Wavelength Selective Switch

Abstract

This patent document discloses, among other things, a wavelength selective switch (WSS) for redirecting an optical WDM signal or channel based on a combination of spatially separated lights of different optical polarizations in an optical birefringent material, and using a diffractive optical device to separate lights of different optical WDM wavelengths into spatially separated light beams to perform wavelength selective optical switching in optical WDM applications. It is noteworthy that the optical device for processing the optical WDM signal in the disclosed optical WSS device is designed to provide a scalable optical WSS device, in which different WDM signals share optical components to reduce the number of optical components designed for different WDM signals.

Description

[0001] Priority claims and related applications

[0002] This patent document is a Chinese national phase application of PCT international application PCT / US2022 / 013011 filed on January 19, 2022, which claims priority and benefits of U.S. Provisional Patent Application No. 63 / 139,084, entitled “Wavelength Selective Switch,” filed on January 19, 2021. The entire disclosure of the above application is incorporated by reference as part of the disclosure of this patent document. Technical Field

[0003] This patent document relates to optical switching in fiber optic networks and other optical devices or systems. Background Art

[0004] An optical switch is a device that redirects light beams. In optical devices, modules, or systems based on optical wavelength division multiplexing (WDM), light beams or signal channels of different optical wavelengths need to be redirected through an optical switch with wavelength selectivity so that optical WDM signals or channels of different optical WDM wavelengths can be redirected to the desired direction or location. In optical WDM fiber networks, for example, such wavelength selective optical switching is used to perform important optical network operations in ROADM (Reconfigurable Optical Add / Drop Multiplexer) and optical cross-connect switches. Summary of the invention

[0005] This patent document discloses, inter alia, a wavelength selective switch (WSS) for redirecting optical WDM signals or channels based on a combination of spatial separation of light of different optical polarizations in an optical birefringent material and spatial separation of light of different wavelengths in a diffractive optical device to perform wavelength selective optical switching in optical network applications. It is noteworthy that the optical devices for processing optical WDM signals in the disclosed optical WSS device are designed to provide a scalable optical WSS device in which different WDM signals share optical components and packaging.

[0006] In one embodiment, the disclosed technology can be implemented to provide, for example, a wavelength selective optical switch, which includes a linear array of optical fibers spaced apart from each other along a first direction to form a first plane having a normal direction along a second direction perpendicular to the first direction; an optical birefringent material, which is positioned to receive output light from a fiber terminal port of the linear array of optical fibers and is configured to spatially separate the light output from each optical fiber into two spatially separated light beams of two linear orthogonal optical polarizations to define a second plane having a normal direction parallel to the first direction; and a collimating lens, which is located away from the optical birefringent material to receive a spatially divergent light beam of a linear orthogonal optical polarization from each optical fiber of the linear array of optical fibers and is spaced apart from the fiber terminal port of the linear array of optical fibers by the focal length of the collimating lens to respectively transform the two spatially divergent light beams of the two linear orthogonal optical polarizations from each optical fiber into two spatially separated and parallel light beams of two orthogonal optical polarizations. An optical polarization rotator is positioned and constructed to receive a light beam of only one of two linear orthogonal optical polarizations from the optical fiber linear array to rotate the polarization of the light beam of only one of the two linear orthogonal optical polarizations received from the optical fiber linear array to be parallel to the other of the two linear orthogonal optical polarizations, so that two spatially separated and parallel light beams from each optical fiber are in the same linear polarization; and a grating is positioned downstream of the optical polarization rotator and the collimating lens to receive two spatially separated and parallel light beams of the same linear polarization from each optical fiber of the optical fiber linear array, and diffract each light beam into different diffracted output light beams of different light wavelengths in different diffracted beam directions. The optical switch also includes an optical deflector array positioned relative to the grating to receive different diffracted output beams of different light wavelengths in different diffracted beam directions from each optical fiber of the optical fiber linear array, and redirect the different diffracted output beams of different light wavelengths in different diffracted beam directions received from each optical fiber of the optical fiber linear array back to the grating, the optical polarization rotator, the collimating lens, the optical birefringent material and the optical fiber terminal port of the optical fiber linear array; and a control device coupled to the optical deflector array to apply deflector control signals to the optical deflectors, respectively, so that each optical deflector responds to the corresponding applied control signal to guide the diffracted output beam from the grating back to the grating in a desired direction based on the corresponding applied control signal, wherein the deflector control signal is generated to achieve the desired wavelength selective optical switching in the optical fiber linear array.

[0007] In some embodiments, the above example of a wavelength selective optical switch may further include the following lenses: a first cylindrical lens is located between the grating and the optical deflector array and is spaced apart from each of the grating and the optical deflector array by a focal length of the first cylindrical lens. The first cylindrical lens is positioned to process and transmit light associated with a light beam that is transmitted through the optical polarization rotator. A second cylindrical lens is located between the grating and the optical deflector array and is spaced apart from each of the grating and the optical deflector array by a focal length of the second cylindrical lens. The second cylindrical lens is positioned to process and transmit light associated with other light beams that are not transmitted through the optical polarization rotator, wherein each of the first and second cylindrical lenses is oriented to provide optical power for bending light in a second plane while exhibiting no optical power in the first plane. A third and fourth cylindrical lens are located between the grating and the optical deflector array, and each of the third and fourth cylindrical lenses is oriented to provide optical power for bending light in the first plane while exhibiting no optical power in the second plane. The third cylindrical lens is located closer to the grating and is spaced apart from the grating by a focal length of the third cylindrical lens, and the fourth cylindrical lens is located closer to the optical deflector array and is spaced apart from the optical deflector array by a focal length of the fourth cylindrical lens. The third and fourth cylindrical lenses are spaced apart from each other by a distance equal to the sum of the focal lengths of the third and fourth cylindrical lenses, so that the third and fourth cylindrical lenses form a telecentric lens system located between the grating and the optical deflector array.

[0008] In another embodiment, the disclosed technology can be implemented to provide a wavelength selective optical switch, which includes a linear array of optical fibers spaced apart from each other along a first direction to form a first plane having a normal direction along a second direction perpendicular to the first direction; an optical birefringent material, which is positioned to receive output light from an optical fiber terminal port of the linear array of optical fibers and is configured to spatially separate the light output from each optical fiber into two spatially separated light beams of two linear orthogonal optical polarizations to define a second plane having a normal direction parallel to the first direction; and a collimating lens, which is positioned away from the optical birefringent material to receive the orthogonal optical polarizations from each optical fiber of the linear array of optical fibers. The device further comprises a grating disposed downstream of the optical polarization rotator and the collimating lens to receive two spatially divergent light beams of the same polarization from each optical fiber of the optical fiber linear array and to be spaced apart from the optical fiber terminal port of the optical fiber linear array by the focal length of the collimating lens to transform the two spatially divergent light beams of the two linear orthogonal optical polarizations from each optical fiber into two spatially separated and parallel light beams of the two linear orthogonal optical polarizations respectively; and an optical polarization rotator disposed and configured to receive a light beam of only one of the two linear orthogonal optical polarizations from the optical fiber linear array to rotate the polarization of the light beam of only one optical polarization received from the optical fiber linear array to be parallel to the other optical polarization of the two linear orthogonal optical polarizations, so that the two spatially separated and parallel light beams from each optical fiber are in the same polarization. The device further comprises a grating disposed downstream of the optical polarization rotator and the collimating lens to receive two spatially separated and parallel light beams of the same polarization from each optical fiber of the optical fiber linear array and to diffract each light beam into different diffracted light beams of different light wavelengths in different diffracted light beam directions respectively. The grating is a reflective grating and guides the different diffracted light beams of different light wavelengths in different diffracted light beam directions to the same side of the grating. The optical deflector array is arranged in the optical path of different diffracted beams of different light wavelengths in different diffracted beam directions from the grating to reflect the different diffracted beams back toward the grating, thereby redirecting the received different diffracted beams from the grating to the collimating lens, the optical birefringent material, and the fiber terminal port of the optical fiber linear array. The device also includes: a control device, which is coupled to the optical deflector array to apply deflector control signals to the optical deflectors respectively, so that each optical deflector responds to the corresponding applied control signal to guide the diffracted beam from the grating in a desired direction toward the collimating lens, the optical birefringent material, and the fiber terminal port of the optical fiber linear array based on the corresponding applied control signal for optical switching, wherein the deflector control signal is generated to achieve the desired wavelength selective optical switching in the optical fiber linear array.In some implementations of this embodiment, the device may include an additional optical fiber linear array stacked on top of the optical fiber linear array in a second direction perpendicular to the first direction to guide light through the optical birefringent material, the collimating lens, the optical polarization rotator and the grating; and the additional optical deflector array is positioned to receive light from the additional optical fiber linear array and reflect it back to the grating to perform the desired optical switching.

[0009] Various applications of these features can be made, including stacking two or more linear optical fiber arrays that share the same optics and packaging in the disclosed optical WSS device to form a scalable optical WSS switch in fiber optic networks and other systems.

[0010] The above described and other features of the disclosed technology are described in more detail in the drawings, the description, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1-6 Here is an example using numbers to represent the parts:

[0012] 1, 2 and 3 - three optical axes of three separate lens systems;

[0013] 4-Fiber Array;

[0014] 5-Wollaston prism;

[0015] 6-optical path compensator;

[0016] 7-Polarization rotator (half-wave plate);

[0017] 8- Collimating / focusing lens (can be a spherical mirror);

[0018] 9-Dispersion grating (can be reflective type);

[0019] 10&13-cylindrical lens (telecentric);

[0020] 11 & 12 - Cylindrical Fourier lens; and

[0021] 14-LCoS spatial light modulator or MEMS array.

[0022] Figure 1 An example of one implementation of an optical wavelength selective switch (WSS) is shown.

[0023] Figure 2 Shown as Figure 1 Details of various optical components in an example of an optical WSS device are shown.

[0024] Figure 3A top view of the hardware components in the YZ plane is shown, further illustrating the use of an optical channel separated into two parallel optical paths of two linear orthogonal polarizations processed in parallel by processing and switching. Figure 1 and Figure 2 The WSS device in the

[0025] Figure 4 The invention shows that the optical fiber array is replaced by two or more optical fiber arrays stacked on each other in the XZ plane along the Y direction. Figure 1 Example of an Mx(1xN)WSS device obtained with a single fiber array in the XZ plane.

[0026] The following Figure 5 An example of an optical WSS device using reflective gratings in both the XZ plane and the YZ plane is further shown, where the 1-D fiber array is placed in the switching plane (XZ plane).

[0027] Figure 6 Shown is a method for implementing Figure 5 An example of an apparatus implementation of a wavelength selective switch in an optical system. DETAILED DESCRIPTION

[0028] Wavelength selective switch (WSS) devices have a wide range of applications. The structures of various wavelength selective switch (WSS) devices in optical fiber networks are often complex and expensive; and as the number of optical WDM channels increases, it may be difficult to expand such optical WSS devices. However, some wavelength selective switch (WSS) devices deployed in optical networks may be limited to the network core, mainly due to their relatively high cost and poor scalability.

[0029] There is a need for a lower cost solution with improved scalability so that WSS can be used not only in core networks but also in metropolitan area networks, access networks and data centers. The design of the optical WSS device disclosed in this patent document combines the technical features of sharing of optical components for processing different light beams, use of optical polarization diversity and unique design of optical lens systems to provide a scalable and high-performance optical WSS platform.

[0030] Figure 1An example of an embodiment of an optical WSS switch is shown and includes two figures in two perspective views in the YZ plane and the XZ plane, respectively. The fiber array (4) in this example is a one-dimensional linear fiber array in a first direction marked as the X direction, and the optical axis of the optical switch is along the Z direction. The Y direction is a direction perpendicular to the X direction and the Z direction. The XZ plane formed by the optical fiber (4) is parallel to the optical fiber (in a normal direction parallel to the Y direction) and constitutes a switching plane in which certain light beams are redirected to perform optical switching. In order to accommodate high channel counts, a small fiber pitch (e.g., 127 microns or less) can be used in the fiber array.

[0031] like Figure 1 As shown by the dotted lines in , the output fiber ports of the optical fibers are aligned with each other at the dotted lines. Each optical fiber carries its own light, which can be a single optical channel of a specific optical WDM wavelength or a combination of two or more different optical channels of different optical WDM wavelengths. The optical birefringent material (5) is arranged to receive the output light from the fiber port of the optical fiber linear array (4), and is configured to spatially separate the light output from each optical fiber into two spatially separated light beams of two linear orthogonal optical polarizations in the YZ plane. The optical birefringent material (5) can be implemented in different ways. For example, a Wollaston prism formed by two pieces of birefringent crystal material whose crystal optical axes are arranged to be perpendicular to each other can be used to separate P and S polarized light into two independent light beams in the YZ plane as marked by the black and blue light rays in the figure. As Figure 1 As shown in the figure above, one linear polarization light output by the birefringent material (5) is guided to the upper half above the optical axis (z direction), while another orthogonal linear polarization light is guided to the lower half below the optical axis. The two divergent light beams of the two orthogonal polarizations are generally spherical beams or Gaussian beams, whose centers are substantially close to the optical axis and are separated by a certain distance due to the optical path difference. The Wollaston prism can be a very thin sheet, which can be directly attached to the optical fiber port.

[0032] Next, in an optical system for an optical WSS device, a collimating lens (8) is configured to receive spatially divergent light beams of orthogonal P and S optical polarizations from each optical fiber of the optical fiber linear array (4) in the YZ plane from the Wollaston prism (5). The collimating lens (8) is spaced apart from the optical fiber terminal port of the optical fiber linear array (4) by the focal length of the collimating lens (8) to transform the two spatially divergent light beams of two orthogonal P and S optical polarizations from each optical fiber into two spatially separated and parallel light beams, which still maintain the two P and S orthogonal optical polarizations. The collimating lens (8) can be rotationally symmetric to provide optical power and collimation in all directions including both the YZ and XZ planes as shown in the figure. For example, various lenses such as spherical, aspherical, or lens group lenses can be used to implement the lens.

[0033] Next, the two spatially separated and parallel light beams of P and S orthogonal optical polarizations are processed by an optical polarization rotator (7) downstream of the collimating lens (8) to rotate the polarization of one of the two parallel light beams of P and S orthogonal optical polarizations by 90 degrees while keeping the polarization of the other of the two parallel light beams unchanged, so that after this transformation by the optical polarization rotator (7), the two light beams will be in the same polarization. The optical polarization rotator can be implemented using an optical half-wave plate or other device formed of a birefringent crystal material. This polarization rotation allows the two light beams to be in the same linear polarization perpendicular to the grooves of the downstream grating (9) to ensure effective operation of the grating (9), which is often sensitive to the optical polarization in the grating operation. In Figure 1 In the embodiment, the grooves of the grating (9) are parallel to the X direction and spaced apart from each other in the Y direction so that the dispersion or diffraction is located as follows Figure 1 In the YZ plane shown. In other embodiments, an optical polarization rotator can be placed between the collimating lens and the Wollaston prism.

[0034] The following Figure 2 It further shows Figure 1 Details of the various optical components in this example of an optical WSS device.

[0035] In the YZ plane, due to the different optical paths of the two light beams of different polarizations from the Wollaston prism (5) to the collimating lens (8), at least one optical path compensator (6) can be set in one of the two light beams to make the optical path lengths of the different light beams equal. Such an optical path compensator (6) can include a glass plate or a glass wedge to correct the beam center dispersion between the s-polarized light beam and the p-polarized light beam caused by the birefringence of the Wollaston prism (5). Depending on the material of the Wollaston prism (5), the compensator (6) can be placed in the upper half or the lower half. The compensator (6) can be placed before the collimating lens (8) or after the collimating lens (8). If the Wollaston prism (5) is a very thin sheet and the effect on the optical path difference is small enough or negligible, the optical path compensator (6) can be eliminated. The optical path compensator (6) can be replaced by a beam discrete crystal, which changes the beam path based on the optical polarization or optical frequency of the light beam. In one embodiment, for example, instead of being in an S or P polarized beam and having an effect on the S or P polarization like a glass compensator, such a discrete crystal can be designed to span the S and P polarized beams and have an effect on both S and P polarizations simultaneously to have better optical path compensation and aberration correction.

[0036] In this example, a grating (9) is positioned downstream of the optical polarization rotator (7) and the collimating lens (8) to receive two spatially separated and parallel light beams of the same polarization from each optical fiber of the optical fiber linear array (4). The grating (9) operates to diffract different spectral components contained in each light beam into different diffracted output light beams of different optical wavelengths in different diffracted beam directions. As described above, the light from each optical fiber may include light of different optical WDM wavelengths and Figure 2 This is illustrated by showing the red and green spectral components separated by the grating (9).

[0037] like Figure 2As shown, the optical deflector array (14) is configured to change the beam directions of different diffracted output beams of different light wavelengths in different diffracted beam directions generated by the grating (9) in the XZ plane to cause an optical switching operation, so that as a result of the optical switching operation, certain light channels received from the optical fiber can be switched to other optical fibers. A control module is coupled to the optical deflector array (14) to apply control signals to individual deflectors to achieve the desired optical switching. The optical deflector array (14) can be a one-dimensional array of micro-electromechanical system (MEMS) mirrors, or a two-dimensional array of liquid crystal on silicon (LCoS) cells or other controllable devices for changing the direction of light. Under the control of the control signal applied to the individual deflector, the deflector (14) redirects the different diffracted output beams of different light wavelengths in different diffracted beam directions received from each optical fiber of the optical fiber linear array back to the grating (9), the optical polarization rotator (7), the collimating lens (8), the Wollaston prism (5), and the optical fiber terminal port of the optical fiber linear array (4).

[0038] Figure 1 and Figure 2 The optical WSS device in operates by redirecting the light beam and thereby switching the light beam from fiber to fiber in the XZ plane (also referred to as the "switching plane" in this document). Figure 2 The lower figure in the XZ plane shows that one of the optical deflectors or reflectors (14) is controlled to redirect light between two optical fibers in the fiber array (the top fiber shown in the XZ plane of the 1D fiber array and the middle fiber shown in the XZ plane of the 1D fiber array).

[0039] In the example of using an LCoS spatial light modulator array in the optical WSS device described above, the LCoS unit is used to generate the desired phase modulation in the X direction, so that light beams of different wavelengths are reflected at different angles in the XZ plane to achieve the optical switching operation. The reflected light beams of different wavelengths are guided back and focused on the desired different fiber ports as output. This is Figure 2 In some embodiments, each wavelength and part or all of its two polarizations can be individually manipulated to couple to different fiber ports (with a deflection angle corresponding to a specific fiber port).

[0040] refer to Figure 1 and Figure 2In the example of FIG. 1 , two additional lens systems are provided as part of the optical WSS device in addition to a common collimating lens (8) for all beams from the optical fiber. The first lens system is formed by a first cylindrical lens (11) and a second cylindrical lens (12) for the upper beam path and the lower beam path in the YZ plane. In this specific example, the first cylindrical lens (11) is located between the grating (9) and the optical deflector array (14) and is spaced apart from each of the grating (9) and the optical deflector array (14) by the focal length of the first cylindrical lens (11). The first cylindrical lens (11) is positioned to process and transmit light associated with the beam transmitted through the optical polarization rotator (7).

[0041] Similarly, a second cylindrical lens (12) is located between the grating (9) and the optical deflector array (14) and is spaced apart from each of the grating (9) and the optical deflector array (14) by the focal length of the second cylindrical lens (12). The second cylindrical lens (12) is positioned to process and transmit light associated with other light beams that do not pass through the optical polarization rotator (7). It is noteworthy that due to this particular design, each of the first and second cylindrical lenses (11, 12) is oriented to provide optical power for bending light in a second plane, shown as the YZ plane, while not exhibiting optical power for bending or refracting light in a first plane, shown as the XZ plane. Lenses 11 and 12 are Fourier lenses because the light distribution on the deflector (14) is the Fourier transform of the light distribution on the grating (9) in the YZ plane.

[0042] therefore, Figure 1 and Figure 2 The example of the optical WSS device shown has 3 lens systems with three different optical axes marked as "1", "2" and "3" in the accompanying drawings. First, after passing through the Wollaston prism (5), the two linear orthogonal polarized light beams are spatially separated into two different divergent optical paths in the YZ plane and are guided into a collimating lens (8), which transforms the two light beams of the two optical polarizations into two spatially separated but parallel upper and lower light beams in the YZ plane. The optical axis of the collimating lens (8) is the first optical axis (1) of the three optical axes. The first lens system is shown by the components in the left frame. Secondly, the upper light beam is guided to a cylindrical Fourier lens (12) having an optical axis as the second optical axis (2). Thirdly, the lower light beam is guided to another cylindrical Fourier lens (11), which has an optical axis as the third optical axis (3). The second and third lens systems are shown in the right frame.

[0043] The lens system formed by two cylindrical Fourier lenses (11, 12) enables the diffracted light beams of different light wavelengths generated by the grating (9) to be closely focused on the corresponding optical deflector (14) in the YZ plane for proper optical switching.

[0044] refer to Figure 1 In the lower figure of FIG. 1 , the optical WSS device provides another lens system formed by a third and a fourth cylindrical lens (10, 13) located between a grating (9) and an optical deflector array (14) as a telecentric lens system. Each of the third and the fourth cylindrical lenses (10, 13) is arranged in a direction to provide an optical focal length for bending or refracting light in a first plane (XZ plane) and not exhibiting an optical focal length in a second plane (YZ plane). The third cylindrical lens (10) is located closer to the grating (9) and is spaced apart from the grating (9) by the focal length of the third cylindrical lens (10), and the fourth cylindrical lens (13) is located closer to the optical deflector array (14) and is spaced apart from the optical deflector array (14) by the focal length of the fourth cylindrical lens (13). The third and fourth cylindrical lenses (10, 13) are spaced apart from each other by a distance equal to the sum of the focal lengths of the third and fourth cylindrical lenses (10, 13), so that the third and fourth cylindrical lenses (10, 13) form a telecentric lens system between the grating and the optical deflector array. The telecentric lens system is used to ensure the required angular alignment and lateral alignment of the light beam in the optical switch and to achieve matching of the beam waist.

[0045] The WSS designs disclosed above can be implemented to provide various technical features in optical switching. For example, a 1×N WSS device can be constructed. Figure 3 Shown based on the use of Figure 2 An example of a 1×NWSS device of the disclosed technology in terms of hardware components and layout.

[0046] Figure 3 A top view of the hardware components in the YZ plane is shown, further illustrating the use of an optical channel separated into two parallel optical paths of two linear orthogonal polarizations processed in parallel by processing and switching. Figure 1 and Figure 2 The WSS device in the Figure 3 The following figure in shows the hardware components in the XZ plane and the routing of light from one fiber to another in the fiber array due to the deflection of a deflector array (e.g., an LCoS array or an MEMS array) in the XZ plane.

[0047] Figure 3The WSS device in is an example of a 1×N WSS device, where the optical system images each wavelength channel into a thin strip on the deflector array, and multiple thin strips of light from different wavelength channels of the fiber array are directed onto the deflector array, and one of the N fibers is used to provide all the channels to be switched as input, and the remaining (N-1) fibers serve as output fibers so that the deflector array can be controlled to provide the desired optical switching.

[0048] In some embodiments, Figure 3 The optical fiber array in the embodiment may have a constant spacing between its optical fiber ports. In other embodiments, Figure 3 The fiber array in a fiber array can be designed to have different spacings between its fiber ports: unevenly spaced fibers in a fiber array can be used to reduce undesirable optical crosstalk between different channels during switching.

[0049] Figure 3 The 1×N WSS device can be used as follows Figure 4 Two or more optical fiber arrays stacked on top of each other along the Y direction in the XZ plane are shown to replace a single optical fiber array in the XZ plane and be expanded into an M×(1×N) WSS device.

[0050] exist Figure 4 In the example of FIG. 9 , M fiber arrays, each having N fibers, are stacked along the Y direction, and all M×N fibers share the same set of optical devices. Due to the spatial separation of the M fiber arrays in the Y direction, light beams from fiber arrays at different positions have different incident angles on the grating (9) and are guided to the gratings as shown in FIG. Figure 4 In each region corresponding to each optical fiber array, different wavelength channels are arranged at the same Figure 3 The same way as shown in the 1×N WSS embodiment is further spatially divided into different bands. M different 1D fiber arrays are stacked along the Y direction, and switching occurs in each YZ plane.

[0051] Figure 5 An example of an optical WSS device using reflective gratings in both the XZ plane (switching plane in the lower figure) and the YZ plane (in the upper figure) is further shown, where the 1D fiber array is placed in the switching plane (XZ plane).

[0052] exist Figure 5In this example, a 1D fiber array (4) is located on the front focal plane of a collimating / focusing lens (8), and a Wollaston prism (5) is placed at the fiber port of the optical fiber (4) to spatially separate the light from the optical fiber into two spatially divergent beams of two linear orthogonal polarizations. The collimating / focusing lens (8) transforms the two linear orthogonal polarized two beams into parallel beams in the upper and lower parts of the YZ plane. A half-wave plate HWP (7) is placed in one of the two beams in the YZ plane to rotate the polarization of the beam by 90 degrees so that the two parallel beams in the YZ plane are in the same polarization when incident on a reflective grating (9) located downstream of the collimating lens (8) and the HWP (7). In some embodiments, the common polarization of the two beams is controlled to achieve a polarization with high diffraction efficiency at the reflective grating (9). The optical deflector array (14) is placed in the optical path of the diffracted light beam generated by the reflective grating (9), so that the light from the collimating lens (8) is first diffracted and reflected by the reflective grating (9) into Figure 5 The spatially separated light beams of different spectral components are shown in the above figure in the YZ plane in FIG. The spatially separated light beams of different spectral components are reflected by the reflective grating (9) toward the optical deflector array (14), and the optical deflector array (14) reflects the light from the reflective grating (9) back to the reflective grating (9). The fiber port of the fiber array (4) is placed on the front focal plane of the collimating lens (8), and the optical deflector array (14) is located on the back focal plane of the collimating lens (8). The optical deflectors in the optical deflector array (14) are controlled by the optical WSS control module so that different optical deflectors are individually controlled to reflect the light to the reflective grating (9) in the desired direction toward the collimating lens (8), the Wollaston prism (5) and back to the 1D fiber array (4) to achieve the desired optical switching operation.

[0053] like Figure 5 As shown in the above figure showing the device in the YZ plane (diffraction plane), the optical deflector array (14) can be implemented as an array of LCoS spatial light modulators (SLM) or MEMS elements located on the back focal plane of the first and second cylindrical Fourier lenses (11, 12), while the reflective grating (9) is located on the front focal plane of the first and second cylindrical Fourier lenses (11, 12). The LCoS SLM can be configured to perform their phase modulation in the X direction so that light beams of different wavelengths are reflected at different angles in the XZ plane. The reflected light beams of different wavelengths are returned all the way back and focused into different output fibers. Figure 1-4 The device design is different. Figure 5 The optical system in is simplified by eliminating the telecentric lens system formed by two lenses.

[0054] In devices using stacked fiber arrays, scalability may be affected by Wollaston prisms. In general, it is desirable to keep stacked fiber arrays closely spaced. In order to have a sufficiently large angle of incidence on the grating while keeping the spacing between rows small, a pair of lenses in a telecentric telescope configuration can be used in front of the grating to increase the angle of incidence on the grating (the beam size is simultaneously reduced). In some designs, a deformable prism can also be used to adjust the beam size for better diffraction effects. In some embodiments, each LCoS spatial light modulator (SLM) can generate first-order and higher-order diffracted beams, and the optical switch is designed to switch the first diffraction order beam. It may be necessary to manage the optical focal length with other orders to reduce undesirable optical crosstalk. In this regard, uneven / irregular spacing can be used between the optical fibers in a row of fiber arrays to reduce or eliminate the undesired coupling of high diffraction order light into adjacent fiber ports (crosstalk reduction).

[0055] The above examples describe novel transmit optics based on optical polarization to generate two parallel beams with polarization diversity for downstream optical switching operations, and combined with the sharing of optical components, provide scalability of the disclosed WSS device with high port count WSS. In some embodiments, the disclosed WSS design can be used to build a WSS array for N×M wavelength selective cross-connect matrix switches using a single LCoS engine.

[0056] Figure 6 shows the use of a reflective grating to achieve Figure 5An example of a specific embodiment of a wavelength selective switch of a grating (9) in the optical input arm of the reflective grating (9). The embodiment example of the device is characterized by adopting a folded optical system design, by combining a reflective grating (9) with three reflectors (621, 622, and 623) and a prism (640) on the optical input arm of the reflective grating (9), so as to achieve a small or compact overall footprint of the device. In this embodiment, a rhombus prism (650) and a rhombus prism (660) are provided to separate two polarized diffracted light beams on the optical output arm of the reflective grating (9). A lens array (610) of different lenses is placed between an optical fiber array (4) having a plurality of optical fiber lines and a Wollaston prism (5), wherein each lens in the lens array (610) corresponds to a specific optical fiber line in the optical fiber array (4), so that there is a one-to-one correspondence between the optical fiber line and the lens. In some embodiments, an image of the output surface of the optical fiber can be imaged inside the Wollaston prism (5). The output light from each optical fiber line is received by its corresponding lens after the lens array (610) and imaged into different beam sizes. The use of the lens array (610) can control the size of each light beam from the fiber optic line as it passes through the optical system of the device to and from the reflective grating (9). The prism (640) and the reflective grating (9) form a grating-prism combination Grism, which can provide significantly greater dispersion and substantially simultaneously separate the output arm of the reflective grating (9) from the input arm. In this specific example, a prism (630) is added between the collimating lens (8) and the reflective grating (9) to further control the beam size on the input arm of the reflective grating (9). In the placement of the prism (630) as shown, the two light beams of the same polarization incident on the front surface of the prism (630) are oriented at or close to the Brewster angle, so that the two light beams of the same polarization pass through the front surface without or minimizing optical reflection. Similarly, the two light beams of the same polarization incident on the input surface of the prism (640) are substantially close to the Brewster angle to maximize light transmission and reduce undesirable light reflections. In addition to the optical path compensator (6) placed in the second light beam, a rhombus prism (650) and a rhombus prism (660) are placed in the optical path of the first light beam to make the corresponding optical paths of the two light beams initially separated by the Wollaston prism (5) equal. Figure 5 In the optical design, the LCoSSLM or MEMS array (14) and the reflective grating (9) are located on the front focal plane and the back focal plane of the lenses 11 and 12 respectively.

[0057] Although this patent document contains many details, these details should not be interpreted as limitations on the scope of any invention or the scope that may be claimed, but rather as descriptions of features that may be specific to a particular embodiment of a particular invention. Certain features described in the context of a separate embodiment in this patent document may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination. In addition, although the features may be described above as working in certain combinations and even initially claimed as such, in some cases, one or more features from the claimed combination may be removed from the combination, and the claimed combination may involve a sub-combination or a deformation of a sub-combination.

[0058] Similarly, although operations are depicted in a particular order in the figures, this should not be understood as requiring that such operations be performed in the particular order shown or in a sequential order or that all illustrated operations be performed to achieve the desired results. In addition, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.

[0059] Only a few implementations and examples are described, and other implementations, enhancements, and variations may be made based on what is described and illustrated in this patent document.

Claims

1. A wavelength selective optical switch, characterized in that: include: a linear array of optical fibers spaced apart from one another along a first direction to form a first plane, the first plane having a normal direction in a second direction perpendicular to the first direction; an optical birefringent material positioned to receive output light from a fiber terminal port of the linear array of optical fibers and configured to spatially separate the light output from each optical fiber into two spatially separated beams of two orthogonal optical polarizations to define a second plane having a normal direction parallel to the first direction; a collimating lens located away from the optical birefringent material to receive the spatially divergent light beams of the orthogonal optical polarizations from each optical fiber of the optical fiber linear array and spaced apart from the optical fiber terminal port of the optical fiber linear array by the focal length of the collimating lens to transform the two spatially divergent light beams of the two orthogonal optical polarizations from each optical fiber into two spatially separated and parallel light beams of the two orthogonal optical polarizations, respectively; an optical polarization rotator positioned and configured to receive a light beam of only one of the two orthogonal optical polarizations from the linear array of optical fibers to rotate the polarization of the light beam of only one optical polarization received from the linear array of optical fibers to be parallel to the other of the two orthogonal optical polarizations such that the two spatially separated and parallel light beams from each optical fiber are at the same polarization; a grating disposed downstream of the optical polarization rotator and the collimating lens to receive the two spatially separated and parallel light beams of the same polarization from each optical fiber of the optical fiber linear array and to diffract each light beam into different diffracted output light beams of different optical wavelengths in different diffracted beam directions; an optical deflector array positioned relative to the grating to receive the different diffracted output beams of different optical wavelengths in different diffracted beam directions from each optical fiber of the optical fiber linear array, respectively, and redirect the different diffracted output beams of different optical wavelengths in different diffracted beam directions received from each optical fiber of the optical fiber linear array back to the grating, the optical polarization rotator, the collimating lens, the optical birefringent material, and the optical fiber terminal port of the optical fiber linear array; a first cylindrical lens and a second cylindrical lens located between the grating and the optical deflector array and on different sides of the optical axis of the collimating lens, wherein the first cylindrical lens is spaced apart from each of the grating and the array of optical deflectors by a focal length of the first cylindrical lens, wherein the first cylindrical lens is positioned to process and transmit light associated with the light beam transmitted through the optical polarization rotator, the second cylindrical lens being spaced apart from each of the grating and the array of optical deflectors by a focal length of the second cylindrical lens, the second cylindrical lens being positioned to process and transmit light associated with other light beams that do not pass through the optical polarization rotator; and A control device is coupled to the optical deflector array to apply deflector control signals to the optical deflectors respectively, so that each optical deflector responds to the corresponding applied control signal to direct the diffracted output light beam from the grating back to the grating in a desired direction based on the corresponding applied control signal, wherein the deflector control signal is generated to achieve the desired wavelength selective optical switching in the optical fiber linear array.

2. The wavelength selective optical switch according to claim 1, characterized in that: in, The first or second cylindrical lens is oriented to provide optical power for bending light in the second plane while exhibiting no optical power in the first plane.

3. The wavelength selective optical switch according to claim 1, characterized in that: in, Each of the first cylindrical lens and the second cylindrical lens is oriented to provide optical power for bending light in the second plane while exhibiting no optical power in the first plane.

4. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: in, Each of the first cylindrical lens and the second cylindrical lens is positioned to process and transmit a light beam of the same one of the two orthogonal optical polarizations.

5. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: in, The first cylindrical lens and the second cylindrical lens are Fourier lenses.

6. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: include: a third cylindrical lens and a fourth cylindrical lens located between the grating and the optical deflector array, wherein each of the third cylindrical lens and the fourth cylindrical lens is oriented to provide optical power for bending light in the first plane and exhibit no optical power in the second plane, wherein the third cylindrical lens is located closer to the grating and is spaced apart from the grating by the focal length of the third cylindrical lens, and the fourth cylindrical lens is located closer to the optical deflector array and is spaced apart from the optical deflector array by the focal length of the fourth cylindrical lens, and Wherein, the third cylindrical lens and the fourth cylindrical lens are spaced apart from each other by a distance equal to the sum of the focal lengths of the third cylindrical lens and the fourth cylindrical lens, so that the third cylindrical lens and the fourth cylindrical lens form a telecentric lens system located between the grating and the optical deflector array.

7. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: in, The optical deflector array comprises a micro-electromechanical system (MEMS) mirror array.

8. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: in, The optical deflector array includes an array of liquid crystal on silicon (LCoS) cells.

9. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: Also includes: A lens array of different lenses is located between the optical fiber linear array and the optical birefringent material to respectively receive the light beams from the optical fibers and control the size of the light beams.

10. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: in, The collimating lens is a lens system with a variable focal length.

11. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: in, The grating is configured to generate the different diffracted output light beams of different light wavelengths in different diffracted light beam directions by light transmission.

12. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: in, The grating is configured to generate the different diffracted output light beams of different light wavelengths in different diffracted light beam directions by light reflection.

13. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: in, The optical birefringent material includes two sheets of birefringent crystal material forming a Wollaston prism.

14. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: in, The optical polarization rotator comprises a half-wave plate.

15. The wavelength selective optical switch according to any one of claims 1 to 3, characterized in that: Also includes: an optical path compensator positioned between the optical birefringent material and the grating to adjust the optical path length of light associated with one of the two spatially divergent light beams of the two orthogonal optical polarizations from each optical fiber relative to the optical path length of light associated with the other of the two spatially divergent light beams of the two orthogonal optical polarizations from each optical fiber.

16. A wavelength selective optical switch, characterized in that: include: a linear array of optical fibers spaced apart from one another along a first direction to form a first plane having a normal direction in a second direction perpendicular to the first direction; an optical birefringent material positioned to receive output light from the linear array of optical fibers and configured to spatially separate the light output from each optical fiber into two spatially separated beams of two orthogonal optical polarizations to define a second plane having a normal direction parallel to the first direction; a collimating lens located away from the optical birefringent material to receive the spatially divergent light beams of the orthogonal optical polarizations from each optical fiber of the optical fiber linear array and spaced apart from the optical fiber terminal port of the optical fiber linear array by the focal length of the collimating lens to transform the two spatially divergent light beams of the two orthogonal optical polarizations from each optical fiber into two spatially separated and parallel light beams of the two orthogonal optical polarizations, respectively; an optical polarization rotator positioned and configured to receive a light beam of only one of the two orthogonal optical polarizations from the linear array of optical fibers to rotate the polarization of the light beam of only one optical polarization received from the linear array of optical fibers to be parallel to the other of the two orthogonal optical polarizations such that the two spatially separated and parallel light beams from each optical fiber are at the same polarization; a grating disposed downstream of the optical polarization rotator and the collimating lens to receive the two spatially separated and parallel light beams of the same polarization from each optical fiber of the optical fiber linear array and to diffract each light beam into different diffracted light beams of different light wavelengths in different diffracted light beam directions, wherein the grating is a reflective grating and guides the different diffracted light beams of different light wavelengths in different diffracted light beam directions to the same side of the grating; an optical deflector array disposed in the optical paths of the different diffracted beams of the different optical wavelengths in the directions of the different diffracted beams from the grating to reflect the different diffracted beams back toward the grating, thereby redirecting the received different diffracted beams from the grating toward the collimating lens, the optical birefringent material, and the optical fiber terminal port of the optical fiber linear array; a first cylindrical lens and a second cylindrical lens located between the grating and the optical deflector array and on different sides of the optical axis of the collimating lens, wherein the first cylindrical lens is spaced apart from each of the grating and the array of optical deflectors by a focal length of the first cylindrical lens, wherein the first cylindrical lens is positioned to process and transmit light associated with the light beam transmitted through the optical polarization rotator, the second cylindrical lens being spaced apart from each of the grating and the array of optical deflectors by a focal length of the second cylindrical lens, the second cylindrical lens being positioned to process and transmit light associated with other light beams that do not pass through the optical polarization rotator; and A control device, coupled to the optical deflector array, to apply deflector control signals to the optical deflectors respectively, so that each optical deflector responds to the corresponding applied control signal to guide the diffracted light beam from the grating in a desired direction toward the collimating lens, the optical birefringent material, and the optical fiber terminal port of the optical fiber linear array based on the corresponding applied control signal for optical switching, wherein the deflector control signal is generated to achieve the desired wavelength selective optical switching in the optical fiber linear array.

17. The wavelength selective optical switch according to claim 16, characterized in that: in, Each of the first cylindrical lens and the second cylindrical lens is oriented to provide optical power for bending light in the second plane while exhibiting no optical power in the first plane.

18. The wavelength selective optical switch according to claim 16 or 17, characterized in that: Also includes: A lens array of different lenses is located between the optical fiber linear array and the optical birefringent material to respectively receive the light beams from the optical fibers and control the size of the light beams.

19. The wavelength selective optical switch according to claim 16 or 17, characterized in that: Also includes: A plurality of reflectors are located at different positions in the optical path between the optical fiber linear array and the grating to fold the optical path so as to reduce the occupied area of ​​the wavelength selective optical switch.

20. The wavelength selective optical switch according to claim 16 or 17, characterized in that: in, Each of the first cylindrical lens and the second cylindrical lens is positioned to process and transmit a light beam of the same one of the two orthogonal optical polarizations.

Images