U.S. patent application number 13/800634 was filed with the patent office on 2014-01-02 for reconfigurable optical networks.
The applicant listed for this patent is Alcatel-Lucent USA Inc.. Invention is credited to Pietro Bernasconi, Young-Kai Chen, Po Dong, David T. Neilson.
Application Number | 20140003810 13/800634 |
Document ID | / |
Family ID | 49778272 |
Filed Date | 2014-01-02 |
United States Patent
Application |
20140003810 |
Kind Code |
A1 |
Dong; Po ; et al. |
January 2, 2014 |
RECONFIGURABLE OPTICAL NETWORKS
Abstract
A system, e.g. a reconfigurable optical channel router, includes
an input waveguide optically connected to a wavelength
demultiplexer. A first input microcavity resonator set including a
plurality of microcavity resonators is located adjacent the input
waveguide. The microcavity resonators are configured to
controllably couple to a corresponding one of a plurality of
frequency channels of an optical signal propagating within said
input waveguide.
Inventors: |
Dong; Po; (Murray Hill,
NJ) ; Neilson; David T.; (Murray Hill, NJ) ;
Bernasconi; Pietro; (Genestrerio, CH) ; Chen;
Young-Kai; (Murray Hill, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Alcatel-Lucent USA Inc. |
Murray Hill |
NJ |
US |
|
|
Family ID: |
49778272 |
Appl. No.: |
13/800634 |
Filed: |
March 13, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61667374 |
Jul 2, 2012 |
|
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61667380 |
Jul 2, 2012 |
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Current U.S.
Class: |
398/48 ;
29/592.1; 385/24; 398/45 |
Current CPC
Class: |
Y10T 29/49002 20150115;
G02B 6/29338 20130101; G02F 2002/008 20130101; G02B 6/43 20130101;
H04Q 2011/0058 20130101; H04J 14/0212 20130101; G02B 6/293
20130101; G02F 1/011 20130101; H04Q 2011/0039 20130101; H04Q
2011/0032 20130101; H05K 13/04 20130101; G02F 2/004 20130101 |
Class at
Publication: |
398/48 ; 385/24;
398/45; 29/592.1 |
International
Class: |
G02B 6/293 20060101
G02B006/293; G02B 6/43 20060101 G02B006/43 |
Claims
1. A system comprising: a first plurality of separate sets of
optical ring resonators; a second plurality of separate sets of
optical ring resonators; and an optical multiplexer/demultiplexer
having a set of optical inputs and a set of optical outputs; and
wherein: each set of the first plurality of separate sets is
optically connected to a corresponding one of the optical inputs of
the optical multiplexer/demultiplexer; and each set of the second
plurality of separate sets is optically connected to a
corresponding one of the optical outputs of the optical
multiplexer/demultiplexer.
2. The system of claim 1, further comprising a plurality of first
devices, each first device being connected to modulate digital data
streams onto optical carriers via the ring resonators of a
corresponding one of the sets of the first plurality.
3. The system of claim 2, further comprising a plurality of first
apparatuses, each first apparatus being connected to demodulate
digital data streams from optical carriers via the ring resonators
of a corresponding one of the sets of the second plurality.
4. The system of claim 1, further comprising a plurality of first
apparatuses, each first apparatus being connected to demodulate
digital data streams from optical carriers via the ring resonators
of a corresponding one of the sets of the second plurality.
5. The system of claim 1, further comprising an electronic
controller capable of separately adjusting resonant frequencies of
some of the ring resonators of the sets of the first plurality.
6. The system of claim 1, wherein the electronic controller is
capable of separately adjusting resonant frequencies of some of the
ring resonators of the sets of the second plurality.
7. The system of claim 1, further comprising: a plurality of first
optical fibers, each first optical fiber connecting a corresponding
one of the sets of the first plurality to a multi-wavelength
channel optical source.
8. The system of claim 7, wherein each first optical fiber connects
to a corresponding one of the optical inputs of the optical
multiplexer/demultiplexer.
9. A system, comprising: an input waveguide optically connected to
an input of an optical demultiplexer; and a first microcavity
resonator set including a plurality of microcavity resonators
located adjacent said input waveguide such that each microcavity
resonator is able to couple to a corresponding one of a plurality
of wavelength channels of an optical signal propagating within said
input waveguide.
10. The system of claim 9, further comprising a plurality of output
waveguides, each output waveguide being optically connected to a
corresponding optical output of said wavelength demultiplexer.
11. The system of claim 10, further comprising a plurality of
output microcavity resonator sets each including a corresponding
plurality of microcavity resonators, each microcavity resonator set
being optically coupled to a corresponding one of said output
waveguides, the microcavity resonators of each output set being
able to separately couple to wavelength channels of an optical
signal propagating within said corresponding one of the output
waveguides.
12. The system of claim 11, further comprising a plurality of
optoelectric transducers, each of said transducers being optically
coupled to convert an optical signal within a corresponding one of
said output microcavity resonators to an electrical signal.
13. The system of claim 9, wherein said wavelength demultiplexer
comprises an arrayed waveguide grating.
14. The system of claim 9, further comprising control electronics
configured to control a resonant frequency of said microcavity
resonators.
15. The system of claim 9, wherein said wavelength demultiplexer is
a wavelength-cyclic optical demultiplexer.
16. The system of claim 9, wherein said each microcavity resonator
of said plurality of microcavity resonators is a ring
resonator.
17. A method comprising: providing an input waveguide optically
connected to a wavelength demultiplexer; and providing a first
input microcavity resonator set including a plurality of
microcavity resonators located adjacent said input waveguide such
that each microcavity resonator is able to couple to a
corresponding one of a plurality of wavelength channels propagating
within said input waveguide.
18. The method of claim 17, further comprising providing a
plurality of output waveguides optically connected to said
wavelength demultiplexer.
19. The method of claim 18, further comprising providing a
plurality of output microcavity resonator sets each including a
corresponding plurality of microcavity resonators, each microcavity
resonator set being optically coupled to a corresponding one of
said output waveguides.
20. The method of claim 19, further comprising providing a
plurality of optoelectric transducers, each of said transducers
being optically coupled to a corresponding one of said microcavity
resonators.
21. The method of claim 17, wherein said wavelength demultiplexer
comprises an arrayed waveguide grating.
22. The method of claim 17, further comprising providing control
electronics configured to modulate a resonant frequency of some of
said microcavity resonators.
23. The method of claim 17, wherein said microcavity resonators are
ring resonators.
24. A method, comprising: providing a first substrate having an
input waveguide optically connected to a wavelength demultiplexer,
and a first input microcavity resonator set including a plurality
of microcavity resonators located adjacent said input waveguide,
each of said microcavity resonators being configured to couple to a
different frequency of an optical signal propagating within the
input waveguide; providing a second substrate having an electronic
controller formed thereover, said controller configured to control
said microcavity resonators to controllably couple to a
corresponding one of the frequency channels; and joining said first
and second substrates thereby connecting said controller to said
microcavity resonators.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to U.S. patent application Ser.
No. 13/538,525 (the '525 Application) filed on Jun. 29, 2012 and
incorporated by reference herein. This application is further
related to U.S. patent application Ser. No. 13/800,403 (the "'403
Application") filed on even date herewith and incorporated by
reference herein. The present application claims the benefit to the
previously filed U.S. Provisional Patent Application No. 61/667,374
also of the same title, filed Jul. 2, 2012, and which is
incorporated herein by reference in its entirety. The present
application further claims the benefit to the previously filed U.S.
Provisional Patent Application No. 61/667,380 (the '380
Application) of the same title, filed Jul. 2, 2012, and which is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] This application is directed, in general, to optical
communications systems and methods.
BACKGROUND
[0003] This section introduces aspects that may be helpful to
facilitating a better understanding of the inventions. Accordingly,
the statements of this section are to be read in this light and are
not to be understood as admissions about what is in the prior art
or what is not in the prior art.
[0004] Optical switching networks employ a switching topology that
may be referred to as an "optical switch fabric." As the size and
speed of such networks grows, new optical switch fabrics that
provide greater capability are needed to keep pace with such
growth. One aspect of capability to be addressed is configuration
of such optical networks.
BRIEF SUMMARY OF ILLUSTRATIVE EMBODIMENTS
[0005] One aspect provides a system, e.g. a reconfigurable optical
channel router. The system includes an input waveguide optically
connected to a wavelength demultiplexer and configured to propagate
a plurality of wavelength channels of an optical carrier signal. A
first input microcavity resonator set is located adjacent the input
waveguide. The set includes a plurality of microcavity resonators
that are each configured to controllably couple to a corresponding
one of a plurality of frequency channels of an optical signal
propagating within the input waveguide.
[0006] Another aspect provides a method, e.g. for forming an
optical system, e.g. a reconfigurable optical channel router. The
method includes forming an input waveguide optically connected to a
wavelength demultiplexer. Microcavity resonators of a first input
set of microcavity resonators are formed located adjacent the input
waveguide. Each microcavity resonator is configured to controllably
couple to a corresponding one of a plurality of frequency channels
propagating within the input waveguide.
[0007] Yet another aspect provides a method, e.g. for forming an
optical system, e.g. a reconfigurable optical router. In a first
step of the method a first substrate is provided. The first
substrate has an input waveguide optically connected to a
wavelength demultiplexer. A first input microcavity resonator set
including a plurality of microcavity resonators located adjacent
the input waveguide. The microcavity resonator set includes a
plurality of microcavity resonators, each being configured to
couple to a different frequency channel of an optical signal
propagating within the input waveguide. In a second step of the
method a second substrate is provided. The second substrate has an
electronic controller formed thereover. The controller is
configured to control each of the microcavity resonators to
controllably couple to a corresponding one of the frequency
channels. In a third step of the method the first and second
substrates are joined, thereby operably connecting the controller
to the microcavity resonators.
[0008] In any embodiment a plurality of output waveguides may be
formed, each waveguide being optically connected to the wavelength
demultiplexer. In such embodiments the wavelength demultiplexer may
be configured to route each carrier signal to a corresponding one
of the output waveguides. Any embodiment may include forming a
plurality of output microcavity resonator sets. Each resonator set
includes a corresponding plurality of microcavity resonators. Each
microcavity resonator of each output set is located adjacent a same
corresponding one of the output waveguides such that the
microcavity resonators of each output set may controllably couple
to a corresponding different wavelength channel propagating within
the corresponding output waveguide.
[0009] In some such embodiments a plurality of optoelectric
transducers may be formed, with each of the transducers being
optically coupled to a corresponding one of the output microcavity
resonators. Each transducer is configured to convert an optical
signal within its corresponding resonator to an electrical
signal.
[0010] In any embodiment the wavelength demultiplexer may include
an arrayed waveguide grating (AWG). In any embodiment the AWG may
be configured to provide cyclic permutations of optical paths of
the wavelength channels between inputs and outputs of the AWG. In
any embodiment the waveguide and wavelength demultiplexer may be
formed from silicon. Any embodiment may include control electronics
configured to modulate a resonant frequency of the microcavity
resonators. In any embodiment the microcavity resonators may be
ring resonators.
[0011] One embodiment is a system comprising a first plurality of
separate sets of optical ring resonators, a second plurality of
separate sets of optical ring resonators, and an optical
multiplexer/demultiplexer. The optical multiplexer/demultiplexer
has a set of optical inputs and a set of optical outputs. Each set
of the first plurality of separate sets is optically connected to a
corresponding one of the optical inputs of the optical
multiplexer/demultiplexer. Each set of the second plurality of
separate sets is optically connected to a corresponding one of the
optical outputs of the optical multiplexer/demultiplexer.
[0012] Some such embodiments further comprise a plurality of first
devices, each first device being connected to modulate digital data
streams onto optical carriers via the ring resonators of a
corresponding one of the sets of the first plurality. Some such
embodiments further comprise a plurality of first apparatuses, each
first apparatus being connected to demodulate digital data streams
from optical carriers via the ring resonators of a corresponding
one of the sets of the second plurality. Some such embodiments
further comprise a plurality of first apparatuses, each first
apparatus being connected to demodulate digital data streams from
optical carriers via the ring resonators of a corresponding one of
the sets of the second plurality. Some such embodiments further
comprise an electronic controller capable of separately adjusting
resonant frequencies of some of the ring resonators of the sets of
the first plurality. Some such embodiments further comprise a
plurality of first optical fibers, each first optical fiber
connecting a corresponding one of the sets of the first plurality
to a multi-wavelength channel optical source. In some such
embodiments each first optical fiber connects to a corresponding
one of the optical inputs of the optical
multiplexer/demultiplexer.
BRIEF DESCRIPTION OF DRAWINGS
[0013] Reference is now made to the following descriptions taken in
conjunction with the accompanying drawings, in which:
[0014] FIG. 1 illustrates a system, e.g. an M.times.N
reconfigurable optical network according to one embodiment, that
provides optical domain switching of received wavelength channels
of wavelength division multiplexed (WDM) signals;
[0015] FIG. 1A schematically illustrates operation of the optical
network of FIG. 1 in a nonlimiting embodiments to optically provide
data connections between input electrical devices and output
electrical devices;
[0016] FIG. 2 illustrates aspects of a frequency comb including a
number of wavelength channels;
[0017] FIG. 3 illustrates an opto-electric domain converter used in
various embodiments to convert a modulated optical signal to the
electrical domain;
[0018] FIG. 4A illustrates a signal routing in one illustrative
embodiment by an arrayed waveguide grating that may be used in a
switching stage of the system of FIG. 1;
[0019] FIG. 4B illustrates another signal routing in one
illustrative embodiment by an arrayed waveguide grating that may be
used in a switching stage of the system of FIG. 1;
[0020] FIG. 4C illustrates another signal routing in one
illustrative embodiment by an arrayed waveguide grating that may be
used in a switching stage of the system of FIG. 1;
[0021] FIG. 5A illustrates an embodiment in which portions of the
system are formed on separate substrates that are joined to form
the system, e.g. the system of FIG. 1;
[0022] FIG. 5B illustrates another embodiment in which portions of
the system are formed on separate substrates that are joined to
form the system, e.g. the system of FIG. 1;
[0023] FIG. 5C illustrates another embodiment in which portions of
the system are formed on separate substrates that are joined to
form the system, e.g. the system of FIG. 1; and
[0024] FIG. 6 presents a flow diagram of a method, e.g. for forming
a system, e.g. the system of FIG. 1, according to various
embodiments; and
[0025] FIG. 7 presents a flow diagram of a method, e.g. for forming
a system, e.g. the system of FIG. 1, according to various
embodiments.
DETAILED DESCRIPTION
[0026] The inventors believe that a compact and flexible
architecture for switching data in an optical network may be
implemented using microcavity resonators coupled to waveguides to,
e.g. selectively add and drop modulated optical signals within an
opto-electric switching matrix. Embodiments may be used to provide
compact and low-cost signal routing at a small scale, e.g. within a
photonic integrated circuit, a medium scale, e.g. within a data
center, or large-scale, e.g. long-haul optical communication
system.
[0027] Some structures and/or methods described in '380
Application, and/or the '403 Application, may be suitable for
making or using similar structures and/or methods of the present
application.
[0028] FIG. 1 presents a system 100, e.g. an embodiment of an
MN.times.NM reconfigurable electrical cross-connect 100. The
cross-connect 100 uses optical wavelength channels to selectively
route digital data signal streams between M electrical ports of N
output devices to N ports of M input devices in a one-to-one manner
with respect to individual ports of the input and output devices.
The individual input ports are indexed by a pair of integers (m,
n), i.e., m=1, 2, . . . M and n=1, 2, . . . N, and the individual
output ports are indexed by a pair of integers (n, m), i.e., n=1,
2, . . . N and m=1, 2, . . . M. The parameter N describes a number
of wavelength division multiplexed (WDM) carriers available to
transmit data. The system 100 includes three principal sections
that are described in turn, a location-distributed transmitter
stage 105, a passive switching stage 110, and a
location-distributed receiver stage 115. The system 100 is
configurable to support different values of M and N. Accordingly a
generalized architecture is used to describe the system 100, with
more specific examples being used to describe some detailed aspects
of the system 100.
[0029] The transmit stage 105 includes N optical power waveguides
120-1, 120-2 . . . 120-N, collectively referred to as waveguides
120. The transmit stage 105 further includes N input microcavity
resonator sets 125-1, 125-2 . . . 125-N, wherein each set is
optically coupled to a corresponding one of the optical power
waveguides 120-1, 120-2 to 120-N. Each of the microcavity resonator
sets 125-1 to 125-N includes M microcavity resonators 130, as
further described below. Each microcavity resonator set 125 may
include, e.g. an optical ring resonator (microring) or an optical
disk resonator (microdisk) reconfigurably configured to resonate at
an optical wavelength, e.g. in the S band (1460 nm-1530 nm), the C
band (1530 nm-1565 nm) or the L band (1565 nm-1625 nm). The
remaining discussion refers to the microcavity resonators as ring
resonators without limitation thereto. The microcavity resonator
sets 125 may therefore also be referred to as ring resonators sets
125.
[0030] Each of the N waveguides 120-1 to 120-N receives an
unmodulated, multi-channel, optical signal 200 (see FIG. 2) that is
a superposition of unmodulated wavelength components. FIG. 2
schematically illustrates the spectrum of a representative
unmodulated, multi-channel, optical signal 200 that includes six
equally spaced, wavelength components .lamda..sub.1, . . .
.lamda..sub.6. The individual wavelengths may be spaced by a WDM
grid, frequency spacing .DELTA.f (or equivalent wavelength spacing
.DELTA..lamda.), e.g. a regular, about even spacing of the
wavelength components by a same frequency difference, e.g. about
100 GHz. Six wavelength components are shown, but embodiments are
not limited to any particular number of wavelength components.
[0031] Returning to FIG. 1, and considering the ring resonator set
125-1 as an example, this set includes M ring resonators 130-11,
130-21 . . . 130-M1. Each of the ring resonators 130-11, 130-21 . .
. 130-M1 may be controlled to operate with a resonant wavelength
approximately equal to one of the center wavelengths, i.e.,
.lamda..sub.1, .lamda..sub.2, . . . .lamda..sub.M, of the M
wavelength components of the unmodulated, multi-channel, optical
signal 200.
[0032] In the transmitter stage 105, each of the ring resonators
130-11, 130-21 . . . 130-M1 is optically coupled to the optical
power waveguide 120-1 such that a wavelength component of an
optical signal having a wavelength near the resonant wavelength of
a particular k-th ring resonator 130-1k couples to that ring
resonator. A controller 135 may provide a quasi-static control
signal that sets a nominal resonant frequency of a unique one of
the ring resonators 130-11, 130-21 . . . 130-M1 to one of the
wavelength components. The nominal resonant frequency may be
changed by electro-optic, thermal or free-carrier modulation of the
optical path lengths of the resonators 130. A data modulator (not
shown) may modulate the resonant frequency of the ring resonators
130 to impart data on the coupled signal, e.g. by binary phase
shift keying or on-off keying. For example, the resonant frequency
of each resonator 130 may be rapidly switched between two resonant
frequencies offset by a small amount from the nominal resonant
frequency. Additional suitable examples of such modulation may be
described in the '525 Application. Thus the controller 135 may
operate to map the data stream delivered to each ring resonator 130
to a particular wavelength channel.
[0033] The wavelength components .lamda..sub.1 . . . .lamda..sub.M
propagating within each waveguide 120 may be modulated
independently. Thus, the transmitter stage can produce M.times.N
independently data-modulated optical carriers. At outputs of the
waveguides 120-1 . . . 120-N each optical signal may have any one
of the wavelengths .lamda..sub.1 . . . .lamda..sub.M.
[0034] In the switching stage 110, a wavelength demultiplexer 145
includes input ports 150-1 . . . 150-N and output ports 155-1 . . .
155-M. At the input ports 150, the wavelength demultiplexer 145
receives the modulated optical signals from the waveguides 120 via
corresponding optical paths 140-1 . . . 140-N. While in the
illustrated embodiments the optical paths 140 are shown as being
physically located between the transmit stage 105 and the switching
stage 110, in other embodiments segments of the optical paths 140
may be physically located between the switching stage 110 and the
receiver stage 115. The optical paths 140 may include, e.g.,
segments of single mode optical fibers of various lengths. Short
path lengths may be used in embodiments for which the system 100 is
implemented as, e.g., an integrated photonic optical processor.
Long path lengths may be used in embodiments for which the system
100 is implemented as, e.g., in a long-haul communication system. A
medium path length may be used in embodiments for which the system
100 is implemented as, e.g., a communication network inside of a
data processing center.
[0035] In various embodiments, the wavelength demultiplexer 145
demultiplexes the wavelength components of the optical carrier
signals received at each input port 150 and routes these components
to the output ports 155 in a wavelength-selective manner. For
example, the wavelength demultiplexer 145 may route each one of the
M wavelength components received from the waveguide 120-1 to a
corresponding one of the M output ports 155.
[0036] In various embodiments, the wavelength demultiplexer 145
typically routes the individual wavelength components of a WDM
optical signal in a sequential and cyclic fashion to the output
ports 155. For example, if the input 150-1 receives a WDM optical
signal with M wavelength components in a wavelength-sequential
sequence .lamda..sub.1, .lamda..sub.2, .lamda..sub.3 . . .
.lamda..sub.M, these components may be routed to the output ports
155 such that a k-th wavelength .lamda..sub.k is output at the
first output 155-1, a next cyclically sequential wavelength
.lamda..sub.k+1 is output at the second output 155-2, and so on
such that the wavelength .lamda..sub.(k+M-1) is output at the M-th
output 155-M. Here, {k+M-1} designates the integer equal to k+M-1
modulo M and located in the interval [1, M].
[0037] Thus, the demultiplexer 145 may be any conventional
wavelength-cyclic optical demultiplexer, e.g., an AWG-based optical
demultiplexer. Herein, such a demultiplexer may be referred to as a
cyclic optical demultiplexer.
[0038] FIGS. 4A-4D illustrate without limitation the ordering of
channel frequencies at the outputs of the wavelength demultiplexer
145 in a more specific embodiment. In the following discussion, for
example and without limitation, N and M are each taken to be 4, and
the wavelength demultiplexer 145 implements cyclic permutations of
wavelength components. The center wavelength of each wavelength
channel is described as .lamda..sub.M. In FIG. 4A, wavelength
components .lamda..sub.1, .lamda..sub.2, .lamda..sub.3, and
.lamda..sub.4 received at the input port 150-1 are
wavelength-selectively routed by the wavelength demultiplexer 145
to the output ports 155-1, 155-2, 155-3, and 155-4, respectively.
In FIG. 4B, wavelength components .lamda..sub.1, .lamda..sub.2,
.lamda..sub.3, and .lamda..sub.4 received at the input port 150-2
are wavelength-selectively routed by the wavelength demultiplexer
145 to output ports 155-4, 155-1, 155-2 and 155-3, respectively. In
FIG. 4C, wavelength components .lamda..sub.1, .lamda..sub.2,
.lamda..sub.3, and .lamda..sub.4 received at the input port 150-3
are wavelength-selectively routed by the wavelength demultiplexer
145 to output ports 155-3, 155-4, 155-1, and 155-2, respectively.
In FIG. 4D, wavelength components .lamda..sub.1, .lamda..sub.2,
.lamda..sub.3, and .lamda..sub.4 received at the input port 150-4
are wavelength-selectively routed by the wavelength demultiplexer
145 to output ports 155-2, 155-3, 155-4 and 155-1,
respectively.
[0039] The wavelength demultiplexer 145 is not limited to any
particular implementation. Some convenient implementations include
an arrayed waveguide grating (AWG) based optical cross-connect. As
known to those skilled in the optical arts, an AWG based optical
cross-connect may be used to route a sequence of wavelength
components of a WDM optical signal to a parallel, spatial sequence
of optical outputs in a wavelength-selective manner. As already
mentioned, an AWG based wavelength selective cross-connect may also
route wavelength channels in a manner that is cyclic in the
sequence of components to the outputs. Moreover, an AWG-based
device may be implemented in a planar waveguide process, e.g.
silica on an SOI substrate, thereby being well suited to
integration in a photonic integrated circuit (PIC).
[0040] Embodiments of the wavelength demultiplexer 145 are not
limited to implementation with an AWG. For example, a cyclic
wavelength demultiplexer may be also based on an Echelle grating.
Such a grating directs substantial amounts of received light into
multiple diffraction orders so that each of the M optical outputs
of device 145 may be connected to receive light from multiple
orders. In some alternate embodiments, the switching stage 110 may
be implemented using an electronically-controlled switching matrix.
For example, 2.times.2 electro-optic switches may be configured to
implement an M.times.N matrix, with the switches being
electronically controlled. Skilled practitioners of the optical
arts are familiar with such switching matrixes. However, the size
of such matrixes may grow rapidly with N making such embodiments
cumbersome and expensive as N becomes large.
[0041] Returning to FIG. 1, the receiver stage 115 includes a
plurality of waveguides 160, e.g. one waveguide 160-1, 160-2 . . .
160-M optically connected to a corresponding one of the output
ports 155 of the wavelength demultiplexer 145. Each waveguide 160
is associated with an output ring resonator set 165. Thus, for
example, the waveguide 160-1 is associated with an output ring
resonator set 165-1, the waveguide 160-2 is associated with an
output ring resonator set 165-2, and so on. The ring resonator set
165-1 includes N ring resonators 170-11 . . . 170-N1, e.g. one ring
resonator corresponding to each of the ring resonator sets 125.
[0042] Each ring resonator 170-11 . . . 170-N1 may be configured to
selectively couple to light propagating within the waveguide 160-1
at one of the channel wavelengths .lamda..sub.1-.lamda..sub.M.
Thus, e.g. the ring resonator 170-11 may be coupled to light
propagating at the ring resonator 170-21 may be coupled to light
propagating at .lamda..sub.2, and so on. Similarly, a ring
resonator 170-12 may be coupled to light propagating at
.lamda..sub.1 within the waveguide 160-2, a ring resonator 170-22
may be coupled to light propagating at .lamda..sub.2 within the
waveguide 160-2, and so on.
[0043] A receiver controller 175 controls the resonant frequency of
each of the ring resonators 170. The controller 175 may configure
each of the ring resonators 170 to have a nominal resonant
frequency corresponding to any one of the channel wavelengths
.lamda..sub.1, .lamda..sub.2, .lamda..sub.3, and .lamda..sub.4.
That is, the resonant frequency of each of the N ring resonators
170-1Q, . . . , 170-NQ of ring resonator set 165-Q may be set to
couple to a selected one of the N channel wavelengths, thereby
selectively coupling one of N wavelength components in the optical
waveguide 160 to that ring resonator 170. Typically, within a
wavelength set 165, each of the channel wavelengths .lamda..sub.1,
.lamda..sub.2, .lamda..sub.3, and .lamda..sub.4 is assigned to only
one ring resonator of a ring resonator set 165-Q.
[0044] Each of the ring resonators 170 is paired with an
optical-to-electrical transducer 300, referred to herein as a
domain converter 300. FIG. 3 illustrates a detail view of a
representative domain converter 300. Each domain converter 300
includes a waveguide section 310 and a photodiode 320. The
waveguide section 310 is located proximate the associated ring
resonator 170 such that light is coupled from the ring resonator
170 to the waveguide section 310. The photodiode 320 converts the
coupled optical signal to a corresponding electrical signal for
further processing, e.g. demodulation of the received data stream.
Each of the domain converters 300 may be identified by the same
suffix as its associated ring resonator 170. Thus, e.g. a domain
converter 300-11 is associated with the ring resonator 170-11, a
domain converter 300-21 is associated with the ring resonator
170-21, etc.
[0045] Returning to FIG. 1, the controllers 135 and 175 act in a
coordinated manner to transmit data from a selected one of the NM
ring resonators 130 to a selected one of the MN ring resonators
170. For example, if it is desired to transmit the data stream
received by the ring resonator 130-21 to the ring resonator 170-22,
the controller 135 may configure the ring resonator 130-21 to
couple to the channel wavelength .lamda..sub.2, thereby modulating
the .lamda..sub.2 carrier with a data stream. The wavelength
demultiplexer 145 routes the .lamda..sub.2 carrier to the output
155-2 (see FIG. 4A). The receiver controller 175 configures the
ring resonator 170-22 to also couple to the channel wavelength
.lamda..sub.2. Then, the transducer 300-22 converts the optical
signal to the electrical domain for processing. It will be apparent
to those skilled in the art that the described principle may be
used to transmit data received by any of the ring resonators 130 to
any desired instance of the transducer 300 thereby implementing a
general M.times.N opto-electrical switching network.
[0046] FIG. 1A schematically illustrates how the optical network
100 may optically provide data connections between N electrical
devices 800-1, . . . , 800-N and M electrical devices 900-1, . . .
, 900-M. Each electrical device 800-R is connected to electrically
transmit M data streams to a corresponding M ring resonator set
125-R. Each electrical device 900-S is connected to electrically
monitor N data streams from a corresponding N ring resonator set
165-S. For that reason, any individual electrical device 800-R is
able to communicate a digital data stream to any individual
electrical device 900-S via the optical network 100. That is, the N
electrical devices 800-1 to 800-N may independently communicate, in
parallel, with the M electrical devices 900-1 to 900-M via the
optical network 100. As an example, the electrical devices 800-1 to
800-N may be N digital data processors of a data center, and the
electrical devices 900-1 to 900-M may be M digital data storage
devices of the data center. Then, the optical network 100 enables
each of the N digital data processors to selectively route a
separate digital data stream to each of the M digital data storage
devices.
[0047] In other embodiments, the optical network 100 may provide
such parallel digital data connections between a first set of N
data devices and a second set of M data devices. In the first set,
the N individual devices may include various types of conventional
devices that output digital data streams. In the second set, the M
individual devices may include various types of conventional
devices that input digital data streams.
[0048] The above embodiments have been described with each of the
ring resonators 130 being configured to couple to one of the same
set of channel wavelengths, e.g. .lamda..sub.1, .lamda..sub.2,
.lamda..sub.3, and .lamda..sub.4. In such embodiments it may be
preferable that the wavelength demultiplexer 145 provide cyclic
permutations of the input channel wavelengths to the outputs, as
previously described in various embodiments. In some other
embodiments, the set of wavelengths at which each ring resonator
set 125 couples to optical carriers is not constrained to be the
same as the set of wavelengths at which the others of the ring
resonator sets 125. In such cases, the wavelength demultiplexer 145
need not provide cyclic permutations of the input wavelength
channels at its outputs. In particular, some such embodiments may
select the wavelengths such that no two channels with a same
wavelength ever simultaneously propagate on a same waveguide.
[0049] In embodiments in which the controllers 135 and 175 are
collocated, coordination of the operation of the controllers may be
easily accomplished using a data path 180 to communicate, e.g.
timing information and/or data conveying the data channels selected
for communications. In embodiments in which the controllers 135 and
175 are physically remote, such as for long-haul communications,
the data path 180 may communicate a selected data channel and/or
channel scheduling data to coordinate operation of the controllers
135 and 175.
[0050] The optical components of the system 100 may be formed
conventionally, e.g. as planar structures formed over a silicon
substrate, e.g. a silicon wafer. A convenient platform on which to
form the system 100 is a silicon-on-insulator (SOI) wafer, but
embodiments of the invention are not limited thereto. For example,
a dielectric layer, e.g. plasma oxide, could be formed on any
suitable substrate, and a silicon layer could be formed thereover
by any suitable method. Other embodiments may use a substrate
formed from, e.g. glass, sapphire or a compound semiconductor.
Those skilled in the pertinent art are familiar with such
fabrication techniques.
[0051] In some embodiments optical and electrical components of the
system 100 are formed on a same substrate. In such a system, e.g.
silicon-based electronic components may be formed on one region of
a photonic integrated circuit (PIC), and optical components may be
formed on another region of the PIC. Interconnects may provide
conductive paths from the domain converters 300 to the control
stage 110.
[0052] In other embodiments, such as represented by FIGS. 5A-5C,
portions of an opto-electronic system may be formed on separate
substrates. FIG. 5A illustrates one such system 500, formed
according to one embodiment. Electrical components are formed on an
electrically active substrate 510, optical components are formed on
an optical substrate 520, and interconnects are formed on an
interconnect substrate 530. The substrates 510, 520 and 530 are
then face-joined to form the operable system 500.
[0053] The electronic substrate 510 may include electronic
components such as transistors, diodes, resistors and capacitors to
implement electrical functions of the system 100. Such functions
may include, but are not limited to, the functions of the
controllers 135 and 175, including switching, signal conditioning
and amplification. The electronic substrate 510 may include a base
layer 540, e.g. a silicon wafer, and active layers 550 that include
electronic devices and interconnects. The substrate 510 may be
formed from any conventional and/or future-discovered processes,
and is not limited to any particular material types. By way of
example, without limitation, such materials may include silicon,
silica, SiN, InP, GaAs, copper interconnects, aluminum
interconnects, and/or various barrier materials.
[0054] The optical substrate 520 may include optical components of
the transmit stage 105, the switching stage 110, and the receiver
stage 115. Such components include, e.g. grating couplers, AWGs,
optical waveguides, microcavity resonators, optical power
splitters, optical power combiners, and photodiodes. The optical
waveguides may be formed from planar or ridge structures by
conventional and/or novel processes. Such components typically
include an optical core region and an optical cladding region. The
core regions may be formed from any conventional or nonconventional
optical material system, e.g. silica, silicon, LiNbO.sub.3, a
compound semiconductor alloys such as GaAlAs, GaAlN or InP, or an
electro-optic polymer. Some embodiments described herein are
implemented in Si as a nonlimiting example. While embodiments
within the scope of the invention are not limited to Si, this
material provides some benefits relative to other material systems,
e.g. relatively low cost and well-developed manufacturing
infrastructure. The cladding region may include homogenous or
heterogeneous dielectric materials, e.g. silica or benzocyclobutene
(BCB). Some portions of the cladding region may include air, which
for the purposes of this discussion includes vacuum.
[0055] The interconnect substrate 530 includes additional
interconnect structures that may configure operation of the system
500. The interconnect substrate 530 may include any dielectric and
conductive (e.g. metallic) materials needed to implement the
desired connectivity. In some cases, formation of the substrate 530
may include the use of a handle wafer to provide mechanical
support, after which the substrate 530 is removed from the
handle.
[0056] The electronic substrate 510 may be joined to the
interconnect substrate 530 by, e.g. a bump process or, as
illustrated, a wafer bonding process. Such processes are well known
to those skilled in semiconductor manufacturing, and may include,
e.g. chemical mechanical polishing (CMP) to prepare the substrate
surfaces for bonding. The interconnect substrate 530 may be joined
to the optical substrate 520 by, e.g. a bump process as illustrated
in FIG. 5A, or a wafer bonding process as illustrated in FIG. 5B.
In the bump process, solder balls 560 join interconnect structures
in the substrate 530 to metalized via structures 570 in the optical
substrate 520. The via structures 570 may provide electrical and/or
mechanical connectivity between substrates 520 and 530.
[0057] FIG. 5C illustrates another embodiment of the system 100 in
which the interconnections and optical functions are combined into
an integrated substrate 580. In the illustrated embodiment the
substrate 580 includes the optical substrate 520 and interconnect
layers 530a and 530b formed on either side of the optical substrate
520. The integrated substrate 580 may then be joined to the
substrate 510 by, e.g. wafer bonding.
[0058] The separate formation of the electronic substrate 510, the
interconnect substrate 530 and the optical substrate 520 may serve
at least one of several purposes. First, the thermal budget
required to form some features, e.g. high quality waveguides in the
optical substrate 520, may be incompatible with other features,
such as doping profiles of transistors in the electrically active
substrate 510. Second, the substrates 510, 520 and 530 may be
formed separately by entities with specialized skills and/or
fabrication facilities and joined by another entity. Third, where
security is desired regarding the function of the assembled system
500, the fabrication operations may be assigned to the various
entities such that no one entity acquires sufficient knowledge to
determine the specific functionality of the device. The final
assembly may then be completed under secure conditions to ensure
confidentiality of the operation of the assembled system 500.
[0059] Turning to FIG. 6, a method 600 is provided for, e.g.
forming the system 100 according to various embodiments. The steps
of the method 600 are described without limitation by reference to
elements previously described herein, e.g. in FIGS. 1-5. The steps
of the method 600 may be performed in another order than the
illustrated order, and in some embodiments may be omitted
altogether and/or performed concurrently or in parallel groups.
This method 600 is illustrated without limitation with the steps
thereof being performed in serial fashion, such as by separate
processing on different substrates. Other embodiments, e.g. those
utilizing a common multiple substrate, may perform the steps
partially or completely in parallel, and in any order.
[0060] In a step 610, an input waveguide, e.g. the waveguide 120-1,
is formed and optically connected to a wavelength demultiplexer,
e.g. the wavelength demultiplexer 145. In a step 620 microcavity
resonators of a first input set of microcavity resonators are
formed. These resonators are located adjacent the input waveguide
such that each microcavity resonator is configured to controllably
couple to a corresponding one of a plurality of frequency channels
propagating within the input waveguide.
[0061] Some embodiments of the method 600 include a step 630, in
which a plurality of output waveguides is formed. Each waveguide is
optically connected to the wavelength demultiplexer. The wavelength
demultiplexer is configured to route each carrier signal to a
corresponding one of the output waveguides.
[0062] Some such embodiments include a step 640, in which a
plurality of output microcavity resonator sets is formed. Each
resonator set includes a corresponding plurality of microcavity
resonators. Each microcavity resonator of each output set is
located adjacent a same corresponding one of the output waveguides
such that the microcavity resonators of each set may controllably
couple to a corresponding different wavelength channel propagating
within the corresponding output waveguide.
[0063] FIG. 7 presents a method 700, e.g. of forming the system
100. The steps of the method 700 are described without limitation
by reference to elements previously described herein, e.g. in FIGS.
1-5. The steps of the method 700 may be performed in another order
than the illustrated order, and in some embodiments may be omitted
altogether and/or performed in parallel or in parallel groups.
Herein and in the claims, "provided" or "providing" means that a
device, substrate, structural element, etc., may be manufactured by
the individual or business entity performing the disclosed method,
or obtained thereby from a source other than the individual or
entity, including another individual or business entity.
[0064] The method includes a step 710, in which a first substrate
is provided. The substrate has an input waveguide optically
connected to a wavelength demultiplexer. A first input microcavity
resonator set including a plurality of microcavity resonators is
located adjacent the input waveguide.
[0065] In a step 720 a second substrate is provided. The second
substrate has an electronic controller formed thereover. The
controller is configured to control the microcavity resonators to
controllably couple each to a corresponding one of a plurality of
frequency channels of an optical signal propagating within the
input waveguide.
[0066] In a step 730 the first and second substrates are joined,
thereby connecting the controller to the microcavity
resonators.
[0067] Those skilled in the art to which this application relates
will appreciate that other and further additions, deletions,
substitutions and modifications may be made to the described
embodiments.
* * * * *