Optical switch employing a virtually imaged phase-array disperser

A WSS device in which a VIPA is used as a spectral disperser. In an example embodiment, the VIPA is configured to produce two or more diffraction orders on the LCOS micro-display of the WSS device. The LCOS micro-display is configurable to independently process light corresponding to different diffraction orders. For example, the LCOS micro-display may be used to implement: (i) optical-signal switching by applying different relative phase shifts to light of different diffraction orders to cause constructive interference at a selected one of the optical ports of the WSS device; (ii) optical-signal splitting by steering light of different diffraction orders to at least two different selected optical ports of the WSS device; and (iii) controllable optical-signal attenuation by applying different relative phase shifts to different diffraction orders to control the relative degree of constructive and destructive interference at a selected one of the optical ports of the WSS device.

BACKGROUND

Field

Various example embodiments relate to optical communication equipment and, more specifically but not exclusively, to optical switches.

Description of the Related Art

An optical cross-connect (OXC) switch is an optical device that is used, e.g., by telecommunications carriers, to switch optical signals in a fiber-optic network. A representative N×M OXC switch interconnects any of its N optical input ports to any of its M optical output ports in an optically transparent fashion, where N and M are positive integers, and at least one of N and M is greater than one. The telecommunications industry develops, manufactures, sells, deploys, and services a large variety of OXC switches.

SUMMARY OF SOME SPECIFIC EMBODIMENTS

Disclosed herein are various embodiments of a wavelength-selective-switch (WSS) device in which a virtually imaged phase array (VIPA) is used as a spectral disperser. In an example embodiment, the VIPA disperser is configured to produce two or more diffraction orders on the liquid-crystal-on-silicon (LCOS) micro-display of the WSS device. The LCOS micro-display is configurable to independently process light corresponding to different diffraction orders. For example, the LCOS micro-display may be used to implement: (i) optical-signal switching by applying different relative phase shifts to light of different diffraction orders to cause mainly constructive interference at a selected one of the optical ports of the WSS device; (ii) optical-signal splitting by steering light of different diffraction orders to at least two different selected optical ports of the WSS device; and (iii) controllable optical-signal attenuation by applying different relative phase shifts to different diffraction orders to control the relative degree of constructive and destructive interference at a selected one of the optical ports of the WSS device.

Some embodiments of the disclosed WSS device are advantageously capable of achieving a spectral resolution finer than approximately 1 GHz.

Some embodiments of the disclosed WSS device are advantageously capable of independently performing optical-signal switching and controllable optical-signal attenuation.

According to an example embodiment, provided is an apparatus, comprising: an array of optical ports including a first optical port and a plurality of second optical ports; a beam-steering device optically coupled to the array of optical ports and having a beam-steering surface including a plurality of configurable pixels; and a virtually imaged phase-array (VIPA) disperser optically coupled between the array of optical ports and the beam-steering device; and wherein the apparatus is configurable to selectively route a plurality of wavelength channels between the first optical port and a selected set of the second optical ports by way of the VIPA disperser and the beam-steering surface.

DETAILED DESCRIPTION

Some embodiments may benefit from at least some features disclosed in U.S. Pat. Nos. 9,188,831, 9,225,458, 9,369,783, and 10,073,221, all of which are incorporated herein by reference in their entirety.

A wavelength-selective switch (WSS) is an OXC switch that operates on wavelength-division-multiplexed (WDM) signals without having to fully physically demultiplex their constituent WDM components, e.g., into individual dedicated ports. A WSS can be used, for example, to implement a reconfigurable optical add/drop multiplexer (ROADM). In some cases, substantially the same device architecture can be used to implement both a WSS and a ROADM, with the classification of the resulting physical device as the former or the latter depending mostly on the degree of switching enabled by such physical device. An optical-WDM network employing WSS and/or ROADM devices has many attractive features that help to accelerate service deployment, accelerate rerouting around points of failure in the network, reduce capital and operating expenses for the service provider, and provide a network topology that is amenable to future network upgrades. Currently, there is a high market demand for OXC switches, WSS devices, and ROADM devices that have one or more, and possibly all, of the following beneficial characteristics: (i) low production cost; (ii) small form factor; (iii) high port count; (iv) fine spectral resolution, e.g., smaller than 10 GHz; (v) high switching speed; (vi) controllable per-channel attenuation; and (vii) low insertion loss.

A WSS typically employs a reconfigurable beam-steering device to optically connect the selected sets of input and output optical ports in a wavelength-dependent manner Some WSS systems employ two-dimensional pixelated MEMS mirror arrays as beam-steering devices. Some other WSS systems employ liquid-crystal-on-silicon (LCOS) micro-displays as beam-steering devices. In a MEMS implementation of the beam-steering device, the MEMS mirrors in the array can be controllably tilted to steer the corresponding sub-beams in the respective intended directions. In an LCOS implementation of the beam-steering device, the phase shift imparted onto the corresponding optical beam by the individual pixels of the micro-display can be appropriately controlled to create approximately linear optical-phase retardation in the direction of the intended deflection of the diffracted beam. In some cases, MEMS mirror arrays and LCOS micro-displays may be interchangeable to provide substantially the same beam-steering functions.

FIG.1shows a block diagram of a WSS device100in which at least some embodiments may be practiced. Device100has N optical input ports1101-110Nand M optical output ports1501-150M, where N and M are (either the same or different) integers greater than one. Each of optical input ports110and optical output ports150may have an appropriate connector for end-connecting a respective optical fiber (not explicitly shown inFIG.1). In operation, each of these optical fibers may transport a respective optical WDM signal. In principle, each of the transported WDM signals can have an arbitrary number of WDM components (e.g., modulated carrier wavelengths or optical channels), with the total number K of unique carrier wavelengths that are being handled by device100being independent of the numbers N and/or M.

Device100comprises N (1×M) wavelength-selective switches1201-120Nand M (1×N) wavelength-selective switches1401-140M, interconnected as shown inFIG.1. A 1×N wavelength-selective switch is typically a (re)configurable optical multiplexer/demultiplexer that can be configured to route the full set or a selected subset of the K carrier wavelengths between the common port thereof and a variety of its N ports. As used herein, the term “common port” refers to a port having the following features of a 1×N wavelength-selective switch. When an input port, a common port can be configured to variously distribute the received carrier wavelengths among the N ports such that different ones of the N ports internally receive and externally output different subsets of the K carrier wavelengths. One of the possible switch configurations can be such that all wavelengths externally applied to the common port go to a single one of the N ports while others of the N ports receive no carrier wavelengths from the common port. When an output port, a common port can internally collect and externally output up to K carrier wavelengths from the different N ports such that different ones of the N ports contribute different subsets of the K wavelengths. Again, one of the possible switch configurations can be such that all carrier wavelengths collected by the common port originate from a single one of the N ports while other ones of the N ports contribute no carrier wavelengths to the common port. It is customary to depict a 1×N WSS using a block diagram in which (i) the common port is shown at the side having a single port (e.g., seeFIG.1) and (ii) each of the N ports is shown as being located at the side having the N ports (also seeFIG.1), but the actual physical locations of the N+1 ports of such a 1×N WSS may be different (e.g., seeFIG.3).

In device100, each wavelength-selective switch120ihas its common port optically coupled to the corresponding input port110i. Similarly, each wavelength-selective switch140jhas its common port optically coupled to the corresponding output port150j. The sets of M ports of the 1×M wavelength-selective switches1201-120Nare optically coupled to the sets of N ports of the 1×N wavelength-selective switches1401-140Mas indicated inFIG.1. The latter connections can be implemented through free space, e.g., with mirrors and lenses, or through optical fibers or on-board optical waveguides.

Each 1×M wavelength-selective switch120is configured to operate as a configurable demultiplexer that routes optical signals from the common input port to various ones of the M output ports. Each 1×N wavelength-selective switch140is configured to operate as a configurable multiplexer that routes optical signals from various ones of the N input ports to the common output port. Using the routing characteristics of wavelength-selective switches120and140, device100is capable of directing any carrier wavelength or any set of two or more carrier wavelengths from any input port110to any output port150. In operation, device100may employ a switch controller (not explicitly shown inFIG.1) that is connected to control the routing configurations of the 1×M and 1×N wavelength-selective switches1201-120Nand1401-140M. The controller may use appropriate routing algorithms, e.g., to avoid signal collisions at any of output ports1501-150M, with a collision being an event in which two different optical signals having the same carrier wavelength arrive simultaneously at the same output port150.

Example embodiments of wavelength-selective switches that can be used as wavelength-selective switches120and/or140in device100are described in more detail below in reference toFIGS.2-12. From the provided description, a person of ordinary skill in pertinent art will understand that an example embodiment of a wavelength-selective switch disclosed herein advantageously enables WSS device100to have a relatively high port count and/or a relatively low cost per port.

FIGS.2A-2Bshow schematic views of a wavelength-selective switch200that can be used in the WSS device100(FIG.1) according to an embodiment. For illustration purposes, the schematic view ofFIG.2Acan be referred to as the “side view,” and the schematic view ofFIG.2Bcan be referred to as the “top view.” The relative orientation of the views is indicated by the XYZ-coordinate triad shown in each ofFIGS.2A and2B. The X, Y, Z coordinates shown inFIGS.3-6are also consistent with the XYZ-coordinate triad ofFIGS.2A-2B.

Switch200has a total of P optical ports2021-202P, where P is an integer greater than two. One of optical ports2021-202Pis configured to operate as a common port. Some or all of the remaining optical ports2021-202Pare configured to operate as the M or N ports. In some embodiments, one or more of optical ports2021-202Pmay be idle or used for blocking (e.g., dropping) one or more unwanted WDM components. An embodiment of switch200having P≥M+1 ports can be used, e.g., as a wavelength-selective switch120(FIG.1). An embodiment of switch200having P≥N+1 ports can be used, e.g., as a wavelength-selective switch140(FIG.1).

In the embodiment shown inFIGS.2A-2B, optical ports2021-202Pare arranged, e.g., in a regularly spaced or irregularly spaced, linear array lined up parallel to the Z-coordinate axis. As a result, the P optical ports2021-202Pappear stacked on top of one another in the top view shown inFIG.2B. In an example embodiment, an optical port202may include a length of optical fiber or waveguide and/or a fiber connector for connecting an external optical fiber. In operation, an optical port202may be configured to receive a respective optical WDM signal either from an external optical link or from the interior part of switch200.

In an alternative embodiment (not shown), ports202may be arranged in a regular or irregular two-dimensional array.

FIG.3shows an end view of optical ports2021-202Palong the X-coordinate axis according to an embodiment. In this particular embodiment, the P similar optical ports2021-202Pare arranged in a regularly spaced, linear array oriented parallel to the Z-coordinate axis. Optical port2021is designated as the common port. In alternative embodiments, other optical-port assignments may be used.

Referring back toFIGS.2A-2B, switch200comprises lenses230112303to provide relay/imaging/focusing optics configured to appropriately optically couple the various constituent optical elements of the switch, e.g., as further explained below. Although each of lenses230112303is illustratively shown inFIGS.2A-2Bas consisting of a single spherical lens, various possible embodiments are not so limited. For example, in a possible alternative embodiment, some or all of lenses230112302may be replaced by any suitable combination of lenses and/or minors. Both cylindrical and spherical lenses and/or cylindrical, spherical, and parabolic minors may be used. A person of ordinary skill in the art will appreciate that, in some embodiments, wavelength-selective switch200may include one or more additional sets of relay/imaging/focusing optics (not explicitly shown inFIGS.2A-2B).

In the shown embodiment, lenses2301and2302are positioned between optical ports2021-202Pand a virtually imaged phase-array (VIPA) disperser240. In an example embodiment, lenses2301and2302are configured to perform one or more of the following optical functions:(i) To relay light between optical ports2021-202Pand VIPA disperser240;(ii) To change the beam sizes. For example, it might be beneficial to have a larger or smaller beam size for individual optical beams at VIPA disperser240than at optical ports2021-202P; and(iii) To accommodate dynamic light switching between optical ports2021-202Pby being a part of an optical imaging system that is configured to image, in a wavelength-dependent manner, each common port onto a corresponding set of other ports, or vice versa. As explained below, another part of said optical imaging system is lens2303. Lens2303is positioned between the VIPA disperser240and an LCOS micro-display250. The VIPA disperser240can alter the spatial spread of light and introduce relative phase shifts between different optical sub-beams. An example structure and principle of operation of the VIPA disperser240are described in more detail below in reference toFIG.4.

A front side248of the LCOS micro-display250is located in a Fourier plane of lens2303. Lens2303therefore operates to convert the phase-shifted spatial spread of the optical sub-beams generated by the VIPA disperser240into a spatial/angular separation of different WDM components at the front side248. Thereat, the sub-beams may produce narrow strips of light, with each such strip containing light of the corresponding WDM component. In an example embodiment, each WDM component may produce between two and ten respective narrow strips of light at the front side248, e.g., as explained below in reference toFIGS.5and6. Each of such strips corresponds to a different respective diffraction order of the optical sub-beams. Illustratively,FIG.2Bshows three such diffraction orders, which are labeled Om−1, Om, and Om+1, respectively.

Different portions of front side248of LCOS micro-display250can be individually configured, using a routing controller260, to impart different respective phase shifts. The pattern of phase shifts so imparted may best be understood as being a result of a hologram displayed by the LCOS micro-display250. As such, routing controller260controls wavelength-dependent beam routing between optical ports2021-202Pby displaying appropriate holograms and, when needed, by changing the displayed holograms.

Lens2303further operates to relay the light variously steered by the LCOS micro-display250back to VIPA disperser240. VIPA disperser240further operates to directionally recombine each of the subsets of the steered light intended for the same output port into a respective recombined optical beam and direct each of the recombined optical beams, via lenses2301-2302, to the respective ones of optical ports2021-202P.

FIG.4pictorially illustrates certain optical and physical characteristics of VIPA disperser240according to an embodiment. As shown inFIG.4, VIPA disperser240comprises a transparent-dielectric (e.g., glass) plate410. Plate410is flat and has a constant thickness, t. In an example embodiment, the thickness t can be smaller than 1 mm, e.g., can be approximately 0.1 mm. The opposing main sides of plate410are labeled inFIG.4using the reference numerals408and412, respectively. Plate sides408and412are referred to as being the “main” sides because each of them has two relatively large dimensions. Each of the other sides of plate410has one relatively large dimension and one relatively small dimension (i.e., t). Collectively, the latter sides of plate410may be referred to as edges of the plate.

The plate side408has a first portion thereof coated with an anti-reflective (AR) film406and has a second portion thereof coated with a highly reflective film404. In an example embodiment, the highly reflective film404may comprise a metal or metal alloy and may have a reflectivity of substantially 100%. The plate side412is coated with a partially reflective film414. In an example embodiment, the partially reflective film414may comprise a metal or metal alloy and may have a reflectivity between 50% and 98%.

In some embodiments, the AR film406may be absent, and the corresponding portion of the plate side408may be bare.

When a collimated optical beam400is directed toward VIPA disperser240at an incidence angle θ, a lens402can be positioned such that the optical beam passes through AR film406and is focused on (e.g., has a beam waist BW at) the plate side414as indicated inFIG.4. The focused beam400is partially transmitted through and partially reflected back from the partially reflective film414. The transmitted portion of the focused beam400creates a first sub-beam4201. The reflected portion of the focused beam400optically reverberates between the reflective films404and414, and the light that leaks through the partially reflective film414at each impingement thereupon creates sub-beams4202,4203, . . . ,4208, and so on. The distance d between the center axes of two adjacent sub-beams420depends on the thickness t and the incidence angle θ. In various embodiments, the total number Q of the sub-beams420generated in this manner may be, e.g., in the range between Q=10 and Q=500.

The illumination pattern produced by the Q sub-beams420generated by the VIPA disperser240is similar to that created by Q light sources, which include the light source BW and the plurality of light sources located at the virtual images VI2, VI3, . . . , VI6, etc. of the light source BW. These light sources are characterized by a gradually decreasing optical power due to the gradual leakage of the reverberating light through the partially reflective film414. This tentative analogy of the optical effect of the VIPA disperser240with the optical effect of multiple virtually imaged light sources is captured by the VIPA acronym in the term “VIPA disperser.”

Due to its Fabry-Perot etalon geometry, a VIPA disperser240is generally capable of providing a much larger angular dispersion compared to that of a conventional (e.g., blazed or ruled) optical grating typically used in conventional WSS devices. For example, a rectangular VIPA disperser240having a thickness t=0.5 mm, a first side length of 24 mm (in the wavelength direction), and a second side length of 30 mm (in the port direction) may create more than 400 virtual light sources, i.e, Q>400 (also seeFIGS.2A and2Bfor the orientation of the port and wavelength directions). In this particular example, the maximum optical-path-length difference can be more than 40 cm, which corresponds to a 2-ns time delay in fused silica. The inverse of this time delay indicates that the spectral resolution of such a VIPA disperser240can potentially approach 0.5 GHz. Advantageously, this spectral resolution is more than ten times finer than that of a conventional optical grating typically used in conventional WSS devices. The free spectral range (FSR) of such a VIPA disperser240can be approximately 200 GHz, as determined by the optical-path-length difference between two neighboring virtual sources VI (seeFIG.4). The spectral resolution of the VIPA disperser240can potentially be further enhanced, e.g., by undertaking suitable design and configuration changes directed at reducing the FSR.

FIG.5shows an example illumination pattern500that can be created on the front side248of the LCOS micro-display250of switch200according to an embodiment. This particular illumination pattern is created by monochromatic (194-THz) CW light delivered through optical port2021, which operates as a common port of switch200(also seeFIG.3). Four diffraction orders of the light, labeled Om−2, Om−1, Om, and Om+1, are evident inFIG.5.

Using different respective holograms displayed on the front side248by the LCOS micro-display250, switch200may perform the following optical operations on the light: (A) steer substantially all of the monochromatic light to a selected one of optical ports2022-202Pwhile applying different relative phase shifts to different diffraction orders of the monochromatic light in a manner that causes mainly constructive interference of the light at that optical port, thereby implementing a signal-switching operation; (B) direct light of different diffraction orders of the monochromatic light to different selected optical ports202, thereby implementing a signal-splitting operation; and (C) apply different relative phase shifts to different diffraction orders of the monochromatic light in a manner that controls the relative degree of constructive and destructive interference of the light at a selected one of optical ports2022-202P, thereby implementing a controllable signal-attenuating operation. With respect to the signal-splitting operation (B), it should be noted that, for the illumination pattern500, an optical signal may be split into two different optical ports, three different optical ports, or four different optical ports, with the maximum number of target optical ports being equal to (i.e., limited by) the total number of diffraction orders on the front side248of the LCOS micro-display250. With respect to the signal-switching operation (A) and signal-attenuating operation (C), it should be noted that these two operations can be performed in switch200independently (from one another). In other words, signal attenuation and port steering are fully isolated (decoupled) from each other in switch200. This particular feature may be beneficial, e.g., for crosstalk reduction and for avoiding delicate and complicated hologram optimization caused by interdependence of these two operations in conventional WSS devices.

When polychromatic light (e.g., corresponding to two or more different WDM channels) is delivered through optical port2021, illumination patterns similar to the illumination pattern ofFIG.5are created for each constituent wavelength of the polychromatic light in different respective portions of the front side248of LCOS micro-display250. As such, switch200can be operated, using controller260, to independently apply the above-indicated operations (A), (B), and (C) to different WDM channels.

FIG.6graphically illustrates spectral characteristics of an output-intensity envelope602of the VIPA disperser240on the front side248of LCOS micro-display250in switch200according to an embodiment. Output-intensity envelope602spans four diffraction orders Om−2, Om−1, Om, and Om+1(also seeFIG.5). Each of the diffraction orders Om−2, Om−1, Om, and Om+1is illustratively shown as containing spatially dispersed wavelength components λ1, . . . , λn. The relative intensities of the spatially dispersed wavelength components λ1, . . . , λnfollow the output intensity envelope602as indicated inFIG.6. In this particular example, the diffraction orders Om−1and Omare adjacent to and in symmetric locations on opposite sides of a centerline CL of the front side248. The diffraction orders Om−2and Om+1are also in symmetric locations on opposite sides of the centerline CL. Such relative positions of the diffraction orders Om−2, Om−1, Om, and Om+1on the front side248may be beneficial in terms of the relative ease of programming controller260for implementing the above-mentioned signal-splitting operation (B) and signal-attenuating operation (C).

FIGS.7-10graphically show examples of optical transmission characteristics that can be exhibited by switch200(FIGS.2A-2B) according to an embodiment.

FIG.7shows a spectral range corresponding to one FSR of the VIPA disperser240. The shown transmission curves were experimentally measured in a configuration of switch200in which optical port2021was the common port to which “white” light (i.e., light having a constant spectral power density across the shown spectral range) was applied. This white light was used to model twenty 10-GHz channels. When consecutively numbered from1to20, these twenty wavelength channels have ten “odd” channels and ten “even” channels. Controller260was used to cause the LCOS micro-display250to display a hologram that directed the light of odd channels to optical port2022and directed the light of even channels to optical port2023. Excellent flat-top transmission bands corresponding to the different channels are evident inFIG.7.

FIG.8graphically shows transmission curves experimentally measured in a configuration of switch200in which ten consecutive 10-GHz channels of the white light applied to optical port2021were demultiplexed by being directed to optical ports2022-20211, respectively. Again, excellent flat-top transmission bands corresponding to the different wavelength channels are evident inFIG.8.

FIG.9graphically illustrates an example dependence of the shape of a single transmission band in switch200on the band's spectral width, which is indicated in the provided legend. Excellent flat-top transmission-band shapes are evident at least down to the 10-GHz spectral width. The estimated resolution is <3 GHz based on a metric that uses the spectral range within which the band's transmission changes from 90% to 10% with respect to the transmission level of the band's flat top.

FIG.10graphically shows transmission curves experimentally measured in a configuration of switch200in which fourteen 10-GHz channels were de-interleaved such that the light of odd channels was directed to optical port2022and the light of even channels was directed to optical port2023. In addition, the odd channels were gradually attenuated with 1.5 dB increments. The results ofFIG.10clearly show that signal attenuation and port steering can be decoupled from each other in switch200.

FIGS.11-12show example LCOS holograms that can be used in switch200according to an embodiment. More specifically,FIG.11shows the LCOS hologram that was used in the switch configuration corresponding toFIG.7.FIG.12shows the LCOS hologram that was used in the switch configuration corresponding toFIG.10. Both of the shown holograms were displayed on the front side248of LCOS micro-display250by appropriately configuring individual pixels of the LCOS micro-display. In both examples, only the diffraction orders Om−1and Omare used for light steering.

According to an example embodiment disclosed above, e.g., in the summary section and/or in reference to any one or any combination of some or all ofFIGS.1-12, provided is an apparatus comprising: an array of optical ports (e.g.,2021-202P,FIGS.2A,2B,3) including a first optical port (e.g.,2021,FIGS.2A,2B,3) and a plurality of second optical ports (e.g.,2022-202P,FIGS.2A,3); a beam-steering device (e.g.,250,FIGS.2A-2B) optically coupled to the array of optical ports and having a beam-steering surface (e.g.,248,FIGS.2A-2B) including a plurality of configurable pixels; and a virtually imaged phase-array (VIPA) disperser (e.g.,240,FIGS.2A,2B,4) optically coupled between the array of optical ports and the beam-steering device; and wherein the apparatus is configurable to selectively route a plurality of wavelength channels between the first optical port and a selected set of the second optical ports by way of the VIPA disperser and the beam-steering surface.

In some embodiments of the above apparatus, the VIPA disperser comprises an optically transparent plate (e.g.,410,FIG.4) having opposing first and second main sides (e.g.,408,412,FIG.4), the first main side having an optically transparent first portion and having a second portion thereof coated with a highly reflective film (e.g.,404,FIG.4), the second main side being coated with a partially reflective film (e.g.,414,FIG.4).

In some embodiments of any of the above apparatus, the optically transparent plate is oriented to cause light received from the first optical port to optically reverberate between the highly reflective film and the partially reflective film after entering the optically transparent plate through the optically transparent first portion.

In some embodiments of any of the above apparatus, the optically reverberating light undergoes at least 100 reflections from the highly reflective film (e.g., Q>100).

In some embodiments of any of the above apparatus, the optically transparent first portion of the first main side is coated with an anti-reflective film (e.g.,406,FIG.4).

In some embodiments of any of the above apparatus, the VIPA disperser is configured to produce two or more diffraction orders (e.g., Om−2, . . . , Om+1,FIG.5) on the beam-steering surface.

In some embodiments of any of the above apparatus, the beam-steering device is configurable to independently process light corresponding to different ones of the diffraction orders.

In some embodiments of any of the above apparatus, the beam-steering device is configurable to implement optical-signal switching (e.g., operation (A) described in reference toFIG.5) by applying different relative phase shifts to light of different ones of the diffraction orders corresponding to a selected one of the wavelength channels to cause mainly constructive interference of the light at a selected one of the second optical ports.

In some embodiments of any of the above apparatus, the beam-steering device is configurable to implement optical-signal splitting (e.g., operation (B) described in reference toFIG.5) by steering light of different ones of the diffraction orders corresponding to a selected one of the wavelength channels to at least two different selected ones of the second optical ports.

In some embodiments of any of the above apparatus, the beam-steering device is configurable to implement controllable optical-signal attenuation (e.g., operation (C) described in reference toFIG.5) by applying different relative phase shifts to different ones of the diffraction orders corresponding to a selected one of the wavelength channels to control a relative degree of constructive and destructive interference of the light at a selected one of second optical ports.

In some embodiments of any of the above apparatus, the beam-steering device is configurable to perform optical-signal switching and controllable optical-signal attenuation independently of one another.

In some embodiments of any of the above apparatus, the VIPA disperser is configured to produce at least four diffraction orders (e.g., Om−2, . . . , Om+1,FIG.5) on the beam-steering surface.

In some embodiments of any of the above apparatus, the plurality of configurable pixels comprise pixels of a liquid-crystal-on-silicon (LCOS) micro-display (e.g.,250,FIGS.2A-2B).

In some embodiments of any of the above apparatus, the apparatus further comprises an electronic controller (e.g.,260,FIG.2B) to cause the LCOS micro-display to display a hologram (e.g.,FIGS.11-12).

In some embodiments of any of the above apparatus, the electronic controller is configured to cause the LCOS micro-display to change the hologram.

In some embodiments of any of the above apparatus, the apparatus further comprises imaging optics (e.g.,2301-2303,FIGS.2A-2B) interposed between the array of optical ports and the beam-steering surface of the beam-steering device such that the beam-steering surface is located in a Fourier plane of the imaging optics.

In some embodiments of any of the above apparatus, the VIPA disperser has a free spectral range smaller than 200 GHz.

While this disclosure includes references to illustrative embodiments, this specification is not intended to be construed in a limiting sense. Various modifications of the described embodiments, as well as other embodiments within the scope of the disclosure, which are apparent to persons skilled in the art to which the disclosure pertains are deemed to lie within the principle and scope of the disclosure, e.g., as expressed in the following claims.

For the purposes of this specification, a MEMS device is a device having two or more parts adapted to move relative to one another, where the motion is based on any suitable interaction or combination of interactions, such as mechanical, thermal, electrical, magnetic, optical, and/or chemical interactions. MEMS devices are fabricated using micro- or smaller fabrication techniques (including nano-fabrication techniques) that may include, but are not necessarily limited to: (1) self-assembly techniques employing, e.g., self-assembling monolayers, chemical coatings having high affinity to a desired chemical substance, and production and saturation of dangling chemical bonds and (2) wafer/material processing techniques employing, e.g., lithography, chemical vapor deposition, patterning and selective etching of materials, and treating, shaping, plating, and texturing of surfaces. The scale/size of certain elements in a MEMS device may be such as to permit manifestation of quantum effects. Examples of MEMS devices include, without limitation, NEMS (nano-electromechanical systems) devices, MOEMS (micro-opto-electromechanical systems) devices, micromachines, microsystems, and devices produced using microsystems technology or microsystems integration.

It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain the nature of this disclosure may be made by those skilled in the art without departing from the scope of the disclosure, e.g., as expressed in the following claims.

Unless otherwise specified herein, the use of the ordinal adjectives “first,” “second,” “third,” etc., to refer to an object of a plurality of like objects merely indicates that different instances of such like objects are being referred to, and is not intended to imply that the like objects so referred-to have to be in a corresponding order or sequence, either temporally, spatially, in ranking, or in any other manner.

Unless otherwise specified herein, in addition to its plain meaning, the conjunction “if” may also or alternatively be construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” which construal may depend on the corresponding specific context. For example, the phrase “if it is determined” or “if [a stated condition] is detected” may be construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event].”

Throughout the detailed description, the drawings, which are not to scale, are illustrative only and are used in order to explain, rather than limit the disclosure. The use of terms such as height, length, width, top, bottom, is strictly to facilitate the description of the embodiments and is not intended to limit the embodiments to a specific orientation. For example, height does not imply only a vertical rise limitation, but is used to identify one of the three dimensions of a three dimensional structure as shown in the figures. Such “height” would be vertical where the electrodes are horizontal but would be horizontal where the electrodes are vertical, and so on.

Also for purposes of this description, the terms “couple,” “coupling,” “coupled,” “connect,” “connecting,” or “connected” refer to any manner known in the art or later developed in which energy is allowed to be transferred between two or more elements, and the interposition of one or more additional elements is contemplated, although not required. Conversely, the terms “directly coupled,” “directly connected,” etc., imply the absence of such additional elements. The same type of distinction applies to the use of terms “attached” and “directly attached,” as applied to a description of a physical structure. For example, a relatively thin layer of adhesive or other suitable binder can be used to implement such “direct attachment” of the two corresponding components in such physical structure.

“SUMMARY OF SOME SPECIFIC EMBODIMENTS” in this specification is intended to introduce some example embodiments, with additional embodiments being described in “DETAILED DESCRIPTION” and/or in reference to one or more drawings. “SUMMARY OF SOME SPECIFIC EMBODIMENTS” is not intended to identify essential elements or features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.