2f wavelength selective switch

Abstract

The application provides a 2f wavelength selection switch, belonging to the technical field of optical switches, comprising a fiber array mirror group, a polarization mirror group, a shaping lens group, a grating, a cylindrical mirror and a beam deflection control device, the fiber array mirror group, the shaping lens group and the beam deflection control device constitute a 2f structure, and the grating, the cylindrical mirror and the beam deflection control device constitute a 2f structure; the fiber array mirror group emits a single beam of light which is shaped by a wave front and expanded, the single beam of light is modulated into double beams of light which are parallel to each other with an included angle of 0° by the polarization mirror group, the double beams of light are dispersed after entering the grating, and different wavelength beams are emitted to the cylindrical mirror, are collimated by the cylindrical mirror and are converged on the beam deflection control device, and the shaping lens group realizes shaping of the light beams, the polarization processing of the polarization mirror group is changed to parallel light emission in the switch, an input light path is separated, the degree of freedom is increased, the design process is simplified, and production and assembly are facilitated.

Description

Technical Field

[0001] This invention relates to the field of optical switch technology, specifically to a 2f wavelength selective switch. Background Technology

[0002] In recent years, with the rise of new technologies such as 5G and artificial intelligence, data traffic in communication networks and data centers has grown exponentially, posing significant challenges to data transmission and switching nodes. Utilizing wavelength-selective switches to form OXC (Optical Cross-Connect) nodes allows the input light of an optical fiber array to be deflected to any output port, enabling high-volume data exchange in a short time. This approach offers advantages such as interference resistance, low latency, and high-speed parallel computing, making it a key product for future data centers and communication networks. To expand bandwidth and increase data transmission rates, multi-wavelength, multi-port wavelength-selective switches based on wavelength division multiplexing (WDM) technology have become the mainstream for OXC switching nodes.

[0003] The typical structure of the wavelength selective switch described above includes a multi-port fiber array 700, a prism grating 800, and a beam deflection control device 600. To reduce the overall device size, the current mainstream structure adopts a 4f optical structure. Figure 1 Using a large cylindrical mirror 500 as the main optical element, the above three types of devices are placed at its focal point, that is, the distance from the cylindrical mirror is the focal length f of the mirror.

[0004] The input port of the multi-port fiber array 700 guides the optical signal into the optical path structure. After shaping, it enters the polarizer group 200 and is split into two linearly polarized beams with an angle between 0° and 90°. These polarized beams are collimated into parallel light by the cylindrical mirror 500 and then incident on the prism grating 800 via the port shaping lens group 300. The beams passing through the prism grating 800 finally undergo polarization combining and dispersion spectrum expansion at the beam deflection control device 600.

[0005] The problem with this 4F structure is that most of the components in the optical path are located at the focal plane of the shaping lens group 300. Due to the overall size of the chassis and housing, optical components such as the multi-port fiber array 700, polarizer group 200, prism grating 800, and beam deflection control device 600 are crammed into the same area at the focal plane, increasing the difficulty of assembly and debugging. In addition, the flexibility of the optical path design is limited by the cylindrical reflector 500. If its focal length is too small, it will make the positions of other components more crowded and easily block light; if the focal length is too large, it will exceed the overall size. The fixed focal length range increases the design difficulty. Secondly, the polarizer group 200 mostly adopts a birefringent prism scheme, which splits the input light into two polarized beams at an angle. The subsequent single-path modulation element is prone to blocking light during the optical path assembly process. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention provides a 2f wavelength selective switch, which changes the polarization processing of the polarizing mirror group to parallel light output and separates the input optical path (fiber array mirror group, polarizing mirror group, shaping lens group), increasing the degree of freedom, simplifying the design process, and facilitating production and assembly.

[0007] To achieve the above technical objectives, the adopted technical solution is: a 2f wavelength selective switch, comprising a fiber array mirror group, a polarizing mirror group, a shaping lens group, a grating, a cylindrical mirror, and a beam deflection control device. The fiber array mirror group and the beam deflection control device are located at the focal plane of the shaping lens group, the grating and the beam deflection control device are located at the focal plane of the cylindrical mirror, the shaping lens group is located between the grating and the polarizing mirror group, and / or between the grating and the cylindrical mirror. The fiber array mirror group, the shaping lens group, and the beam deflection control device constitute a 2f structure. A single beam of light is emitted from the fiber array mirror group after wavefront shaping and beam expansion. The single beam is modulated into a double beam with a 0° angle between them by the polarizing mirror group. After the double beam enters the grating for dispersion, the beams of different wavelengths diverge and are emitted to the cylindrical mirror. After being collimated by the cylindrical mirror, they converge on the beam deflection control device. The shaping lens group realizes the shaping of the beam.

[0008] The beneficial effects are: the fiber array mirror group, polarizing mirror group, and shaping lens group are separated, which is not affected by the overall size of the chassis and housing, making assembly convenient and debugging easier. Furthermore, the independent components do not block the incident light in front of the cylindrical mirror, and the designed focal length is more reasonable. Its design as a 2f structure simplifies the design of the optical path.

[0009] The fiber array mirror group includes a fiber array and a shaping mirror group. The fiber array is a multi-port fiber array with its ports arranged in the x-direction. The shaping mirror group is used to perform wavefront shaping and beam expansion on the beam emitted from the fiber array.

[0010] The beneficial effects are: it not only has the function of emitting light, but also performs preliminary shaping and beam expansion during light emission, making the emitted beam more uniform and of better quality.

[0011] The polarizing mirror assembly includes a prism, a lens, and a waveplate. The two opposite inclined surfaces of the prism are coated with multiple layers of polarizing beam-splitting film and a reflective film, respectively. The incident light is split into two beams on the polarizing beam-splitting film layer. The first beam is reflected and then reflected twice by the reflective film into the waveplate for polarization conversion, transforming it into a beam with the same polarization state as the transmitted second beam. The second beam is directly transmitted into the lens.

[0012] The beneficial effects are: the polarizing lens group can not only modulate the incident beam into two parallel beams with an angle of 0°, but also compensate for the deviation in the spot size and optical path when the beams are finally combined on the surface of the beam deflection control device by modulating the thickness and curvature of the lens.

[0013] The prism, lens, and waveplate are fixed together by adhesive bonding.

[0014] The beneficial effects are: the formed polarizing mirror assembly is simple to assemble and can realize multiple functions such as dual parallel beams, conversion of multiple polarization states to a single linear polarization state, optical path compensation, and beam modulation. It avoids the disadvantages of design and assembly processes that require frequent repositioning to prevent affecting energy distribution due to non-fixed positions.

[0015] The shaping lens group includes at least one optical modulation device for the curvature of the port x-direction, and the optical modulation device is a cylindrical lens.

[0016] The beneficial effect is that it can be freely combined and adjusted according to the characteristics of the optical path to achieve beam shaping and collimation in the x-direction.

[0017] The grating can be any one of a blazed grating, a phase grating, or a prism grating.

[0018] The beneficial effect is that there are no restrictions on the types of gratings, and the type of grating can be freely selected according to needs.

[0019] The beam deflection control device is any one of an LC spatial light modulator, an LCOS spatial light modulator, or a MEMS spatial light modulator.

[0020] The beneficial effect is that different types of beam deflection control devices can be used to achieve selective output control at different wavelengths and ports.

[0021] The optical path side of the polarizing mirror assembly can be increased with a reflector for folding and compressing the optical path.

[0022] The beneficial effect is that by adding mirrors to fold and compress the optical path, the optical path length can be shortened. Multiple folds will make the optical path more complex, but the shorter length can match systems with high size requirements. Adding optical modulation devices to the optical path can improve aberration and dispersion performance. The beneficial effect is that adding optical modulation devices optimizes the optical path performance. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the existing technology structure; Figure 2 This is a schematic diagram of the structure of the present invention; Figure 3 This is a structural diagram of a polarizing mirror assembly using existing technology. Figure 4 This is the equivalent optical path diagram in the port direction of the present invention; Figure 5 This is the equivalent optical path diagram for the polarization direction of the present invention; Figure 6 This is the equivalent optical path diagram of the dispersion direction of the present invention; Figure 7 This is a schematic diagram of the polarizing mirror assembly in this invention.

[0024] In the diagram: 1. Fiber optic array mirror group, 2. Polarizing mirror group, 3. Shaping lens group, 400. Grating, 500. Cylindrical mirror, 600. Beam deflection control device, 700. Multi-port fiber array, 800. Prism grating, 101. Fiber array, 102. Shaping mirror group, 201. Prism, 202. Lens, 203. Waveplate. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0026] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0027] The structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0028] Wavelength selective switches are used as optical exchanges to selectively output wavelength division multiplexed signals. Their optical structure typically includes a multi-port fiber array 700, a prism grating 800, and a beam deflection controller 600. Currently, the beam deflection controller 600 in existing technologies is mostly an LCOS spatial light modulator.

[0029] To reduce the overall size of the optical path structure, facilitate miniaturization, and improve integration, the current mainstream wavelength selective switch is... Figure 1The 4f structure shown places the multi-port fiber array 700, prism grating 800, and beam deflection control device 600 on the focal plane of cylindrical mirror 500. The input beam reaches the surface of beam deflection control device 600 after four reflections (path length f). Since the prism grating 800 and beam deflection control device 600 are polarization-dependent devices, and the multi-port fiber's output beam polarization state is mostly random nonlinear polarization due to manufacturing defects and stress birefringence caused by bending, the wavelength selective switch often adds a polarizing mirror group 200 to achieve polarization conversion of the fiber array's output beam to reduce loss. A common polarizing mirror group 200 structure is shown below. Figure 3 As shown, the incident single beam is split into two polarized beams with an angle of 0° < 90° at the birefringent prism interface. After optical path modulation, they rejoin as a single beam on the surface of the beam deflection control device 600.

[0030] Figure 1 The optical path structure shown has the following problems: ① The 4f optical path structure causes most of the optical components to be concentrated on one side of the optical path, increasing the difficulty of production and assembly due to space constraints. Precision optical coupling is prone to failure due to accidental contact of optical components by the fixture, requiring a restart. ② Figure 3 The polarization-based beam splitting method, exemplified by this design, increases the difficulty of design, manufacturing, and assembly. After two polarized beams are emitted at an angle, a half-wave plate needs to be added to one of them to change the polarization state. During the design process, the positional parameters of this optical element directly affect the energy distribution of the two beams. During manufacturing and assembly, this element is prone to blocking light, further amplifying the impact of energy distribution issues arising from the design.

[0031] This invention proposes a 2f wavelength selective switch. The structure includes a fiber array mirror group 100, a polarizing mirror group 200, a shaping lens group 300, a grating 400, a cylindrical mirror 500, and a beam deflection control device 600. The fiber array mirror group 100 and the beam deflection control device 600 are located at the focal plane of the shaping mirror group 300. The grating 400 is located at the focal plane of the cylindrical mirror 500. The beam deflection control device 600 is also located at the focal plane of the cylindrical mirror 500. The polarizing mirror group 200 is located after the fiber array mirror group 100 and converts the incident single beam from the fiber array mirror group 100 into parallel, identically polarized dual beams and corrects the optical path and spot differences of different polarized light on the beam deflection control device 600. The optical path structure of this 2f wavelength selective switch is a 2f optical path. The fiber array mirror group 100, the shaping lens group 300, and the beam deflection control device 600 in the port dimension (XZ) constitute the 2f structure, and the grating 400, the cylindrical mirror 500, and the beam deflection control device 600 in the polarization dispersion dimension (YZ) constitute the 2f structure.

[0032] The aforementioned fiber array lens group 100 includes a fiber array 101 and a shaping lens group 102. 101 is a multi-port fiber array with ports arranged in the x-direction as shown in the figure, used for incident and outgoing beams. The shaping lens group 102 is used for wavefront shaping and beam expansion of the outgoing beam from the fiber array 101.

[0033] The aforementioned polarizing mirror group 200 modulates the single beam emitted from the fiber array lens group 100 into a double beam that is parallel to each other at an angle of 0°, with the plane of the double beam being... Figure 2 The dual beams are in the YZ plane. Their polarization directions are consistent, aligning with the operating directions of the grating 400 and the beam deflection control device 600. The optical path length and spot size of the dual beams are modulated; this modulation is used to address the differences in optical path length and spot size between the beams reaching the surface of 600.

[0034] Figure 7 A specific embodiment of a polarizing mirror assembly 200 is shown. The polarizing mirror assembly 200 includes a prism 201, a lens 202, and a waveplate 203. The two parallel inclined surfaces of the prism 201 are coated with multiple layers of polarizing beam-splitting film and a reflective film, respectively. Incident light is split into two beams on the polarizing beam-splitting film. The first beam is reflected and then reflected a second time by the reflective film. The second beam is directly transmitted into the lens 202. The thickness and curvature of the lens 202 respectively achieve optical path compensation and beam spot modulation for the second beam. Because the two parallel beams follow different paths in the optical path structure, a deviation in the beam spot size and optical path occurs when they finally converge at the surface of the beam deflection control device 600. This deviation can be compensated for by modulating the thickness and curvature of the lens 202. The waveplate 203 is used to polarize the first beam reflected by the prism 201, converting it into a beam with the same polarization state as the transmitted second beam. All three components are fixed together by adhesive bonding. In this combination, the three bonded fixing elements can accomplish multiple functions, such as splitting a single beam into two parallel beams, converting multiple polarization states into a single linear polarization state, optical path compensation, and beam spot modulation. In this configuration, the half-wave plate is bonded to the polarization beam splitter, avoiding the drawbacks of frequent repositioning during design and assembly to prevent affecting energy distribution due to non-fixed positions.

[0035] The aforementioned port shaping lens group 300 includes at least one optical modulation device for port direction (x) curvature, which is mostly a cylindrical lens, used to achieve beam shaping and collimation in the x direction.

[0036] The aforementioned shaping lens group 300 can be positioned between the fiber array lens group 100 and the beam deflection control device 600. In existing 4f systems, it is often placed near the grating in the middle position. In this design, it can be placed between the grating 400 and the polarizing mirror group 200, or between the grating 400 and the cylindrical mirror 500, or... Figure 2As shown, shaping lens groups 300 are installed between the grating 400 and the polarizing mirror group 200, and between the grating 400 and the cylindrical mirror 500.

[0037] The aforementioned grating 400 can be a blazed grating, a phase grating, or a prism grating, etc., used to achieve multi-wavelength dispersion, with the dispersion plane being the YZ plane.

[0038] The aforementioned beam deflection control device 600 can be a spatial light modulator based on LC, LCOS, or MEMS, used to achieve selective output control at different ports with different wavelengths.

[0039] The aforementioned reflector can be added to the optical path side of polarizing mirror group 200 to fold and compress the optical path. At this time, the position of fiber array mirror group 100 is determined according to the optical path direction and is located at the focal position of 300.

[0040] Optical modulation devices, such as lenses and prisms, can be added to the aforementioned 2f wavelength selection switch to improve aberration and dispersion performance.

[0041] This invention proposes a simplified 2f wavelength selection switch, separating the first path of light from the 4f structure, allowing it to directly enter the grating 400 for dispersion without being shaped by the cylindrical mirror 500. Figure 2 As shown, a single beam exits from the input port of the fiber array 101 and undergoes initial beam shaping via a shaping lens group 102. The shaped beam then enters a polarizing mirror group 200, which splits it into two beams. The first beam is directly transmitted, while the second beam, after reflection, exits parallel to the first beam at a certain distance. This distance is greater than the beam's spot size to avoid obstructing light. At this point, the polarization states of the two beams are perpendicular. After polarization conversion and optical path and spot modulation by the polarizing mirror group 200, they become parallel beams with consistent polarization states. The parallel beams from the polarizing mirror group 200 are then incident on a shaping lens group 300 for beam shaping in the x-direction and dispersed by a grating 400. After dispersion by the grating 400, beams of different wavelengths diverge and are shaped in the y-direction by a cylindrical mirror 500, becoming collimated beams that are parallel to each other. The parallel beams of different polarization states, shaped in the y-direction, converge into a converged beam at the beam deflection control device 600. Ultimately, on the surface of the beam deflection control device 600, light spots of different wavelengths are arranged in parallel, and light spots with different polarizations converge into a single light spot. The simplified equivalent optical path diagram is shown below. Figure 4 In the process, the input light at the input port is shaped by the shaping lens group 300 and then incident on the surface of the beam deflection control device 600. After the beam deflection control device 600 completes the beam deflection control, the returning beam returns parallel to the target output port. Figure 5 In the process, the parallel light modulated by 200 is focused onto the 600 surface after being modulated by 500. Figure 6In the image, the diverging beams of different wavelengths dispersed by 400 are modulated by 500 and arranged as parallel beams according to their wavelengths on the 600 surface. f1 and f2 represent different focal lengths.

[0042] The above analysis shows that only when f1 > f2 can the port deflection and wavelength selection functions be guaranteed. Furthermore, when f2 is fixed, the positions of the grating 400, cylindrical mirror 500, and beam deflection control device 600 are fixed, but the positions of the polarizer group 200 and fiber array mirror group 100 are not limited by the focal length f2 and can be placed arbitrarily. This offsets them from other components, solving the optical path congestion problem and increasing design flexibility. In existing 4f wavelength selection switches, the distance between the polarizer group 200 and the cylindrical mirror 500 is also f2, thus limiting the distance and restricting design flexibility.

Claims

1. A 2f wavelength selective switch, characterized in that: The device includes a fiber array mirror group (100), a polarizing mirror group (200), a shaping lens group (300), a grating (400), a cylindrical mirror (500), and a beam deflection control device (600). The fiber array mirror group (100) and the beam deflection control device (600) are located at the focal plane of the shaping lens group (300), the grating (400) and the beam deflection control device (600) are located at the focal plane of the cylindrical mirror (500), the shaping lens group (300) is located between the grating (400) and the polarizing mirror group (200), and / or between the grating (400) and the cylindrical mirror (500). The fiber array mirror group (100), the shaping lens group (300), and the beam deflection control device (600) constitute a 2f structure. A single beam of light, after wavefront shaping and beam expansion, is emitted from the fiber array mirror group (100). The single beam is modulated into a double beam with a 0° angle between them by the polarizing mirror group (200). After the double beam enters the grating (400) and is dispersed, the beams of different wavelengths diverge and are emitted to the cylindrical mirror (500). After being collimated by the cylindrical mirror (500), they converge on the beam deflection control device (600). The shaping lens group (300) realizes the shaping of the beam.

2. A 2f wavelength selective switch as described in claim 1, characterized in that: The fiber array mirror group (100) includes a fiber array (101) and a shaping mirror group (102). The fiber array (101) is a multi-port fiber array with its ports arranged in the x-direction. The shaping mirror group (102) is used to perform wavefront shaping and beam expansion on the beam emitted from the fiber array (101).

3. A 2f wavelength selective switch as described in claim 1, characterized in that: The polarizing mirror assembly (200) includes a prism (201), a lens (202), and a waveplate (203). The two opposing inclined surfaces of the prism (201) are coated with multiple layers of polarizing beam splitting film and reflective film, respectively. The incident light is split into two beams on the polarizing beam splitting film layer. The first beam is reflected and then reflected twice by the reflective film into the waveplate (203) for polarization conversion, which is converted into a beam with the same polarization state as the transmitted second beam. The second beam is directly transmitted into the lens (202).

4. A 2f wavelength selective switch as described in claim 1 as described in claim 3, characterized in that: The prism (201), lens (202) and waveplate (203) are fixed together by adhesive bonding.

5. The 2f wavelength selective switch as described in claim 1, characterized in that: The shaping lens group (300) includes at least one optical modulation device for the curvature of the port x direction, and the optical modulation device is a cylindrical lens.

6. The 2f wavelength selective switch as described in claim 1, characterized in that: The grating (400) is any one of a blazed grating, a phase grating, or a prism grating.

7. The 2f wavelength selective switch as described in claim 1, characterized in that: The beam deflection control device (600) is any one of an LC spatial light modulator, an LCOS spatial light modulator, or a MEMS spatial light modulator.

8. The 2f wavelength selective switch as described in claim 1, characterized in that: The optical path side of the polarizing mirror assembly (200) can be increased with a reflector for folding and compressing the optical path.

9. The 2f wavelength selective switch as described in claim 1, characterized in that: Optical modulation devices can be added arbitrarily to the optical path to improve aberration and dispersion performance.

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