U.S. patent application number 15/299310 was filed with the patent office on 2017-05-18 for optical interconnect for switch applications.
The applicant listed for this patent is Kaiam Corp.. Invention is credited to Charles Amsden, John Heanue, Bardia Pezeshki, Lucas Soldano.
Application Number | 20170139145 15/299310 |
Document ID | / |
Family ID | 58690974 |
Filed Date | 2017-05-18 |
United States Patent
Application |
20170139145 |
Kind Code |
A1 |
Heanue; John ; et
al. |
May 18, 2017 |
OPTICAL INTERCONNECT FOR SWITCH APPLICATIONS
Abstract
A switch module includes a switch integrated circuit (IC), a
silicon photonics chips, and an interface having removably coupled
first side and second side. The first side includes a lens array
optically coupled to a SiP chip and the second side includes a
connector having a plurality of planar lightwave circuits (PLCs)
optically coupled to another lens array.
Inventors: |
Heanue; John; (Boston,
MA) ; Pezeshki; Bardia; (Menlo Park, CA) ;
Amsden; Charles; (Fremont, CA) ; Soldano; Lucas;
(Milan, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kaiam Corp. |
Newark |
CA |
US |
|
|
Family ID: |
58690974 |
Appl. No.: |
15/299310 |
Filed: |
October 20, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62244083 |
Oct 20, 2015 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/12011 20130101;
G02B 6/30 20130101; G02B 6/124 20130101; G02B 6/4249 20130101; G02B
6/4204 20130101; G02B 6/12004 20130101; H04Q 2011/0022 20130101;
G02B 6/32 20130101; G02B 6/12019 20130101; G02B 2006/12121
20130101; G02B 6/34 20130101; G02B 6/4292 20130101; G02B 2006/12145
20130101; G02B 2006/12102 20130101; G02B 6/4214 20130101 |
International
Class: |
G02B 6/30 20060101
G02B006/30; G02B 6/124 20060101 G02B006/124; G02B 6/42 20060101
G02B006/42; G02B 6/12 20060101 G02B006/12; G02B 6/32 20060101
G02B006/32 |
Claims
1. An optical connector for a silicon photonics chip, comprising: a
housing; a plurality of lenses at least partially within the
housing; a plurality of planar lightwave circuits (PLCs),
positioned at least partially within the housing, to pass light to
or receive light from the lenses; a plurality of optical fibers
coupled to the PLCs.
2. The optical connector of claim 1, wherein the plurality of
lenses are arranged in a plurality of linear arrays.
3. The optical connector of claim 1, wherein the plurality of
lenses form a matrix.
4. The optical connector of claim 1, where the plurality of lenses
provide part of an expanded beam connector.
5. The optical connector of claim 1, wherein the plurality of
lenses are at a first opening of the housing.
6. The optical connector of claim 1, wherein the plurality of PLCs
include at least one optical multiplexer and at least one optical
demultiplexer.
7. The optical connector of claim 6, wherein the optical
multiplexer and the optical demultiplexer include arrayed waveguide
gratings (AWGs).
8. The optical connector of claim 1, wherein a first of the
plurality of PLCs include an optical multiplexer and a second of
the plurality of PLCs include an optical demultiplexer.
9. The optical connector of claim 1 wherein the plurality of PLCs
are positioned in parallel to one another.
10. The optical connector of claim 1, wherein the housing is part
of a cable.
11. An optical system, comprising: a silicon photonics (SiP)
integrated circuit (IC) chip including a plurality of grating
couplers for use in passing light through a boundary of the SiP IC
chip, a plurality of modulators for modulating light received by at
least first set of the plurality of grating couplers and provided
to a second set of the plurality of grating couplers, and a
plurality of photodiodes for generating electrical signals based on
light received by at least a third set of the plurality of grating
couplers; a first array of lenses positioned on top of the SiP chip
to pass light from the plurality of grating couplers; an optical
cable connector coupled to the SiP IC, the optical cable connector
including a second array of lenses positioned to pass light from
the first array of lenses, and a plurality of planar lightwave
circuits (PLCs) positioned to receive light from the second array
of lenses.
12. The optical system of claim 11, wherein the first array of
lenses and the second array of lenses form an expanded beam optical
connector.
13. The optical system of claim 11, wherein the plurality of PLCs
include a first PLC for providing first input optical signals to
the first set of grating couplers, a second PLC for receiving
output optical signals from the second set of grating couplers, and
a third PLC for providing second input optical signals to the third
set of grating couplers.
14. The optical system of claim 13 wherein the second PLC includes
an optical demultiplexer and the third PLC includes an optical
multiplexer.
15. The optical system of claim 14 wherein the optical
demultiplexer and the optical multiplexer include arrayed waveguide
gratings (AWGs).
16. The optical system of claim 11, further comprising a plurality
of fiber assemblies coupled to the plurality of PLCs.
17. A switch module comprising: a switch integrated circuit (IC)
chip including a switch for routing inputs to outputs of the switch
IC chip; a silicon photonics (SiP) chip including photodetectors
for use in converting first optical signals to first electrical
signals and modulators for modulating second optical signals in
accordance with second electrical signals, outputs of the
photodetectors being coupled to inputs of the switch IC chip and
outputs of the switch IC chip being coupled to the modulators; and
an interface including a first side and a second side, the first
side including a first lens array optically coupled to the SiP
chip, the second side including a connector having a plurality of
planar lightwave circuits (PLCs) optically coupled to a second lens
array, the second lens array and the first lens array positioned to
pass light to each other.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of the filing date of
U.S. Provisional Patent Application No. 62/244,083, filed on Oct.
20, 2015, the disclosure of which is incorporated by reference
herein.
BACKGROUND OF THE INVENTION
[0002] The present application relates generally to fiber optic
communications, and more particularly to optical connections for
silicon photonics chips.
[0003] Fiber optic communications lines are often used to pass data
between electronic units. The fiber optic communications lines may
be used both for long haul telecommunications applications and for
shorter applications, such as for communications between servers in
a data center. In either case, electro-optic conversion is provided
between the electrical data of the electronic units and light
passed by the fiber optic communication lines.
[0004] Generally the equipment used to perform electro-optic
conversion is in the form of a transceiver that is plugged in to a
faceplate of the electronic units, and there may be many such
transceivers for any specific electronic unit, for example a server
or a switch. For example, typical switches used in datacenters can
have tens or even hundreds of optical transceivers that populate
the front plate of the unit. Unfortunately, it may be difficult to
cool the transceivers in the front panel. In addition, the data
signals passed between the transceivers and the electronic switch
circuitry are often high frequency signals that may suffer
degradation during travel between the electronic switch circuitry,
generally on circuit boards within the unit, and the transceivers,
generally at a face plate of the unit.
[0005] Silicon Photonics (SiP) integrated circuit (IC) chips may be
used to perform electro-optic conversion, and the SiP IC chips may
be placed on boards with or near other electronic integrated
circuits of an electronic unit such as a switch. However, light
signals carried by the fiber optic communications would still need
to be brought within the electronic equipment, for example the
switch, and provided to the SiP IC chips. There may be difficulties
in doing so, as for example as the SiP chip may be subject to
various handling and processing operations, for example post-chip
manufacturing operations.
BRIEF SUMMARY OF THE INVENTION
[0006] One aspect of the invention provides an optical connector
for a silicon photonics chip, comprising: a housing; a plurality of
lenses at least partially within the housing; a plurality of planar
lightwave circuits (PLCs), positioned at least partially within the
housing, to pass light to or receive light from the lenses; a
plurality of optical fibers coupled to the PLCs.
[0007] Another aspect of the invention provides an optical system,
comprising: a silicon photonics (SiP) integrated circuit (IC) chip
including a plurality of grating couplers for use in passing light
through a boundary of the SiP IC chip, a plurality of modulators
for modulating light received by at least first set of the
plurality of grating couplers and provided to a second set of the
plurality of grating couplers, and a plurality of photodiodes for
generating electrical signals based on light received by at least a
third set of the plurality of grating couplers; a first array of
lenses positioned on top of the SiP chip to pass light from the
plurality of grating couplers; an optical cable connector coupled
to the SiP IC, the optical cable connector including a second array
of lenses positioned to pass light from the first array of lenses,
and a plurality of planar lightwave circuits (PLCs) positioned to
receive light from the second array of lenses.
[0008] Another aspect of the invention provides a switch module
comprising: a switch integrated circuit (IC) chip including a
switch for routing inputs to outputs of the switch IC chip; a
silicon photonics (SiP) chip including photodetectors for use in
converting first optical signals to first electrical signals and
modulators for modulating second optical signals in accordance with
second electrical signals, outputs of the photodetectors being
coupled to inputs of the switch IC chip and outputs of the switch
IC chip being coupled to the modulators; and an interface including
a first side and a second side, the first side including a first
lens array optically coupled to the SiP chip, the second side
including a connector having a plurality of planar lightwave
circuits (PLCs) optically coupled to a second lens array, the
second lens array and the first lens array positioned to pass light
to each other.
[0009] These and other aspects of the invention are more fully
comprehended upon review of this disclosure.
BRIEF DESCRIPTION OF THE FIGURES
[0010] Aspects of the disclosure are illustrated by way of
examples.
[0011] FIG. 1 is a semi-block diagram of an interface for optical
interconnect applications that includes a removable optical
connector, including planar lightwave circuits (PLC), for a silicon
photonics (SiP) chip in accordance with aspects of the
invention.
[0012] FIG. 2 is a semi-block diagram of a further view of the
interface for optical interconnect applications that includes a
removable optical connector, including planar lightwave circuits
(PLCs), for a silicon photonics (SiP) chip in accordance with
aspects of the invention.
[0013] FIG. 3 shows an example of a PLC in accordance with aspects
of the invention.
[0014] FIG. 4 shows a schematic of a silicon photonics (SiP) chip
in accordance with aspects of the invention.
[0015] FIG. 5 illustrates a switch having a switch package
comprising a switch IC and optical modules in accordance with
aspects of the invention.
[0016] FIG. 6 illustrates a switch architecture with optical
connection directly on silicon photonic (SiP) ICs.
[0017] FIG. 7 illustrates a view of an IC side of an interface for
optical interconnection in accordance with aspects of the
invention.
[0018] FIG. 8A illustrates a view of a connector side and an IC
side of an interface for optical interconnection in accordance with
aspects of the invention.
[0019] FIG. 8B illustrates an alternate view of a connector side
and an IC side of an interface for optical interconnection in
accordance with aspects of the invention.
DETAILED DESCRIPTION
[0020] FIG. 1 is a semi-block diagram of an interface for optical
interconnect applications that includes a removable optical
connection for a silicon photonics (SiP) integrated circuit (IC)
chip, in accordance with aspects of the invention. As illustrated
in FIG. 1, a first lens array 117 is mounted to a SiP IC chip 119.
As shown in FIG. 1 the first lens array is shown in oversized form
with respect to the SiP IC chip, as are other components. The first
lens array 117 in some embodiments is mounted directly on top of
the SiP IC chip 119, as shown in FIG. 1. Lenses of the first lens
array are positioned to direct light into or receive light from
grating couplers of the SiP IC chip. In various embodiments the
lenses of the first lens array are arranged in linear arrays, for
example forming rows, with the linear arrays providing a matrix of
lenses.
[0021] The connection includes a removable connector 110. The
connector includes a housing 110 which is mounted to the SiP IC
chip and/or the first lens array 117, such that an end cavity of
the housing is positioned to generally receive light from and/or
pass light to the first lens array 117. In some embodiments the end
cavity of the housing is sized with respect to a carrier for the
first lens array 117 such that the housing securely mates by way of
a compression fit to the carrier of the first lens array 117. In
some embodiments the housing includes a mating connector for
connecting to the carrier of the first lens array. In some
embodiments the connector is on MXC connector.
[0022] A second lens array 115 is within the housing near the end
of the cavity. The second lens array is positioned within the
cavity so as to be generally optically aligned with the first lens
array with the housing mounted to the first lens array and/or SiP
IC chip. The first lens array and the second lens array therefore
provide a beam connector. In various embodiments the lenses of the
lens arrays are lenses that expand beams that propagate towards the
lenses of the other lens array, with the lens arrays therefore
forming an expanded-beam connector.
[0023] The housing includes at least one planar lightwave circuitry
(PLC), and in most embodiments a plurality of PLCs. The PLCs are
within the housing on a side of the second lens array away from the
first lens array. In some embodiments the PLCs include a
demultiplexer (DMUX) for providing wave division multiplexed
optical input signals to the second lens array, a multiplexer (MUX)
for carrying optical output signals from the second lens array, and
either pass through paths or a DMUX for carrying optical signals,
to be modulated by the SiP IC chip, from laser diodes. In some
embodiments the laser diodes are included in the housing of the
connector, along with, in some embodiments, a MEMS structure to
couple light of the lasers into waveguides of one of the PLCs. The
PLC 113 in some embodiments is mounted directly on top of the lens
array 115. In some embodiments fiber assemblies to carry optical
signals to and from the PLCs are bonded to an opposing side of the
PLCs, away from the second lens array.
[0024] The connector, for example, serves to form a removable
optical connection between the PLC and the SiP chip by removably
coupling both ends of the interface together for passing of light
between the PLC and the SiP chip. In operation, the interface
receives light from fibers. The light may be demultiplexed by the
PLC, for example by a demultiplexing arrayed waveguide grating
(AWG) into separate waveguides. Light from these waveguides may be
deflected into the lens array 115, with the lens array 115 focusing
the light into the lens array 117. The lens array 117 may focus the
light into the SiP chip 119 for converting optical signals to
electrical signals. For example, the SiP chip may include grating
couplers that send light into waveguides into the SiP chip where
light from the waveguides is received by photodetectors, which
provide electrical signals. The electrical signals are amplified by
a TIA, and in some embodiments equalized and clocked by a CDR and
exit the SiP chip assembly.
[0025] In some embodiments, the interface serves to output or
transmit light, for example, to transmit fibers. For example,
continuous wave (CW) lasers are coupled to waveguides in the PLC,
within some embodiments the lasers being in the housing of the
connector. Light from these waveguides are directed into the SiP
chip by the lens arrays and enter waveguides in the SiP chip
through the grating couplers of the SiP chip. The light in the
waveguides are then modulated by modulators and exit the SiP chip
through the grating couplers. The SiP chip then passes the light to
the lens array 117 which in turn, focuses the light into the lens
array 115. The lens array 115 may provide the light to waveguides
in the PLC. The PLC may include a transmit arrayed waveguide
grating (AWG) for multiplexing light in the waveguides into a
single output, which is provided to the transmit fibers.
[0026] FIG. 2 is a semi-block diagram of an interface for optical
interconnect applications that includes a removable optical
connection between planar lightwave circuits (PLCs) and a silicon
photonics (SiP) chip in accordance with aspects of the invention.
In some embodiments the embodiment of FIG. 2 may be considered a
side view of the embodiment of FIG. 1. As shown in FIG. 2, a first
side of the interface includes a first lens array 217 coupled to a
SiP chip 219. A second side of the interface includes a connector
211 having a plurality of PLCs 213 coupled to a second lens array
215. The connector 211 may be the same as the connector 111 in
various embodiments. The first lens array 217 in some embodiments
is mounted directly atop the SiP chip 219. The plurality of PLCs
213 in some embodiments are mounted directly atop the second lens
array 215. Fiber assemblies 221 extend from the PLCs. In some
embodiments, each of the plurality of the PLCs is stacked next to
(or on top of) one another. In some embodiments, each of the first
and second lens array includes four rows of lens elements, with
each row including sixteen lens elements for up to sixty-four total
optical connections.
[0027] The connector 211 may form a removable optical connection
between the plurality of PLCs and the SiP chip 219 by removably
coupling or connecting the first and second sides of the interface
together for passing of optical signals between the plurality of
PLCs and the SiP chip 219. In operation, the interface receives
optical signals which are provided to one of the plurality of PLCs
for demultiplexing the signals, for example by a demultiplexing
AWG, into various waveguides. Light from the waveguides may be
deflected into the seconds lens array which in turn, focuses the
light to the first lens array. The first lens array then may focus
the light into the SiP chip 219 for converting optical signals to
electrical signals. For example, the SiP chip may include grating
couplers that send light into waveguides into the SiP chip where
lights from the waveguides are received by germanium
photodetectors, which provide electrical signals. The electrical
signals are amplified by a TIA, and in some embodiments equalized
and clocked by a CDR and exit the SiP chip.
[0028] In some embodiments, the interface outputs optical signals,
for example, to transmit optical fibers. For example, continuous
wave (CW) lasers are coupled to waveguides in another of the
plurality of PLCs. Light from these waveguides are passed by the
lenses of the lens arrays into the SiP chip and enter waveguides in
the SiP chip through the grating couplers of the SiP chip. The
light in the waveguides are then modulated by modulators and exit
the SiP chip through other grating couplers. The light then is
routed to other lenses of the first lens array and in turn, the
first lens array focuses the light into other lenses of the second
lens array. The second lens array then routes the light to
waveguides in the other PLC. The other PLC may include a transmit
AWG for multiplexing or combining light in the waveguides into a
single output provided to the transmit fibers.
[0029] FIG. 3 shows an example of a PLC 313 in accordance with
aspects of the invention. On the right hand side of the figure,
where the PLC interfaces to fibers and lasers, there are four
features. At the very top of the figure is an input waveguide (301)
coupled to a demultiplexer structure. This input waveguide would be
aligned and affixed to a capillary and fiber assembly. Immediately
below the input waveguide are a plurality of input waveguides (302)
that connect to a laser assembly (not shown). In some embodiments,
the plurality of input waveguides is sixteen input waveguides.
Immediately below the plurality of input waveguides is an output
waveguide (303) that connects to an output capillary and fiber. At
the bottom is a spare waveguide (315), which in some embodiments
may be an input or output waveguide connecting to a capillary and
fiber assembly. In some embodiments, however, each of the
waveguides are provided on a separate PLC.
[0030] In addition, there are four structures on the PLC of FIG. 3.
These four structures, however, may be provided on separate PLCs,
for example when the waveguides previously mentioned are on
separate PLCs. Three of the four structures include a
demultiplexing arrayed waveguide grating (AWG) (304), waveguide
connections (319), and a multiplexing AWG (305). A fourth structure
(311) in some embodiments may be a demultiplexing AWG or
multiplexing AWG.
[0031] The left hand side of the PLC of FIG. 3 includes
demultiplexed waveguides (306) that connect to a receiver,
waveguides (308) that come from modulators and are subsequently
multiplexed on the PLC, waveguides (307) that send continuous wave
(CW) signals from the laser assembly into input of the modulators,
and spare waveguides (317) that may be utilized as demultiplexed
waveguides or waveguides from modulators. In some embodiments, the
PLC includes sixteen demultiplexed waveguides (306), sixteen
waveguides (307), sixteen waveguides (308), and sixteen spare
waveguides (317). In some embodiments, such as those in which the
waveguides 301, 302, 303, and 315, correspondingly with the
structures 304, 319, 305, and 311, respectively, are on different
PLCs, the waveguides 700, 307, 308, and 317are on the corresponding
different PLCs as well.
[0032] Accordingly, in some embodiments, features of the PLC 313
may be implemented in a plurality of PLCs. For example, a first PLC
may include the input waveguide (301), the demultiplexing AWG
(304), and the demultiplexed waveguides (306). A second PLC may
include the plurality of input waveguides (302), the waveguide
connections (319), and the waveguides (307) for sending CW signals
from the laser assembly. A third PLC may include the output
waveguide (303), the multiplexing AWG (305), and the waveguides
(308) that come from modulators and are multiplexed on the third
PLC. And a fourth PLC may include the spare waveguide (315), the
fourth structure (311), and the spare waveguides (317). In some
embodiments, each of the plurality of PLCs is stacked on top of one
another.
[0033] FIG. 4 shows a schematic of a silicon photonics (SiP) chip
in accordance with aspects of the invention. As shown in FIG. 4, a
SiP chip 419 includes, on the right hand side of the figure,
optical inputs and outputs that are received from a connector, for
example the connector of FIG. 1 or 2, and onto grating couplers
405. The SiP chip further includes receiver inputs 407, inputs 408
from lasers which go to modulators 403, and modulated outputs 409
of a transmitter. The inputs and outputs are shown on the right
hand side of the Figure for convenience, in most embodiments the
inputs and outputs are arranged, for example in linear rows, on a
top surface of the SiP chip so as to provide light to or receive
light from a lens array, such as the first lens array of FIG.
1.
[0034] The input chain of the receiver goes to high speed
photodetectors 401 that are integrated with the SiP chip and in
turn goes to transimpedence amplifiers 402. The CW laser inputs go
to the modulators 403 and then exit the SiP chip. Optionally, one
may have low speed photodetectors on the chip that tap a small
amount of the transmit or receive chain. Those tapping the receive
chain 406 can monitor the input power and adjust the laser bias to
compensate for temperature variations of laser output power or for
aging. The output of these detectors are particularly useful in the
MEMS alignment process, because position of microlenses preferably
make use of some sort of a signal to optimize position. The taps on
the output 405, for example, could be used to monitor the health of
the modulators and set off an alarm should the power vary outside
the specifications. The SiP chip could of course also contain
electronics 410 for control of signals or to process signals. The
control and driver function can also be implemented in a separate
chip that would be bonded to the main SiP chip.
[0035] In some embodiments, the number of channels may be sixteen.
In some embodiments, thirty six channels modulated at 25 Gbaud
using PAM4 modulation would result in a total bandwidth of 1.8 Tb/s
and only a single input fiber would be needed at the input and
another at the output. The wavelength spacing could be placed close
together and the entire system temperature controlled for
additional channels.
[0036] FIG. 5 illustrates a switch having a switch package
comprising a switch IC and optical modules in accordance with
aspects of the invention. As illustrated in FIG. 5, a switch module
500 includes a central package 511 including a switch IC 513 and
optical/electrical (OE) conversion modules 515 that convert
electrical input/output (I/O) of the switch chip to optical
signals. In some embodiments, the OE conversion modules are
included within a SiP chip (not shown).
[0037] The switch IC includes a switch (not shown), which routes
data between switch inputs and switch outputs. The routing of the
data is generally controlled by a switch IC processor (not shown),
which for example may utilize information of the data, for example
in packet headers, as well as routing table maintained by the
processor in determining routing of the data between switch inputs
and switch outputs.
[0038] In some embodiments, on a transmit path, the OE conversion
modules transmits optical signals to a first lens array 527, which
focuses the optical signals into a second lens array 525. The first
lens array may be mounted to the SiP chip, for example as discussed
with respect to FIGS. 1 and 2. The second lens array 525, which is
coupled to a plurality of PLCs 523, then routes the optical signals
to one of the plurality of PLCs for outputting a combined or
multiplexed optical signal to one of patch panels 519 by way of one
of inside fiber links 517, with the inside fiber links coupled to
the plurality of PLCs. The second lens array and the PLCs, for
example, may be within a cable connector, as discussed for example
with respect to FIGS. 1 and 2.
[0039] In some embodiments, on a receive path, another of the patch
panels 519 receives optical signals, by way of one of outside fiber
links 521, and route the optical signals to another of the
plurality of PLCs. The other PLC passes demultiplexed optical
signals to the second lens array, with the second lens array
focusing the demultiplexed optical signals to the first lens array.
The first lens array then focuses the demultiplexed optical signals
to the OE conversion modules for conversion of the optical signals
to electrical input signals to the switch IC.
[0040] In some embodiments, the central package may be cooled by a
common central heatsink (not shown). At the front panel of the
switch module there is no need for transceivers as the patch panels
519 connect the inside fiber links to the outside fiber links. The
electrical link between the switch IC and the OE modules are very
short and therefore may not require reshaping, or in some
embodiments retiming. Eliminating these equalization circuits may
save considerable amount of power and complexity. In addition,
front panel density may be increased since the patch panels can be
connected tightly and one can get much denser I/O than when using
optical transceiver subassemblies. There is no heat generated in
the front panel where cooling is more difficult. The OE modules
that generate heat, do so at the center of the board where there is
room for a large heatsink and good airflow. Since no extra
packaging is required for the electronics of the transceivers, and
there are no CDRs, the OE modules are cheaper than transceivers and
thus the overall cost of a populated switch is much cheaper with
this configuration.
[0041] FIG. 6 is a switch architecture with optical connectors
directly on silicon photonic (SiP) ICs. As shown in FIG. 6, eight
MXC-type optical connectors 611 are packaged together in the switch
architecture, with a pair of the optical connectors connected to
SiP ICs 613 mounted on each side of a 4-sided breadboard or
platform. Each of the optical connectors in some embodiments may be
the connector of FIG. 1 or the connector of FIG. 2. The optical
connectors serve to form removable optical connection between PLCs
(not shown) and the SiP ICs. Each of the optical connectors may
include a heatsink 615 to assist in dissipating heat, for example
generated by lasers, if in the optical connectors, and the optical
connectors may also incorporate a PCB with control electronics for
the lasers. In some embodiments, each of the optical connectors is
an expanded-beam connector, having lens elements incorporated
within the connector. In some embodiments, four rows of sixteen
lens elements per row are incorporated in each of the optical
connectors for a total of up to 64 connections. As such, the switch
architecture shown in FIG. 6 may include up to 512 connections.
[0042] As further shown in FIG. 6, each of the optical connector
includes an end connected to one of the SiP ICs 613 and another end
being covered by a cap 617. The cap may be removed to connect the
other end of the optical connector to, for example, optical fibers
connected to a front panel of a switch module.
[0043] FIG. 7 shows a detailed view of an IC side of an interface
for optical interconnection in accordance with aspects of the
invention. In FIG. 7, the IC side includes a lens array 715 that is
mounted directly on top of the SiP IC 719, with the SiP IC mounted
on a breadboard or platform.
[0044] The lens array may be, for example, the first lens array of
FIGS. 1 and/or 2. The lens array includes four rows of lens with
sixteen lens per row for up to 64 total connections. Each lens
serves to focus light into a grating coupler on the SiP IC surface.
In some embodiments, one row may be used for 16 Rx signals, one row
may be used for 16 Tx signals, one row may be used to bring light
from lasers to the SiP IC, and one row may be used as a spare
row.
[0045] FIG. 8A shows a detailed view of a connector side and an IC
side of an interface for optical interconnection in accordance with
aspects of the invention. In FIG. 8A, the connector side includes a
MEMS coupling device 821, for example as discussed in U.S. patent
application Ser. No. 14/621,273 filed on Feb. 12, 2015 entitled
PLANAR LIGHTWAVE CIRCUIT ACTIVE CONNECTOR, and/or U.S. Pat. No.
8,346,037 issued on Jan. 1, 2013 entitled MICROMECHANICAL ALIGNED
OPTICAL ASSEMBLY, the disclosures of which are incorporated herein
by reference for all purposes, a plurality of stacked PLCs 813, and
a lens array 815. The MEMS coupling device couples lasers (not
shown) to one of the plurality of stacked PLCs, with the plurality
of stacked PLCs coupled to the lens array 815. In some embodiments,
however, the MEMS coupling device and lasers are located elsewhere,
for example near a front panel of a unit including the SiP IC. In
some embodiments, the lens array 815 includes four rows of lens
with sixteen lens per row for up to 64 total connections.
[0046] The IC side, similar to or same as the IC side shown in FIG.
7, includes a lens array 817 coupled to a SiP IC 819, with the SiP
IC mounted on a breadboard or platform. In some embodiments, the
lens array 817 is mounted directly on top of the SiP IC.
[0047] FIG. 8B shows an alternate view of a connector side and an
IC side of an interface for optical interconnection in accordance
with aspects of the invention. In FIG. 8B, lasers 823 are coupled
to the side of one of the plurality of stacked PLCs using the MEMS
coupling device 821. Light from the lasers is passed to the SiP IC
by way of the PLC, the lens array 815, and the lens array 817, with
the SiP IC modulating the light from the lasers. The modulated
light or optical signals then exit the SiP chip and enter another
of the plurality of stacked PLCs, by way of the lens arrays 817 and
815, for multiplexing into a single output for transmission.
[0048] In various embodiments:
[0049] The switch module yield and reliability are potentially
higher, because the lasers are external to the switch.
[0050] A failed laser assembly can be replaced independent of the
switch ICs.
[0051] Switch packaging may require that the components be able to
survive solder reflow. With the PLC/LD assemblies external, those
components may not have a designed requirement to endure such a
process flow.
[0052] The expanded beam connector does not require good physical
contact in order to achieve high coupling efficiency; therefore,
insertion force for the connection can be low. This may result in a
switch assembly less prone to mechanical damage during cable attach
or servicing.
[0053] The lasers are somewhat removed from the switch IC, which
generates a lot of heat. This allows for the possibility of
lower-temperature operation of the lasers, enabling higher LD
reliability and lower power operation. Increased heat sink capacity
can be included with the cable assemblies.
[0054] Interconnection from the top surface of the ICs can be
advantageous compared to an edge-connection approach as the
required data capacities increase, because interconnection can be
made across the 2D top area of the IC rather than being limited to
the perimeter. Cable exit from the top can also be an advantage for
routing within the switch since less total space may be required
for bringing the cables together in a bundle.
[0055] In an expanded-beam arrangement, mode-shaping is possible
with the lenses, by using different focal length elements on each
side of the connection or by using anamorphic elements. This may
result in simpler PLC designs, since structures such as
mode-shaping periodic segmented waveguides may not be included.
[0056] Although the invention has been discussed with respect to
various embodiments, it should be recognized that the invention
comprises the novel and non-obvious claims supported by this
disclosure.
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