Scalable optical circuit switch structure

Abstract

To provide a non-blocking scalable OXC switch architecture that allows the number of ports to be extended.SOLUTION: There are provided a method and apparatus for optical cross-connection for reflectively coupling at least a first inter-module optical signal from at least one input optical fiber port of a source OCS module to an output optical port of a destination OCS module. The coupling includes steering the inter-module optical signal to an intermediate optical reflector of the source OCS module, using the intermediate optical reflector to steer the optical signal out of the source OCS module to the destination OCS module, and steering the optical signal to an output optical fiber port within the destination OCS module.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an optical circuit switch.

Background Art

[0002] In an optical fiber network, data encoded with modulated optical pulses is transmitted between nodes on an optical fiber cable. This technology has become important for various types and sizes of telecommunications networks because of its extremely high ability to transmit information. One important feature in the operation of an optical fiber network is the high-speed switching of connections between nodes. All-optical switching is one of several possible approaches to network switching. The advantages of all-optical switching include high bandwidth and transparency to network protocols. An all-optical switch can also be non-blocking.

[0003] An optical cross-connect (OXC) is a device that can implement all-optical switching between different optical fibers in an optical network. An OXC can include optical interfaces for individual optical fibers or pairs of optical fibers that carry incident or outgoing optical signals. Within an OXC, each connection is achieved by controllably establishing an optical path between an input optical fiber and an output optical fiber. These optical paths can be reconfigured at high speed, for example, by using a MEMS mirror or an LCOS array under appropriate digital control.

[0004] In particular, the recent increase in the scale of core optical networks has begun to challenge the capacity of existing infrastructure. As a result, there has been interest in increasing the number of ports of switching devices such as OXCs as network requirements increase.

Summary of the Invention

[0005] Various embodiments provide a non-blocking scalable OXC switch architecture that enables expansion of the port count by adding optical circuit switch (OCS) modules to an OXC node. Each OCS module can operate independently to establish a connection between its own input and output. The modularity of these embodiments provides the further advantage of creating independent failure regions, and as a result, a single point of failure can often be avoided.

[0006] In various implementations, the OCS module includes a modular submatrix switch card. The port count of the OXC switch node to which the OCS module belongs can be expanded by adding the OCS module to the OXC node. Additional OCS modules can be added to the OXC without affecting existing optical paths. Intermediate optical reflectors located within the OCS module can be used to direct incident light toward the input or output steering matrix of the intended module. The intermediate optical reflector may be active or passive. In an embodiment, the optical reflector may be, for example, a mirror.

[0007] Each OCS module has an array of input optical fiber ports and an array of output optical fiber ports. Each OCS module may include imaging optics, an input and output steering matrix or an input / output steering matrix, and an intermediate optical reflector that interfaces with the input and output matrices.

[0008] The intermediate optical reflector can send the input optical beam to a destination OCS module different from the OCS module where the beam first entered. In some cases, the input optical beam can be directly routed to the output optical fiber port of the destination module. In other cases, the beam can be routed to a sub-component within the destination OCS module that acts on the beam before reaching the output optical fiber port. For example, the beam can first be routed to the output steering matrix of the destination OCS module and then the beam can be routed to the output optical fiber port of the destination OCS module. Another example of a sub-component of the destination OCS module that can usefully act on the beam before the beam reaches the output optical fiber port can be an optical element or a mirror set that reduces the incident angle of the beam to the output steering matrix.

[0009] Accordingly, in a first aspect, an electronic device related to an apparatus has, thereon, a plurality of module connectors and a plurality of optical circuit switches (OCS) modules removably and mechanically attached to the electronic device by the module connectors. Each of the OCS modules has a plurality of input optical fiber ports and a plurality of output optical fiber ports.

[0010] Each of the OCS modules has a reconfigurable arrangement of optical reflectors that can selectively optically cross-connect one of the input optical fiber ports of the same OCS module to one of the output optical fiber ports of the same OCS module. Further, a particular one of the OCS modules can be selectively configured to route light received from one of its optical input optical fiber ports, through the arrangement of its optical reflectors, to one or more other ones of the OCS modules.

[0011] In an embodiment, the routing of light from a particular one to other ones of the OCS modules is via one or more free space optical paths coupling the particular one to one or more other ones of the OCS modules.

[0012] In an embodiment, at least one of the OCS modules is configurable to route light from one of its input optical fiber ports to a second OCS module among the OCS modules via a free space optical path that traverses an intervening third OCS module among the OCS modules.

[0013] In an embodiment, the electronic device comprises an electronic controller communicatively coupled to operate a reconfigurable arrangement of optical reflectors of the OCS module.

[0014] In an embodiment, the reconfigurable arrangement of optical reflectors within each OCS module comprises an input optical reflector arranged to receive light from an input optical fiber port, an output optical reflector arranged to transmit light to an output optical fiber port, and an intermediate optical reflector array comprising intermediate reflectors capable of reflectively coupling the input optical reflector to the output optical reflector.

[0015] In an embodiment, the input optical reflector is configurable to selectively direct light to one or more other ones of the OCS modules via the intermediate optical reflector array. In some embodiments, the intermediate optical reflector array comprises configurable reflectors configurable to act with the input optical reflector to selectively direct light to one or more other ones of the OCS modules.

[0016] In an embodiment, the electronic device comprises an electronic controller communicatively coupled to operate a reconfigurable arrangement of optical reflectors of the OCS module.

[0017] In an embodiment, the reconfigurable arrangement of optical reflectors within each particular OCS module of the OCS modules is configurable to direct light received from different OCS modules among the OCS modules to one or more of the output optical fiber ports of the particular OCS module among the OCS modules.

[0018] In an embodiment, the input optical reflector and the output optical reflector can be a MEMS mirror array.

[0019] In an embodiment, the intermediate optical reflector array includes an in-module intermediate reflector that can reflectively couple a specific input optical reflector of one of the OCS modules to a specific output optical reflector of one of the OCS modules, and the intermediate optical reflector array further includes at least one inter-module intermediate reflector that can reflectively couple a specific input optical reflector of one of the OCS modules to a different one or a plurality of OCS modules. In some embodiments, each of the inter-module intermediate reflectors can be a static mirror. In other embodiments, each of the inter-module intermediate reflectors can be a reconfigurable mirror.

[0020] In a second aspect, the present disclosure relates to a method including the step of causing a first optical circuit switch (OCS) module to receive an optical signal from a first input optical fiber port of the first OCS module by reconfiguring at least one optical reflector of the first OCS module to reflect the optical signal onto an optical path that terminates at a second OCS module.

[0021] The method further includes causing the received optical signal to be output by the second OCS module by reconfiguring the optical reflector of the second OCS module to direct the received optical signal to an output optical fiber port of the second OCS module, thereby forming an inter-module coupling.

[0022] The method further includes causing an optical signal from a second input optical fiber port of the first OCS module to be output by the first OCS module by reconfiguring at least one optical reflector of the first OCS module, and directing the optical signal from the second input optical fiber port to an output optical fiber port of the first OCS module, thereby performing an intra-module coupling.

[0023] In an embodiment, the optical path terminated by the second OCS module can be a free-space optical path.

[0024] In an embodiment, forming an intra-module coupling includes reconfiguring the input optical reflector of the first OCS module and reconfiguring the output optical reflector. Forming an inter-module coupling includes reconfiguring the input optical reflector of the first OCS module and reconfiguring the output optical reflector of the second OCS module. In each of the OCS modules, the respective input and output optical reflectors are reflection-coupled via an intermediate optical reflector. In an embodiment, forming an inter-module coupling further includes reconfiguring the intermediate optical reflector of the first OCS module.

[0025] In an embodiment, an intra-module coupling and an inter-module coupling are performed simultaneously with a plurality of other intra-module couplings and inter-module couplings. Forming a plurality of simultaneous couplings in such an embodiment includes selecting input and output OCS modules for implementing each coupling from a set of desired couplings, and the selection is made from a plurality of OCS modules including the first and second OCS modules.

[0026] Forming a plurality of simultaneous couplings further includes selecting each input optical fiber port and each output optical fiber port of the OCS modules selected for implementing each desired coupling, obtaining a set of optical reflector configurations for implementing each desired coupling, and reconfiguring at least some of the input and output optical reflectors of the selected input and output OCS modules according to the obtained configurations to form the desired couplings.

[0027] In an embodiment, forming a plurality of simultaneous couplings further includes reconfiguring at least some of the intermediate optical reflectors of the selected input and output OCS modules according to the obtained configurations.

Brief Description of the Drawings

[0028]

Figure 1

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Best Mode for Carrying Out the Invention

[0029] An example of beam steering using a MEMS mirror is provided in R.R yf et al., ″1296-port MEMS transparent Optical crossconnect with 2.07 petabit / s switch capacity″, ″OFC 2001 Optical Fiber Communication Conference and Exhibit Technical Digest Postconference Edition, Anaheim, California, USA (2001) pages PD28-PD28, which is hereinafter cited as ″RYF 2001″ and incorporated herein by reference.

[0030] MEMS-based optical switching is also discussed in the following publications, each of which is incorporated herein by reference in its entirety: J. Leuthold et al., ″nonblocking all-optical crossconnect with all-optical wavelength conversion based on terabit / second and low-power MEMS switch fabric″, OFC2001 Optical Fiber Communication Conference Postconference Edition (Technical Digest. 01CH37171), IEEE Cat, Anaheim, California, USA (2001) page PD16-PD16, R, R, mission apollo: ArXiv, abs / 2208.10041 (2022), hereinafter cited as ″URATA2022″.

[0031] Figure 1 is a schematic diagram of the first optical arrangement described in RYF2001. In the arrangement of Figure 1, the light beam from the input fiber array 001 with lens is guided onto the output fiber array 004 with lens by the MEMS mirror arrays 002 and 003. Figure 2 is a schematic diagram of the second optical arrangement also described in RYF2001. In the arrangement of Figure 2, the fiber array 005 with lens carries both the input optical signal and the output optical signal. The optical output from the fiber array 005 is incident on the MEMS mirror array 006 and is reflected from there onto the retroreflective folding mirror 007. The retroreflective beam from the mirror 007 returns to the MEMS mirror array 006 and is reflected back from there to the fiber array 005. The first part of the MEMS mirrors of the array 006 is assigned to the input optical fiber port and another part is assigned to the output optical fiber port. Thus, a single MEMS mirror array 006 and a single fiber array 005 with lens can implement an optical cross-connect. RYF2001 reported the success of the operation of a 1296-port MEMS transparent optical cross-connect using the optical arrangement of Figure 2.

[0032] In contrast, Figure 3 schematically shows the optical arrangement within an exemplary OCS module that may be useful for practicing the new approach described herein. In the arrangement of Figure 3, the light beam from the input fiber array 011 is guided by the MEMS mirror array 012 onto the optical reflectors of the intermediate optical reflector array 013. After reflection from the optical reflector array 013, the input light beam is incident on the MEMS mirror array 014 and is reflected from there onto the output fiber array 015. Importantly, unlike the prior art represented, for example, by RYF2001, the intermediate optical reflector array 013 includes fixed or variable mirrors or other reflector elements that can relay the incident light beam to optical elements within other OCS modules.

[0033] For the intermediate light reflector array, one possible alternative to the mirror is provided by a liquid crystal on silicon (LOCOS) array. In a LOCOS array, a special hologram can be used to control the directional distribution of the refractive power. A typical LOCOS array has a relatively small angular displacement, but the effective angular range can be extended using imaging optics. Reducing the pixel pitch of the LOCOS array can also increase the angular displacement.

[0034] FIG. 4 is a schematic perspective view of a single exemplary OCS module 100 of a type that may be useful in practicing the techniques described herein. As shown in the figure, the module includes various components mounted on a case or chassis frame 105. Typically, the case 105 is adapted to be inserted into and engaged with a slot of a rack (not shown) having an array of a plurality of slots for receiving and engaging a number of modules similar to the module 100. A typical length of the OCS module 100 can be on the order of several tens of centimeters, measured, for example, from the front wall, i.e., the wall shown in the figure as supporting the input and output optical fiber ports, to the rear wall, i.e., the wall shown in the figure as supporting the steering matrix. As will be appreciated by those skilled in the art, the module may require the overall size to accommodate non-optical constraints such as mechanical and heating requirements.

[0035] Referring further to the figure, it can be seen that the OCS module 100 includes an array 110 of input optical fiber ports 115, an array 120 of output optical fiber ports 125, an input steering matrix 130 of a beam steering element 135, and an output steering matrix 140 of a beam steering element 145. The OCS module further includes imaging optics 150, 155 for conditioning the input and output beams, respectively.

[0036] The embodiments of FIG. 4 and subsequent figures include both an input steering matrix 130 and an output steering matrix 140, but it should be understood that this is merely an example. In other embodiments, matrices 130, 140 may be replaced by a single steering matrix having, for example, different parts serving input and output steering functions, without departing from the scope of the principles described herein. Thus, references to input and output steering arrays in the following description should be understood to include, respectively, an input sub-array and an output sub-array of a single steering array.

[0037] The imaging optical system is an optical component necessary for light signals to be properly routed and aligned to and from the steering optical reflectors and the input and output optical fiber ports. Typical examples of imaging optical systems include, but are not limited to, a collimator lens array, a double telecentric lens, a polarization diversity element, and a Fourier lens.

[0038] The OCS module further includes an array 160 of intermediate optical reflectors most readily seen in the inset of the figure.

[0039] In the non-limiting example shown in FIG. 4, the array 160 consists of a light reflector 161 configured at an incident angle suitable for guiding light between the input steering array and the output steering array within its home OCS module 100, and light reflectors 162 and 163, which are each configured at an incident angle suitable for directing light between the steering array of the home OCS module 100 and the steering arrays of respective other OCS modules (not shown).

[0040] In some exemplary embodiments, the input 135 and output 140 steering matrices may be implemented as an array of MEMS mirrors. In other exemplary embodiments, they may be implemented as an array of LCOS pixels.

[0041] In an embodiment, the intermediate optical reflector of the array 160 can be a fixed reflector such as a mirror oriented at an appropriate angle of incidence for combining the optical beams incident from the local input steering matrix 130 to the output steering matrix or other elements of the home OCS module or respective destination OCS modules. In other embodiments, the intermediate optical reflector of the array 160 may be, for example, a MEMS mirror having a variable angle of incidence. In some embodiments, the same steering intermediate optical reflector can support either intra-module coupling or inter-module coupling depending on how its angle of incidence is set.

[0042] In this regard, it is worth noting that in order to facilitate inter-module coupling, it may be necessary for the optical reflector elements of the steering array to have a relatively large angular range so that they can fully reach within the intermediate optical reflector region. However, a reconfigurable intermediate optical reflector, rather than a fixed one, can potentially relax this requirement. That is, an appropriately oriented intermediate optical reflector can reflect the incident beam to the destination OCS module even when the beam is incident on the same spot on the intermediate optical reflector used for inter-module coupling.

[0043] The OCS module of FIG. 4 can be a fully functional optical circuit switch in which any of its optical inputs can be coupled to any of its optical outputs. However, it also has the additional feature of being extensible. That is, the intermediate optical reflector array can direct the beam to a MEMS mirror array or other optical elements located within an OCS module other than the home OCS module.

[0044] In this regard, it is worth noting that the input optical fiber port and the output optical fiber port are not necessarily limited to one fiber each. As is known in the art, various types of spatial multiplexing including the use of multi-core fibers can be used. The OCS module described herein is more typically used in spatial division multiplexing, and all wavelengths belonging to a core will be switched together using two dimensions of the steering matrix for spatial switching. However, it is also worth noting that in an embodiment, the imaging optical system sub-component of the OCS module can be used for wavelength demultiplexing. That is, it can be used to separate different wavelengths present in a core, and as a result, wavelength channels can be switched independently. Such an approach leaves one dimension of the steering matrix for spatial switching and uses the other for wavelength switching. Alternatively, an additional steering layer can be used for wavelength switching.

[0045] In the example of FIG. 4, the light beam 170 incident from the input optical fiber port 115 of the input array 110 is incident on the steering element 135 of the input steering matrix 130 and is reflected therefrom as the light beam 171. The light beam 171 is incident on the reflector 161 of the intermediate light reflector array 160 and is reflected therefrom as the light beam 172. The light beam 172 is incident on the steering element 145 of the output steering matrix 140 and is reflected therefrom as the light beam 173. The light beam 173 is incident on the output optical fiber port 125 of the output array 120 and can be extracted therefrom, for example, into an optical fiber cable (not shown). It should be noted that in the example of FIG. 4, the light beams 170 to 173 propagate in free space.

[0046] FIG. 5 provides another schematic view of an OCS module 200 similar to the OCS module 100 of FIG. 4. FIG. 5 shows a cross section of the OCS module 200. For the sole purpose of simplifying the presentation of FIG. 5 which is intended for educational purposes only, the input array 110 is shown to be located on the upper side of the figure, and the output array 120 is shown to be located on the lower side of the figure. Some elements common to FIGS. 4 and 5 are designated by similar reference numerals.

[0047] As shown in FIG. 5, the intermediate optical reflector array 160 includes an optical reflector 164 for coupling the local input steering matrix 130 to the local output steering matrix 140, and an optical reflector 165 for coupling the local input or output steering matrix for inter-module coupling to elements of different OCS modules. By way of example, the figure shows an optical beam 175 that is reflected from the optical reflector 165 and exits the module 200 through the inter-module gate 205. The gate 205 is a free-space optical port within the case 105 that enables a propagation path from the module 200 to other destination modules. In an embodiment, the case 105 can be configured such that the gate 205 is normally closed, but opens when the module 200 is coupled, for example, by inserting it into a slot in a rack. In some embodiments, the case 105 can be provided with an open side, or an open top or bottom to enable free-space optical access. In this regard, it should be noted that the inter-module coupling can be established between modules sharing the same vertical level on a rack and / or between modules occupying different vertical levels on a rack.

[0048] In an example embodiment, inter-module propagation is free-space propagation. In an embodiment, inter-module free-space propagation may be limited to propagation between adjacent OCS modules. However, in other embodiments, free-space propagation from a source module to a non-adjacent destination module may be permitted. Direct transfer from a source module to a destination module may be beneficial because it is not affected by failures of elements along a propagation path that might otherwise be used to relay a beam to that destination. However, for a particular system size, it may still be advantageous to use intermediate relay elements. In some cases, inter-module propagation may occur wholly or partially within a waveguide medium such as an optical fiber or a planar optical waveguide.

[0049] The imaging optical systems 150, 155 may typically include lenses for collimation or focusing. Although the optical systems 150 and 155 are shown in the figure as separate elements, it should be noted that an optical design is achievable in which at least some sub-components of the imaging optical system are shared between the input optical beam and the output optical beam.

[0050] Referring further to FIG. 5, it can be seen that the OCS module 200 is aligned between the guide rails 210 of the OXC node that hold the OCS modules 100 and 200, which may be manufactured, for example, as part of a rack into which the OCS module 200 is inserted. In particular, when inter-module propagation is through free space, it is important to have proper alignment between the modules. A precision rail system may be useful for this purpose. In addition, there are known automatic calibration mechanisms that can be implemented to enhance alignment for inter-module routing. In an example of automatic calibration, light is inserted for each port and the output power is measured while performing a small-angle adjustment of a reflective element to maximize the output power. For example, MEMS mirrors can be adjusted by changing the voltage that controls their orientation.

[0051] As will be understood from the above discussion, the optical reflectors for optical steering within an OCS module as described herein should have an angular range sufficient to direct the reflected light beam onto those portions of the intermediate array 160 that are directed towards the optical fiber ports located within other OCS modules. This inter-module coupling makes it possible to increase the number of ports of the optical switch by adding more OCS modules to the same OXC node and to do so without affecting existing optical paths. For example, a two-dimensional MEMS mirror array can provide an angular range exceeding ±6°, and if necessary, additional expansion optics can be used to extend the angular range. Since the same intermediate optical reflector spot can be reconfigured to be used for both intra-module and inter-module links, the use of active intermediate optical reflectors can substantially reduce the angular reach required from the input / output steering optical reflectors.

[0052] One of the design constraints for an exemplary OCS module of the type described herein is that it typically requires sufficient space for an intermediate optical reflector array that includes an optical reflector for inter-module coupling. Another constraint is that the steering optical reflector has a tilt angle capacity sufficient to reach the portion of the intermediate optical reflector array that provides the inter-module coupling. Yet another constraint is that there is typically an optical propagation path between the mutually coupled OCS modules. As described above, these paths can be paths in free space or can be achieved using an optical waveguide medium such as an optical fiber or a planar waveguide. The inventors believe that using current capabilities in optical system design, all of these constraints can be satisfied in a realizable manner.

[0053] FIG. 6 is a schematic cross-sectional view of an ensemble of three OCS modules 301, 302, 303 mounted in a rack of the same OXC node having a guard rail 305 and interconnected by inter-module optical propagation paths. Elements common to FIGS. 5 and 6 are designated with like reference numerals except that the reference numerals of the repeating elements are suffixed with ".1", ".2", or ".3" to indicate the corresponding OCS module. Within each OCS module, clusters of optical beams 311, 312, 313 are shown directed from respective input optical fiber ports of input optical fiber port arrays 110.1, 110.2, 110.3 to respective selected output optical fiber ports of output arrays 120.1, 120.2, 120.3 within the same module.

[0054] To illustrate the possibility of inter-module coupling, two optical beams 320, 325 are also shown. In a first example, optical beam 320 enters OCS module 301 through one of the input optical fiber ports of input array 110.1, reflects from input steering matrix 130.1 of the same OCS module 301, and is incident on optical reflector 341 of the intermediate optical reflector array of the same OCS module 301. Due to a particular orientation of optical reflector 341, after reflecting from optical reflector 341, optical beam 320 exits module 301 and enters module 302 through respective inter-module gates. Within OCS module 302, optical beam 320 is incident on output steering matrix 140.2 of OCS module 302 and is reflected therefrom to a selected output optical fiber port of output array 120.2.

[0055] In the second example, the optical beam 325 enters the OCS module 303 through one of the input optical fiber ports of the input array 110.3 and is incident on the input steering matrix 130.3 of the same OCS module 303. Due to the specific configuration of the steering matrix 130.3, when the optical beam 325 is reflected from the steering matrix, it bypasses the intermediate optical reflector array of the OCS module 303, exits the OCS module 303, and enters the OCS module 302 through its respective gates. The optical beam 325 passes through the OCS module 302, exits the OCS module 302, and enters the OCS module 301 through the respective gates of these OCS modules 302 and 301. Inside the module 301, the optical beam 325 is incident on the optical reflector 342 of the intermediate optical reflector array therein. Due to the specific orientation of the optical reflector 342, after being reflected from the optical reflector 342, the optical beam 325 is incident on the output steering matrix 140.1 of the same OCS module 301 and is reflected therefrom to the selected output optical fiber port of the output array 120.1. The feature of the optical beam 325 is that, in order to couple the first OCS module 303, which is the first OCS module in the propagation path, to the OCS module 301, which is the last module in the propagation path, the input steering matrix 130.3 of the first OCS module 303 reflects the incident optical beam to the intermediate optical reflector of the last OCS module 301.

[0056] The examples of the optical beams 320 and 325 are provided to illustrate a more general point that, with the proper placement of the intermediate optical reflectors, any input optical fiber port in a collection of several OCS modules can, in principle, be coupled to any output optical fiber port in the same collection.

[0057] Referring to FIG. 6, it will be appreciated that in order to bypass the intermediate optical reflectors of the intervening OCS modules on the same rack of the OXC node, the propagation paths of optical beams 320 and 325 must pass either in front of or behind the bypassed intermediate optical reflectors. In this context, the terms "front" and "behind" relate only to the view of the modules as represented in the figure. FIG. 7, which is next referred to, has a depth dimension that provides a more complete view of an exemplary propagation path.

[0058] FIG. 7 is a schematic perspective view of an ensemble of three OCS modules similar to the OCS module ensemble of FIG. 6. Elements common to FIGS. 6 and 7 are given like reference numerals. For simplicity of presentation, only three intermediate optical reflectors are shown in the intermediate optical reflector array of each module.

[0059] In FIG. 7, optical beam 400 is shown entering OCS module 301 and reflecting from input steering matrix 130.1 onto reflector 405 of intermediate optical reflector array 331 of the same OCS module 301. When reflecting from reflector 405, optical beam 400 passes through OCS module 302 without reflection and is incident on output steering matrix 140.3 of OCS module 303. Output steering matrix 140.3 directs optical beam 400 towards the output optical fiber ports of output array 120.3.

[0060] As briefly described above, embodiments can be designed using fixed passive inter-module routing, where each OCS module has an intermediate optical reflector array with reflection elements dedicated to the interconnection to the output steering matrix of each respective OCS module. Alternative embodiments can be designed with active inter-module routing where the tilt angle of the intermediate optical reflectors can be adjusted to reach the desired destination OCS module.

[0061] Also, as described above, the input and output steering matrices as well as the intermediate optical reflectors can be implemented with various technologies including MEMS and LCOS. MEMS mirrors for optical switching have been reported in the technical literature. For example, as reported in J. I. DADAP et al., “Modular MEMS-based optical cross-connect with large port-count”, in IEEE Photonics Technology Letters, vol. 15, no. 12, (Dec. 2003) 1773-1775, cited hereinafter as “DADAP 2003”, an example of a MEMS mirror is an electrostatically actuated double gimbal tilt mirror of gold-plated single crystal silicon suspended by torsion springs. Closed-loop servo control may be provided, for example, by a digital signal processor (DSP) with ADC and DAC interfaces. In this regard, the conference and exhibition on optical fiber communication, R.R yf et al., “1296-port MEMS transparent optical cross-connect with 2.07 petabit / s switch capacity” OFC 2001 can also be usefully referred to. Technical Digest (Optical Society of America, 2001), Anaheim, California, USA, (2001) pages PD28-PD28, hereinafter referred to as “RYF 2001”. DADAP2003 and RYF2001 are hereby incorporated by reference in their entireties.

[0062] Appropriate controller technologies are known. Nonlinear servo control technology that may be useful in this regard is reported, for example, in I. Brener et al., "Nonlinear servo control of MEMS mirrors and the performance in a large port-count optical switch", OFC 2003, Atlanta, Georgia, Mar. 2003, pp. 385-386, the entire content of which is incorporated herein by reference. Further information on controller technologies that may be useful in this regard can be found in G.F. Franklin, J.D. Powell, and M.L. Workman, Digital Control of Dynamic Systems. Reading, MA: Addison-Wesley, 1998, particularly pages 323-325 (incorporated herein by reference).

[0063] LCOS for optical switching has also been reported in the technical literature. For example, N.K. Fontaine et al., "Few-Mode Fiber Wavelength Selective Switch with Spatial-Diversity and Reduced-Steering Angle," in Optical Fiber Communication Conference, OSA Technical Digest (online) (Optica Publishing Group, 2014), paper Th4A.7 can be usefully referred to, the entire content of which is incorporated herein by reference. With respect to the LCOS steering matrix or other types of reconfigurable steering matrices, it is noted that the matrix transfer function of the hologram or grating type reflectors can be adapted to reduce loss and crosstalk according to the angular range required for the number of OCS modules in place. This can be significant, particularly since the required tilt angle increases with the number of OCS modules being coupled.

[0064] FIG. 8 is a conceptual block diagram showing the functional elements of an optical switching system having an OCS module. FIG. 8 is presented for educational purposes only.

[0065] As shown in FIG. 8, the fibers from the optical fiber cable 500 carrying the input optical signal plug enter the input optical fiber ports of the ensemble 505 of OCS modules. The fibers from the optical fiber cable 510 carrying the output optical signal plug enter the output optical fiber ports of the OCS module ensemble 505. The control function is implemented by the control unit 515. The control function includes a module 520 for monitoring the calibration of the steering elements of the OCS modules of the module ensemble 505, a module 530 for generating control signals and transmitting them to the steering elements, and a switching controller 535 for implementing servo control of the steering elements and setting the defined intra-module and inter-module couplings between the input optical fiber ports and output optical fiber ports of the various OCS modules. The mirror switching controller 535 can also use the feedback from the monitor module 530 to implement a training algorithm that operates the steering elements through the mirror switching controller 535 to initialize and recalibrate the various OCS modules of the ensemble 505. The control function may be implemented by any suitably configured processing circuit or combination of circuits, such as a digital signal processor.

[0066] Precise optical reflector angle adjustment can be used to correct residual position deviations through the monitoring channel. As an example, URATA2022 cited above describes the use of a camera module operating at an out-of-band wavelength to provide a monitor signal.

[0067] The mirror switching controller 535 may also be operable to minimize the impact on already established couplings when a new optical path is being established.

[0068] In at least some embodiments, coupling additional modules to the system leaves the relative positions of the steering matrix and the intermediate optical reflector unchanged in the OCS module that was already in place. In such cases, additional training may not be required for the internal couplings within the existing OCS module. However, training will generally be required for module - to - module connectivity with newly inserted OCS modules of the ensemble 505. For example, training can be used to identify spots within the intermediate optical reflector or to identify the configuration angles of the reconfigurable intermediate optical reflector to optimize the signal quality of the module - to - module coupling.

[0069] FIG. 9 is a flowchart showing steps in an exemplary procedure for operating an apparatus of the type described herein, e.g., any of the apparatuses of FIGS. 3 - 8. It should be understood that FIG. 9 is merely exemplary and is not limiting with respect to any aspect of the operating procedure.

[0070] In block 601, an input OCS module and an output OCS module are selected for each optical beam coupling.

[0071] In block 602, the input optical fiber ports and the output optical fiber ports of the OCS modules selected in block 601 are selected for each optical beam coupling.

[0072] In block 603, the positions of the steering optical reflector and the intermediate optical reflector are determined for each respective coupling. In embodiments, instead of making new determinations of the optical reflector positions, some or all of the desired optical reflector positions can be obtained by referring to a look - up table.

[0073] In block 604, each optical signal is received at a selected optical fiber port. If inter-module coupling is specified, this will result in one or more beams of light being transmitted from the intermediate optical reflector array of the source module to the elements of the destination module and ultimately to the output optical fiber port of the destination module. Inter-module transmission may include, in an exemplary embodiment, free-space transmission through a free-space optical port or gate between each module.

[0074] FIG. 10 is a schematic diagram of an electronic device 700 for optical switching in which a plurality of switch modules 705 are removably and mechanically fixed to an electronic device 700 by a plurality of module connectors 710. The module connectors 710 can achieve a rigid mechanical attachment and electrical coupling. For example, a switch module can be plugged into a module connector and cannot be plugged out from the module connector. The module connectors 710 may be arranged such that the switch modules can be organized into an array such as a square or rectangular array having one or more rows and / or columns.

[0075] Each switch module 705 has a plurality of input optical fiber ports 715 and a plurality of output optical fiber ports 720. Each switch module 705 also has a reconfigurable optical reflector array 725 that can selectively perform an optical cross-connect between one of the input optical fiber ports of its own switch module and one of the output optical fiber ports of its own switch module, as described above. Each switch module 705 is also selectively reconfigurable to send light received from one of its input optical fiber ports, through its own optical reflector array 725, to one or more other of the optical switch modules.

[0076] The free-space optical port 730 within the switch module 705 enables routing of light between the switch modules.

Claims

1. an electronic device having a plurality of module connectors thereon; a plurality of optical circuit switch (OCS) modules, each removably mechanically secured to the electronic device by at least one of the plurality of module connectors, the OCS modules having a plurality of input optical fiber ports and a plurality of output optical fiber ports; each of the plurality of OCS modules having a reconfigurable arrangement of optical reflectors capable of selectively optically cross-connecting a plurality of the input optical fiber ports of a same one of the plurality of OCS modules to a plurality of the output optical fiber ports of a same one of the plurality of OCS modules; an apparatus comprising: an optical fiber optics module configured to selectively route light received from a plurality of the plurality of input optical fiber ports to one or more other of the plurality of OCS modules via an arrangement of a plurality of optical reflectors;

2. 2. The apparatus of claim 1 , wherein routing from particular ones of the plurality of OCS modules to other ones is via one or more free space optical paths coupling particular ones of the plurality of OCS modules to the one or more others.

3. 2. The apparatus of claim 1, wherein at least one of the plurality of OCS modules is configurable to route light from one of its plurality of input optical fiber ports to a second of the plurality of OCS modules via a free space optical path that traverses a third of the plurality of OCS modules.

4. 10. The apparatus of claim 1, wherein the electronic device comprises an electronic controller communicatively coupled to operate a reconfigurable arrangement of the plurality of optical reflectors of the plurality of OCS modules.

5. 2. The apparatus of claim 1, wherein in each of the plurality of OCS modules, the reconfigurable arrangement of the plurality of optical reflectors comprises: an input optical reflector arranged to receive light from the plurality of input optical fiber ports; an output optical reflector arranged to transmit light to the plurality of output optical fiber ports; and an intermediate optical reflector array having intermediate reflectors capable of reflectively coupling the input optical reflectors to the output optical reflectors.

6. 6. The apparatus of claim 5, wherein the input light reflector is configurable to selectively direct light through the intermediate light reflector array to one or more others of the plurality of OCS modules.

7. 7. The apparatus of claim 6, wherein the intermediate optical reflector array comprises a configurable reflector configured to act in cooperation with the input optical reflector to selectively direct light to one or more others of the plurality of OCS modules.

8. 10. The apparatus of claim 1, wherein the electronic device comprises an electronic controller communicatively coupled to operate a reconfigurable arrangement of the plurality of optical reflectors of the plurality of OCS modules.

9. 2. The apparatus of claim 1, wherein the reconfigurable arrangement of the plurality of optical reflectors in each particular one of the plurality of OCS modules is configurable to direct light received from a different one of the plurality of OCS modules to one or more of the plurality of output optical fiber ports of the particular one of the plurality of OCS modules.

10. the reconfigurable arrangement of the plurality of optical reflectors in each of the plurality of OCS modules comprises an intermediate optical reflector array having input optical reflectors arranged to receive light from the plurality of input optical fiber ports, output optical reflectors arranged to transmit light to the plurality of output optical fiber ports, and intermediate reflectors capable of reflectively coupling the input optical reflectors to the output optical reflectors; the input light reflector is a MEMS mirror array; 2. The apparatus of claim 1, wherein the output light reflector is a MEMS mirror array.

11. the reconfigurable arrangement of the plurality of optical reflectors in each particular one of the plurality of OCS modules comprises an input optical reflector arranged to receive light from the plurality of input optical fiber ports, an output optical reflector arranged to transmit light to the plurality of output optical fiber ports, and an intermediate optical reflector array; the intermediate optical reflector array comprises an intra-module intermediate reflector capable of reflectively coupling the input optical reflectors of a particular one of the plurality of OCS modules to the output optical reflectors of a particular one of the plurality of OCS modules; 2. The apparatus of claim 1, wherein the intermediate optical reflector array further comprises at least one inter-module intermediate reflector capable of reflectively coupling the input optical reflectors of a particular one of the plurality of OCS modules to one or more different ones of the plurality of OCS modules.

12. 12. The apparatus of claim 11, wherein each of the inter-module intermediate reflectors is a static mirror.

13. 12. The apparatus of claim 11, wherein each of the inter-module intermediate reflectors is a reconfigurable mirror.

14. causing an optical signal from a first input optical fiber port of a first optical circuit switch (OCS) module to be received by the second OCS module by reconfiguring at least one optical reflector of the first OCS module to reflect the optical signal onto an optical path that terminates in the second OCS module; causing the received optical signal to be output by the second OCS module by reconfiguring an optical reflector of the second OCS module to direct the received optical signal to an output optical fiber port of the second OCS module, thereby forming an inter-module coupling; and causing an optical signal from a second input optical fiber port of the first OCS module to be output by the first OCS module by reconfiguring at least one optical reflector of the first OCS module, and directing the optical signal from the second input optical fiber port to an output optical fiber port of the first OCS module, thereby forming an intra-module coupling.

15. 15. The method of claim 14, wherein the optical path terminating in the second OCS module is a free space optical path.

16. forming the intra-module coupling includes reconfiguring an input optical reflector and reconfiguring an output optical reflector of the first OCS module; forming the inter-module coupling includes reconfiguring an input optical reflector of the first OCS module and reconfiguring an output optical reflector of the second OCS module; 15. The method of claim 14, wherein within each of the OCS modules, the input optical reflector and the output optical reflector are each reflectively coupled via an intermediate optical reflector.

17. The method of claim 16 , wherein forming the inter-module coupling further comprises reconfiguring the intermediate optical reflector of the first OCS module.

18. The intra-module coupling and the inter-module coupling are performed simultaneously with a plurality of other intra-module couplings and inter-module couplings, forming the plurality of simultaneous couplings comprising: selecting, from a plurality of OCS modules including the first OCS module and the second OCS module, an input OCS module and an output OCS module for implementing each combination from a set of desired combinations; selecting respective input and output fiber optic ports of the selected OCS modules to implement respective desired couplings; obtaining a set of optical reflector configurations for implementing each desired coupling; and reconfiguring at least some of the input and output optical reflectors of the selected input and output OCS modules in accordance with the obtained configuration to form the desired coupling.

19. 20. The method of claim 18, wherein forming the multiple simultaneous combinations further comprises reconfiguring at least some of the intermediate optical reflectors of the selected input OCS module and output OCS module according to the obtained configuration.

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