Wavelength Selection Device and Method with Low Polarization Mode Dispersion

Abstract

The present invention relates to a wavelength selection device and method with low polarization mode dispersion. It includes: a wavelength selection switch for performing wavelength selection on signal light, which includes an optical fiber collimation array, a polarization processing device based on a polarization beam splitter, and a beam deflection device adapted to the polarization processing device; a polarization mode dispersion compensation unit for compensating the optical path of the first polarized light and the second polarized light, wherein the first polarized light and the second polarized light are incident on the beam deflection device through the polarization mode dispersion compensation unit; after the first polarized light is deflected by the beam deflection device, it returns to the polarization processing device along the optical path of the second polarized light; at the same time, after the second polarized light is deflected by the beam deflection device, it returns to the polarization processing device along the optical path of the first polarized light; when the polarization processing device uses a polarization beam splitter to polarize the signal light in the present invention, the polarization-related loss and polarization mode dispersion can be effectively reduced, and the cost and assembly difficulty of wavelength selection can be reduced.

Description

Technical Field

[0001] The present invention relates to a wavelength selection device and method, in particular to a wavelength selection device and method with low polarization mode dispersion. Background Art

[0002] In an optical communication system, a wavelength selective optical switch is a device for selecting optical signals of specific wavelengths. Such an optical switch is usually used in a wavelength division multiplexing (WDM) system, and it can select, combine or separate optical signals of corresponding wavelengths as needed.

[0003] Currently, the core device of the mainstream wavelength selection switch is a liquid crystal on silicon (LCOS) platform. Commonly used LCOS has polarization correlation. Of course, there are also polarization-independent LCOSs, but their manufacturing processes are relatively complex, so the cost is too high. When using polarization-correlated LCOS, a polarization processing device is required to process the input optical signal with unknown polarization into a single polarization signal. The polarization processing device is generally a polarization beam splitter (PBS) and a Wollaston prism composed of a birefringent crystal. The addition of the polarization processing device will bring problems such as polarization-dependent loss and polarization mode dispersion. Therefore, in the industry, a birefringent crystal is generally used to compensate the optical path of the polarized light of the light beam. However, when using a birefringent crystal to compensate the optical path, the related cost and assembly difficulty will be increased. Here, the birefringent crystal can be the above-mentioned Wollaston prism or other prisms based on birefringent crystals.

[0004] In order to reduce the cost and assembly difficulty, the polarization processing device generally uses a polarization beam splitter; when using a polarization beam splitter, how to reduce the polarization-dependent loss and polarization mode dispersion while realizing polarization processing is a technical problem to be solved urgently at present. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a wavelength selection device and method with low polarization mode dispersion, which can effectively reduce the polarization-dependent loss and polarization mode dispersion, and reduce the cost and assembly difficulty of wavelength selection when the polarization processing device uses a polarization beam splitter to polarize the signal light.

[0006] According to the technical solution provided by the present invention, a wavelength selection device with low polarization mode dispersion, the wavelength selection device includes:

[0007] A wavelength selection switch for wavelength selection of signal light, comprising an optical fiber collimation array, a polarization processing device based on a polarization beam splitter, and a beam deflection device adapted to the polarization processing device. When wavelength selection is performed on the signal light loaded by the optical fiber collimation array, the polarization processing device forms a first polarized light and a second polarized light after polarization processing;

[0008] A polarization mode dispersion compensation unit for compensating the optical path of the first polarized light and the second polarized light. The first polarized light and the second polarized light are incident on the beam deflection device through the polarization mode dispersion compensation unit;

[0009] After the first polarized light is deflected by the beam deflection device, it returns to the polarization processing device along the optical path of the second polarized light;

[0010] At the same time, after the second polarized light is deflected by the beam deflection device, it returns to the polarization processing device along the optical path of the first polarized light;

[0011] The polarization processing device converges the two returned light beams, and the converged light beam is output through the optical fiber collimation array to obtain the wavelength-selected light beam.

[0012] The polarization mode dispersion compensation unit includes a compensation column mirror and a Fourier lens unit, where

[0013] The Fourier lens unit includes at least one Fourier lens;

[0014] The first polarized light and the second polarized light are reflected by the compensation column mirror to the Fourier lens unit;

[0015] The first polarized light is incident on the beam deflection device through the Fourier lens unit, and the deflected light beam returns to the polarization processing device along the optical path of the second polarized light through the Fourier lens unit and the compensation column mirror;

[0016] The second polarized light is incident on the beam deflection device through the Fourier lens unit, and the deflected light beam returns to the polarization processing device along the optical path of the first polarized light through the Fourier lens unit and the compensation column mirror.

[0017] The Fourier lens unit includes only one Fourier lens, or the Fourier lens unit includes a compensation grating and at least one Fourier lens, where

[0018] When the Fourier lens unit includes only one Fourier lens, the Fourier lens in the Fourier lens unit is an equivalent Fourier lens;

[0019] When the Fourier lens unit includes a compensation grating and at least one Fourier lens, the Fourier lens in the Fourier lens unit is a basic Fourier lens, where the focal length of the equivalent Fourier lens is half of the focal length of the basic Fourier lens;

[0020] When the Fourier lens unit includes a compensation grating and at least one Fourier lens, the first polarized light and the second polarized light reflected by the compensation column mirror are incident on the beam deflection device through the basic Fourier lens and the compensation grating in sequence;

[0021] The beam deflected by the beam deflection device is incident on the polarization processing device through the compensation grating, the basic Fourier lens, and the compensation column mirror in sequence.

[0022] A selection lens unit is further provided between the fiber collimation array and the polarization processing device, where,

[0023] The selection lens unit includes at least one cylindrical lens;

[0024] A beam waist plane is formed between the polarization processing device and the compensation column mirror, where, based on the selection lens unit and the compensation column mirror, the beam waist on the beam waist plane is configured to be consistent with the beam waist on the beam deflection device, and the radius of the beam waist on the beam deflection device is not greater than 30 μm.

[0025] The compensation grating includes a prism grating and a reflecting prism, where,

[0026] The reflecting prism corresponds to the beam deflection device;

[0027] The first polarized light and the second polarized light are incident on the prism grating after passing through the basic Fourier lens, and are incident on the beam deflection device through the reflecting prism.

[0028] The polarization processing device includes a deflection beam splitter, a spot compensator, and a half-wave plate, where,

[0029] The spot compensator includes an upper spot compensation crystal and a lower spot compensation crystal connected to the upper spot compensation crystal, and the refractive index of the upper spot compensation crystal is greater than that of the lower spot compensation crystal;

[0030] The half-wave plate corresponds to the lower spot compensation crystal;

[0031] The signal light is polarization-processed by the polarization beam splitter to generate the first polarized light and the second polarized light;

[0032] The first polarized light or the second polarized light is incident on the polarization mode dispersion compensation unit through the upper spot compensation crystal;

[0033] The second polarized light or the first polarized light is incident on the polarization mode dispersion compensation unit after passing through the lower spot compensation crystal and the half-wave plate.

[0034] Along the optical path directions of the first polarized light and the second polarized light, the thickness of the upper crystal for spot compensation is greater than the thickness of the lower crystal for spot compensation;

[0035] The half-wave plate is attached to the lower crystal for spot compensation, or the half-wave plate is located behind the lower crystal for spot compensation.

[0036] The fiber collimation array includes a fiber clamping plate, a fiber array assembled on the fiber clamping plate, and a collimating lens array assembled on the fiber clamping plate, wherein,

[0037] The fiber array includes a plurality of collimating fibers arranged in sequence, and the interval between the collimating fibers in the fiber array is 80 μm to 250 μm;

[0038] The collimating lens array includes a plurality of collimating lenses. Among them, the number of collimating lenses in the collimating lens array is not less than the number of collimating fibers in the fiber array, and the collimating fibers and the collimating lenses are in one-to-one correspondence.

[0039] When selecting a wavelength, the beam deflection device operates in a stepped blazed grating state.

[0040] A wavelength selection method with low polarization mode dispersion, for any signal light, wavelength selection is performed based on the above-mentioned wavelength selection device.

[0041] Advantages of the present invention: For the first polarized light and the second polarized light generated by being processed by the polarization processing device, the optical path compensation is performed by using the polarization mode dispersion compensation unit, that is, the first polarized light and the second polarized light are incident on the beam deflection device through the polarization mode dispersion compensation unit; after the first polarized light is deflected by the beam deflection device, it returns to the polarization processing device along the optical path of the second polarized light; at the same time, after the second polarized light is deflected by the beam deflection device, it returns to the polarization processing device along the optical path of the first polarized light; thus, the polarization mode dispersion compensation can be realized by performing the optical path compensation, achieving the purpose of low polarization mode dispersion, and further effectively reducing the polarization-related loss, reducing the cost and assembly difficulty of wavelength selection. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic structural diagram of an embodiment of the wavelength selection device of the present invention.

[0043] Figure 2 is Figure 1 A schematic optical path diagram of an embodiment of the wavelength selection device in the deflection plane in

[0044] Figure 3 is Figure 1 A schematic optical path diagram of an embodiment of the wavelength selection device in the dispersion plane in

[0045] Figure 4 This is a schematic structural diagram of an embodiment of the polarization processor device of the present invention.

[0046] Figure 5 This is a schematic diagram of an embodiment of the Fourier lens unit of the present invention.

[0047] Figure 6 This is a schematic diagram of an embodiment of the beam deflection device of the present invention in the state of a stepped blazed grating.

[0048] Figure 7 This is a schematic diagram of an embodiment of the fiber collimation array of the present invention;

[0049] Figure 8 This is a schematic working diagram of an embodiment of the compensation column mirror of the present invention in the dispersion plane.

[0050] Figure 9 This is a schematic diagram of an embodiment of the selection lens unit and the fiber collimation array in cooperation of the present invention.

[0051] Figure 10 This is a schematic diagram of an embodiment of the compensation grating and the beam deflection device in cooperation of the present invention.

[0052] Explanation of reference numerals: 1 - fiber collimation array, 2 - selection lens unit, 3 - polarization processor device, 4 - beam waist plane, 5 - compensation column mirror, 6 - basic Fourier lens, 7 - compensation grating, 8 - reflecting prism, 9 - beam deflector PCB board, 10 - beam deflection device, 11 - signal light, 12 - first polarized light, 13 - second polarized light, 14 - converging selection beam, 15 - first deflected light, 16 - second deflected light, 17 - polarization beam splitter, 18 - crystal under spot compensation, 19 - half-wave plate, 20 - crystal above spot compensation, 21 - equivalent Fourier lens, 22 - folding optical path reflecting prism, 23 - compensation grating gap, 24 - collimated fiber, 25 - fiber clamp, 26 - collimating lens array, 27 - prism grating. Detailed implementation manners

[0053] The present invention will be further described below in conjunction with specific drawings and embodiments.

[0054] When the polarization beam splitter 17 is used to polarize the signal light 11 in the polarization processor device 3, in order to effectively reduce polarization-related loss and polarization mode dispersion, for the wavelength selection device with low polarization mode dispersion, in an embodiment of the present invention, the wavelength selection device includes:

[0055] A wavelength selective switch for wavelength selection of signal light 11, comprising an optical fiber collimation array 1, a polarization processing device 3 based on a polarization beam splitter 17, and a beam deflection device 10 adapted to the polarization processing device 3. When wavelength selection is performed on the signal light 11 loaded by the optical fiber collimation array 1, the polarization processing device 3 forms a first polarized light 12 and a second polarized light 13 during polarization processing;

[0056] A polarization mode dispersion compensation unit for compensating the optical path of the first polarized light 12 and the second polarized light 13. The first polarized light 12 and the second polarized light 13 enter the beam deflection device 10 through the polarization mode dispersion compensation unit;

[0057] After the first polarized light 12 is deflected by the beam deflection device 10, it returns to the polarization processing device 3 along the optical path of the second polarized light 13;

[0058] At the same time, after the second polarized light 13 is deflected by the beam deflection device 10, it returns to the polarization processing device 3 along the optical path of the first polarized light 12;

[0059] The polarization processing device 3 converges the two returned light beams, and the converged light beam is output through the optical fiber collimation array 1 to obtain the wavelength selected light beam.

[0060] As can be seen from the above description, the signal light 11 is the input light for wavelength selection. When wavelength selection is performed on the signal light 11, the wavelength selection device at least includes a wavelength selective switch, that is, the wavelength selective switch is the basic unit of the wavelength selection device, and the wavelength selection of the signal light 11 can be realized by using the wavelength selective switch. In order to reduce costs and assembly complexity, the wavelength selective switch generally receives the signal light 11 through the optical fiber collimation array 1, and uses the polarization processing device 3 based on the polarization beam splitter 17 to perform polarization processing on the signal light 11, and uses the beam deflection device 10 to realize the deflection of the light beam. Thus, it can be seen that the wavelength selective switch at least includes the optical fiber collimation array 1, the polarization processing device 3, and the beam deflection device 10.

[0061] As can be seen from the above description, when the polarization processing device 3 uses a polarization beam splitter 17 during wavelength selection, polarization mode dispersion will occur. In order to compensate for the polarization mode dispersion, in an embodiment of the present invention, a polarization mode dispersion compensation unit is used for polarization mode dispersion compensation. When the polarization processing device 3 performs polarization processing on the signal light 11, a first polarized light 12 and a second polarized light 13 can be formed. When the polarization mode dispersion compensation unit is used for polarization mode dispersion compensation, the first polarized light 12 and the second polarized light 13 enter the beam deflection device 10 through the polarization mode dispersion compensation unit, and the beam deflection device 10 can realize the deflection of the light beam, that is, the first polarized light 12 and the second polarized light 13 can be deflected respectively through the beam deflection device 10.

[0062] In order to achieve polarization dispersion mode compensation, in an embodiment of the present invention, after the beam deflector 10 deflects the first polarized light 12, a first deflected light 15 can be formed. The first deflected light 15 returns to the polarization processing device 3 along the optical path direction of the second polarized light 13. At the same time, after the beam deflector 10 deflects the second polarized light 13, a second deflected light 16 can be formed, and the second deflected light 16 can return to the polarization processing device 13 along the optical path direction of the first polarized light 12.

[0063] Specifically, based on the above-mentioned deflection processing of the first polarized light 12 and the second polarized light 13, and the optical path configuration in which the first deflected light 15 and the second deflected light 16 return to the deflection processing device 3, optical path compensation for the first polarized light 12 and the second polarized light 13 can be achieved. Since polarization mode dispersion is related to the optical path, when optical path compensation is performed on the first polarized light 12 and the second polarized light 13, the polarization mode dispersion during wavelength selection of the signal light 11 can be reduced. In addition, based on polarization mode dispersion compensation, the polarization-related loss during wavelength selection of the signal light 11 can also be reduced.

[0064] After the first deflected light 15 and the second deflected light 16 return to the polarization processing device 3, the polarization processing device 3 converges the first deflected light 15 and the second deflected light 16, and thus a converged selection beam 14 can be obtained. The converged selection beam 14 is output through the fiber collimation array 1, that is, the converged selection beam 14 is the beam after wavelength selection of the signal light 11.

[0065] In an embodiment of the present invention, the polarization mode dispersion compensation unit includes a compensating column mirror 5 and a Fourier lens unit, where

[0066] the Fourier lens unit includes at least one Fourier lens;

[0067] The first polarized light 12 and the second polarized light 13 are reflected by the compensating column mirror 5 to the Fourier lens unit;

[0068] The first polarized light 12 is incident on the beam deflector 10 through the Fourier lens unit, and the beam deflected by the deflector 10 returns to the polarization processing device 3 along the optical path of the second polarized light 13 through the Fourier lens unit and the compensating column mirror 5;

[0069] The second polarized light 13 is incident on the beam deflector 10 through the Fourier lens unit, and the beam deflected by the deflector 10 returns to the polarization processing device 3 along the optical path of the first polarized light 12 through the Fourier lens unit and the compensating column mirror 5.

[0070] Figure 1An embodiment of the wavelength selection device is shown. As can be seen from the figure, the polarization mode dispersion compensation unit generally includes a compensation column mirror 5 and a Fourier lens unit. From the above description, it can be known that the compensation column mirror 5 is located on the optical paths of the first polarized light 12 and the second polarized light 13 generated by the polarization processing device 3. The compensation column mirror 5 can adopt the form of a commonly used cylindrical mirror in the prior art, so as to reflect the first polarized light 12 and the second polarized light 13 to the Fourier lens unit.

[0071] When the polarization mode unit adopts the compensation column mirror 5 and the Fourier lens unit, the first polarized light 12 and the second polarized light 13 are incident on the beam deflection device 10 through the Fourier lens unit, and the first deflected light 15 and the second deflected light 16 generated after deflection return to the polarization processing device 3 in sequence after passing through the Fourier lens unit and the compensation column mirror 5.

[0072] In specific implementation, when the polarization mode dispersion compensation unit adopts the compensation column mirror 5 and the Fourier lens unit, when compensating for polarization mode dispersion, the devices required for optical path compensation of the first polarized light 12 and the second polarized light 13 can be reduced, the influence of other devices can be reduced, and the flexibility of the design is improved.

[0073] In an embodiment of the present invention, the Fourier lens unit only includes one Fourier lens, or the Fourier lens unit includes a compensation grating 7 and at least one Fourier lens, where

[0074] When the Fourier lens unit only includes one Fourier lens, the Fourier lens in the Fourier lens unit is an equivalent Fourier lens 21;

[0075] When the Fourier lens unit includes a compensation grating 7 and at least one Fourier lens, the Fourier lens in the Fourier lens unit is a basic Fourier lens 6, where the focal length of the equivalent Fourier lens 21 is half of the focal length of the basic Fourier lens 6;

[0076] When the Fourier lens unit includes a compensation grating 7 and at least one Fourier lens, the first polarized light 12 and the second polarized light 13 reflected by the compensation column mirror 5 are incident on the beam deflection device 10 in sequence through the basic Fourier lens 6 and the compensation grating 7;

[0077] The light beam deflected by the beam deflection device 10 returns to the polarization processing device 3 in sequence through the compensation grating 7, the basic Fourier lens 6 and the compensation column mirror 5.

[0078] For the Fourier lens unit, in an embodiment of the present invention, it can only include one Fourier lens, or include a compensation grating 7 and at least one Fourier lens, which is specifically related to the parameters of the two Fourier lenses. The following is a specific description. Figure 1An embodiment is shown in which the Fourier lens unit includes a compensation grating 7 and a Fourier lens. At this time, the Fourier lens of the Fourier lens unit can be called a basic Fourier lens 6, and the basic Fourier lens 6 can adopt a commonly used existing Fourier lens. During operation, based on the basic Fourier lens 6 or the equivalent Fourier lens 21 of the Fourier lens unit, the first deflected light 15 can be made to return to the polarization processing device 3 along the optical path of the second polarized light 13, and the second deflected light 16 can be made to return to the polarization processing device 3 along the optical path of the first polarized light 12.

[0079] Figure 5 An embodiment is shown in which the compensation grating 7 and the basic Fourier lens 6 can be equivalent to an equivalent Fourier lens 21 during operation. That is, when the Fourier lens unit only includes one Fourier lens, the Fourier lens in the Fourier lens unit can be called an equivalent Fourier lens 21. In a specific implementation, the focal length of the equivalent Fourier lens 21 is half of the focal length of the basic Fourier lens 6. That is, after selecting the basic Fourier lens 6, the equivalent Fourier lens 21 can be selected and determined. When the equivalent Fourier lens 21 is adopted, the optical path of the entire wavelength selection can be further compressed, that is, the optical path of the entire wavelength selection is made more compact.

[0080] For Figure 1 For the Fourier lens unit shown in, when performing wavelength selection on the signal light 11, the first polarized light 12 and the second polarized light 13 reflected by the compensation column mirror 5 will sequentially pass through the basic Fourier lens 6 and the compensation grating 7 and enter the beam deflection device 10. The first deflected light 15 and the second sheet light 16 formed after being deflected by the beam deflection device 10 will sequentially pass through the compensation grating 7, the basic Fourier lens 6, and the compensation column mirror 5 and return to the polarization processing device 3.

[0081] In an embodiment of the present invention, the compensation grating 7 includes a prism grating 27 and a reflecting prism 8, wherein,

[0082] The reflecting prism 8 corresponds to the beam deflection device 10;

[0083] The first polarized light 12 and the second polarized light 13 pass through the basic Fourier lens 6 and then enter the prism grating 27, and enter the beam deflection device 10 through the reflecting prism 8.

[0084] Figure 10In an embodiment of the compensation grating 7 shown in the figure, the compensation grating 7 includes a prism grating 27 and a reflecting prism 8. The reflecting prism 8 corresponds exactly to the beam deflector 10. Both the prism grating 27 and the reflecting prism 8 can adopt the existing common forms. In specific implementation, for the first polarized light 12 and the second polarized light 13, after passing through the basic Fourier lens 6, they are incident on the prism grating 27 and then incident on the beam deflector 10 through the reflecting prism 8. In addition, the first deflected light 15 and the second deflected light 16 formed by the beam deflector 10 are incident on the compensation column mirror 5 in sequence through the reflecting prism 8, the prism grating 27, and the basic Fourier lens 6, and can finally return to the polarization processing device 3.

[0085] In specific implementation, the prism grating 27 can be selected as a transmissive grating or a reflective grating. Among them, a reflective grating is preferably used. When the prism grating 27 is a reflective grating and is combined with the reflecting prism 8 to form a prism grating, the wavelengths can be better separated.

[0086] Figure 10 In the figure, the beam deflector 10 is assembled on the beam deflector PCB board 9. The beam deflector PCB board 9 is generally a flexible PCB board. Through the beam deflector PCB board 9, the beam deflector 10 can be driven to work and the working state of the beam deflector 10 can be configured. Since the polarization processing device 3 is based on a polarization beam splitter 17, the beam deflector 10 can be selected as a liquid crystal on silicon (LCOS) with polarization correlation. Therefore, the beam deflector PCB board 9 can adopt a form adapted to the beam deflector 10 to drive the beam deflector 10 to work and configure the working state of the beam deflector 10. In addition, Figure 10 In the figure, there is a compensation grating gap 23 between the prism grating 27 and the reflecting prism 8.

[0087] In an embodiment of the present invention, when selecting wavelengths, the beam deflector 10 operates in a stepped blazed grating state. Figure 6 In the figure, an embodiment of configuring the beam deflector 10 to operate in a stepped blazed grating state through the beam deflector PCB board 9 is shown. In the figure, the abscissa is the position of the beam deflector 10, and the ordinate is the phase, that is, different positions of the beam deflector 10 can be configured to be in a stepped blazed grating state. At this time, the first polarized light 12 and the second polarized light 13 can be deflected to form the second deflected light 15 and the second deflected light 16 respectively.

[0088] In addition, in order to further fold the optical path, a folding optical path reflecting prism 22 adapted to the beam deflection device 10 may be provided. Among them, the folding optical path reflecting prism 22 may adopt a combination of a conventional mirror and a prism. Through the folding optical path reflecting prism 22, the first polarized light 12 and the second polarized light 13 can be vertically incident on the beam deflection device 10; in addition, the deflected light deflected by the beam deflection device 10 is incident on the polarization mode dispersion compensation unit through the folding optical path reflecting prism 22. The folding optical path reflecting prism 22 is specifically configured to cooperate with the beam deflection device 10 to achieve the purpose of folding the optical path, such as Figure 1 shown.

[0089] In an embodiment of the present invention, a selection lens unit 2 is further provided between the fiber collimation array 1 and the polarization processing device 3, where

[0090] the selection lens unit 2 includes at least one cylindrical lens;

[0091] A beam waist surface 4 is formed between the polarization processing device 3 and the compensation cylindrical mirror 5. Among them, based on the selection lens unit 2 and the compensation cylindrical mirror 5, the beam waist on the beam waist surface 4 is configured to be consistent with the beam waist on the beam deflection device 10, and the radius of the beam waist on the beam deflection device 10 is not greater than 30 μm. Figure 1 An embodiment in which the selection lens unit 2 is further provided in the wavelength selection switch is shown in. The selection lens unit 2 may include at least one cylindrical lens, Figure 1 An embodiment in which four cylindrical lenses are provided in the selection lens unit 2 is shown in. The number of cylindrical lenses in the selection lens unit 2 can generally be selected according to needs. After the selection lens unit 2 is provided, the signal light 11 loaded by the fiber collimation array 1 enters the polarization processing device 3 after passing through the selection lens unit 2. Of course, the selection lens unit 2 can also use conventional lenses and spot transformation prisms. The specific form of the selection lens unit 2 can be selected according to needs to meet the requirement of having a preset spot on the beam waist surface 4. Generally, the preset spot on the beam waist surface 4 is elliptical.

[0092] Figure 1 In, a beam waist surface 4 is provided between the polarization processing device 3 and the compensation cylindrical mirror 5. The beam waist of the beam waist surface 4 can be controlled through the selection lens unit 2. In addition, based on the selection lens unit 2, the ports of the fiber collimation array 1 can be expanded. In addition, based on the selection lens unit 2 and the compensation cylindrical mirror 5, it can also be configured such that the beam waist on the beam waist surface 4 is consistent with the beam waist on the beam deflection device 10, and the radius of the beam waist on the beam deflection device 10 is not greater than 30 μm.

[0093] In specific implementation, when the Fourier lens unit adopts the equivalent Fourier lens 21, the beam waist plane 4 and the beam deflector 10 are located at the front and rear focal points of the equivalent Fourier lens 21. Thus, according to the front and rear focal lengths of the equivalent Fourier lens 21, the position where the beam waist plane 4 is located can be determined. For the first polarized light 12 and the second polarized light 13 generated from the same signal light 11, the first polarized light 12 and the second deflected light 13 will be focused on the same area of the beam deflector 10, that is, they can be deflected by the stepped blazed grating in the same area.

[0094] In an embodiment of the present invention, the fiber collimation array 1 includes a fiber clamp 25, a fiber array assembled on the fiber clamp 25, and a collimating lens array 26 assembled on the fiber clamp 25, wherein,

[0095] The fiber array includes a plurality of collimating fibers 24 arranged in sequence, and the interval between the collimating fibers 24 in the fiber array is 80μm - 250μm;

[0096] The collimating lens array 26 includes a plurality of collimating lenses. Among them, the number of collimating lenses in the collimating lens array 26 is not less than the number of collimating fibers 24 in the fiber array, and the collimating fibers 24 and the collimating lenses are in one-to-one correspondence.

[0097] Figure 7 An embodiment of the fiber collimation array 1 is shown in the figure. In the figure, the fiber collimation array 1 includes a fiber clamp 25, and the fiber array and the collimating lens array 26 can be assembled by using the fiber clamp 25. For the fiber array, generally includes a plurality of collimating fibers 24 arranged in sequence. The collimating fibers 24 can adopt commonly used existing fibers. There is a gap between adjacent collimating fibers 24, and the interval between adjacent collimating fibers 24 is 80μm - 250μm. When the interval between adjacent collimating fibers 24 is set to 80μm - 250μm, the number of collimating fibers 24 can be increased, so that more collimating fibers 24 can be used as output fibers, thereby improving the adaptability of the output after wavelength selection.

[0098] The collimating lens array 26 generally includes collimating lenses. The collimating lenses can adopt commonly used existing lenses. The number of collimating lenses is not less than the number of collimating fibers 24, so that one collimating fiber 24 and one collimating lens are in one-to-one correspondence.

[0099] When performing wavelength selection on the signal light 11, one of the collimating fibers 24 is selected as the input fiber. At this time, the input fiber is used to receive the signal light 11, and the remaining collimating fibers 24 are used as output fibers. The position of the input fiber and the like can be selected according to actual needs. The converged selection beam 14 formed by the polarization processing device 3 is output through the corresponding output fiber. The output fiber selected by the converged selection beam 14 is related to the wavelength of the converged selection beam 14.

[0100] In one embodiment of the present invention, the polarization processing device 3 includes a deflection beam splitter 17, a spot compensator, and a half-wave plate 19. Among them,

[0101] The spot compensator includes an upper spot compensation crystal 20 and a lower spot compensation crystal 18 connected to the upper spot compensation crystal 20. The refractive index of the upper spot compensation crystal 20 is greater than that of the lower spot compensation crystal 18;

[0102] The half-wave plate 19 corresponds to the lower spot compensation crystal 18;

[0103] The polarization beam splitter 17 is used to perform polarization processing on the signal light 11 to generate a first polarized light 12 and a second polarized light 13;

[0104] The first polarized light 12 or the second polarized light 13 is incident on the polarization mode dispersion compensation unit through the upper spot compensation crystal 20;

[0105] The second polarized light 13 or the first polarized light 12 is incident on the polarization mode dispersion compensation unit after passing through the lower spot compensation crystal 18 and the half-wave plate 19.

[0106] The polarization processing device 3 converts the input light with no fixed polarization state into a single deflected light. In one embodiment of the present invention, the single polarization is TM (Transverse magnetic wave) polarization. Figure 4 An embodiment of the polarization processing device 3 is shown. From the above description, it can be seen that the polarization processing device 3 at least includes a polarization beam splitter 17. The polarization beam splitter 17 can adopt an existing common form. Through the polarization beam splitter 17, a first polarized light 12 and a second polarized light 13 can be obtained. Among them, the corresponding polarizations of the first polarized light 12 and the second polarized light 13 are TM polarizations.

[0107] For the first polarized light 12 and the second polarized light 13 obtained through the polarization beam splitter 17, the first polarized light 12 and the second polarized light 13 are parallel to each other. In addition, since the first polarized light 12 and the second polarized light 13 are parallel to each other, therefore, in Figure 1 only the case of one polarized light is shown.

[0108] In order to reduce the insertion loss during wavelength selection, a spot compensator is provided behind the polarization beam splitter 17. The spot compensator can be used to perform spot compensation on the first polarized light 12 and the second polarized light 13, so that the sizes of the two spots on the beam waist plane 4 are the same, thereby achieving the purpose of improving the coupling efficiency. In one embodiment of the present invention, the spot compensator includes an upper spot compensation crystal 20 and a lower spot compensation crystal 18. Figure 4In it, the upper crystal 20 for spot compensation is in contact with the lower crystal 18 for spot compensation. The refractive index of the upper crystal 20 for spot compensation is greater than that of the lower crystal 18 for spot compensation, and along the optical path directions of the first polarized light 12 and the second polarized light 13, the thickness of the upper crystal 20 for spot compensation is greater than that of the lower crystal 18 for spot compensation.

[0109] In specific implementation, the upper crystal 20 for spot compensation can be made of silicon, and the lower crystal 18 for spot compensation can be made of glass. Of course, the upper crystal 20 for spot compensation and the lower crystal 18 for spot compensation can also be made of other materials, as long as the above settings can be satisfied. Since the signal light 11 received by the collimating optical fiber 24 is a Gaussian beam, and the divergence angle of the Gaussian light in the material with a larger refractive index is smaller, therefore, the thicker upper crystal 20 for spot compensation can compress the beam waist broadening brought by the polarization beam splitter 17 to ensure that the spot sizes of the upper and lower two beams are the same at the beam waist plane 4 of the beam.

[0110] In an embodiment of the present invention, the half-wave plate 19 is attached to the lower crystal 18 for spot compensation, or the half-wave plate 19 is located behind the lower crystal 18 for spot compensation. Specifically, the half-wave plate 19 is located behind the lower crystal 18 for spot compensation, that is, in the direction away from the polarization beam splitter 17.

[0111] For Figure 1 the wavelength selection optical path shown in, when selecting the wavelength, it can simultaneously have a dispersion plane and a deflection plane. Figure 2 FIG. is a schematic optical path diagram of an embodiment of the equivalent deflection plane. Figure 3 FIG. is a schematic optical path diagram of an embodiment of the equivalent dispersion plane. The following will be combined with Figure 2 and Figure 3 to describe the optical path for wavelength selection.

[0112] For the dispersion plane, the signal light 11 is input from the fiber collimation array 1, passes through the selection lens unit 2 and the polarization processing device 3 to reach the beam waist plane 4 of the beam, passes through the compensation column mirror 5 and the basic Fourier lens 6 to reach the compensation grating 7. The function of the compensation grating 7 is to convert the wavelength of the signal light 11 from the frequency domain to the spatial domain and irradiate it on the beam deflection device 10, as shown in Figure 3 shown. Figure 3 In, the light beams with different wavelengths are irradiated on different regions of the beam deflection device 10. After being deflected by the beam deflection device 10, the converging selection beams 14 output from different output optical fibers can be obtained, and thus wavelength selection can be realized.

[0113] Such as Figure 8As shown in the figure, in the dispersion plane, the first polarized light 12 and the second polarized light 13 will pass through the compensation column mirror 5 twice. The first time, they are collimated by the compensation column mirror 5, and the second time, they are focused by the compensation column mirror 5. Therefore, in the direction of the dispersion plane, from the above description, it can be known that the beam waist at the beam waist plane 4 is equal to the beam waist on the beam deflection device 10. The radius of the beam waist on the beam deflection device 10 is generally required to be less than 30 μm. At this time, the channel shape can be ensured when selecting the wavelength of the signal light 11.

[0114] Figure 8 In the figure, the radius of the beam waist at the beam waist plane 4 is w1, and the radius of the beam waist on the beam deflection device 10 is w2. From the above description, it can be known that w2 is not greater than 30 μm, and w2 is generally equal to w1.

[0115] For the deflection plane, that is, the plane where the beam deflection device 10 deflects light. The signal light 11 is received by the fiber collimation array 1. After the signal light passes through the lens selection unit 2 and the deflection processing device 3, the first polarized light 12 and the second polarized light 13 can be obtained. The first polarized light 12 and the second deflected light 13 pass through the compensation column mirror 5, the basic Fourier lens 6, and the compensation grating 7 and are incident on the beam deflection device 10. After the first polarized light 12 is deflected by the beam deflection device 10, it returns along the optical path of the second deflected light 13. At the same time, after the second polarized light 13 is deflected by the beam deflection device 10, it returns along the route of the first polarized light 12, thereby compensating for the inconsistent optical path caused by the polarization processing device 3, and further compensating for the polarization mode dispersion caused by the polarization beam splitter 17.

[0116] Furthermore, in the deflection plane, based on the Fourier lens unit, the spot on the beam waist plane 4 and the spot on the beam deflection device 10 can be in a Fourier transform relationship. Thus, by observing the spot on the beam waist plane 4, the spot on the beam deflection device 10 can be obtained.

[0117] Figure 2 and Figure 3 In the figure, two compensation column mirrors 5 and the basic Fourier lens 6 appear on both sides of the compensation grating 7 respectively. This indicates that the beam passes through the two compensation column mirrors 5 and the basic Fourier lens 6 twice, that is Figure 2 and Figure 3 In the figure, the specific optical path is described by the optical path expansion method. For the following cases where two compensation column mirrors 5 and the basic Fourier lens 6 appear, they are all in the form of optical path expansion, and the description here can be referred to.

[0118] Furthermore, in the deflection plane, the appropriate lens selection unit 2 can increase the distance between the returned signal light 11 and the converging selection beam 14, thereby increasing the deflection angle of the beam deflection device 10, and further increasing the number of ports of the fiber collimation array 1 (i.e., the number of collimated optical fibers 11). That is, without changing the subsequent optical path, only by changing the lens selection unit 2 and the fiber collimation array 1 can the expansion of the output ports be achieved. Specifically in this embodiment, 4 to 22 output ports can be achieved, that is, there can be 4 to 22 output optical fibers, as Figure 9 shown. Figure 9 In Figure 9 , the distance between the signal light 11 near the polarization processor 3 and the converging selection beam 14 of the lens unit 2 is d. After passing through the lens selection unit 2, on the side adjacent to the fiber collimation array 1, the distance between the signal light 11 and the converging selection beam 14 is D, where D is greater than d.

[0119] In summary, a wavelength selection method for polarization mode dispersion compensation can be obtained. In an embodiment of the present invention, for any signal light 11, wavelength selection is performed based on the above-mentioned wavelength selection device.

[0120] Specifically, the specific situation of the wavelength selection device can be referred to the above description. The specific situation of using the wavelength selection device to perform wavelength selection on the signal light 11 can be referred to the above description.

[0121] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A wavelength selection device with low polarization mode dispersion, characterized in that: The wavelength selection device comprises: A wavelength selective switch, used for wavelength selection of signal light, comprising a fiber collimation array, a polarization processing device based on a polarization beam splitter, and a beam deflection device adapted to the polarization processing device, wherein the signal light loaded by the fiber collimation array is polarized by the polarization processing device to form a first polarized light and a second polarized light during wavelength selection; A polarization mode dispersion compensation unit, used for performing optical path compensation on the first polarized light and the second polarized light, wherein the first polarized light and the second polarized light are incident on the beam deflection device through the polarization mode dispersion compensation unit; After being deflected by the beam deflection device, the first polarized light returns to the polarization processing device along the optical path of the second polarized light; At the same time, after being deflected by the beam deflection device, the second polarized light returns to the polarization processing device along the optical path of the first polarized light; The polarization processing device converges the two returning light beams, and the converged light beams are output through the optical fiber collimation array to obtain a wavelength-selected light beam; The polarization mode dispersion compensation unit includes a compensation rod reflector and a Fourier lens unit, wherein: The Fourier lens unit includes at least one Fourier lens; The first polarized light and the second polarized light are reflected by the compensation column reflector to the Fourier lens unit; The first polarized light is incident on the beam deflection device through the Fourier lens unit, and the light beam deflected by the deflection device returns to the polarization processing device along the optical path of the second polarized light through the Fourier lens unit and the compensation column reflector; The second polarized light is incident on the beam deflection device through the Fourier lens unit, and the light beam deflected by the deflection device returns to the polarization processing device along the optical path of the first polarized light through the Fourier lens unit and the compensation column reflector; A selection lens unit is also arranged between the optical fiber collimation array and the polarization processing device, wherein: The selection lens unit includes at least one cylindrical lens; A beam waist surface is formed between the polarization processing device and the compensation column reflector, wherein, based on the selection of the lens unit and the compensation column reflector, the beam waist on the beam waist surface is configured to be consistent with the beam waist on the beam deflection device, and the radius of the beam waist on the beam deflection device is not greater than 30μm.

2. The wavelength selection device with low polarization mode dispersion according to claim 1, characterized in that: The Fourier lens unit includes only one Fourier lens, or the Fourier lens unit includes a compensation grating and at least one Fourier lens, wherein: When the Fourier lens unit includes only one Fourier lens, the Fourier lens in the Fourier lens unit is an equivalent Fourier lens; When the Fourier lens unit includes a compensation grating and at least one Fourier lens, the Fourier lens in the Fourier lens unit is a basic Fourier lens, wherein the focal length of the equivalent Fourier lens is half of the focal length of the basic Fourier lens; When the Fourier lens unit includes a compensation grating and at least one Fourier lens, the first polarized light and the second polarized light reflected by the compensation column reflector are incident on the beam deflection device via the basic Fourier lens and the compensation grating in sequence; The light beam deflected by the beam deflection device returns to the polarization processing device through the compensation grating, the basic Fourier lens and the compensation column reflector in sequence.

3. The wavelength selection device with low polarization mode dispersion according to claim 2, characterized in that: The compensation grating includes a prism grating and a reflecting prism, wherein: The reflecting prism corresponds to the light beam deflection device; The first polarized light and the second polarized light are incident on the prism grating after passing through the basic Fourier lens, and are incident on the beam deflection device through the reflection prism.

4. The wavelength selection device with low polarization mode dispersion according to any one of claims 1 to 3, characterized in that: The polarization processing device includes a deflection beam splitter, a spot compensator and a half-wave plate, wherein: The spot compensator comprises a spot compensation upper crystal and a spot compensation lower crystal connected to the spot compensation upper crystal, wherein the refractive index of the spot compensation upper crystal is greater than the refractive index of the spot compensation lower crystal; The half-wave plate corresponds to the crystal under spot compensation; Performing polarization processing on the signal light by using a polarization beam splitter to generate a first polarized light and a second polarized light; The first polarized light or the second polarized light is incident on the polarization mode dispersion compensation unit through the spot compensation upper crystal; The second polarized light or the first polarized light is incident on the polarization mode dispersion compensation unit after passing through the spot compensation lower crystal and the half-wave plate.

5. The wavelength selection device with low polarization mode dispersion according to claim 4, characterized in that: Along the optical path direction of the first polarized light and the second polarized light, the thickness of the upper crystal for spot compensation is greater than the thickness of the lower crystal for spot compensation; The half-wave plate is attached to the spot compensation lower crystal, or the half-wave plate is located behind the spot compensation lower crystal.

6. The wavelength selection device with low polarization mode dispersion according to any one of claims 1 to 3, characterized in that: The optical fiber collimation array comprises an optical fiber clamp, an optical fiber array mounted on the optical fiber clamp, and a collimating lens array mounted on the optical fiber clamp, wherein: The optical fiber array includes a plurality of collimating optical fibers arranged in sequence, and the interval between the collimating optical fibers in the optical fiber array is 80 μm to 250 μm; The collimating lens array comprises a plurality of collimating lenses, wherein the number of the collimating lenses in the collimating lens array is not less than the number of the collimating optical fibers in the optical fiber array, and the collimating optical fibers correspond to the collimating lenses in a one-to-one manner.

7. The wavelength selection device with low polarization mode dispersion according to any one of claims 1 to 3, characterized in that: During wavelength selection, the beam deflection device operates in a step blazed grating state.

8. A wavelength selection method for low polarization mode dispersion, characterized in that: For any signal light, wavelength selection is performed based on the wavelength selection device according to any one of claims 1 to 7.

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