Wavelength-selective switch array

An input section for a wavelength-selective switch array includes a plurality of optical ports. The plurality of optical ports includes a first sub-plurality of optical ports having a plurality of first port optical axes, a second sub-plurality of optical ports having a plurality of second port optical axes, and a plurality of optical power elements. Each one of the plurality of optical power elements is disposed at an end of a respective one of each of the plurality of optical ports. The plurality of optical power elements further includes a first sub-plurality of optical power elements including a plurality of first optical power element optical axes displaced relative to the plurality of first port optical axes and a second sub-plurality of optical power elements including a plurality of second optical power element optical axes displaced relative to the plurality of second port optical axes.

BACKGROUND

The invention relates generally to a wavelength selective switch (WSS) array for use in optical communication networks. Optical networks are employed in order to support present day demand for high-speed, high-capacity advanced telecommunications and data networks. These networks commonly use a technique known as optical wavelength division multiplexing (WDM) to exploit as much of the optical spectrum as possible. Optical WDM is analogous to radio WDM in that data is modulated onto several different carrier waves of different wavelengths, with carriers at different wavelengths referred to as channels. In optical WDM, a light wave is used rather than a radio wave with the different wavelength channels corresponding to different frequencies (wavelengths) of light. Optical communications are commonly employed in and around a wavelength of 1-2 microns.

In many optical networks, optical nodes are employed that correspond to branch points of the optical network. Often, it is desirable for the nodes to employ Reconfigurable Optical Add Drop Multiplexer (ROADM) devices that have a reconfigurable add-drop functionality. Generally speaking, ROADM functionality allows for the removal or addition of one or more wavelength channels at the node.

In order to realize a ROADM system, a WSS may be employed for the routing of any arbitrary wavelength channel. In a WSS, a light beam deflection device such as a spatial light modulator may be used to select a wavelength for deflection to a desired output port, e.g., deflection of a wavelength channel to a drop port will result in that channel being dropped from the WDM signal. Furthermore, WSS's that employ MEMS (Micro-Electro-Mechanical System) or LCOS (Liquid Crystal on Silicon) based spatial light modulators are also currently in use.

Conventionally, ROADM nodes employ the Broadcast and Select (BS) scheme that requires a WSS and an optical splitter. However, future devices may employ route and select (RS) schemes that employ multiple WSS devices without the use of the optical splitter.

SUMMARY

In general, in one aspect, one or more embodiments of the invention are directed to an input section for a wavelength selective switch (WSS) array. The input section includes a plurality of optical ports. The plurality of optical ports includes a first sub-plurality of optical ports having a plurality of first port optical axes, a second sub-plurality of optical ports having a plurality of second port optical axes, and a plurality of optical power elements. Each one of the plurality of optical power elements is disposed at an end of a respective one of each of the plurality of optical ports. The plurality of optical power elements further includes a first sub-plurality of optical power elements including a plurality of first optical power element optical axes displaced relative to the plurality of first port optical axes and a second sub-plurality of optical power elements including a plurality of second optical power element optical axes displaced relative to the plurality of second port optical axes.

In general, in one aspect, one or more embodiments of the invention are directed to a WSS array for switching a first optical wavelength division multiplexed (WDM) signal and a second WDM signal. The WSS array includes an input section, a beam deflection element, an optical system interposed between the input section and a beam deflection element configured to deflect one or more wavelength channels of the first and second WDM signals. The input section further includes a plurality of optical ports and a plurality of optical power elements. The plurality of optical ports further includes a first input port configured to input the first WDM signal, wherein the first input port includes a first input port optical axis, and a second input port configured to input the second WDM signal, wherein the second input port includes a second input port optical axis. Each one of the plurality of optical power elements is disposed at an end of a respective one of each of the plurality of optical ports. The plurality of optical power elements further includes a first optical power element including a first optical power element optical axis displaced a first displacement relative to the plurality of first port optical axis and a second optical power element including a second optical power element optical axis displaced a second displacement relative to the second port optical axis. The first displacement results in a first displacement angle of the first WDM signal after exiting the first input port and the second displacement results in a second displacement angle of the second WDM signal after exiting the second input port. The optical system that is interposed between the input section and the beam deflection element is configured to receive the first and second WDM signals output at the first and second angles, respectively, spectrally disperse the received first and second WDM signals into a first and a second set of wavelength channels, respectively, and project the first set of wavelength channels on a first portion of the beam deflection element and the second set of wavelength channels on a second portion of the beam deflection element.

In general, in one aspect, one or more embodiments of the invention are directed to a method for routing one or more wavelength channels of a plurality of WDM signals using a WSS array. The method includes receiving a first WDM signal from a first input port of a first WSS of the WSS array and receiving a second WDM signal from a second input port of a second WSS of the WSS array. The method further includes passing the first WDM signal through a first optical power element having an optical axis that is displaced from an optical axis of the first input port to direct the first WDM signal along a first angle, passing the second WDM signal through a second optical power element having an optical axis that is displaced from an optical axis of the second input port to direct the second WDM signal along a second angle. The method further includes passing the first and the second redirected WDM signals through a lens configured to convert the first and second angles to first and second displacements on a surface of a beam deflection element, wherein the beam deflection element is located at the focal plane of the lens, and passing the first and second redirected WDM signals through a dispersive element to angularly disperse at least a first and a second wavelength channel from the first and second redirected WDM signals, respectively. The method further includes focusing the first and the second wavelength channels onto a first and a second spatial portion, respectively, of the beam deflection element, deflecting along a third angle, by the beam deflection element, the at least one wavelength channel of the first WDM signal, and deflecting along a fourth angle, by the beam deflection element, the at least one wavelength channel of the second WDM signal. The method further includes passing the at least one deflected wavelength channel of the first and second WDM signals back through the dispersive element and the lens to convert the third and fourth angles to the first and second angles, respectively, and routing the at least one deflected wavelength channel of the first and second WDM signals respectively out of a first and a second output port of the first and second WSS, respectively.

Other aspects and advantages of one or more embodiments of the invention will be apparent from the following description and the appended claims.

DETAILED DESCRIPTION

Specific embodiments of a wavelength-selective switch (WSS) array will now be described in detail with reference to the accompanying figures. Like elements in the various figures (also referred to as FIGS.) are denoted by like reference numerals for consistency.

In the following detailed description of embodiments, numerous specific details are set forth in order to provide a more thorough understanding of the WSS array. However, it will be apparent to one of ordinary skill in the art that these embodiments may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

In general, one or more embodiments relate to a WSS array that employs at least two WSS's in a single package. The WSS array in accordance with one or more embodiments provides for independent operation of each WSS in the WSS array without the need for specialized optical components. Rather, many of the optical components may be shared between the individual WSS devices, and thus, cost and size may be reduced. Such a device is ideally suited for use in modern communication networks, e.g., as a reconfigurable optical add/drop multiplexer (ROADM). Furthermore, one or more coupled two-WSS arrays may be ideally suited as components in a branching node that employs route and select (RS) architecture.

FIG. 1shows a wavelength selective switch (WSS) array in accordance with one or more embodiments. The WSS array101includes two independent WSS devices, WSS-1and WSS-2, each of which may operate as an independent WSS device. As used herein, the term “independent” refers to the capability of WSS-1to independently process one or more WDM signals independently of WSS-2and vice-versa. As used herein, the term “process” is used broadly and includes, e.g., modulating, attenuating, blocking, redirecting, and/or switching of individual wavelength channels that make up a respective WDM signal. The WSS array101further includes an input section103, an optical system105configured to beam-shape the respective WDM signal beams and also configured to spectrally disperse (demultiplex) the respective WDM signals into their constituent wavelength channels (or groups of wavelength channels) and to spectrally combine (multiplex) the dispersed wavelength channels (or groups of wavelength channels) into one or more WDM signals. Furthermore, the WSS array101includes beam deflection element107configured to optically process the dispersed wavelength channels, e.g., to redirect individual wavelength channels along predetermined paths within the WSS array. In accordance with one or more embodiments, the beam deflection element107may be implemented as a pixilated liquid crystal spatial light modulator (referred to herein as a LC deflection element) or as any other suitable pixilated spatial light modulator, e.g., a MEMS based device employing micromirror pixels.

As described in more detail below, the WSS array101employs a symmetric architecture with reference to symmetry axis109thereby allowing a single optical system105and liquid crystal deflection element107to be shared among the several WSS's of the WSS array, e.g., WSS-1and WSS-2in this example. However, while WSS-1and WSS-2may share many of the same optics, the architecture according to one or more embodiments allows for the WSS devices of the WSS array to be independently controllable devices. Thus, the WSS array according to one or more embodiments provides for multi-WSS device having a reduced size and optical complexity yet still retaining the independent processing capability inherent to a larger, more costly device.

In one or more embodiments, the input section103may include several input and output ports for carrying one or more optical WDM signals, e.g., the device may include several optical fibers, planar waveguides, or the like, any of which may be assigned as input or output ports. In the embodiments of the invention described below, the input/output ports are implemented as optical fibers. However, any other type of port may be used without departing from the scope of the present invention.

In the illustrative embodiment shown inFIG. 1, the input section103includes an input section for WSS-1that includes input fiber111aand several output fibers111b,111c, . . .111n, where n is a non-zero integer. The input section103further includes an input section for WSS-2that includes input fiber113aand several output fibers113b,113c, . . .113n, where n is a non-zero integer. Thus,FIG. 1shows, by way of example, an array of two 1×N WSS devices comprising WSS-1and WSS-2. Stated differently, the input section103of WSS array101includes an array of optical fibers111a,111b,111c, . . .111nand113a,113b,113c, . . .113nthat form a fiber stack along the y-axis of the device as shown inFIG. 1. In one or more embodiments, this stack lies in the y-z plane. Furthermore, in one or more embodiments, the symmetry line109also lies in the y-z plane and the input section103may be symmetric about symmetry line109.

The input section103further includes a corresponding array of optical power elements, e.g., an array of collimation lenses in the form of an array of microlenses, or the like, that are each positioned in front of the output/inputs of the optical fibers. As used herein, the term “optical power element” includes any optical element that possesses the ability to guide/alter the direction of a light ray and/or focus a set of light rays, e.g., a refractive lens, a diffractive lens, a prism, a planar wave guiding device, or the like are all optical power elements within the scope of the present disclosure. Returning toFIG. 1, the first group of optical fibers111a,111b,111c, . . . ,111nin combination with a corresponding first group of collimation lenses115a,115b,115c, . . . ,115nform the input section of WSS-1, and a second group of optical fibers113a,113b,113c, . . . ,113nin combination with a corresponding second group of collimation lenses117a,117b,117c, . . . ,117nform the input section of WSS-2. WhileFIG. 1shows the array of optical power elements implemented as an array of microlenses, other types of optical power elements may be used without departing from the scope of the present invention. For example, a planar lightwave circuit (PLC) type beam converter employing a tapered waveguide array, or the like, may be employed.

In one or more embodiments as described in further detail below in reference toFIG. 3, for example, the optical axes of the first group of fibers are displaced relative to the optical axes of the first group of collimation lenses. This relative displacement between the array of ports and the array of collimation lenses results in the first group of input and output beams119being launched into (or out of) the optical system105within the y-z plane and at an angle θ1with respect to symmetry axis109. For example, in the illustrative embodiment shown inFIG. 1, the optical axes of the first group of collimation lenses is displaced along the negative y-direction relative to the optical axes of the first group of fibers. This results in the group of input and output beams119from WSS-1being launched along a direction θ1that is generally downward (i.e., along a general direction having a y-component along the negative y-direction).

Likewise, the optical axes of the second group of fibers are displaced relative to the optical axes of the second group of collimation lenses, resulting in the second group of input and output beams121being launched into (or out of) the optical system105at an angle θ2with respect to symmetry axis109. For example, in the illustrative embodiment shown inFIG. 1, the optical axes of the second group of collimation lenses is displaced along the positive y-direction relative to the optical axes of the second group of fibers. This results in the group of input and output beams121from WSS-2to be launched along a direction θ2that is generally upward (i.e., along a general direction having a y-component along the positive y-direction).

As alluded to above, the illustrative example shown inFIG. 1is a WSS array that employs two 1×N WSS devices: WSS-1and WSS-2. Thus, in the example shown inFIG. 1WSS-1includes one input fiber111athat launches a first WDM signal beam119ainto the device, and also includes one input fiber113athat launches a second WDM signal121ainto the device. The input/output fiber configuration shown here is for the sake of illustration only and is not intended to limit the scope of the present invention. Rather, any useful input/output port combination is possible without departing from the scope of the present invention. For example, if the WSS array disclosed herein is to be used as one part of a ROADM branching node that employs route and select architecture, the ports of WSS-2may be inverted to that shown, e.g., fiber113amay be an output fiber and fibers113b,113c, . . . ,113nmay be input fibers (for connection to another WSS array and for connection to the appropriate add/drop modules. In other words, the WSS-1may serve as a demultiplexer and the WSS-2may serve as a multiplexer and vice-versa.

Returning to the configuration shown inFIG. 1, the first WDM signal is launched into the device from input fiber111a, and after passing through collimation lens115a, forms WDM signal beam119atravelling through optical system105in the y-z plane at an angle θ1. WDM signal beam119athen encounters lens123for shaping the WDM signal beam119ain the x-direction. In one example, lens123may be a cylindrical lens with its cylindrical axis along the y-direction and may work in combination with collimation lens115aas a beam expanding telescope. Thus, lens123does not have an effect on the WDM signal beam as seen in the view shown inFIG. 1.

After passing though lens123, the WDM signal beam119aencounters lens125. In the example shown inFIG. 1, lens125is a cylindrical lens with its cylindrical axis along the x-direction. The action of lens125relies on the LC deflection element107being positioned in the focal plane of lens125. In addition, lens125is centered on the symmetry axis109. Because the LC deflection element107is positioned at the focal plane of lens125, any set of rays that originate from the same height on the LC deflection element107will emerge from lens125as a set of parallel rays. Conversely, any set of parallel rays entering lens125will be focused at the same height on LC deflection element107.

For example, as shown inFIG. 1, any incoming beam travelling along the angle θ1(e.g., WDM signal beam119a) will be directed by lens125to a y-position of −h1on the LC deflection element107. Conversely, the set of rays131,133, and135that originate from a position of −h1on LC deflection element107will exit lens125as parallel rays travelling at the same angle θ1as shown inFIG. 1. Likewise, any incoming beam travelling along the angle θ2(e.g., WDM signal beam121a) will be directed by lens125to a y-position of +h1on the LC deflection element107. Conversely, the set of rays137,139, and141that originate from a position of +h1on LC deflection element107will exit lens125as parallel rays travelling at the same angle θ2as shown inFIG. 1.

Returning to the progression of WDM signal beam119athrough the optical system105, after passing through lens125, the WDM signal beam119apasses through dispersive element127that angularly disperses the wavelength channels of the WDM signal beam119ain the x-z plane as shown in the view of the device shown inFIGS. 2A-2B. In one or more embodiments, the dispersive element127may be a diffraction grating, a prism, or a grism (diffraction grating prism combination), or any other suitably dispersive optic. While the dispersive element127is shown here as a transmissive optic, a reflective optic, e.g., a blazed grating, or the like, may be used without departing from the scope of the present invention.

After passing through the dispersive element127, the dispersed wavelength channels pass through lens129that focuses the dispersed wavelength channels onto the LC deflection element107as shown in further detail inFIGS. 2A-2B. In one or more embodiments, the lens129may be a cylindrical lens with its cylindrical axis along the y-direction.

The LC deflection element107is a 2-dimensional pixelated optical element, e.g., a pixellated spatial light modulator, that may reflect or redirect one or more of the dispersed wavelength channels so that one or more of the wavelength channels may be routed to any one of the output fibers as described in more detail below.

With respect to WSS-1, according to one or more embodiments, because of lens125, all of the rays that originate from a y-position −h1on the LC deflection element will be output from lens125along the angle θ1as shown inFIG. 1but will be displaced relative to each other by an amount that depends on the deflection angle from the LC deflection element107. Accordingly, with the LC deflection angle set appropriately, the reflected output rays (e.g., those that correspond to the set of rays131,133,135, each of which may include one or more of the wavelength channels of the WDM signal beam119a) may be routed to any one of output fibers111b,111c, . . . ,111n. Furthermore, in one or more embodiments, because each of the collimation lenses is displaced relative to its corresponding output fiber by the same amount, the individual output beams can be recoupled into their respective output fibers with improved efficiency.

Likewise, regarding WSS-2, according to one or more embodiments, because of lens125, all of the rays that originate from a y-position +h1on the LC deflection element107will be output from lens125along the angle θ2as shown inFIG. 1but will be displaced relative to each other by an amount that depends on the deflection angle from the LC deflection element. Accordingly, with the LC deflection angle set appropriately, the reflected output beams (e.g., those that correspond to the set of rays137,139, and141, each of which may include one or more of the wavelength channels of the WDM signal beam121a) may be routed to any one of output fibers113b,113c, . . . ,113n. Furthermore, in one or more embodiments, because each of the collimations lenses is displaced relative to its corresponding output fiber by the same amount, the individual output beams can be recoupled into their respective output fibers with improved efficiency.

Thus, the combination of input section103and lens125results in a WSS array device that launches a given set of beams along a given angle, e.g., θ1for WSS-1and θ2for WSS-2and then directs these beams to positions on the LC deflection element that depend only on the input angle (−h1for WSS-1and h2for WSS-2). Thus, the WSS array according to one or more embodiments allows for the two sets of signals119and121to/from each WSS to share the same optical system105and LC deflection element107, while simultaneously preserving the ability of the WSS array to separately process the individual wavelength channels as described in further detail below in reference toFIGS. 2A-2B.

FIG. 2Ashows a WSS array device in accordance with one or more embodiments. More specifically,FIG. 2Ashows an orthogonal view of the same device described above in reference toFIG. 1(a view of the x-z-plane of the device). Accordingly, in this view, the stack of fibers and microlenses that form the input section103is viewed from the top of the fiber stack and thu, only input fiber111ais seen with its corresponding microlens115a. While the following description focuses on WSS-1, precisely the same description will apply for WSS-2due to the symmetry of the system. As described above, for WSS-1, WDM signal beam119ais launched into the system via input fiber111a. In the view shown inFIG. 2A, the launch angle θ1is into the page and thus, not visible. In one or more embodiments, WDM signal beam119aincludes a number of wavelength channels, with the channels having a wavelength range from a longest wavelength λ1to a shortest wavelength λn. In some examples, the number of wavelength channels may be large, e.g., 96 wavelength channels having a spacing of 50 or 100 GHz on a fixed grid. In other examples, the device may be employed in a flexible grid system that may employ frequency spacing of, e.g., 12.5 GHz and having more than 96 wavelength channels, e.g., 130 or more wavelength channels.

Returning toFIG. 2A, the WDM signal beam119afirst encounters lens123that serves to shape the WDM signal beam119ain the x-direction, e.g., to expand the beam to a diameter in the x-direction that is suitable to achieve a desired beam size on the dispersive element127. For example, the collimating lens115aand lens123may serve as a beam expanding telescope. In one or more embodiments, the dispersive element127serves to angularly disperse the wavelength channels of the WDM signal beam as shown inFIG. 2A. After being angularly dispersed by dispersive element127, the wavelength channels λ1to λnare then focused onto the LC deflection element107by the lens129such that the wavelength channels are spatially dispersed in the x-direction according to wavelength on LC deflection element107.

One example of a distribution of wavelength channels on the surface of the LC deflection element is shown more clearly inFIG. 2B, which shows the LC deflection element as viewed along the z-axis. More generally, the wavelength channels may be arranged on the two-dimensional surface of LC deflection element107(e.g., in the x-y pane) as elongated strips or elliptical spots. For simplicity, the wavelength channels are treated as discrete wavelength signals that may be operated on by the LC deflection element independently. However, in one or more embodiments, the LC deflection element need not be limited to operating on individual wavelength channels but may operate on groups of wavelength channels. Furthermore, as shown inFIG. 2B, the wavelength channels or groups of channels themselves need not have a fixed bandwidth because the LC deflection element may be implemented as a LCOS- or MEMS-based spatial light modulator that is fully reconfigurable on a dynamic basis. Accordingly, one or more embodiments of the present invention may be implemented in current fixed grid architectures and/or in current or later-developed flexible grid architectures.

Returning toFIG. 2A, the LC deflection element107may then selectively redirect one or more of the wavelength channels in a direction so as to eventually redirect the selected one or more wavelength channels λ1to λn, to one or more output ports (e.g., one or more of the other optical fibers that are hidden from view underneath fiber111a, e.g., as shown inFIG. 1). In the case of the view shown inFIG. 2A, the redirection accomplished by the LC deflection element107is along an angle located in a plane that is perpendicular to the page (the beams are redirected along an angle in the y-z plane, e.g., as shown and described in further detail above in reference toFIG. 1). Once reflected from the LC deflection element107, the redirected wavelength channels again encounter lens129and are further redirected to the dispersive element127where the redirected wavelength channels are recombined in the y-z plane. For example, those wavelength channels that are redirected along the same angle are recombined into a single beam that is then redirected along a direction that may allow for output of the processed signal at one of the output ports.

For example, consider a WDM signal beam119athat includes three WDM channels having wavelengths λ1, λ2, and λ3and channel bandwidths δλ1, δλ2, and δλ3, respectively. In the example shown inFIG. 1, the WDM signal beam119aenters the system at a launch angle θ1in the y-z plane. Furthermore, the ray representing the WDM signal beam119atraveling at an angle θ1in the y-z plane passes through the center of lens125and therefore is not deflected away from the angle θ1in the y-z plane. Upon passing through the dispersive element127, the three wavelength channels of WDM signal beam119aare then angularly dispersed in a plane that is perpendicular to the y-z plane while all of the angularly dispersed channels still travel at an angle θ1in the y-z plane. These three dispersed wavelength channels are then focused by lens129onto different x-positions on the LC deflection element107as shown inFIG. 2B.

With respect to the routing capability of the device, a number of different routing combinations are now possible. For example, consider that all three wavelength channels are desired to be routed to output port111nshown inFIG. 1. Accordingly, the corresponding portions of the LC deflection element will deflect each of wavelength channels λ1, λ2, and λ3so that each of these wavelength channels returns along the ray131shown inFIG. 1. The action of the dispersive element127on the return path for these channels is to recombine (multiplex) each of the wavelength channels into the same beam now propagating in the y-z plane. This combined beam is then redirected by lens125to propagate along the output ray136having the launch angle θ1in the y-z plane, but now displaced from input WDM signal beam119asuch that the action of collimating lens115nis to couple the recombined and redirected WDM signal to the output fiber111n. Thus, in this mode of operation, the action of WSS-1is pass all three wavelength channels of WDM signal beam119afrom input fiber115ato output fiber111n.

In another example, perhaps it is desired to route several of the wavelength channels separately to different output fibers. For example, perhaps the LC deflection element107deflects the λ1channel along ray133, deflects the λ2channel along ray135, and directs the λ3channel along ray131. Again, the action of the dispersive element is to redirect each of these beams into the y-z plane. However, in this case, the dispersive element will not recombine the beams into a single beam, but rather, will create a fan of three beams travelling in the y-z plane. Furthermore, because each of these beams originated from the same y-position on the LC deflection element107, they will exit lens125as a set of parallel rays that propagate along the same launch angle θ1as the original WDM signal beam119a. However, because each beam entered lens125at a different height, the output beams will be displaced from one another such that, e.g., the λ1channel will propagate along ray138, the λ2channel will propagate along ray140, and the λ3channel will propagate along ray136. Accordingly, in this configuration the action of WSS-1is to route the λ1channel from input fiber111ato output fiber111c, to route the λ2channel from input fiber111ato output fiber111b, and to route the λ3channel from input fiber111ato output fiber111n.

In view of the above, it is clear that in one or more embodiments of the WSS array disclosed herein, the wavelength channels of any WDM signal may be arbitrarily routed to any of the output fibers. Furthermore, due to the symmetry of the system shown inFIG. 1, the above description also applies to routing WDM signals using WSS-2. This is because, as shown inFIG. 2B, the dispersed wavelength channels of WSS-1and WSS-2are eventually focused onto respectively different portions of the LC deflection element107(these portions are separated in the y-direction, as shown inFIG. 1andFIG. 2B). Furthermore, while the example shown inFIGS. 1-3employs one input port and n output ports, one may appreciate that the output ports may be reconfigured as input ports and vice-versa. Furthermore, without departing from the scope of the present invention, any number of input and output ports may be used. Likewise, while the example explicitly shown inFIGS. 1-3is a WSS array that employs two WSS devices, any number of WSS devices may be employed without departing from the scope of the present invention. For example, if the input section is designed to employ four distinct launch angles, the array may accommodate four independent WSS devices.

FIG. 3shows an input section of a WSS array in accordance with one or more embodiments. More specifically,FIG. 3shows a more detailed view of the input section103described in detail in reference toFIG. 1above. As described previously, the input section103includes an input section for WSS-1that includes input fiber111aand several output fibers111b,111c, . . .111n, where n is a non-zero integer. The input section103further includes an input section for WSS-2that includes input fiber113aand several output fibers113b,113c, . . .113n, where n is a non-zero integer. The input section103further includes a corresponding array of collimation lenses, e.g., an array of microlenses, or the like that are each positioned in front of the output/inputs of the optical fibers. Accordingly, the first group of optical fibers111a,111b,111c, . . . ,111nin combination with a corresponding first group of collimation lenses115a,115b,115c, . . . ,115nform the input section of WSS-1, and a second group of optical fibers113a,113b,113c, . . . ,113nin combination with a corresponding second group of collimation lenses117a,117b,117c, . . . ,117nform the input section of WSS-2.

With respect to the array of microlenses, as shown inFIG. 3, this may be an array of contiguous, uniformly spaced micro-optics that is manufactured as an integrated unit. Accordingly, the microlenses may be formed on the surface of a bulk material, e.g., fused silica, silicon, or any other suitable material. In one or more embodiments, the distance between each lens in the array, shown as d1inFIG. 3and commonly referred to as the “lens pitch” may be 250 microns. However, any other lens pitch is also possible depending on the particular design. Examples of some commercially available lens pitches include 125 microns and 500 microns.

With respect to the array of fibers, each fiber is positioned to correspond approximately with its respective microlens. Thus, in one or more embodiments, the fiber pitch d2is approximately equal to the microlens pitch. However, as described above in reference toFIG. 1, the first group of optical fibers that corresponds to WSS-1may be displaced upward relative to the microlens array such that the optical axes of the group of fibers is displaced relative to the optical axes of the microlens array. The relative displacement between fiber axes and microlens array optical axes for the group of fibers and lenses associated with WSS-1is shown as displacement d3. In one or more embodiments, d3may be approximately 10 microns, i.e., the optical axes of the group of fibers111a,111b, . . . ,111nare displaced approximately 10 microns upward relative to the optical axes of the microlenses. In one or more embodiments, this magnitude of displacement may yield a θ1that is approximately a few degrees depending on the precise microlens array used. More generally, for any relative displacement d3between the lens and fiber optical axis, the resulting output angle is

θ=tan-1⁢d3/f,
where f is the focal length of the microlens.

Similar to the first group of optical fibers corresponding to WSS-1, the second group of optical fibers corresponding to WSS-2are also displaced relative to the microlens array such that the optical axes of the group of fibers is displaced relative to the optical axes of the microlens array. However, in the case of WSS-2, because an upward launch angle θ2is desired, the fiber optical axes are displaced downward relative to the micro lens optical axes. This downward displacement is shown as d4. WhileFIG. 3shows a maximum symmetry arrangement where d3=−d4and thus θ1=−θ2, other arrangements are possible without departing from the scope of the present invention. In one or more embodiments, the individual WSS input sections are designed to have different launch angles, but they need not necessarily be the negative of one another. Furthermore, whileFIG. 3shows a configuration showing only two WSS's, any number of WSS's having any number of launch angles may be employed without departing from the scope of the present invention.

FIGS. 4A and 4Bshow a method for routing one or more wavelength channels of a plurality of WDM signals using a WSS array in accordance with one or more embodiments. While the various blocks in this flowchart are presented and described sequentially, one of ordinary skill will appreciate that, in accordance with one or more embodiments, at least a portion of the blocks may be executed in different orders, may be combined or omitted, and at least a portion of the blocks may be executed in parallel.

In step401, the WSS array receives a first and a second WDM signal from a first input port of a first WSS and a second input port of a second WSS, respectively. For example, the first and second WSS may be similar to WSS-1and WSS-2shown and described above in reference toFIGS. 1-3. Likewise, the first and second input ports may be any of the ports shown above inFIGS. 1-3and implemented as, e.g., optical fibers or any other suitable waveguide architecture employed for use in optical networking and/or telecommunications.

In step403, the first WDM signal is passed through a first optical power element, e.g., a first microlens having an optical axis that is displaced from an optical axis of the first input port. Due to the displacement between the port optical axis and the microlens optical axis, the first WDM signal is directed along a first angle as it is outputted from the microlens. For example, as shown inFIGS. 1 and 3, the first WDM signal is launched into the WSS array along an angle θ1(shown as downward in the FIGS.) because the port optical axis is displaced in a positive y-direction, relative to the optical axis of the microlens.

In step405, the second WDM signal is passed through a second optical power element, e.g., a second microlens having an optical axis that is displaced from an optical axis of the second input port. Due to the displacement between the port optical axis and the microlens optical axis, the second WDM signal is directed along a second angle. For example, as shown inFIGS. 1 and 3, the second WDM signal is launched into the WSS array along an angle θ2because the port optical axis is displaced in a negative y-direction, relative to the optical axis of the microlens.

In step407, the first and the second redirected WDM signals are passed through a lens configured to convert the first and second angles to first and second displacements on a surface of a beam deflection element, wherein the beam deflection element is located at the focal plane of the lens. For example, the lens may be similar to lens125shown inFIG. 1. In other words, the lens125may be shared by all WSS devices of the WSS array.

In step409, the first and second redirected WDM signals are passed through a dispersive element to angularly disperse at least a first and a second wavelength channel from the first and second redirected WDM signals, respectively. For example, the dispersive element may be a diffraction grating, a prism, or a combination grating and prism, known as a grism.FIG. 2Ashows one example of a dispersive element127that may be used to angularly disperse one or more wavelength channels (e.g., λ1, λ2, . . . , λn) of the WDM signals. While the dispersive element is shown as a transmissive optical element herein, a reflective dispersive element may be employed without departing from the scope of the present invention.

In step411, the first and the second wavelength channels from the first and second WDM signals are focused onto a first and a second spatial portion, respectively, of the beam deflection element. For example,FIG. 2Ashows that the focusing may be accomplished by lens129andFIG. 2Bshows that the first wavelength channels from the first the first WMD signal may be focused at a position that is offset from the second wavelength channels by a distance2hin the y-direction with the wavelength dispersion direction corresponding to the x-direction. Accordingly, the first and second wavelength channels may be processed independently by separate groups of pixels on the beam deflection element107.

In step413, the liquid crystal beam deflection element deflects at least one wavelength channel of the first WDM signal along a third angle. For example, if the liquid crystal beam deflection element is a liquid crystal on silicon spatial light modulator, the steering (deflection) of the wavelength channel may be accomplished by applying pixel voltages to a corresponding number of pixels impinged upon by the focused spot of the wavelength channel to impart a spatially varying phase onto the corresponding wavelength channel optical beam. Other known methods of beam steering may also be employed, e.g., a micromirror device (e.g., a MEMS chip, or the like) may be employed that steers a wavelength channel by tilting one or more micromirrors.

In step415, the liquid crystal beam deflection element deflects at least one wavelength channel of the second WDM signal along a fourth angle in a manner that is identical to that described above in step413. Graphical examples of the deflections described in steps411and413are shown and described above in reference toFIG. 1.

In step417, the at least one deflected wavelength channel of the first and second WDM signals is passed back through the dispersive element and lens to convert the third and fourth angles to the first angle and second angles, respectively. As described above in reference toFIGS. 1 and 2A-2B, because the beam deflection element107is located in the focal plane of the lens125, all rays that pass through lens125but originate from a common point on the surface of the beam deflection element (e.g., at a position +h or −h as shown inFIGS. 1 and 2B) are converted to a set of parallel rays (i.e., a set of rays that propagate at the same angle). This aspect of lens125is shown and described above in reference toFIGS. 1, 2A, and 2B.

In step419, the deflected wavelength channels of the first and second WDM signals are respectively routed out of a first and a second output port of the first and second WSS, respectively.

The above example describes a WSS array each having at least one input port and one output port. Thus, the scope of the method disclosed herein includes WSS arrays that employ any possible combination of numbers of input and output ports. Accordingly, the method disclosed herein may be employed where two WSS arrays are coupled together to implement a branching network node that employs a route and select architecture and/or one or more WSS array as disclosed herein may be configured as a reconfigurable optical add drop multiplexer (ROADM).