MPLC mode exchanger

Abstract

The embodiment of the utility model discloses an MPLC mode switch, which comprises a few-mode optical fiber, a plurality of optical fibers, a plurality of optical fibers, a plurality of optical fibers, a plurality of optical fibers and a plurality of optical fibers, the few-mode optical fibers are respectively arranged at the input end and the output end of the reflection device; and the reflecting device is used for reflecting and converting the mode light beam. Input mode light beams are transmitted to the reflection device through the few-mode optical fiber, the reflection device can reflect the mode light beams, and mode conversion is carried out according to needs. Through the effect of the reflection device, the mode exchanger can realize conversion and transmission among light beams in different modes, thereby meeting various requirements in an optical communication system. Furthermore, the mode light beam converted by the reflection device is received through the few-mode optical fiber and is output.

Description

Technical Field

[0001] The utility model relates to the technical field of optical communications, in particular to an MPLC mode switch. Background Art

[0002] The transmission capacity of single-mode optical fiber has approached the Shannon limit. In order to meet the needs of high-capacity communication networks, people have proposed a variety of multiplexing technologies, such as wavelength division multiplexing, polarization multiplexing (PDM), and spatial division multiplexing (SDM). In the past few decades, WDM has played an important role in mode division multiplexing (MDM) technology based on few-mode fiber. It is a form of SDM and a very promising way to solve the capacity crisis. MDM communication systems contain orthogonal modes of different orders, such as linearly polarized (LP) and orbital angular momentum (OAM) modes as independent channels within few-mode optical fiber (FMF). Data exchange between different channels is an indispensable function in optical communication networks. Therefore, it is necessary to propose an integrated mode switching device.

[0003] Prior art proposals include free-space beam combiners, all-fiber mode multiplexers, waveguide photonic lanterns, and metasurface mode multiplexers. However, for free-space beam combiners, increasing the number of modes necessitates a cascade of more beam splitters, leading to increased inherent losses. This approach, due to the use of standard optical devices such as traditional phase plates and spatial light modulators, suffers from issues such as thick materials, bulk, long working distances, and relatively low optical precision control. This makes it unsuitable for integrated optical systems and ultra-miniaturized flat-panel optical devices. For all-fiber mode multiplexers, the experimentally obtained mode purity remains very low due to the complexity of fiber processing. Waveguide photonic lanterns can address the difficulty of increasing the number of modes in coupled mode multiplexers. However, they place very strict requirements on longitudinal phase matching, limiting the device's operating bandwidth. Metasurface mode multiplexers can achieve miniaturized systems, but they cannot achieve a high number of modes; you can't have both. Utility Model Content

[0004] Based on this, it is necessary to propose an MPLC mode switch to address the above problems. The mode switch includes:

[0005] A few-mode optical fiber, wherein the few-mode optical fiber is used for inputting and outputting mode beams;

[0006] A reflecting device, wherein the few-mode optical fiber is respectively arranged at the input end and the output end of the reflecting device; the reflecting device is used to reflect and convert the mode light beam.

[0007] The few-mode fiber includes an input few-mode fiber and an output few-mode fiber. The input few-mode fiber is arranged at the input end, and the output few-mode fiber is arranged at the output end.

[0008] The output end of the input few-mode optical fiber is provided with a first self-focusing lens, and the first self-focusing lens is used to collimate the mode light beam and then input it into the reflecting device;

[0009] The input end of the output few-mode optical fiber is provided with a second self-focusing lens, and the second self-focusing lens is used to collimate the mode light beam converted by the reflection device and then input it into the output few-mode optical fiber.

[0010] Wherein, the wavelength of the mode light beam is 300 μm.

[0011] The reflecting device includes a reflecting mirror and a phase plate, and the reflecting surface of the reflecting mirror is arranged opposite to the phase plate; the mode light beam is reflected and converted between the reflecting mirror and the phase plate.

[0012] The mode light beam is reflected and converted four times on the phase plate.

[0013] Wherein, the distance between the reflector and the phase plate is 9.8 mm.

[0014] The substrate of the phase plate is a silicon wafer, and a phase structure is provided on the silicon wafer. The phase structure is a concave structure formed on the surface of the silicon wafer by photolithography and etching.

[0015] The etching wavelengths are light beams of 388 nm, 194 nm, 97 nm and 48 nm.

[0016] Wherein, a gold-plated coating layer is provided on the surface of the phase plate, and the thickness of the gold-plated coating layer is 110 nm.

[0017] The embodiment of the present utility model has the following beneficial effects:

[0018] This utility model transmits an input mode light beam via a few-mode fiber to a reflector, which reflects it and performs mode conversion as needed. Through the reflector, the mode converter can convert and transmit different mode light beams, thus meeting various requirements in optical communication systems. Furthermore, the converted mode light beam is received by the reflector and output via the few-mode fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] in:

[0021] Figure 1 A schematic structural diagram of an embodiment of an MPLC mode switch provided by the present invention;

[0022] Figure 2 A schematic structural diagram of another embodiment of an MPLC mode switch provided by the present invention;

[0023] Figure 3 is the simulated phase plate plane;

[0024] Figure 4 is the simulation mode intensity distribution;

[0025] Figure 5 is the simulation mode phase distribution;

[0026] Figure 6 is the simulation mode crosstalk grayscale matrix. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the utility model for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, Figure 1The present invention provides a schematic diagram of the structure of an MPLC mode switch according to an embodiment of the present invention. An MPLC mode switch 10, the mode switch comprising:

[0029] The few-mode fiber 1 is used for inputting and outputting mode beams.

[0030] Exemplarily, the few-mode fiber 1 includes an input few-mode fiber and an output few-mode fiber. The input few-mode fiber is provided at the input end, while the output few-mode fiber is provided at the output end. Multiple coaxially transmitted mode beams are transmitted through the input few-mode fiber to a reflector. After undergoing mode conversion by the reflector, they are transmitted through the output few-mode fiber and continue to be transmitted within the communication system.

[0031] It should be noted that the selected few-mode optical fiber model 1 is Changfei's four-mode step-index optical fiber.

[0032] The reflecting device 2 and the few-mode optical fiber 1 are respectively arranged at the input end and the output end of the reflecting device 2; the reflecting device 2 is used to reflect the converted mode light beam.

[0033] Exemplarily, the few-mode fiber 1 is respectively arranged at the input end and the output end of the reflector 2. The reflector 2 includes a plurality of phase plates, which modulate the mode beam of the input few-mode light by interference and diffraction, and the modulated beam completes the mode conversion. Specifically, the input mode field of the coaxial input light beam is w in , the output mode field is w out , the distance between the input terminal and the first phase plate is d in The distance between the output end and the last phase plate is d out , the number of phase plates is k, and the spacing between k phase plates can be expressed as p1, p2, ... p k-1 ,p k In order to improve the availability of the device, the phase plate spacing is generally designed to be the same value, denoted as p. in , d out , p is set to 20mm, w in and w out Set to 300μm.

[0034] As can be seen from the above description, the present invention transmits an input mode light beam via a few-mode fiber to a reflector, which then reflects it and performs mode conversion as needed. Through the reflector, the mode switch can achieve conversion and transmission between different mode light beams, thereby meeting various requirements in optical communication systems. Furthermore, the converted mode light beam from the reflector is received by the few-mode fiber and output.

[0035] See also Figure 1 and Figure 2 , Figure 2This is a structural diagram of another embodiment of an MPLC mode switch provided by the present utility model.

[0036] The few-mode fiber 1 includes an input few-mode fiber 11 and an output few-mode fiber 12 . The input few-mode fiber 11 is arranged at the input end, and the output few-mode fiber 12 is arranged at the output end.

[0037] The output end of the input few-mode optical fiber 11 is provided with a first self-focusing lens 3 , which is used to collimate the mode light beam and then input it into the reflection device 2 .

[0038] The input end of the output few-mode optical fiber 12 is provided with a second self-focusing lens 4 , which is used to collimate the mode light beam converted by the reflection device 2 and then input it into the output few-mode optical fiber 12 .

[0039] For example, a first self-focusing lens 3 is fabricated at the output end of the input few-mode fiber 11 to collimate the input of multiple coaxially transmitted mode beams. The modulated beams undergo mode conversion and are focused by a second self-focusing lens 4 at the input end of the output few-mode fiber 12. The focused beams are then coupled into the output few-mode fiber 12 for continued transmission within the communication system.

[0040] The reflecting device 2 includes a reflecting mirror 21 and a phase plate 22 . The reflecting surface of the reflecting mirror 21 is arranged opposite to the phase plate 22 . The mode light beam is reflected and converted between the reflecting mirror 21 and the phase plate 22 .

[0041] For example, referring to Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 , Figure 3 To simulate the phase plate plane, Figure 4 is the simulation mode intensity distribution, Figure 5 is the simulation mode phase distribution, Figure 6 is the simulation mode crosstalk grayscale matrix. Among them, P1, P2, P3, and P4 are phase plates 22. The phase plate 22 and the reflector 21 form a reflecting device 2. The collimated input light beam is obliquely incident and then reflected 7 times to adjust the phase. Specifically, using the wavefront matching algorithm, the simulation realizes the conversion of the four modes LP01, LP11a, LP11b and LP21 of coaxial input. Among them, LP01 is converted to LP11a, LP11a is converted to LP11b, LP11b is converted to LP21, and LP21 is converted to LP01. During the simulation process, the center wavelength is set to 1550nm, the pixel size is set to 8μm, and the phase is in the range of 0-2π. After iterative optimization, the cyclic conversion of the mode is realized by using only 4 phase plates 22.

[0042] The designed phase plate 22 is as follows Figure 3As shown, the phase order is 16, and the surface of the phase plate 22 is provided with a gold coating layer with a thickness of 110nm. After 7 reflections, the LP mode generated in the free space after the exchange is imaged using a charge coupled device. The imaging result is shown in FIG. Figure 4 The phase distribution of the mode is shown as Figure 5 As shown in Figure 1, it is consistent with the designed target mode field, and the mode purity is higher than 85%. Mode crosstalk refers to the interference phenomenon between different modes, which can be characterized by the mode crosstalk matrix. The experimental mode crosstalk matrix calculated is as follows: Figure 6 As shown, the maximum crosstalk between modes is -22dB.

[0043] It should be noted that the wavelength of the mode beam is 300 μm.

[0044] It should also be noted that the distance between the reflector 21 and the phase plate 22 is 9.8 mm.

[0045] The phase plate 22 substrate selected is a silicon wafer. A phase structure is fabricated on the silicon substrate through photolithography and etching processes. The phase structure is a concave structure formed on the surface of the silicon wafer through photolithography and etching. The corresponding phase delay is converted into the etching depth of the silicon wafer. Four etching passes are required at depths of 388, 194, 97, and 48 nm. A gold coating layer is applied to the surface of the phase plate 22 to increase its reflectivity. The thickness of the gold layer is 110 nm. The specific processing flow is as follows:

[0046] (1) Mask processing

[0047] The laboratory used contact exposure as the exposure mode, necessitating a mask design based on multiple phase plates 22. The black and white patterns on the mask represent 0, which indicates light transmission, and 1, which indicates opacity. To achieve 16 phase steps, the simulated phases were divided into four images, each of which was then fabricated as a mask. The four masks corresponded to etching depths of 388, 194, 97, and 48 nm, respectively, representing phases of π, π / 2, π / 4, and π / 8.

[0048] (2) UV exposure

[0049] Before exposure, the silicon wafer is pretreated and coated. First, acetone, alcohol and deionized water are used to ultrasonically clean the silicon wafer, and the ultrasonic time is 20 minutes, 10 minutes and 5 minutes respectively to clean the silicon wafer surface and remove dust and pollutants. Use nitrogen to blow dry the silicon wafer and store it in a drying oven. Secondly, AZ2035 type photoresist is used for coating, the speed is 4000rpm, the running time is 1 minute, and then the silicon wafer is placed on the heating table for pre-baking. The silicon wafer is placed on the tray of the UV mask exposure machine, and the mask is placed on top of the silicon wafer to ensure the alignment accuracy of the mask and the silicon wafer. The exposure time and light intensity are determined according to the required pattern characteristics and the characteristics of the photoresist. Then, the silicon wafer is placed on the heating table for post-baking. After exposure, the unexposed or incompletely exposed photoresist is removed through the development and cleaning steps.

[0050] (3) Plasma etching

[0051] Plasma etching is a type of dry etching process that involves three steps: plasma generation, plasma acceleration, and silicon wafer surface reaction. A gas (such as fluoride or chloride) is ionized in a high-frequency electric field to form a plasma. Plasma contains a large number of free electrons and ions, which are highly energetic and active. The plasma is then accelerated using an electric or magnetic field, giving it sufficient energy to impact the silicon wafer surface. After the plasma impacts the silicon wafer surface, it chemically reacts or physically collides with the silicon surface, removing atoms or molecules from the silicon surface, thereby etching the silicon wafer. The plasma etching process is initiated according to the set process parameters.

[0052] (4) Electron beam evaporation

[0053] To improve reflectivity, a gold film is applied to the surface of the silicon wafer to reduce reflection loss. Electron beam evaporation uses the high energy of an electron beam to bombard a target material, causing the target's surface atoms to evaporate and deposit onto the silicon wafer. The high energy of the electron beam overcomes the melting point of the target material, allowing high-melting-point metals or dielectric materials to evaporate and deposit onto the substrate, forming the desired thin film. During the evaporation process, a microchip is used to monitor the film thickness in real time. After coating, the phase structure of the silicon wafer surface is photographed using a metallographic microscope. Etch depth measurements using a step profiler show an error of less than 10%, demonstrating high accuracy.

[0054] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. An MPLC mode switch, characterized in that: The mode switch comprises: A few-mode optical fiber, wherein the few-mode optical fiber is used for inputting and outputting mode beams; A reflecting device, wherein the few-mode optical fiber is respectively arranged at the input end and the output end of the reflecting device; the reflecting device is used to reflect and convert the mode light beam.

2. An MPLC mode switch according to claim 1, characterized in that: The few-mode optical fiber includes an input few-mode optical fiber and an output few-mode optical fiber. The input few-mode optical fiber is arranged at the input end, and the output few-mode optical fiber is arranged at the output end.

3. An MPLC mode switch according to claim 2, characterized in that: The output end of the input few-mode optical fiber is provided with a first self-focusing lens, and the first self-focusing lens is used to collimate the mode light beam and then input it into the reflecting device; The input end of the output few-mode optical fiber is provided with a second self-focusing lens, and the second self-focusing lens is used to collimate the mode light beam converted by the reflection device and then input it into the output few-mode optical fiber.

4. The MPLC mode switch according to claim 3, wherein: The wavelength of the mode light beam is 300 μm.

5. The MPLC mode switch according to claim 3, characterized in that: The reflecting device comprises a reflecting mirror and a phase plate, wherein the reflecting surface of the reflecting mirror is arranged opposite to the phase plate; the mode light beam is reflected and converted between the reflecting mirror and the phase plate.

6. The MPLC mode switch according to claim 5, characterized in that: The mode light beam is reflected and converted four times on the phase plate.

7. The MPLC mode switch according to claim 6, characterized in that: The distance between the reflector and the phase plate is 9.8 mm.

8. The MPLC mode switch according to claim 5, characterized in that: The substrate of the phase plate is a silicon wafer, and a phase structure is provided on the silicon wafer. The phase structure is a concave structure formed on the surface of the silicon wafer by photolithography and etching.

9. The MPLC mode switch according to claim 8, characterized in that: The etching wavelengths are light beams of 388 nm, 194 nm, 97 nm and 48 nm.

10. The MPLC mode switch according to claim 5, characterized in that: A gold-plated coating layer is provided on the surface of the phase plate, and the thickness of the gold-plated coating layer is 110 nm.

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