U.S. patent application number 09/901474 was filed with the patent office on 2003-01-09 for redundant package for optical components.
This patent application is currently assigned to Scion Photonics, Inc.. Invention is credited to Crafts, Douglas E., Farrell, James F., Farrelly, Mark B., Ramalingam, Suresh.
Application Number | 20030006224 09/901474 |
Document ID | / |
Family ID | 25414254 |
Filed Date | 2003-01-09 |
United States Patent
Application |
20030006224 |
Kind Code |
A1 |
Crafts, Douglas E. ; et
al. |
January 9, 2003 |
REDUNDANT PACKAGE FOR OPTICAL COMPONENTS
Abstract
A redundant package for optical components includes an inner
package enclosing the optical component, and an outer package
enclosing the inner package. A heater may be disposed in the inner
package proximate the optical component to control its temperature,
and to maintain this temperature control, the outer package creates
an isolated air pocket around the inner package which thermally
insulates the inner package from the outside environment. The outer
package is formed of a material having low thermal conductivity, to
promote this insulating function. This package is especially useful
if the optical component comprises a planar lightwave circuit
(PLC), e.g., an arrayed waveguide grating (AWG), which requires
tight temperature control and structural integrity to maintain the
integrity of the optical paths.
Inventors: |
Crafts, Douglas E.; (San
Jose, CA) ; Farrell, James F.; (San Jose, CA)
; Farrelly, Mark B.; (San Jose, CA) ; Ramalingam,
Suresh; (Fremont, CA) |
Correspondence
Address: |
JDS UNIPHASE CORPORATION
1768 AUTOMATION PARKWAY
SAN JOSE
CA
95131
US
|
Assignee: |
Scion Photonics, Inc.
345 Los Coches Street
Milpitas
CA
95035
|
Family ID: |
25414254 |
Appl. No.: |
09/901474 |
Filed: |
July 9, 2001 |
Current U.S.
Class: |
219/209 ;
219/385; 219/520 |
Current CPC
Class: |
G02B 6/1203 20130101;
G02B 6/36 20130101; G02B 6/30 20130101 |
Class at
Publication: |
219/209 ;
219/385; 219/520 |
International
Class: |
H05B 003/00 |
Claims
What is claimed is:
1. An optical component package, comprising: a first, inner package
enclosing the optical component; and a second, outer package
enclosing the inner package.
2. The component package of claim 1, further comprising: a heater
disposed in the inner package proximate the optical component to
control the temperature thereof.
3. The component package of claim 2, wherein the outer package
creates an isolated air space around the inner package which
thermally insulates the device from the outside environment.
4. The component package of claim 3, wherein the outer package is
formed of a material having low thermal conductivity.
5. The component package of claim 2, wherein the heater is formed
of a material having a coefficient of thermal expansion
substantially matched to that of the optical component, with high
thermal conductivity and therefore high temperature uniformity.
6. The component package of claim 1, wherein the inner package
comprises: a base; a heater affixed to the base, wherein the
optical component is affixed to the heater; sidewalls affixed to
the base around the heater; and a lid affixed over the
sidewalls.
7. The component package of claim 6, wherein the heater is formed
of a material having a coefficient of thermal expansion
substantially matched to that of the optical component.
8. The component package of claim 7, wherein the optical component
comprises a planar lightwave circuit (PLC).
9. The component package of claim 8, wherein the PLC comprises an
arrayed waveguide grating.
10. The component package of claim 8, wherein the inner and outer
packages each have at least one fiber port for carrying optical
signals to and/or from the PLC.
11. The component package of claim 1, wherein the optical component
comprises a planar lightwave circuit (PLC).
12. The component package of claim 10, wherein the PLC comprises an
arrayed waveguide grating.
13. A method for packaging an optical component, comprising:
enclosing the optical component in a first, inner package; and
enclosing the inner package in a second, outer package.
14. The method of claim 13, further comprising: disposing a heater
in the inner package proximate the optical component to control the
temperature thereof.
15. The method of claim 14, wherein the outer package creates an
isolated air space around the inner package which thermally
insulates the device from the outside environment.
16. The method of claim 15, further comprising: forming the outer
package from a material having low thermal conductivity.
17. The method of claim 14, further comprising: forming the heater
from a material having a coefficient of thermal expansion
substantially matched to that of the optical component, with high
thermal conductivity and therefore high temperature uniformity.
18. The method of claim 13, further comprising: providing a base
for the inner package; affixing a heater to the base; affixing the
optical component to the heater; affixing sidewalls to the base
around the heater; and affixing a lid over the sidewalls.
19. The method of claim 18, further comprising: forming the heater
from a material having a coefficient of thermal expansion
substantially matched to that of the optical component.
20. The method of claim 19, wherein the optical component comprises
a planar lightwave circuit (PLC).
21. The method of claim 20, wherein the PLC comprises an arrayed
waveguide grating.
22. The method of claim 20, wherein the inner and outer packages
each have at least one fiber port for carrying optical signals to
and/or from the PLC.
23. The method of claim 1, wherein the optical component comprises
a planar lightwave circuit (PLC).
24. The method of claim 23, wherein the PLC comprises an arrayed
waveguide grating.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to component packaging. More
particularly, the present invention relates to a redundant package
for isolating optical components (e.g., arrayed waveguide gratings)
from external stresses.
BACKGROUND OF THE INVENTION
[0002] Fiber optic communication links have been conventionally
employed in long-haul, point-to-point networks with controlled
environments at all interface points. Such highly controlled,
"central office" surroundings usually offer relatively benign
operating environments (temperature, humidity, mechanical) for
components. Consequently, highly functional components could be
developed and installed without considering the impact of other,
more extreme environments.
[0003] Recent technological advances, coupled with increasing
bandwidth demand, are rapidly expanding the use of fiber optic
components beyond the "central office" and into potentially harsher
environments. For example, dense wavelength division multiplexing
(DWDM) enables the transmission of multiple, independent wavelength
streams across a single fiber. Predictably, this capability has
resulted in the requirement to add or drop these optical channels
along the previously untapped long lengths of fiber (and outside of
the central office environment) to provide access to the individual
wavelength streams. Optical add/drop multiplexers (OADMs) are
employed for this function, enabled by arrayed waveguide grating
(AWG) components for filtering and forwarding individual
wavelengths.
[0004] In addition to these technological advances, simple market
forces are pushing fiber networks beyond central offices and into
the diverse terrain of "metro" markets. This ever-increasing need
for bandwidth which only fiber can deliver is resulting in the
widespread deployment of fiber networks, and their associated
components, into the harsher, less environmentally controlled
conditions present in the metro market.
[0005] The demands placed on component designers now reach far
beyond optical performance, and into the realms of thermal and
mechanical insulation. Certain qualification standards (e.g.,
Telcordia) exist for reliability of optical components, and many
customers require qualification under these standards. AWGs however
are thin, fragile chips with narrow waveguides produced using
planar lightwave circuit (PLC) processing techniques. The various
processing tolerances required to meet the requisite optical
specifications are already very tight, and in fact get tighter as
the need to process more and closer channels increases. It is
difficult and costly to impose yet additional requirements on the
chip process in the form of advanced materials, processing
techniques, etc. to satisfy the harsher environmental standards
discussed above.
[0006] Environmentally secure packages therefore now play a vital
role in the widespread commercialization of these devices. Without
adequate packaging, components such as AWGs, with their highly
unique and useful functions, would be relegated to laboratory
environments only.
[0007] What is required, therefore, are advanced packaging
techniques to enable the widespread use of otherwise fragile
optical components in diverse and often stressful environments.
SUMMARY OF THE INVENTION
[0008] These requirements are met, and further advantages are
provided, by the present invention which in one aspect is an
optical component package having a first, inner package enclosing
the optical component, and a second, outer package enclosing the
inner package. A heater may be disposed in the inner package
proximate the optical component to control the temperature thereof,
and to maintain this temperature control, the outer package forms
an isolated sealed airspace around the inner package. This isolated
airspace thermally insulates the AWG device environment from the
outside ambient environment. The thermal isolation reduces the
power consumption required to maintain tight temperature control of
the device and reduces thermally induced mechanical stresses which
could negatively affect the device performance or reliability.
These parameters are critical to the commercial viability of the
device. The outer package is formed of a material having low
thermal conductivity, to promote this insulating function.
[0009] The heater may be formed of a material having a coefficient
of thermal expansion substantially matched to that of the optical
component, to minimize thermal differences and the resultant
stresses at the interface between these elements.
[0010] The inner package, in one example, is formed from a base, a
heater affixed to the base, and the optical component is affixed to
the heater. Sidewalls are affixed to the base around the heater,
and a lid is affixed over the sidewalls.
[0011] This package is especially useful if the optical component
comprises a planar lightwave circuit (PLC), e.g., an arrayed
waveguide grating (AWG), which requires tight temperature control
and structural integrity to maintain the integrity of the optical
paths.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the concluding
portion of the specification. The invention, however, both as to
organization and method of practice, together with further objects
and advantages thereof, may be best understood by reference to the
following detailed description of the preferred embodiment(s) and
the accompanying drawings in which:
[0013] FIG. 1 is a typical AWG PLC requiring packaging;
[0014] FIG. 2 is an exploded view of the redundant package of the
present invention including a PLC mounted in an inner package;
[0015] FIG. 3 is a cross-sectional view of the inner package
containing the PLC; and
[0016] FIG. 4 is an exploded view of the outer package of the
present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0017] With reference to FIG. 1, an exemplary planar lightwave
circuit (PLC) 10 is shown with an arrayed waveguide grating (AWG)
22 on a substrate 20 (e.g., silicon). As known to those in the art,
an AWG uses an array of waveguides 22 having carefully controlled,
differing path lengths which cause constructive phase interference
patterns on the optical signals transmitted therein. This technique
is useful for multiplexing or demultiplexing optical signals passed
between the array input/focusing region 24/25 to the array
output/focusing region 26/27. The tight spatial and thermal
tolerances necessary for proper operation of array 20, as discussed
above, lead to the requirements for effective packaging and sealing
for use in adverse environmental conditions.
[0018] In accordance with the present invention, and with reference
to FIG. 2, a redundant package 100 is disclosed having an inner
package 110 within which the PLC 10 is mounted, and an outer
package 210 for enclosing the inner package. As discussed further
below, both packages are designed with appropriate materials and
structures to maximize thermal and mechanical insulation from
surrounding environments.
[0019] For example, and with reference to FIG. 3 (a cross-sectional
view of the inner package along line AA) the base 112 of this inner
package is similar to a PC board and is formed from FR5, a type of
fiberglass reinforced plastic. A heater element 30 formed of
aluminum nitride is surface-mounted onto base 112, at interface 40.
A layer of J-leads (not shown) may also be disposed at this
interface. Heater 30 is used to ensure that PLC 10 is maintained at
a constant temperature (very uniformly across its surface), since
temperature changes will cause minor structural changes in AWG
signal paths, and negatively impact its optical performance.
[0020] Silicon PLC 10 is then mounted onto heater 30 at interface
50 using, for example, a low modulus silicon material. Aluminum
nitride is chosen for heater 20 since its coefficient of thermal
expansion (CTE) is approximately matched to that of the silicon
PLC, thus preventing any adverse thermo-mechanical stress at this
interface. Other materials with similar thermal conductivities
combined with Si-matched CTEs would serve similar function. These
materials may include Si Carbide or Si. Such materials in general
are highly thermally conductive, providing high uniformity of
temperature across the heater.
[0021] Package walls 116, 118 are also formed from FR5, and joined
to base 112 using an epoxy. V-groove arrays 28 and 29 on PLC 10
provide the interface to input and output fiber ribbons, which are
carried out of the package over upper recesses in the sidewalls,
and FR5 lid 114 is then epoxied in place over walls 116 and 118.
The recessed sidewall openings are also sealed with epoxy.
[0022] With reference to the exploded view of the outer package 210
of FIG. 4, this package is formed from polycarbonate plastic (which
is highly non-thermally conductive). An epoxy is used to affix the
inner package 110 into base 212, and lid 214 is then affixed and
sealed to the base using a silicon epoxy. The fiber input and
output ribbons are accommodated through the side ports, with strain
reliefs 216 and 218. These ports are sealed using epoxy also. The
isolated airspace created around the inner package by the outer
package thermally insulates the AWG device environment from the
outside ambient environment. The thermal isolation reduces the
power consumption required to maintain tight temperature control of
the device and reduces thermally induced mechanical stresses which
could negatively affect the device performance or reliability.
These parameters are critical to the commercial viability of the
device. The outer package is formed of a material having low
thermal conductivity, to promote this insulating function.
[0023] The inner package of the present invention maintains tight
temperature control around the highly temperature-sensitive optical
component (e.g., PLC/AWG). The redundant, outer package ensures
this tight control by the airspace insulation, and through the
choice of non-thermally conductive materials. Moreover, the
redundant outer package ensures greater structural integrity, and
additional sealing from humidity and other environmental
factors.
[0024] While the invention has been particularly shown and
described with reference to preferred embodiment(s) thereof, it
will be understood by those skilled in the art that various changes
in form and details may be made therein without departing from the
spirit and scope of the invention.
* * * * *