AU2015100697A4 - Large scale cross-connect - Google Patents

Description

1 LARGE SCALE CROSS-CONNECT FIELD OF THE INVENTION [0001] The present invention relates to optical switches and in particular to a large scale optical cross connect switch. While some embodiments will be described herein with particular reference to that application, it will be appreciated that the invention is not limited to such a field of use, and is applicable in broader contexts. BACKGROUND [0002] Any discussion of the background art throughout the specification should in no way be considered as an admission that such art is widely known or forms part of common general knowledge in the field. [0003] With the continued growth of information technology such as video-on-demand, mobile data and cloud computing, data traffic is increasing rapidly. To leverage the high data rates achievable using optical wavelengths, modern telecommunications systems are transitioning towards the optical domain. Current systems typically include a hybrid of electronic and optical switching components and data bottlenecks occur where optical to electronic conversion of data (or vice versa) is required. All optical switches are currently being developed but current designs generally have limitations in terms of providing scalability and reconfigurability. A primary application where all optical switches is within datacenters where bulk data storage and transmission occurs. [0004] Large scale switching between optical fibers within an optical network or datacenter is typically performed by optical cross connect switches. PCT Patent Application Publication WO 2005/125264 entitled "Method and system for a distributed wavelength (Lambda) routed (DLR) network' to Intune Networks Limited relates to an optical fiber routed ring network having a scheduler for controlling the access to each node to avoid wavelength contention. [0005] To address wavelength contentions in optical networks, optical burst switching has been proposed. This technique involves the time separated transmission of scheduled wavelength channels across the network using an electronic controller. The time separated channel segments are referred to as 'packets' and these packets are transmitted as 'bursts' over a switching network in a time-division manner. European Patent 1 473 962 entitled "System and method for WDM communication with interleaving of optical signals for efficient wavelength utilization" to Lucent Technologies Inc., relates to 2 an optical ring network incorporating wavelength selective switches configured to provide burst switching of wavelength channels based on a predetermined schedule. US Patent Application Publication 2004/0202472 entitled "Optical WDM-TDM network' assigned to Lucent Technologies Inc., relates to specific scheduling techniques for the types of networks described in EP 1 473 962. In the WDM- TDM ring, a specific wavelength channel or set of channels is assigned to each destination node. Origin nodes transmit intermittently through, for example, tunable lasers to each of various destination nodes. Each transmission to a given destination node is made in one assigned wavelength channel regardless of the node at which the transmission originated. [0006] Each of the systems described in US 2004/0202472, WO 2005/125264 and EP 1 473 962 have preconfigured nodes with unique wavelength associations and switching is performed by tuning to the node wavelength. As such, these systems are not directionless and lack scalability and flexibility to route any wavelength to any node. Accordingly, they are generally not suited for general switching applications in datacenters, which do not generally have ring architectures. SUMMARY OF THE INVENTION [0007] It is an object of the invention, in its preferred form to provide an improved or alternative optical cross connect which is able to address any wavelength from any input port to any output port. [0008] In accordance with a first aspect of the present invention there is provided a reconfigurable optical cross connect including: a series of input ports, each input port configured to project input optical signals at one or more wavelengths; a series of output ports configured to receive switched optical signals; an input multiplexing module to combine the optical signals into one or more first combined optical beams; a reconfigurable switching module including: one or more passive demultiplexing elements, each configured to divide a corresponding first combined beam into a plurality of second combined beams; a plurality of demultiplexing wavelength selective switches (WSS) to divide the optical signals from the second combined beams and dynamically route the optical signals along respective switching trajectories, each of the first 3 WSS including M inputs and N outputs and M and N are both greater than 1; and a plurality of output passive demultiplexing elements to couple the switched optical signals to corresponding output ports. [0009] In one embodiment, the input multiplexing module includes a plurality of passive optical combiners. [0010] In one embodiment, the outputs of the passive optical combiners are the first combined beams. The input multiplexing module preferably includes at least one multiplexing WSS, wherein the outputs of the passive optical combiners are the inputs to the at least one multiplexing WSS and the outputs of the at least one multiplexing WSS are the first combined beams. The combined beams are preferably input to respective input passive demultiplexing elements. [0011] In one embodiment, N is greater than M. Each input passive demultiplexing element preferably includes a number of outputs equal to M. [0012] In one embodiment, the input passive demultiplexing elements are input array waveguide gratings (AWGs) having a single input and multiple waveguide outputs. The input AWGs are preferably cyclic so as to output consecutive optical signals through respective outputs cyclically. Each input AWG preferably includes M waveguide outputs and wherein respective waveguide outputs from each input AWG are coupled to a corresponding demultiplexing WSS input. [0013] In one embodiment, the output passive demultiplexing elements are output array waveguide gratings (AWGs). The output AWGs are preferably cyclic so as to output consecutive wavelengths through respective outputs cyclically. Preferably an output AWG is included for each WSS output for each demultiplexing WSS. [0014] In one embodiment, the input passive demultiplexing elements include one or more optical interleavers. [0015] In one embodiment, each demultiplexing WSS includes a liquid crystal on silicon (LCOS) optical phase modulator. Switching in LCOS regions preferably reconfigures the wavelength routing in the cross connect. [0016] In one embodiment, ach demultiplexing WSS includes a micro electromechanical mirror (MEMS) optical phase modulator. [0017] In one embodiment, the number of input ports is equal to the number of output ports.

4 [0018] In accordance with a first aspect of the present invention there is provided an optical system including: a plurality of tunable laser sources, each to transmit an optical signal at a tunable output wavelength over a predetermined time period; a plurality of optical receivers, each to receive the optical signals; a reconfigurable optical cross connect according to claim 1 the tunable laser sources are coupled to respective input ports and the optical receivers are coupled to respective output ports; and a system controller configured to: dynamically tune the output wavelengths of the respective laser sources in a time division manner; and selectively control the switching performed by the respective first WSS to dynamically route the optical signals between predetermined laser sources and optical receivers. BRIEF DESCRIPTION OF THE DRAWINGS [0019] Preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: FIG. 1 is a schematic illustration of an optical cross connect for switching optical channels between 320 input ports and 320 output ports; FIG. 2 is a schematic illustration of an alternate input multiplexing module for an optical cross connect; FIG. 3 is a schematic illustration of an exemplary 1 -by-4 cyclic arrayed waveguide grating, showing exemplary input and output wavelength channels; FIG. 4 is a front view of a liquid crystal on silicon device illustrating the distribution of elongated optical channels into four rows corresponding to four input ports; FIG. 5 is a schematic illustration of an alternative reconfigurable switching module for an optical cross connect; FIG. 6 an expanded view of a subset of the deinterleavers of FIG. 5; and 5 FIG. 7 is a schematic illustration of an optical system utilizing the optical cross connect of FIG. 1. DETAILED DESCRIPTION [0020] Referring to Fig. 1 there is provided a reconfigurable optical cross connect 1 for switching optical signals in the form of optical beams between 320 input ports 3 and 320 output ports 5. Although embodiments described herein relate to a 320-by-320 (320x320) optical cross connect, it will be appreciated by those skilled in the relevant art that the cross connect can be scaled up or down to include more or less input and output ports by appropriate addition or removal of passive and active switching elements or replacement with higher or lower capacity switching elements. Generally, the fundamental limits of the cross connect are the channel limits of each wavelength selective switch (WSS) and the overall optical loss imposed by the cross connect. [0021] Each of the input 3 and output ports 5 are adapted to be optically coupled to corresponding optical fibers (not shown) for guiding the optical signals through a datacenter or other optical system. By way of example, the optical signals transmitted through input fibers may represent the outputs of a databoard within a datacenter. Upon coupling to respective optical fibers, input ports 3 project an input optical signal at a particular wavelength channel into the cross connect 1. A wavelength channel is an optical signal propagating at a predefined wavelength or finite range of wavelengths. The input optical signals at each input port are defined by respective tunable laser sources (not shown) located elsewhere in the optical system. The output wavelength of each tunable laser source is controlled by a global system controller 7, which tunes the output wavelengths to specific wavelengths at certain times based on the desired output port to transmit data and the current system traffic. [0022] Cross connect 1 can be generally broken down into three main components; an input multiplexing module 9, a reconfigurable switching module 11 and output passive demultiplexing elements in the form of output cyclic AWGs 13. [0023] Input multiplexing module 9 combines the input optical signals into four first combined optical beams 15-18. These combined beams include a number of wavelengths multiplexed together in the wavelength domain. Different forms of input multiplexing module 9 can be realized, as described below. [0024] As shown in Fig. 1, input multiplexing module 9 includes four passive optical combiners 23-26. Combiners can be arrayed waveguide gratings (AWGs) or other passive optical multiplexing elements such as optical interleavers produced by Finisar 6 Corporation. Each combiner includes eighty inputs for receiving eighty individual optical signals from eighty input ports. In other embodiments having greater or fewer input ports, combiners 23-26 have corresponding greater or fewer inputs. Each combiner combines, in the wavelength domain, the respective eighty optical signals into a single first combined beam 15-18. Optical amplifiers 31-34 are incorporated into cross connect 1 to amplify the optical power of the combined beams. In other embodiments, optical amplifiers are incorporated into cross connect 1 at other locations to further amplify the optical power of the optical signals. [0025] Referring now to Fig. 2, there is illustrated a second embodiment of an input multiplexing module 39. In module 39, corresponding features of module 9 of Fig. 1 are designated with the same reference numerals. Module 39 includes eighty 4x1 passive optical combiners 41, each for combining four input optical signals into a single input beam, e.g. 43. Combiners can be AWGs or other passive optical multiplexing elements. The input beams (e.g. 43) are coupled as inputs to four 20x1 multiplexing WSS 45-48. Each multiplexing WSS includes twenty inputs for receiving twenty input beams 43 and combines the beams as a single multiplexed output as the first combined beams 15-18 after amplification by amplifiers 31-34. [0026] Returning to Fig. 1, combined beams 15-18 are passed to reconfigurable switching module 11. Module 11 includes four passive demultiplexing elements in the form of 1x4 cyclic AWGs 53-56. Each AWG 53-56 includes a single input for receiving a corresponding first combined beam 15-18. The AWGs are each configured to divide the first combined beams into four second combined beams, e.g. 61, making a combined total of sixteen second combined beams. [0027] Input AWGs 53-56 are cyclic such that consecutive wavelengths within a first combined beam are coupled out of consecutive outputs in a cyclic fashion. This is achieved by making the phase delay of each waveguide within each input AWG equal to the spectral spacing of the optical signals in the first combined beams. In typical optical systems, wavelength channels are spaced apart in frequency by 25 GHz, 50 GHz, 100 GHz or 200 GHz. Each fifth consecutive wavelength channel is coupled into the first port. To illustrate this, reference is made to Fig. 3, wherein an exemplary first combined beam 62 including wavelength channels A,A 2

,A

3 , ---,A, is passed through input AWG 63. At the output of AWG 63, the optical signals are cyclically distributed across the four outputs. [0028] In other embodiments, other types of passive optical combiners are used in place of input AWGs X and the optical signals are distributed in a banded fashion. For 7 example, a first output of the combiner may output wavelength channels A 1 to A 2 0 , and the second, third and fourth combiner outputs respectively output wavelength channels A 21 to

A

40 , A 41 to A 6 o and A 61 to A 8 0 . [0029] Returning to Fig. 1, the second combined beams are coupled to respective inputs of four demultiplexing WSS 57-60. Each demultiplexing WSS includes four multi wavelength WSS inputs for receiving the second combined beams 15-18. As shown in Fig. 1, one second combined beam from each of the four AWGs 53-56 is input to each demultiplexing WSS 57-60. The cyclic distribution of optical signals by AWGs 53-56 ensures that no single wavelength channel is present at more than one port of each demultiplexing WSS 57-60. This aids in reducing wavelength contention in the cross connect. Each demultiplexing WSS includes sixteen single-wavelength WSS outputs for outputting the individual optical signals along respective switching trajectories, e.g. 67. In general, the number of single-wavelength WSS outputs is greater than the number of multi-wavelength WSS inputs. A requirement of cross connect 1 is that each input AWG 53-56 include a number of outputs equal to the number of multi-wavelength WSS inputs of each demultiplexing WSS 57-60. [0030] Each demultiplexing WSS 57-60 includes a dispersive element (not shown) such as a diffraction grating or prism for spatially dispersing the various optical signals and a reconfigurable optical phase modulator for dynamically switching the optical signals to predetermined outputs. Referring to Fig. 4, there is illustrated schematically a liquid crystal on silicon (LCOS) device 69 as an example of an optical phase modulator. Device 69 includes a two dimensional array of liquid crystal cells 71 mounted onto a reflective silicon substrate 73. Each cell is individually electronically drivable at one of a plurality of voltages to dynamically control the local phase of optical signals incident thereon. The general switching operation of device 69 occurs in a manner known in the art such as that described in US Patent 7,092,599 to Frisken entitled "Wavelength manipulation system and method'. Equivalently, an optical phase modulator can be constructed using a transmissive liquid crystal display or a two dimensional array of individually controllable micro-electromechanical mirror (MEMS). In a MEMS-based optical phase modulator, the optical signals are directionally switched by establishing a steering phase function using a combination of mirror angles. [0031] The cell region of LCOS device 69 is divided into four rectangular regions 75-78 extending longitudinally in a dispersion dimension. Each region 75-78 is located so as to receive spatially dispersed optical signals from a corresponding one of the four WSS inputs. The dispersive element (not shown) spatially disperses the optical signals 8 according to wavelength along each region 75-78, as shown in Fig. 4. The cyclic nature of the input AWGs causes respective wavelengths to fall within separate regions 75-78. In other embodiments having different input/output configurations, LCOS 69 has different numbers of inputs and outputs and can be divided into different arrangements of regions 75-78. [0032] Switching of the wavelengths occurs in the dimension perpendicular to the dispersion dimension and is controlled by varying the voltage applied to each liquid crystal cell. Control of LCOS device 69 is performed by global controller 7. In combination with the control of the input wavelengths, controller 7 is capable of routing an optical signal from any input port to any output port in cross connect 1. Controller 7 is also capable of providing other functionality in relation to time division burst control of optical signals through cross connect 1. This is described below. [0033] Controller 7 sets predefined switching states for switching optical signals between a predetermined WSS input to a predetermined WSS output. Reconfiguration of the switching states in regions 75-78 acts to reconfigure the routing of optical signals in cross connect 1. In cross connect 1, 80 channels are input to each demultiplexing WSS 57-60 through the four WSS inputs. Each demultiplexing WSS 57-60 switches these 80 channels to any one of the 16 outputs. [0034] Each demultiplexing WSS 57-60 is configured to dynamically route the optical signals through corresponding WSS outputs along respective switching trajectories, e.g. 67. The trajectories from each WSS output of each WSS lead to one of sixty four 1x5 output cyclic AWGs 13. Output AWGs 13 each include five outputs for coupling the switched optical signals to corresponding output ports 5. Like input AWGs 53-56, output AWGs 13 are cyclic in nature so as to output consecutive optical signals through one of five outputs cyclically. The five outputs of each of the sixty four output AWGs 13 are all connected to different ones of the 320 output ports 5. The dashed and bold lines in Fig. 1 illustrate exemplary switching paths of two optical signals through cross connect 1. [0035] In cross connect 1, the number of demultiplexing WSS 57-60 is equal to the number of outputs of each input AWG 53-56. Similarly, the number of output AWGs is equal to the total number of outputs from all of the demultiplexing WSS 57-60. The required number of demultiplexing WSS 47-60 and the configurations of the elements depends on the requirements of cross connect 1 in the context of the surrounding datacenter or optical network. Taking into account practical losses, most current commercially available WSS devices are capable of dynamically switching about 100 optical channels simultaneously at a channel spacing of 50 GHz. Accordingly, the capacity 9 of a system of four WSS devices operating in parallel (such as in cross connect 1) is about 400 channels. Cross connect 1 only switches 320 channels so as to provide switching redundancy of 80 channels across the four demultiplexing WSS 57-60 to address potential wavelength contention, as described below. [0036] Referring now to Fig. 5, there is illustrated an alternative embodiment switching module 85. Module 85 includes twelve optical deinterleavers 87-98 divided into four groups of three, with each group corresponding to a first combined beam. Deinterleavers 87-98 replace the four input AWGs 53-56 in cross connect 1 of Fig. 1. Optical deinterleavers are the reverse of an optical interleaver (or simply an interleaver operating in reverse), which is a passive device for combining two sets of multiplexed wavelengths. Optical deinterleavers receive a single set of input multiplexed wavelengths and divide the input wavelengths into two sets of output wavelengths in an odd/even basis. The output wavelengths have a spectral spacing that is twice that of the spectral spacing of the input wavelengths. Exemplary suitable optical interleavers include 50 GHz interleavers sold by Finisar Corporation. [0037] Referring to Fig. 6, there is illustrated an expanded view of combined beam 15 and deinterleavers 87-89. Deinterleaver 87 divides the wavelength set contained in combined beam 15 into two output beams 99 and 101 having respective wavelength sets with a spacing of twice that of combined beam 15. Each output beam 99 and 101 is input to corresponding deinterleavers 88 and 89, which simultaneously divide beams 99 and 101 into the second combined beams 103-106. Deinterleavers 90-98 operate in the same way as described here. Module 85 operates in a substantially similar manner to module 11 of Fig. 1. [0038] Referring to Fig. 7, there is illustrated schematically an optical system 107 incorporating cross connect 1. System 107 includes 320 transmitters Tx (only three are shown for simplicity), each including a respective tunable laser source 109-111. Each source is electrically controlled by global controller 7 to transmit an optical signal at a tunable output wavelength over a predetermined time period. Transmitters Tx are coupled to respective input ports 3 of cross connect 1, which dynamically routes the optical signals to output ports 5. 320 optical receivers Rx (only three are shown for simplicity) are coupled to respective output ports 5 and are configured to receive one or more routed optical signals. Controller 7 selectively controls the switching performed by the respective first WSS to dynamically route the optical signals between predetermined transmitters Tx and receivers Rx.

10 [0039] In operation, controller 7 controls the routing of the optical signals between transmitters TX and receivers Rx. After receiving a network request to transmit data between two locations in the datacenter, controller 7 determines a suitable wavelength and switching path to route the data from the transmitter of the origin to the receiver of the destination such that no contention with other optical signals at the same wavelength occur. [0040] By dynamically tuning the output wavelengths of the respective laser sources in a time division manner, contentions between signals of the same wavelength can be significantly reduced or avoided completely. To further reduce wavelength contention, in the input multiplexing module 9, optical signals having the same wavelength are restricted from entering input ports of the same combiner 23-26 at the same time. This restriction is provided by global controller 7, which either: 1. Routes the optical signals having like wavelengths to ports of different combiners 23-26; 2. Tunes one of the optical signals to a different wavelength; or 3. Separates out the transmissions of the like channels in time through burst transmission control. [0041] The number of channels that can be routed using the cross connect is determined by the capacity of each WSS. Some redundancy is required if wavelength contention is to be addressed. As mentioned above, a typical LCOS based WSS generally has capacity for switching about 100 channels at a standard 50 GHz spacing. However, in cross connect 1, each demultiplexing WSS 57-60 is only required to simultaneously route 80 optical signals. Therefore, there is redundancy for 20 additional optical signals in each demultiplexing WSS 57-60. This redundancy can be utilized by controller 7 by tuning one transmitter to output an optical signal at a different wavelength corresponding to a free wavelength channel. [0042] To determine an appropriate transmission wavelength, in some embodiments, global controller 7 accesses a look up table of preferred wavelengths to transmit for the various transmitters. For example, one exemplary transmitter may have three preferred output wavelengths (A 1 , A 2 and A 3 ) with an order of preference. If a potential wavelength contention is detected using A 1 , controller 7 sets the output wavelength to A 2 or A 3 . In some embodiments, controller 7 also operates as a scheduler wherein, if the switching paths within cross connect 1 are busy or contentions may occur, certain data transfers are scheduled for another less contentious time.

11 CONCLUSIONS [0043] It will be appreciated that the disclosure above provides various significant embodiments of an optical cross connect which is able to address any wavelength from any input port to any output port. [0044] The cyclic distribution of optical signals using cyclic AWGs ensures that no single wavelength channel is present at more than one port of each demultiplexing WSS 57-60. This aids in reducing wavelength contention in the cross connect. A redundancy in available wavelength channels provides further wavelength contention avoidance. [0045] The ability to control both the transmitted wavelength and the switching path by the demultiplexing WSS provides complete reconfigurability in the cross connect. INTERPRETATION [0046] Throughout this specification, use of the term "element" is intended to mean either a single unitary component or a collection of components that combine to perform a specific function or purpose. [0047] Throughout this specification, use of the term "orthogonal" is used to refer to a 900 difference in orientation when expressed in a Jones vector format or in a Cartesian coordinate system. Similarly, reference to a 900 rotation is interpreted to mean a rotation into an orthogonal state. [0048] Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as "processing," "computing," "calculating," "determining", analyzing" or the like, refer to the action and/or processes of a computer or computing system, or similar electronic computing device, that manipulate and/or transform data represented as physical, such as electronic, quantities into other data similarly represented as physical quantities. [0049] In a similar manner, the term "processor" may refer to any device or portion of a device that processes electronic data, e.g., from registers and/or memory to transform that electronic data into other electronic data that, e.g., may be stored in registers and/or memory. A "computer" or a "computing machine" or a "computing platform" may include one or more processors. [0050] Reference throughout this specification to "one embodiment", "some embodiments" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one 12 embodiment of the present disclosure. Thus, appearances of the phrases "in one embodiment", "in some embodiments" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments. [0051] As used herein, unless otherwise specified the use of the ordinal adjectives "first", "second", "third", etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. [0052] In the claims below and the description herein, any one of the terms comprising, comprised of or which comprises is an open term that means including at least the elements/features that follow, but not excluding others. Thus, the term comprising, when used in the claims, should not be interpreted as being limitative to the means or elements or steps listed thereafter. For example, the scope of the expression a device comprising A and B should not be limited to devices consisting only of elements A and B. Any one of the terms including or which includes or that includes as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others. Thus, including is synonymous with and means comprising. [0053] It should be appreciated that in the above description of exemplary embodiments of the disclosure, various features of the disclosure are sometimes grouped together in a single embodiment, Fig., or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claims require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of this disclosure. [0054] Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the disclosure, and form different embodiments, as would be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

13 [0055] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the disclosure may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. [0056] Similarly, it is to be noticed that the term coupled, when used in the claims, should not be interpreted as being limited to direct connections only. The terms "coupled" and "connected," along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Thus, the scope of the expression a device A coupled to a device B should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. "Coupled" may mean that two or more elements are either in direct physical, electrical or optical contact, or that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other. [0057] Thus, while there has been described what are believed to be the preferred embodiments of the disclosure, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the disclosure, and it is intended to claim all such changes and modifications as fall within the scope of the disclosure. For example, any formulas given above are merely representative of procedures that may be used. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present disclosure.

Claims (19)

1. A reconfigurable optical cross connect including: a series of input ports, each input port configured to project input optical signals at one or more wavelengths; a series of output ports configured to receive switched optical signals; an input multiplexing module to combine the optical signals into one or more first combined optical beams; a reconfigurable switching module including: one or more passive demultiplexing elements, each configured to divide a corresponding first combined beam into a plurality of second combined beams; a plurality of demultiplexing wavelength selective switches (WSS) to divide the optical signals from the second combined beams and dynamically route the optical signals along respective switching trajectories, each of the first WSS including M inputs and N outputs and M and N are both greater than 1; and a plurality of output passive demultiplexing elements to couple the switched optical signals to corresponding output ports.

2. A reconfigurable optical cross connect according to claim 1 wherein the input multiplexing module includes a plurality of passive optical combiners.

3. A reconfigurable optical cross connect according to claim 2 wherein the outputs of the passive optical combiners are the first combined beams.

4. A reconfigurable optical cross connect according to claim 2 wherein the input multiplexing module includes at least one multiplexing WSS, wherein the outputs of the passive optical combiners are the inputs to the at least one multiplexing WSS and the outputs of the at least one multiplexing WSS are the first combined beams.

5. A reconfigurable optical cross connect according to claim 2 wherein the combined beams are input to respective input passive demultiplexing elements.

6. A reconfigurable optical cross connect according to claim 1 wherein N is greater than M. 15

7. A reconfigurable optical cross connect according to claim 6 wherein each input passive demultiplexing element includes a number of outputs equal to M.

8. A reconfigurable optical cross connect according to claim 1 wherein the input passive demultiplexing elements are input array waveguide gratings (AWGs) having a single input and multiple waveguide outputs.

9. A reconfigurable optical cross connect according to claim 8 wherein the input AWGs are cyclic so as to output consecutive optical signals through respective outputs cyclically.

10. A reconfigurable optical cross connect according to claim 8 wherein each input AWG includes M waveguide outputs and wherein respective waveguide outputs from each input AWG are coupled to a corresponding demultiplexing WSS input.

11. A reconfigurable optical cross connect according to claim 1 wherein the output passive demultiplexing elements are output array waveguide gratings (AWGs).

12. A reconfigurable optical cross connect according to claim 11 wherein the output AWGs are cyclic so as to output consecutive wavelengths through respective outputs cyclically.

13. A reconfigurable optical cross connect according to claim 11 including an output AWG for each WSS output for each demultiplexing WSS.

14. A reconfigurable optical cross connect according to claim 1 wherein the input passive demultiplexing elements include one or more optical interleavers.

15. A reconfigurable optical cross connect according to claim 1 wherein each demultiplexing WSS includes a liquid crystal on silicon (LCOS) optical phase modulator.

16. A reconfigurable optical cross connect according to claim 15 wherein switching in LCOS regions reconfigures the wavelength routing in the cross connect.

17. A reconfigurable optical cross connect according to claim 1 wherein each demultiplexing WSS includes a micro-electromechanical mirror (MEMS) optical phase modulator. 16

18. A reconfigurable optical cross connect according to claim 1 wherein the number of input ports is equal to the number of output ports.

19. An optical system including: a plurality of tunable laser sources, each to transmit an optical signal at a tunable output wavelength over a predetermined time period; a plurality of optical receivers, each to receive the optical signals; a reconfigurable optical cross connect according to claim 1 the tunable laser sources are coupled to respective input ports and the optical receivers are coupled to respective output ports; and a system controller configured to: dynamically tune the output wavelengths of the respective laser sources in a time division manner; and selectively control the switching performed by the respective first WSS to dynamically route the optical signals between predetermined laser sources and optical receivers.