Phase chip optimization design method and cascade transmission-type wavelength division multiplexer
By optimizing the design of the transmissive phase chip and cascade structure, the stability and loss problems of the reflective multiplexer were solved, realizing a high-efficiency beam conversion and low-loss optical communication device.
Patent Information
- Application Number
- CN202511512177.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-22
- Publication Date
- 2026-01-13
AI Technical Summary
Reflective multiplexers suffer from problems such as degraded output mode, instability, and difficulty in controlling the incident angle, resulting in high experimental difficulty and uncontrollable losses.
By employing a phase chip optimization design method, a cascaded transmissive wavelength division multiplexer is used to perform beam shaping using a transmissive phase chip. Combined with maskless grayscale lithography, the phase distribution and coupling efficiency are optimized to achieve the conversion between high-order LP modes and the input Gaussian beam.
It improves the stability and experimental efficiency of the device, reduces losses and debugging difficulty, and enhances the conversion efficiency and isolation of the beam.
Smart Images
Figure CN121328126A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of wavelength division multiplexer, more particularly, to a phase chip optimization design method and a cascaded transmission type wavelength division multiplexer. BACKGROUND
[0002] The reflective multiplexer is a passive device used in optical communication systems, and its basic function is to reflect specific wavelength optical signals to realize bidirectional transmission of multiple different wavelength optical signals in the same optical fiber, thereby improving the utilization efficiency of optical fibers. This device usually uses thin film filter technology to complete the transmission of uplink signals and the reception of downlink signals at the same time in the terminal node, simplifying the system structure and reducing the complexity and cost of the device. At present, the reflective multiplexer has been widely used in short and medium distance communication scenarios such as fiber access network and 5G front transmission, and its low cost and high reliability make it one of the mainstream technologies in passive optical networks. However, the reflective multiplexer also has certain limitations, such as high insertion loss, limited channel isolation, and limited performance in supporting ultra-high rate transmission or a large number of wavelength channels. With the development of optical communication technology, the reflective multiplexer is evolving towards higher integration and lower loss, and is combined with other technologies such as silicon optical integration to meet the future high-speed and large-capacity communication needs. Overall, the reflective multiplexer still occupies an important position in the field of optical communication due to its unique functional advantages, and is constantly optimizing its application scenarios.
[0003] However, the reflective multiplexer still has the following defects: (1) uncontrollable loss, the light beam is folded between the mirror and the phase chip, so the incident angle, the reflectivity of the mirror surface, the reflectivity of the phase chip surface and the cleanliness of the space jointly limit the loss of the output mode; (2) poor stability: because the mirror and the phase chip are a whole, a slight vibration during use will cause a slight change in the angle of the mirror or the phase chip, which will cause the overall optical path to change, thereby causing the final output mode to deteriorate, because all the phase structures are on a phase chip, so only the final mode after passing through all the phase structures can be seen; (3) difficult experiment: because the light path of the incident light is determined, the accuracy requirement during experimental debugging is also extremely high, and during the experiment, a slight tilt of the phase is also difficult to detect, but this slight tilt will cause the final experiment to fail. SUMMARY
[0004] The present application aims to overcome the deficiencies of the prior art reflective multiplexer, such as poor output mode, instability, and difficulty in controlling the incident angle, and provides a cascaded transmission type wavelength division multiplexer that can effectively improve the stability of the device and facilitate debugging. On the other hand, the present application also provides a phase chip optimization design method that can effectively reduce the loss of the device.
[0005] To solve the above technical problems, the technical scheme adopted by the present application is: The present application provides a phase chip optimization design method, which is used to realize the conversion between high-order LP modes and input Gaussian beams; comprising the following steps: S1. Determine the design parameters: including determining the input and output modes, the number of phase chips, and the spacing between phase chips; S2. Initialize the phase chip; S3. Establish the optimization objective function OBF:
[0006] In the formula, E f is the forward light field, E b is the reverse light field, represents complex conjugate; OBF represents the coupling efficiency between the forward mode and the reverse mode; S4. Iterative optimization: update the phase chip using the wavefront matching method, constantly update the phase chip, and calculate the OBF value until the OBF value reaches the preset convergence condition.
[0007] Further, the step S2 comprises: calculating the forward propagation of the Gaussian beam array to the LP mode using the ray propagation theory; calculating the reverse propagation of the LP mode to the Gaussian beam array using the ray propagation theory; superimposing the results of the forward propagation and the reverse propagation to obtain the phase distribution of the initial phase chip.
[0008] Further, the wavefront matching method is represented as:
[0009] In the formula, represents the phase distribution, represents the phase distribution of forward propagation, represents the phase distribution of reverse propagation.
[0010] Further, the phase distribution is calculated by the following method:
[0011] In the formula, represents the phase distribution, represents the refractive index change, d represents the lithography depth, and λ represents the light wavelength.
[0012] Further, the preset convergence condition comprises: the coupling efficiency OBF between the forward mode and the reverse mode reaches the maximum value.
[0013] Further, the method further comprises: making the mode dependent loss of different modes consistent by optimizing the phase distribution, wherein the mode dependent loss MDL is calculated by the following formula:
[0014] In the formula, Pi represents the power of mode i; Pj represents the power of mode j.
[0015] The application further provides a cascaded transmission type wavelength division multiplexer, comprising a plurality of transmission type phase chips, a shell for clamping the phase chips, a fiber array and a coupler; the shell has a channel for light beams to pass through, the plurality of phase chips are arranged in parallel at intervals in the channel of the shell, the incident light emitted by the fiber array is transmitted through the plurality of phase chips in turn, the incident light is shaped once each time when passing through a phase chip, and the light beam is shaped into a light beam of a required mode after being transmitted through the plurality of phase chips, and is finally integrated and output through the coupler; the phase structure is distributed on the phase chip, and the phase structure on the phase chip is obtained by the above-mentioned optimization design method.
[0016] The cascaded transmission type wavelength division multiplexer of the application can shape the incident light into a light beam of a required mode, such as an HG, LG or OAM mode, through the transmission type phase chips arranged in cascade, and the light beam is shaped once each time when passing through a phase chip, and the light beam is finally shaped into a light beam of a required mode, such as an HG, LG or OAM mode; in the application, there is only one phase structure on each phase chip, the light spot after passing through each phase chip can be clearly seen, and the phase structure of each phase chip can be designed according to requirements, since the light spot after transmission can be clearly seen for each phase chip, only the phase chips are multiplexed one by one during debugging, and the output mode of each phase chip is confirmed to be normal, so that the mode of the final output multiplexer is also normal, thereby greatly improving the efficiency of experiments and reducing the difficulty of debugging.
[0017] Further, the incident light is vertically incident on the phase chip. The incident light is vertically incident, and the phase chips are arranged in parallel with each other, so that the incident light vertically passes through each phase chip, without causing the loss caused by oblique incidence, thereby reducing the loss to a certain extent.
[0018] Further, one phase structure is arranged on each phase chip. Only one phase structure is arranged on each phase chip, so that the spacing of each channel of the fiber array can be reduced, the corresponding beam angle is also smaller, the mode can be more concentrated, and the isolation can be significantly improved.
[0019] Furthermore, the phase chip is fabricated using a maskless grayscale lithography method. This invention employs maskless grayscale lithography technology, which, by increasing the number of phase mask steps (128 steps) and optimizing the phase distribution, makes the phase modulation closer to the ideal continuous phase, thereby significantly improving conversion efficiency and reducing insertion loss and mode crosstalk.
[0020] Furthermore, a plurality of slots are installed on the side wall of the channel, the slots being spaced apart, and the phase chip is detachably installed in the slots.
[0021] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a phase chip optimization design method and a cascaded transmissive wavelength division multiplexer. The multiplexer uses cascaded transmissive phase chips. Incident light passes through several phase chips sequentially, and each time it passes through a phase chip, it undergoes a shaping process. The final beam is shaped into the desired beam pattern. Each phase chip has only one phase structure, and the beam spot after passing through each phase chip can be clearly seen. The phase structure is designed using a phase optimization design method. Since the transmitted beam spot can be clearly seen from each phase chip, during debugging, it is only necessary to repeatedly use the phase chips one by one to confirm that the output mode of each phase chip is correct. Then, the final output mode of the multiplexer will also be normal. This greatly improves the efficiency of the experiment and reduces the difficulty of debugging. Attached Figure Description
[0022] Figure 1 This is a flowchart illustrating a phase chip optimization design method. Figure 2 This is a schematic diagram of a cascaded transmission wavelength division multiplexer.
[0023] In the attached diagram: 1. Phase chip; 2. Housing; 3. Fiber array; 4. Coupler; 5. Card slot. Detailed Implementation
[0024] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.
[0025] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.
[0026] Example 1 This embodiment is an example of an optimized design method for a phase chip 1, where the phase chip 1 is used to realize the conversion between a high-order LP mode and an input Gaussian beam; such as Figure 1 As shown, it includes the following steps: Step S1. Determine design parameters: including determining the input / output mode, the number of phase chips 1, and the spacing between phase chips 1.
[0027] Input / Output Modes: Select the appropriate LP mode as the input and output mode according to the actual application requirements. For example, you can choose LP01, LP11a, LP11b, and LP21 modes.
[0028] Number of Phase Chips 1: The number of Phase Chips 1 determines the complexity and conversion efficiency of the MPLC device. Generally, the more Phase Chips 1 there are, the higher the conversion efficiency, but the more difficult the device is to manufacture and the more challenging the experiments become.
[0029] Phase chip 1 spacing: The spacing of phase chip 1 affects beam transmission and diffraction, thus impacting conversion efficiency. An appropriate spacing needs to be selected based on the beam characteristics and target mode.
[0030] Step S2. Initialize phase chip 1.
[0031] Forward propagation: Calculates the forward propagation of a Gaussian beam array into LP mode using ray propagation theory. This typically involves calculating beam diffraction and interference.
[0032] Backpropagation: Calculates the backpropagation of LP modes to a Gaussian beam array using ray propagation theory. This typically involves calculating the coupling efficiency between modes.
[0033] Superposition: The results of forward propagation and backward propagation are superimposed to obtain the initial phase plane.
[0034] Step S3. Establish the optimization objective function OBF.
[0035] Coupling efficiency (OBF) is used to evaluate the efficiency of optical field conversion, and is usually measured by the coupling efficiency between forward and reverse modes.
[0036] The objective function OBF can be expressed as:
[0037] In the formula, E f It is a positive light field. E b It is a reverse light field. OBF represents the coupling efficiency between the forward and reverse modes; Step S4. Iterative Optimization: Update phase chip 1 using the wavefront matching method, iteratively updating phase chip 1 and calculating the OBF value until the OBF value reaches the preset convergence condition. The preset convergence condition includes: the coupling efficiency OBF between the forward and reverse modes reaches its maximum value.
[0038] Wavefront matching: The phase plane is updated using the wavefront matching method, which is the superposition of the conjugate propagation of the forward light field and the propagation of the reverse light field; the wavefront matching method is expressed as:
[0039] In the formula, Indicates phase distribution, This represents the phase distribution during forward propagation. This represents the phase distribution during backward propagation.
[0040] The phase distribution is calculated as follows:
[0041] In the formula, Indicates phase distribution, Indicates the change in refractive index. d λ represents the lithography depth, and λ represents the wavelength of light. Traditional multi-step etching techniques typically achieve only 8 phase steps. The maskless grayscale lithography technique used in this embodiment achieves 128 phase steps in a single exposure, resulting in a phase distribution closer to the ideal continuous phase. The more steps, the smoother the phase distribution and the less loss caused by diffraction and scattering.
[0042] This invention also includes: optimizing the phase distribution to make the mode-dependent loss of different modes tend to be consistent, wherein the mode-dependent loss MDL is calculated by the following formula:
[0043] In the formula, Indicates the power of mode i; This represents the power of mode j.
[0044] In this embodiment, the coupling efficiency between the forward and inverse modes is maximized by using a wavefront matching algorithm, thereby reducing insertion loss and mode crosstalk. By optimizing the phase distribution, the conversion efficiency of different modes is made more consistent, further reducing the overall loss.
[0045] This embodiment is based on the wavefront matching method, which achieves high-efficiency beam conversion by optimizing the phase distribution on multiple phase chips 1. The design process involves determining the input / output modes, the number and spacing of phase planes, initializing the phase planes, establishing the optimization objective function, and iterative optimization. Maskless grayscale lithography technology can precisely control the phase distribution, thereby enabling high-precision manufacturing of MPLC LP mode multiplexers.
[0046] Example 2 This embodiment is a first embodiment of a cascaded transmission wavelength division multiplexer, such as... Figure 2 As shown, the device includes several transmissive phase chips 1, a housing 2 for holding the phase chips 1, an optical fiber array 3, and a coupler 4. The housing 2 has a channel for light beams to pass through. Several phase chips 1 are spaced apart and arranged parallel to each other in the channel of the housing 2. The incident light emitted by the optical fiber array 3 passes through several phase chips 1 in sequence. The incident light is shaped once after passing through each phase chip 1. After passing through several phase chips 1, the light beam is shaped into a light beam of the desired mode and finally integrated and output by the coupler 4. The phase chips 1 have phase structures distributed on them. The phase structures on the phase chips 1 are obtained by the optimization design method described in Embodiment 1.
[0047] In this embodiment, the incident light is perpendicularly incident on the phase chip 1. Since the incident light is perpendicularly incident and the phase chips 1 are arranged parallel to each other, the incident light passes perpendicularly through each phase chip 1, avoiding the loss caused by oblique incidence, thereby reducing the loss to a certain extent.
[0048] In this embodiment, each phase chip 1 is provided with a phase structure. Since only one phase structure is provided on each phase chip 1, the spacing between each channel of the fiber array 3 can be reduced. A smaller spacing results in a smaller beam angle and a more concentrated beam pattern, significantly improving isolation.
[0049] In this embodiment, the phase chip 1 is fabricated using a maskless grayscale lithography method. This invention employs maskless grayscale lithography technology, which, by increasing the number of phase mask steps (128 steps) and optimizing the phase distribution, makes the phase modulation closer to the ideal continuous phase, thereby significantly improving conversion efficiency and reducing insertion loss and mode crosstalk.
[0050] This embodiment of a cascaded transmissive wavelength division multiplexer uses cascaded transmissive phase chips 1. Incident light sequentially passes through several phase chips 1, undergoing shaping at each phase chip 1, ultimately shaping the beam into the desired mode, such as HG, LG, or OAM. In this invention, each phase chip 1 has only one phase structure, allowing a clear view of the light spot after passing through each phase chip 1. The phase structure of each phase chip 1 can be designed according to requirements. Since the transmitted light spot can be clearly seen from each phase chip 1, during debugging, it is only necessary to repeatedly use each phase chip 1 to confirm that the output mode of each phase chip 1 is correct, thus ensuring that the final output mode of the multiplexer is also normal. This greatly improves experimental efficiency and reduces debugging difficulty.
[0051] Example 3 This embodiment is a second embodiment of a cascaded transmission wavelength division multiplexer. This embodiment is similar to the first embodiment, except that a plurality of slots 5 are installed on the side wall of the channel, and the slots 5 are spaced apart. The phase chip 1 is detachably installed in the slots 5. The slots 5 in the channel facilitate the installation and removal of the phase chip 1.
[0052] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.
[0053] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A phase chip optimization design method, characterized in that, The phase chip (1) is used to realize the conversion between the higher-order LP mode and the input Gaussian beam; it includes the following steps: S1. Determine design parameters: including determining the input / output mode, the number of phase chips (1), and the spacing between phase chips (1); S2. Initialize the phase chip (1); S3. Establish the optimization objective function OBF: In the formula, E f It is a positive light field. E b It is a reverse light field. OBF represents the coupling efficiency between the forward and reverse modes; S4. Iterative optimization: Update the phase chip (1) using the wavefront matching method, iteratively update the phase chip (1) continuously, and calculate the OBF value until the OBF value reaches the preset convergence condition.
2. The phase chip optimization design method according to claim 1, characterized in that, Step S2 includes: using the ray propagation theory to calculate the forward propagation of the Gaussian beam array to the LP mode; using the ray propagation theory to calculate the reverse propagation of the LP mode to the Gaussian beam array; and superimposing the results of the forward and reverse propagation to obtain the phase distribution of the initial phase chip (1).
3. The phase chip optimization design method according to claim 1, characterized in that, The wavefront matching method is expressed as follows: In the formula, Indicates phase distribution, This represents the phase distribution during forward propagation. This represents the phase distribution during backward propagation.
4. The phase chip optimization design method according to claim 3, characterized in that, The phase distribution is calculated as follows: In the formula, Indicates phase distribution, Indicates the change in refractive index. d λ represents the lithographic depth, and λ represents the wavelength of light.
5. The phase chip optimization design method according to any one of claims 1 to 4, characterized in that, The preset convergence condition includes: the coupling efficiency OBF between the forward mode and the reverse mode reaches its maximum value.
6. The phase chip optimization design method according to claim 5, characterized in that, Also includes: By optimizing the phase distribution, the mode-dependent loss of different modes tends to be consistent. The mode-dependent loss MDL is calculated using the following formula: In the formula, Indicates the power of mode i; This represents the power of mode j.
7. A cascaded transmission wavelength division multiplexer, characterized in that, The device includes several transmissive phase chips (1), a housing (2) for holding the phase chips (1), an optical fiber array (3), and a coupler (4); the housing (2) has a channel for the light beam to pass through, and several phase chips (1) are spaced apart and parallel to each other in the channel of the housing (2). The incident light emitted by the optical fiber array (3) passes through several phase chips (1) in sequence. The incident light is shaped once after passing through each phase chip (1). After passing through several phase chips (1), the light beam is shaped into a light beam of the desired mode and finally integrated and output by the coupler (4); the phase chips (1) have phase structures distributed on them, and the phase structures on the phase chips (1) are obtained by the optimization design method described in any one of claims 1 to 6.
8. The cascaded transmission wavelength division multiplexer according to claim 7, characterized in that, The incident light is perpendicularly incident on the phase chip (1); each phase chip (1) is provided with a phase structure.
9. The cascaded transmission wavelength division multiplexer according to claim 7, characterized in that, The phase chip (1) is prepared by a maskless grayscale lithography method.
10. The cascaded transmission wavelength division multiplexer according to claim 7, characterized in that, A plurality of slots (5) are installed on the side wall of the channel, and the plurality of slots (5) are spaced apart. The phase chip (1) is detachably installed in the slots (5).