimated multi-wavelength light
beam 510-1 is shown for ease of illustration, since the other
collimated multi-wavelength light beams travel optical paths that
are the same as the shown optical path OP but in y-z planes shifted
in the x-direction.
[0083] The light beam 510-1 enters the glass block section 160S at
the anti-reflection coating 192. Thus, the fiber interface device
400 being "operably disposed" adjacent the back end 354 of the
precision TFF POSA 350 refers to the arrangement being such that
this operation of the light beams can occur. The collimated light
beam 510-1 then travels over an optical path OP while the TFF
members 110S (110Sa, 110Sb, 110Sc and 110Sd) transmit their
respective wavelength and reflect the other wavelengths, thereby
resulting in transmitted light beams 510a-1, 510b-1, 510c-1 and
510d-1 at the front end 352 of the TFF POSA 350. The zig-zag
optical path OP is generated by the parallelepiped shape of the
glass block section 160S.
[0084] FIG. 8B is an elevated view of four stacked fiber interface
devices 400, denoted 400a through 400d, such as might be operably
disposed adjacent the front end 352 of the precision TFF POSA 350.
The stacking is along the y-direction so that the lens array units
480 run in the x-direction, which is the same direction as the long
direction of the TFF members 110S. In other words, the device axes
AD of the fiber interface devices 400 run in the same direction as
the TFF member axes AM of the TFF members 110S. The fiber interface
devices 400 are thus said to be parallel to the TFF POSA 350, and
the stacked fiber interface devices are said to be parallel fiber
interface devices.
[0085] FIG. 8B illustrates two example WDM light beams, namely
light beam 510a of wavelength Aa and light beam 510d of wavelength
Ad. FIG. 8B also shows for each example light beam 510a and 510d
their respective sub-channels, namely 510a-1 through 510a-4 and
510d-1 through 510d-4, as received by or transmitted from the two
example fiber interface devices 400a and 400d, respectively. The
example of four wavelengths (four channels) each having four
sub-channels defines a total of sixteen optical communication
lanes. Fewer or greater numbers of optical communication lanes can
be defined using different configurations for the TFF POSA 350 and
fiber interface devices 400.
[0086] FIG. 8C is similar to FIG. 8A and further includes the
stacked fiber interface devices 400a through 400d operably disposed
adjacent the front end 352 of the precision TFF POSA 350 to define
a WDM system 600. FIG. 8D is a side view of the WDM system 600 of
FIG. 8C. The fiber interface devices 400 have the aforementioned
parallel configuration with respect to the TFF POSA 350, and in
example, the position of each fiber interface device 400 is
independently adjustable, as indicated by a first and second
adjustment arrows aa1 and aa2. The first adjustment arrow aa1 shows
how each fiber interface device 400 can be linearly translated in
at least the y-direction. The second adjustment arrow aa2 shows how
each fiber interface device 400 can be rotated at least about the
x-axis. In an example, each fiber interface device is operably
supported by an adjustable mount 610 (see FIG. 8D). This enables
the WDM system 600 to be actively aligned by positionally adjusting
one or more of the fiber interface devices 400 using the adjustable
mounts until a maximum optical signal is obtained and then fixing
the position of each fiber interface device for optimization of the
optical signal for each channel and sub-channel.
[0087] The independent adjustability of the fiber interface devices
400 allows for compensating optical transmission errors that can
cause slight deviations in the optical path OP. Note that one
source of optical path deviation, namely the curvature of the TFF
120 on the TFF members 110S, is substantially reduced or eliminated
by the TFF 120 being substantially flat by virtue of the
fabrication method used to form the TFF POSA 350. In addition, the
parallel configuration of the fiber interface devices 400 relative
to the TFF members 110S allows for independent positional
adjustment for each wavelength channel since there is one fiber
interface device for each wavelength channel. Such adjustments are
not possible with conventional vertically oriented photonic devices
arrays having fixed positions of the photonic devices and that
attempt to cover all of the wavelength channels using a single
device structure.
[0088] It will be apparent to those skilled in the art that various
modifications to the preferred embodiments of the disclosure as
described herein can be made without departing from the spirit or
scope of the disclosure as defined in the appended claims. Thus,
the disclosure covers the modifications and variations provided
they come within the scope of the appended claims and the
equivalents thereto.
* * * * *