Devices and methods for tuning polarization of two or more beams for wavelength division multiplexing

Abstract

The present disclosure relates to an optical device for wavelength division multiplexing two or more input beams. The present disclosure proposes the optical device and a corresponding method for operating an optical device. The optical device comprises: a multiplexer and two or more channels for two or more input beams, where each channel is configured to receive one of the two or more input beams and to provide a rotating beam to the multiplexer, the polarization of the rotating beam is rotated compared to the polarization of the corresponding input beam, and wherein at least one of the two or more channels is configured to rotate the polarization of the corresponding input beam in a different direction than at least one other of the two or more channels.

Description

Technical Field

[0001] The present disclosure relates to an optical device for wavelength division multiplexing two or more input beams. The present disclosure proposes an optical device and a corresponding method for operating the optical device. The optical device includes a multiplexer and two or more channels, wherein the two or more channels include means for individually rotating the polarization of the two or more input beams. Background Art

[0002] Intensity modulated direct detection (IM-DD) technology is commonly used as a cost-effective and power-effective optical interface solution in data center networks (DCNs). However, with the increase in data rates and the advanced modulation formats used, IM-DD-based implementations begin to suffer from fiber-related impairments. For example, in wavelength division multiplexing (WDM) systems with wavelengths close to the zero dispersion region of the fiber, four-wave-mixing (FWM) penalties occur. The idle frequencies generated cause crosstalk with the input signal and incur penalties in the transmission system. Since the signal generated by FWM is proportional to the cubic power of the input signal, the higher the input power of the input signal, the greater the FWM penalty. Therefore, FWM prevents the increase in input power to further increase the link budget of the system. Therefore, FWM weakens the optical system to achieve a high link budget.

[0003] Conventional WDM system comprises two or more channels, and wherein each channel corresponds to the central wavelength of the corresponding wave beam transmitted by the channel.In order to set polarization state (state of polarization, SOP), for example, the vertical SOP between adjacent channels, conventional devices need the extra polarization combiner in the system, which increases cost.In addition, conventional devices may include extra polarization control (for example, the transmitter of different polarizations) and extra isolation for each channel, to prevent reflected signal from affecting corresponding optical fiber, which increases the complexity of device design. Summary of the invention

[0004] In summary, the present disclosure is intended to increase the flexibility of adjusting the polarization of input beams to support multiplexing. For example, the purpose may be to reduce four-wave mixing during wavelength division multiplexing. In addition, the purpose may be to reduce the complexity and / or cost of optical devices configured to perform wavelength division multiplexing and / or polarization division multiplexing.

[0005] These and other objects are achieved by the present disclosure as described in the attached independent claims. Advantageous implementations are further described in the dependent claims.

[0006] The present disclosure may be based on the following considerations: FWM is sensitive to the SOP of the input signal. For example, when the SOPs between adjacent channels are perpendicular to each other, the FWM cost may be significantly reduced.

[0007] A first aspect of the present disclosure provides an optical device for wavelength division multiplexing two or more input beams, wherein the optical device includes: a multiplexer and two or more channels for the two or more input beams, wherein each channel is configured to: receive one of the two or more input beams and provide a rotated beam to the multiplexer, the polarization of the rotated beam being rotated compared to the polarization of the corresponding input beam, and wherein at least one of the two or more channels is configured to: rotate the polarization of the corresponding input beam in a direction different from at least one other of the two or more channels.

[0008] The SOP of a corresponding beam (eg, one of two or more input beams) of each channel can be individually tuned to any angle.

[0009] Each channel may correspond to a beam, which is referred to as the "corresponding beam of the channel". Each channel may include only the corresponding beam of the channel. For each channel, the corresponding beam of the channel may be modified by the channel. For example, the polarization of the corresponding beam of the channel may be rotated and / or the corresponding beam of the channel may be attenuated by a linear polarizer. The rotated beam may be based on the input beam and may be a variation of the corresponding beam of the channel provided to the multiplexer.

[0010] The optical device can simultaneously implement arbitrary polarization division multiplexing and wavelength division multiplexing, wherein the cost and / or complexity of the optical device can be reduced compared to conventional devices.

[0011] The optical device can be used in any IM-DD WDM based optical system, for example, an optical module connected to a router, switch or any type of host board with an optical module interface.

[0012] In an implementation of the first aspect, each channel includes an optical isolator segment configured to restrict the light transmission through the channel to a direction toward the multiplexer.

[0013] The optics can have both feedback tolerance and arbitrary polarization multiplexing for each channel. The optical isolator segments can prevent back reflections of the corresponding beams of the channels.

[0014] Polarization interleaving can be achieved by placing an isolator segment for each channel in front of the output of the channel before the multiplexer.

[0015] Each isolator segment may not add insertion loss.Each optical isolator segment may include an optical isolator, such as a conventional optical isolator or an optical diode.

[0016] The optical device may include N channels, and the two or more input signals may be N input signals, where N is a positive integer greater than one.

[0017] The rotating beams provided by the two or more channels may be two or more rotating beams.

[0018] In another implementation of the first aspect, for each channel, the optical isolator segment includes a rotator segment, which is configured to: rotate the polarization of the corresponding beam of the channel, and wherein, for at least one channel, the rotator segment is configured to: rotate the corresponding beam of the channel in a direction different from the rotator segment of at least one other channel of the two or more channels.

[0019] The corresponding beam of the channel may be based on the input beam of the channel. For example, the corresponding beam of the channel may be the input beam of the channel or a modified input beam modified by other segments of the channel.

[0020] The rotator segment may be a first rotator segment.

[0021] The optical device may include N first rotator segments.

[0022] In another implementation of the first aspect, each optical isolator segment includes: a first polarizer segment and a second polarizer segment, wherein, for each channel, the rotator segment is positioned between the first polarizer segment and the second polarizer segment, and wherein the second polarizer segment is positioned between the rotator segment and the multiplexer, wherein, for each channel, the rotator segment is configured to: rotate the polarization of the corresponding beam of the channel to form a first rotated beam, wherein each first polarizer segment includes a linear polarizer configured to primarily transmit a beam of a first polarization direction, and wherein each second polarizer segment includes a linear polarizer configured to primarily transmit a beam having the polarization of the corresponding first rotated beam of the channel.

[0023] The first rotated beam may be a rotated beam provided to the multiplexer.

[0024] For each channel, the linear polarizer of the first polarizer segment may be a first linear polarizer, and the linear polarizer of the second polarizer segment may be a second linear polarizer.

[0025] Each linear polarizer can be configured to primarily transmit beams having an SOP that matches the corresponding azimuth angle of the linear polarizer, but can also transmit beams having different SOPs. The beams having an SOP that matches the corresponding azimuth angle of the linear polarizer can be attenuated to a minimum compared to beams having different SOPs.

[0026] The first polarization direction of each channel may be the same. For each channel, the first polarization direction may be the same as the polarization direction of the input beam of the channel.

[0027] In another implementation of the first aspect, each channel also includes a second rotator segment, wherein the second rotator segment is positioned between the multiplexer and the optical isolator segment, and wherein the second rotator segment is configured to: for example, rotate the polarization of the corresponding beam of the channel after the polarization of the corresponding beam of the channel is rotated by the first rotator segment.

[0028] In another implementation of the first aspect, for each channel, the corresponding first rotated beam is the rotated beam provided by the channel, or wherein, for each channel, the second rotator segment is configured to: rotate the polarization of the corresponding beam of the channel to form a second rotated beam, and wherein, for each channel, the corresponding second rotated beam is the rotated beam provided by the channel.

[0029] In another implementation of the first aspect, each channel further comprises a third rotator segment, wherein the optical isolator segment is positioned between the third rotator segment and the multiplexer, and wherein the third rotator segment is configured to: for example, rotate the polarization of the corresponding beam of the channel to the first polarization direction before the polarization of the corresponding beam of the channel is rotated by the first rotator segment, for example, to form a third rotated beam.

[0030] Thus, for each channel, the SOP of the third rotated beam may be matched to the polarization angle of the first polarizer segment and / or may be matched to the input polarization angle of the isolator segment.

[0031] The input beam of each channel may be considered to be "modified" by the third rotator segment. Thus, the isolator segment of a channel may receive a corresponding beam of the channel that is considered to be the "modified" input beam or a corresponding beam of the channel based on the input beam.

[0032] Each channel's input beam may be considered to be "modified" by other segments positioned before the isolator segment. Thus, the channel's isolator segment may receive a corresponding beam for the channel that is considered to be a "modified" input beam or a corresponding beam for the channel that is based on the input beam.

[0033] The term "positioned before" may refer to a channel segment being configured to receive a corresponding beam of a channel before corresponding other segments of the channel during the process of the channel receiving an input beam and providing a rotated beam to a multiplexer.

[0034] In another implementation of the first aspect, the two or more input beams have the same polarization.

[0035] In another implementation of the first aspect, each of the two or more input beams has a different central wavelength.

[0036] In another implementation of the first aspect, each channel is associated with a center wavelength of the corresponding input beam of the channel, wherein each channel and one or two other channels form an adjacent channel, and the one or two other channels are associated with an input beam having a next larger or next smaller center wavelength among the two or more input beams.

[0037] The two or more channels may include two channels that form only one adjacent channel with the two or more other channels, respectively. Other channels of the two or more channels may form two adjacent channels with the two or more other channels, respectively.

[0038] For each channel, if two or more channels include only one other channel, and the other channel satisfies one of the conditions associated with an input beam having the next larger wavelength or an input beam having the next smaller wavelength compared to the input beam associated with the channel, then the channel forms only one adjacent channel with the other channel.

[0039] For each channel, if two or more channels include two other channels, and the two other channels satisfy one of the conditions associated with an input beam having the next larger wavelength or an input beam having the next smaller wavelength compared to the input beam associated with the channel, then the channel forms two adjacent channels with the two other channels.

[0040] In another implementation of the first aspect, each channel is configured to rotate the polarization of the corresponding input beam in a different direction than the one or two adjacent channels of the channel.

[0041] In another implementation of the first aspect, for each channel, the rotator segment is configured to rotate the polarization of the corresponding beam of the channel in a different direction than the rotator segments of the one or two adjacent channels of the channel.

[0042] In another implementation of the first aspect, each channel is configured to rotate the polarization of the corresponding input beam in a direction different from that of the one or two adjacent channels of the channel, so that the corresponding rotated beams provided by adjacent channels have polarizations orthogonal to each other.

[0043] In another implementation of the first aspect, for each channel, the rotator segment is configured to: rotate the polarization of the corresponding beam of the channel in a direction different from the rotator segment of the one or two adjacent channels of the channel, so that the corresponding rotated beams provided by adjacent channels have polarizations orthogonal to each other.

[0044] For example, since the corresponding rotated beams provided by adjacent channels have polarizations that are orthogonal to each other, the possibility of four-wave mixing interference can be reduced.

[0045] In another implementation of the first aspect, each channel is configured to rotate the polarization of the corresponding input beam by the same absolute amount, but in a different direction than the one or two neighboring channels of the channel.

[0046] In another implementation of the first aspect, for each channel, the rotator segment is configured to rotate the polarization of the corresponding beam of the channel by the same absolute amount but in a different direction than the rotator segment of the one or two adjacent channels of the channel.

[0047] In another implementation of the first aspect, each channel is configured to rotate the polarization of the corresponding input beam by 45° in a first plane, and the one or two adjacent channels of the channel are configured to rotate the polarization of the corresponding input beam by -45° in the first plane.

[0048] In another implementation of the first aspect, for each channel, the rotator segment is configured to rotate the polarization of the corresponding beam of the channel by 45° in a first plane, and the rotator segment of one or two adjacent channels of the channel is configured to rotate the polarization of the corresponding beam of the channel by -45° in the first plane.

[0049] Therefore, the optical isolator segment can maximally prevent the back reflection of the corresponding beam of the channel. For example, the optical isolation can be maximized.

[0050] In another implementation of the first aspect, for each channel, the rotator segment of the optical isolator segment is configured to: rotate the polarization of the corresponding beam of the channel by a maximum absolute amount, and the maximum absolute amount satisfies the condition that the corresponding rotated beams provided by adjacent channels are orthogonal to each other.

[0051] For example, it may be beneficial to perform polarization rotations of 45° and -45° in an optical isolator because said rotations result in maximum isolation. However, because other optical components may be configured to modify the respective beams of the channels and / or positioned after the rotator stage, the maximum absolute amount by which the condition that the respective rotated beams provided by adjacent channels are orthogonal to each other may deviate from 45°, where the maximum absolute amount of polarization rotation maximizes isolation.

[0052] In another implementation of the first aspect, each channel is configured to: rotate the polarization of the corresponding input beam to a second direction orthogonal to a third direction, and wherein the third direction is the polarization direction of the corresponding rotated beam provided by one or two adjacent channels of the channel.

[0053] The second direction of a first channel of the two or more channels may be different from the second direction of another channel of the two or more channels.

[0054] A third direction of a first channel of the two or more channels may be different from a third direction of another channel of the two or more channels.

[0055] The SOP of each channel can be tuned individually.

[0056] In another implementation of the first aspect, each rotated beam provided by the two or more channels to the multiplexer has a fourth polarization or a fifth polarization, wherein the fourth polarization is orthogonal to the fifth polarization.

[0057] The two or more rotated beams may include beams of only two different SOPs.

[0058] In another implementation of the first aspect, the two or more channels include: a first group of channels and a second group of channels, wherein each channel in the first group of channels is an adjacent channel to one or two channels in the second group of channels, wherein each channel in the second group of channels is an adjacent channel to one or two channels in the first group of channels, wherein, for each channel in the first group of channels, the corresponding rotated beam provided by the channel has the fourth polarization, and wherein, for each channel in the second group of channels, the corresponding rotated beam provided by the channel has the fifth polarization.

[0059] The phrase "adjacent channel" may refer to "adjacent channels" as described above.

[0060] The fourth polarization direction and the fifth polarization direction may be different from each other and / or may be different from the first polarization direction.

[0061] The fourth polarization direction and the fifth polarization direction may be the same as the second polarization direction and the third polarization direction, respectively.

[0062] The two or more channels may be divided into two groups associated with different polarizations.The two or more channels may consist of a first group of channels and a second group of channels.

[0063] In another implementation of the first aspect, each channel further comprises a polarization transmitter segment, wherein the optical isolator segment is positioned between the polarization transmitter segment and the multiplexer, and / or wherein the third rotator segment is positioned between the polarization transmitter segment and the optical isolator segment.

[0064] In another implementation of the first aspect, for each channel, the polarization direction of the polarization transmitter segment matches the first polarization direction, and / or for each channel, the polarization transmitter segment is configured to: receive one of the two or more input beams and provide the input beam to the optical isolator segment or the third rotator segment.

[0065] In another implementation of the first aspect, the multiplexer is a wavelength multiplexer and / or a polarization multiplexer, and wherein the multiplexer is configured to combine all rotated beams provided to the multiplexer by the two or more channels.

[0066] In another implementation of the first aspect, each rotator segment comprises a Faraday rotator, and / or wherein each optical isolator segment comprises a Faraday rotator.

[0067] For example, each of the first rotator segment, the second rotator segment, and / or the third rotator segment may include a Faraday rotator.

[0068] Based on the non-isotropic characteristic of the Faraday rotator, the polarization of the corresponding beam of each channel is rotated, and the Faraday rotator may be a Faraday magnetic rotator.

[0069] Each Faraday magnetic rotator can be combined with a linear polarizer and a free-space multiplexing filter.

[0070] A second aspect of the present disclosure provides a method of operating an optical device for wavelength division multiplexing two or more input beams, wherein the optical device includes: a multiplexer and two or more channels for the two or more input beams, wherein the method includes: receiving one of the two or more input beams with each channel, providing a rotated beam to the multiplexer with each channel, the polarization of the rotated beam being rotated compared to the polarization of the corresponding input beam, and rotating the polarization of the corresponding input beam in a direction different from at least one other of the two or more channels with at least one of the two or more channels.

[0071] The method of the second aspect may have an implementation method corresponding to the implementation method of the device of the first aspect. The method of the second aspect and its implementation method achieve the advantages and effects described above with respect to the device of the first aspect and its corresponding implementation method.

[0072] In this disclosure, the phrases "linear polarizer" and "linear polarization filter" may be used interchangeably.

[0073] Furthermore, in the present disclosure, the phrases "SOP," "polarization direction," "polarization," and "direction" may be used interchangeably when referring to polarization.

[0074] Furthermore, in the present disclosure, each corresponding beam of a channel of two or more channels may be based on an input beam of the channel. For example, the corresponding beam of the channel may be an input beam of the channel or a modified input beam modified by other segments of the channel.

[0075] In addition, in the present disclosure, for each channel, the corresponding beam of the channel can be considered to be the same corresponding beam of the channel after being modified or affected by any of the above-mentioned segments or optical components (e.g., any of the above-mentioned polarizer segments, any of the above-mentioned isolator segments, any of the above-mentioned rotator segments, or any of the above-mentioned polarization transmitter segments).

[0076] Furthermore, in the present disclosure, for each channel, a rotated beam, a first rotated beam, a second rotated beam, and / or a third rotated beam may refer to different variations or versions of the same corresponding beam of the channel.

[0077] Furthermore, in the present disclosure, for each channel, a corresponding beam of the channel may include a rotated beam, and may further include at least one of a first rotated beam, a second rotated beam, and / or a third rotated beam.

[0078] Furthermore, in the present disclosure, for each channel, the rotated beam, the first rotated beam, the second rotated beam, and / or the third rotated beam may be parts of a corresponding beam of the channel.

[0079] Furthermore, in the present disclosure, for each channel, the rotated beam, the first rotated beam, the second rotated beam, and / or the third rotated beam may be a modified version of and / or based on an input beam of the channel.

[0080] In addition, in the present disclosure, for each channel, the rotated beam, the first rotated beam, the second rotated beam and / or the third rotated beam can be respectively considered as the rotated beam, the first rotated beam, the second rotated beam and / or the third rotated beam after being modified by a polarizer (e.g., the first polarizer or the second polarizer).

[0081] Furthermore, in the present disclosure, for each channel, the phrases "before" and "after" may be defined with reference to a path along the channel from a channel segment configured to receive an input beam for the channel to a channel segment configured to provide a rotated beam to a multiplexer.

[0082] It should be noted that all devices, elements, units and apparatus described in the present disclosure may be implemented in software or hardware elements or any type of combination thereof. All steps performed by the various entities described in the present disclosure and the functions to be performed by the various entities described are intended to mean that the corresponding entities are suitable for or configured to perform the corresponding steps and functions. Although in the following description of the specific embodiments, the specific functions or steps to be performed by the external entity are not reflected in the description of the specific detailed elements of the entity that performs the specific steps or functions, it should be clear to the technician that these methods and functions can be implemented in the corresponding software or hardware elements or any type of combination thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] In conjunction with the accompanying drawings, the above-mentioned various aspects and their implementation methods will be described in the following description of the specific implementation methods. In the drawings:

[0084] Figure 1 An optical device according to an embodiment of the present disclosure is shown.

[0085] Figure 2 An optical device further comprising an isolator segment is shown according to an embodiment of the present disclosure.

[0086] Figure 3 Optical devices also including other segments are shown according to embodiments of the present disclosure.

[0087] Figure 4 An exemplary optical isolator segment according to an embodiment of the present disclosure is shown.

[0088] Figure 5An exemplary optical device according to an embodiment of the present disclosure is shown, wherein corresponding beams of adjacent channels have orthogonal SOPs of 45° and -45°.

[0089] Figure 6 Exemplary optics and exemplary SOPs of corresponding beams for each channel are shown according to embodiments of the present disclosure.

[0090] Figure 7 A method according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0091] Figure 1 An optical device 100 of an embodiment of the present disclosure is shown. The optical device 100 includes a multiplexer 102 and two or more channels 101 for two or more input beams 200. Each channel 101 is configured to receive one input beam 200a of the two or more input beams 200 and provide a rotated beam 201a to the multiplexer 102, the polarization of which is rotated compared to the polarization of the corresponding input beam 200a. At least one channel 101a of the two or more channels 101 is configured to rotate the polarization of the corresponding input beam 200a in a different direction than at least one other channel 101b of the two or more channels 101.

[0092] Figure 2 The optical device 100 is shown further comprising two or more optical isolator segments 103 , wherein each channel 101 a , 101 b comprises one optical isolator segment 103 a , 103 b of the two or more optical isolator segments 103 , respectively.

[0093] Figure 3 An exemplary optical device 100 is shown, wherein the device may further include two or more second rotator segments 104, wherein each channel 101a, 101b may include one second rotator segment 104a, 104b, respectively. Figure 3 It is shown that the optical device 100 may further include two or more third rotator segments 105, wherein each channel 101a, 101b may include one third rotator segment 105a, 105b, respectively. Figure 3 It is shown that the optical device 100 may also include two or more polarization transmitter segments 106 , wherein each channel 101 a , 101 b may include one polarization transmitter segment 106 a , 106 b , respectively.

[0094] The optical device 100 may include two or more third rotator segments 105 or two or more second rotator segments 104. Alternatively, the optical device 100 may include both two or more third rotator segments 105 and two or more second rotator segments 104.

[0095] Figure 4 An exemplary optical isolator segment 103a according to an embodiment of the present disclosure is shown. The optical isolator segment 103a may include: a first linear polarization filter, a Faraday rotator, and a second linear polarization filter. In addition, Figure 4 It is shown that the optical isolator segment 103a can be configured to receive a linearly polarized input beam having polarization in an exemplary first direction. The first linear polarization filter can be configured to mainly transmit the beam of the first polarization direction. Therefore, the input beam can be attenuated to a minimum by the first linear polarization filter. After being transmitted by the first linear polarization filter, the beam polarization can be rotated 45° by a Faraday rotator, and a first rotated beam 201a can be formed. The second linear polarization filter can be configured to mainly transmit the beam of the 45° rotated polarization direction. Therefore, the first rotated beam 201a can be attenuated to a minimum by the second linear polarization filter, and can be transmitted by the second linear polarization filter and form an output beam of the optical isolator segment 103a, such as the first rotated beam 201a.

[0096] The output beam of optical isolator segment 103a can be transmitted and / or attenuated by the second linear polarization filter from the reflection of the optical element positioned after optical isolator segment 103a or from the beam of other opposite directions entering optical isolator segment 103a from the direction opposite to two or more input beams. Therefore, the transmission beam will have the SOP of the first rotation beam 201a, and will be rotated 45 ° in the same direction as the input beam by the Faraday rotator, even if the propagation of the beam is in the opposite direction. Therefore, the transmission beam will have the SOP orthogonal to the orientation of the first linear polarization filter after the Faraday rotator, and will be fully attenuated by the first linear polarization filter. Therefore, each optical isolator segment 103a can be configured to: the light transmission by the channel is limited to the direction towards the multiplexer 102.

[0097] Figure 5 An exemplary optical device 100 is shown in accordance with an embodiment of the present disclosure, wherein respective beams of adjacent channels have orthogonal SOPs of 45° and −−45°. Figure 5 Four polarization transmitter sections 106, four optical isolator sections 103 and multiplexer 102 are shown. Figure 5The corresponding four channels 101 of the four polarization transmitter segments 106 and the four optical isolator segments 103 positioned adjacent to each other may form adjacent channels. For example, compared to the input beam transmitted through the polarization transmitter segment Tx2, the input beams transmitted through the polarization transmitter segments Tx1 and Tx3 may have the next largest and next smallest wavelengths of two or more input beams 200, respectively. Therefore, during multiplexing in the multiplexer 102, FWM may be minimized because the corresponding rotated beams 201a, 201b of the adjacent channels after the four isolator segments may have orthogonal SOPs.

[0098] Figure 6 An exemplary optical device 100 and an exemplary SOP of the corresponding beam of each channel 101a, 101b according to an embodiment of the present disclosure are shown. The optical device 100 includes: a multiplexer 102 and two or more channels 101, and the two or more channels 101 include: two or more polarization transmitter segments 106, two or more optical isolator segments 103 and two or more second rotator segments 104. Each of the two or more channels 101 includes the following five segments:

[0099] 1. Linear polarization transmitters 106, wherein each of the two or more input beams 200 transmitted by each polarization transmitter 106a, 106b may have a different wavelength and the same SOP.

[0100] 2. A first linear polarizer, wherein a polarization angle of the first linear polarizer may be a first polarization direction and may match a polarization angle of a polarization transmitter (eg, a SOP of a corresponding input beam).

[0101] 3. A rotator section for: rotating the SOP of the corresponding beam of the channel by + / -–45° polarization relative to the corresponding first polarization direction of the channel to form a corresponding first rotated beam, wherein the corresponding first rotated beams of adjacent channels have orthogonal SOPs.

[0102] 4. A second linear polarizer, wherein a polarization angle of the second linear polarizer is consistent with the corresponding SOP of the corresponding first rotated beam of channel 101a.

[0103] 5. A second rotator section 104a, wherein, in this example, the second rotator section 104a only slightly rotates or does not rotate the SOP of the corresponding beam of the channel 101a.

[0104] The multiplexer 102 (eg, wavelength multiplexer 102) may be configured to combine output beams of two or more channels 101, such as the rotated beams 201a, 201b.

[0105] Figure 7A method 300 according to an embodiment of the present disclosure is shown. The method 300 may be performed by an optical device 100, wherein the optical device 100 comprises: a multiplexer 102 and two or more channels 101 for two or more input beams. The method 300 comprises a step 301 of receiving one input beam 200a of the two or more input beams with each channel 101a. In addition, the method 300 comprises a step 302 of providing a rotated beam 201a to the multiplexer 102 with each channel 101a, wherein the polarization of the rotated beam 201a is rotated compared to the polarization of the corresponding input beam 200a. In addition, the method 300 comprises a step 303 of rotating the polarization of the corresponding input beam 200a in a direction different from that of at least one other channel 101b of the two or more channels 101 with at least one of the two or more channels 101.

[0106] The present disclosure has been described in conjunction with various embodiments as examples and in conjunction with implementations. However, from a study of the drawings, the present disclosure and the independent claims, other variations will be understood and implemented by those skilled in the art in implementing the claimed subject matter. In the claims and in the specification, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfil the functions of several entities or items recited in the claims. The fact that certain measures are recited in mutually different dependent claims does not in itself mean that a combination of these measures cannot be used in an advantageous implementation.

Claims

1. An optical device (100) for wavelength division multiplexing two or more input beams (200), in, The optical device (100) comprises: a multiplexer (102) and two or more channels (101) for the two or more input beams (200), Each channel (101) is configured to: receive one input beam (200a) of the two or more input beams (200) and provide a rotated beam (201a) to the multiplexer (102), wherein the polarization of the rotated beam (201a) is rotated compared to the polarization of the corresponding input beam (200a), and Wherein, at least one channel (101a) of the two or more channels (101) is configured to rotate the polarization of the corresponding input beam (200a) in a direction different from that of at least one other channel (101b) of the two or more channels (101).

2. The optical device (100) according to claim 1, in, Each channel (101) includes an optical isolator segment (103) configured to restrict light transmission through the channel to a direction toward the multiplexer (102).

3. The optical device (100) according to claim 2, in, For each channel (101), the optical isolator segment (103) comprises a rotator segment configured to: rotate the polarization of the corresponding beam of the channel, and Wherein, for at least one channel (101a), the rotator segment is configured to rotate the corresponding beam of the channel in a direction different from the rotator segment of at least one other channel (101b) of the two or more channels (101).

4. The optical device (100) according to claim 3, in, Each optical isolator segment (103) comprises: a first polarizer segment and a second polarizer segment, wherein, for each channel (101), the rotator segment is positioned between the first polarizer segment and the second polarizer segment, and wherein the second polarizer segment is positioned between the rotator segment and the multiplexer (102), wherein, for each channel (101), the rotator section is configured to: rotate the polarization of the corresponding beam of the channel to form a first rotated beam, wherein each first polarizer segment comprises a linear polarizer configured to transmit primarily a beam of a first polarization direction, and wherein each second polarizer segment comprises a linear polarizer configured to primarily transmit a beam having the polarization of the corresponding first rotated beam of the channel.

5. The optical device (100) according to any one of claims 2 to 4, in, Each channel (101) further comprises a second rotator section (104), wherein the second rotator section (104) is positioned between the multiplexer (102) and the optical isolator section (103), and Wherein the second rotator section (104) is configured to: rotate the polarization of the corresponding beam of the channel.

6. The optical device (100) according to claim 4 or 5, in, For each channel (101), the corresponding first rotated beam is the rotated beam provided by the channel, or wherein, for each channel (101), the second rotator section (104) is configured to: rotate the polarization of the corresponding beam of the channel to form a second rotated beam, and Therein, for each channel (101), the corresponding second rotated beam is the rotated beam provided by the channel.

7. The optical device (100) according to any one of claims 2 to 4, in, Each channel (101) further comprises a third rotator section (105), wherein the optical isolator section (103) is positioned between the third rotator section (105) and the multiplexer (102), and Wherein, the third rotator section (105) is configured to rotate the polarization of the corresponding beam of the channel to the first polarization direction.

8. The optical device (100) according to any one of the preceding claims, wherein: The two or more input beams (200) have the same polarization.

9. The optical device (100) according to any one of the preceding claims, in, Each of the two or more input beams (200) has a different central wavelength.

10. The optical device (100) according to claim 9, in, Each channel (101) is associated with a center wavelength of said corresponding input beam of said channel, Each channel (101) forms an adjacent channel with one or two other channels, wherein the one or two other channels are associated with an input beam having a next larger or next smaller central wavelength among the two or more input beams (200).

11. The optical device (100) according to claim 10, in, For each channel (101), the rotator segment is configured to rotate the polarization of the corresponding beam of the channel in a different direction than the rotator segments of one or two adjacent channels of the channel.

12. The optical device (100) according to claim 11, in, For each channel (101), the rotator segment is configured to rotate the polarization of the corresponding beam of the channel in a direction different from the rotator segment of the one or two adjacent channels of the channel, so that the corresponding rotated beams provided by adjacent channels have polarizations orthogonal to each other.

13. The optical device (100) according to claim 11 or 12, in, For each channel (101), the rotator segment is configured to rotate the polarization of the corresponding beam of the channel by the same absolute amount but in a different direction than the rotator segments of the one or two adjacent channels of the channel.

14. The optical device (100) according to claim 13, in, For each channel (101), the rotator segment is configured to rotate the polarization of the corresponding beam of the channel by 45° in a first plane, and the rotator segment of the one or two adjacent channels of the channel is configured to rotate the polarization of the corresponding beam of the channel by -45° in the first plane.

15. The optical device (100) according to any one of claims 10 to 14, in, For each channel (101), the rotator section of the optical isolator section (103) is configured to rotate the polarization of the corresponding beam of the channel by a maximum absolute amount that satisfies the condition that the corresponding rotated beams provided by adjacent channels are orthogonal to each other.

16. The optical device (100) according to claim 10 or 15, in, Each channel (101) is configured to: rotate the polarization of the corresponding input beam to a second direction orthogonal to the third direction, and The third direction is the polarization direction of the corresponding rotated beam provided by the one or two adjacent channels of the channel.

17. The optical device (100) according to any one of the preceding claims, in, Each rotated beam provided by the two or more channels (101) to the multiplexer (102) has a fourth polarization or a fifth polarization, wherein the fourth polarization is orthogonal to the fifth polarization.

18. The optical device (100) according to any one of claims 10 to 17, in, The two or more channels (101) include: a first group of channels and a second group of channels, wherein each channel (101) in the first group of channels is an adjacent channel to one or two channels in the second group of channels, wherein each channel (101) in the second group of channels is an adjacent channel to one or two channels in the first group of channels, wherein, for each channel (101) of the first set of channels, the corresponding rotated beam provided by the channel has the fourth polarization, and Wherein, for each channel (101) in the second group of channels, the corresponding rotated beam provided by the channel has the fifth polarization.

19. The optical device (100) according to any one of the preceding claims, in, Each channel (101) also includes a polarization transmitter segment (106), Wherein, the optical isolator segment (103) is positioned between the polarization transmitter segment (106) and the multiplexer (102), and / or wherein the third rotator segment (105) is positioned between the polarization transmitter segment (106) and the optical isolator segment (103).

20. The optical device (100) according to claim 19, in, For each channel (101), the polarization direction of the polarization transmitter section (106) matches the first polarization direction, and / or Wherein, for each channel (101), the polarization transmitter segment (106) is configured to: receive one input beam (200a) of the two or more input beams (200) and provide the input beam to the optical isolator segment (103) or the third rotator segment (105).

21. The optical device (100) according to any one of the preceding claims, in, The multiplexer (102) is a wavelength multiplexer (102) and / or a polarization multiplexer (102), and Wherein, the multiplexer (102) is configured to combine all the rotated beams provided to the multiplexer (102) by the two or more channels (101).

22. The optical device (100) according to any one of the preceding claims, in, Each rotator segment comprises a Faraday rotator, and / or Wherein each isolator segment (103) comprises a Faraday rotator.

23. A method (300) of operating an optical device (100) for wavelength division multiplexing two or more input beams (200), in, The optical device (100) comprises: a multiplexer (102) and two or more channels (101) for the two or more input beams (200), Wherein, the method comprises: receiving (301) one input beam (200a) of the two or more input beams (200) using each channel (101), providing (302) a rotated beam to the multiplexer (102) with each channel (101), the polarization of the rotated beam being rotated compared to the polarization of the corresponding input beam (200a), and Using at least one channel (101a) of the two or more channels (101), the polarization of the corresponding input beam (200a) is rotated (303) in a direction different from that of at least one other channel (101b) of the two or more channels (101).

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