Beam splitting and combining device and use method
By optimizing the design of the main waveguide and coupled waveguide boundary curves of the beam splitter and combiner, and combining them with the reflection suppression terminal structure, the problems of narrow bandwidth, large reflection, and high cost of existing beam splitters and combiners have been solved, achieving efficient optical energy transmission and stability in the OCL band.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN POST & TELECOMM RES INST CO LTD
- Filing Date
- 2026-03-25
- Publication Date
- 2026-05-12
AI Technical Summary
Existing beam splitters and combiners suffer from problems such as narrow operating bandwidth, wavelength sensitivity, high manufacturing precision, high cost, and susceptibility to reflection due to impedance mismatch.
The boundary curves of the main waveguide and coupled waveguide are designed using parametric optimization and gradient optimization methods. Combined with particle swarm optimization and Maxwell's equation gradient calculation, a set curve is formed to optimize optical transmission performance. A reflection suppression terminal structure is then used to reduce reflection.
It achieves stable and balanced power splitting and combining over an extremely wide frequency range, reducing insertion loss and return loss, and improving transmission efficiency and functional stability.
Smart Images
Figure CN122018084A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optoelectronics and passive device technology, specifically to a beam splitter and combiner and its usage method. Background Technology
[0002] Beam splitters and combiners are key passive devices in optical communication and integrated optics, used to achieve power distribution and combining of optical or microwave signals. Currently, the main types of beam splitters and combiners include: traditional directional coupler-type beam splitters and combiners, Y-branch beam splitters and combiners, and 1×2 multimode interference beam splitters and combiners.
[0003] However, traditional directional coupler-type beam splitters typically use straight waveguides or fixed-curvature bent waveguides for coupling, which have a narrow operating bandwidth, are sensitive to wavelength, and are prone to reflection at the port due to impedance mismatch, resulting in increased insertion loss and decreased signal integrity.
[0004] While Y-branch type beam splitters and combiners can achieve ultra-wide bandwidth beam splitting through boundary optimization, they are highly sensitive to boundaries and have small process tolerances, thus requiring very high processing precision and resulting in high costs.
[0005] The main drawback of multimode interferometer-type beam splitters and combiners is that different wavelengths of light correspond to different interference region lengths, resulting in a narrow bandwidth. Summary of the Invention
[0006] This application provides a beam splitter / combiner and its usage method, which can achieve stable and balanced power splitting and combining over an extremely wide frequency range.
[0007] In a first aspect, embodiments of this application provide a beam splitter / combiner, the beam splitter / combiner comprising: The main waveguide, the width of which varies along a predetermined curve in the directional coupling region; Two coupling waveguides are symmetrically arranged on both sides of the main waveguide along the axis of the main waveguide, and the width of each coupling waveguide in the directional coupling region changes synchronously with the set curve; Two curved waveguides, each of which is connected to one of the coupled waveguides respectively; The set curve is configured as follows: By setting multiple parameterized points along the propagation direction within the directional coupling region to define the boundary shape of the main waveguide, the gradient of the influence of the boundary shape on the optical transmission performance within the target communication band is calculated. The positions of the parameterized points are iteratively optimized along the gradient descent direction, and the optimized parameterized points are connected to form the set curve.
[0008] In conjunction with the first aspect, in one implementation, it further includes: A straight waveguide, one end of which is connected to the main waveguide, and the other end is connected to a reflection suppression terminal structure.
[0009] In conjunction with the first aspect, in one embodiment, the reflection suppression terminal structure is a helical ring waveguide.
[0010] In conjunction with the first aspect, in one embodiment, the straight waveguide and the main waveguide have the same width at the connection point; The straight waveguide and the helical ring waveguide have the same width at the connection point.
[0011] In conjunction with the first aspect, in one embodiment, the curved waveguide and the coupled waveguide have the same width at the connection point.
[0012] In conjunction with the first aspect, in one implementation, the set curve is formed by connecting the parameterized points of the optimal position through an interpolation method that satisfies the condition of continuous differentiability.
[0013] In conjunction with the first aspect, in one embodiment, the set curve is formed by connecting multiple segments of continuously differentiable function curves, including circular curves, Euler curves, or cubic function curves.
[0014] Secondly, embodiments of this application provide a method for using a beam splitter / combiner, the method of using the beam splitter / combiner including: The incident light is input through the main waveguide and coupled into the two coupling waveguides; The light coupled to the coupled waveguide is output through the corresponding curved waveguide, and the bandwidth is split.
[0015] In conjunction with the first aspect, in one implementation, it further includes: The beam splitter also includes a straight waveguide, one end of which is connected to the main waveguide, and the other end is connected to a reflection suppression terminal structure. The light in the main waveguide is input to the reflection suppression terminal structure through the straight waveguide.
[0016] In conjunction with the first aspect, in one implementation, it further includes: Incident light is input through the two curved waveguides and transmitted to the corresponding two coupled waveguides. The light is coupled into the main waveguide through the two coupled waveguides to achieve bandwidth combining.
[0017] The beneficial effects of the technical solutions provided in this application include: The beam splitter / combiner in this application includes a main waveguide 1, two coupling waveguides 2, and two curved waveguides 3. The width of the main waveguide 1 in the directional coupling region varies along a set curve. The two coupling waveguides 2 are symmetrically arranged on both sides of the main waveguide 1 along the axial direction, and the width of each coupling waveguide 2 in the directional coupling region varies synchronously with the set curve. Each of the two curved waveguides 3 is connected to one coupling waveguide 2. The set curve is configured by setting multiple parameterized points along the propagation direction in the directional coupling region to define the boundary shape of the main waveguide 1, calculating the gradient of the influence of the boundary shape on the optical transmission performance in the target communication band, iteratively optimizing the position of the parameterized points along the gradient descent direction, and connecting the optimized parameterized points to form the set curve.
[0018] Therefore, this application designs the boundary curves of the main waveguide and the coupled waveguide using a parameterized optimization method based on gradient descent. This enables precise optimization of the optical transmission performance within the target communication band, allowing the waveguide structure to achieve a more ideal optical field distribution and energy coupling characteristics within that band. This significantly improves the transmission performance and functional stability of the beam splitter / combiner within the target communication band. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is a top view of one embodiment of the beam splitter / combiner in this application; Figure 2 For this application Figure 1 The front view; Figure 3 For this application Figure 1 A cross-sectional view along the AA direction; Figure 4 For this application Figure 1 A cross-sectional view along the BB direction; Figure 5 This is a flowchart illustrating the beam splitting process of the beam splitter / combiner used in this application. Figure 6 This is a flowchart illustrating the method of using the beam splitter and combiner in this application, specifically during beam combining.
[0021] In the diagram: 1. Main waveguide; 2. Coupled waveguide; 3. Bent waveguide; 4. Straight waveguide; 5. Helical ring waveguide. Detailed Implementation
[0022] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.
[0023] The first aspect of this application provides a beam splitter / combiner.
[0024] In one embodiment, reference is made to Figure 1 , Figure 1 This is a schematic diagram of the structure of one embodiment of the beam splitter / combiner of this application. Figures 1 to 4 As shown, the beam splitter / combiner includes: a main waveguide 1, two coupling waveguides 2 and two curved waveguides 3.
[0025] The width of the main waveguide 1 in the directional coupling region varies along a set curve; two coupling waveguides 2 are symmetrically arranged on both sides of the main waveguide 1 along the axial direction of the main waveguide 1, and the width of each coupling waveguide 2 in the directional coupling region varies synchronously with the set curve; each curved waveguide 3 is correspondingly connected to one of the coupling waveguides 2.
[0026] In this embodiment, the set curve is configured as follows: by setting multiple parameterized points along the propagation direction in the directional coupling region to define the boundary shape of the main waveguide 1, calculating the gradient of the influence of the boundary shape on the optical transmission performance in the target communication band, iteratively optimizing the position of the parameterized points along the gradient descent direction, and connecting the optimized parameterized points to form the set curve.
[0027] It is worth noting that the directional coupling region refers to the coupling area between the main waveguide 1 and the two coupling waveguides 2, that is, the overlapping portion along the propagation direction. Furthermore, the distance from the curve on each side of the main waveguide 1 to its axis is determined by the shape of the set curve. If the main waveguide 1 is an axisymmetric shape, then the width of the main waveguide 1 is twice the distance from the set curve to the axis. Similarly, the same applies to the coupling waveguides 2; the width variation of the coupling waveguides 2 can be referenced from that of the main waveguide 1.
[0028] Compared to existing technologies that use straight waveguides or fixed-curvature curved waveguides for coupling, in this embodiment, the width of the main waveguide 1 in the directional coupling region varies along a predetermined curve. This embodiment employs a reverse design approach, determining the boundary curves of the main waveguide 1 and the two coupled waveguides 2 through parameterized optimization and gradient optimization. This ensures that the optical transmission performance within the target communication band remains within a relatively stable range, overcoming the problem of wavelength sensitivity and transmission efficiency that only reaches a high level at a specified wavelength, while fluctuating significantly in other wavelength ranges in existing technologies. This breaks through the bandwidth limitations of traditional directional couplers, enabling stable and balanced power splitting and combining over an extremely wide frequency range.
[0029] In this embodiment, the target communication band is the OCL band, which includes the O band (Original), C band (Conventional), and L band (Long-wavelength). The final target curve is then obtained through design variable definition, objective function construction, and constraint optimization.
[0030] Specifically, the waveguide boundary is first represented as a parameterized curve, such as a spline curve, and control point coordinates are set. Then, an objective function is defined for multiple wavelength points within the OCL band, including the power information of the output port at each wavelength point. Finally, constraints are set, such as a minimum linewidth limit, which restricts the width of the waveguide curve variation to be no less than the minimum linewidth of the fabrication process. In addition, continuity and differentiability conditions need to be set, such as ensuring the continuity of the first derivative and second-order differentiability.
[0031] In this embodiment, the final set curve is determined by combining the Particle Swarm Optimization (PSO) algorithm and Maxwell's equation gradient calculation. The PSO algorithm creates multiple particles, each representing a set of waveguide parameters. Each particle has a position (current solution) and a velocity (search direction). Maxwell's equation gradient calculation can employ the adjoint variable method, allowing simulation to calculate the gradients of all design parameters. The physical meaning of the gradient is to indicate how fine-tuning the waveguide shape can maximize performance improvement; a gradient of zero indicates reaching a local optimum (maximum output power).
[0032] In the particle swarm optimization algorithm, gradient information is mainly used to guide particles to move to a better region and accelerate the convergence process, thereby avoiding getting trapped in local optima. The gradient descent direction represents the direction in which the objective function decreases the fastest, which is the direction in which the output power increases the fastest.
[0033] Then, through multiple iterations of optimization, key control points are extracted from the optimization results, and spline interpolation is used to connect these points to ensure continuous differentiability, bounded curvature, and a minimum linewidth. In this embodiment, the boundary of the main waveguide 1 is composed of continuously differentiable functions, such as circular curves, Euler curves, or cubic function curves, to ensure adiabatic transmission of the optical field and reduce losses.
[0034] Finally, the set curve is generated, and the results can be verified by checking performance indicators such as spectrophotometer fluctuation and insertion loss.
[0035] In this embodiment, rigorous numerical simulations were performed to verify the transmission performance of the present invention. Three key wavelengths covering the OCL band were selected: 1310nm, 1550nm, and 1630nm. The transmission efficiency of different bands was compared in the simulation, as shown in Table 1. Table 1 Comparison of transmission efficiency at different wavelengths
[0036] Experimental tests show that, within the OCL communication band, this embodiment achieves a splitting ratio close to 50:50, additional loss less than 0.5 dB, and return loss better than 20 dB, fully demonstrating its excellent ultra-wide bandwidth and anti-reflection characteristics.
[0037] Furthermore, to address the port reflection issue, the beam splitter / combiner also includes a straight waveguide 4. One end of the straight waveguide 4 is connected to the main waveguide 1, and the other end is connected to a reflection suppression terminal structure. Preferably, the reflection suppression terminal structure is a helical ring waveguide 5, which is composed of multiple semi-circular waveguide segments connected together. The waveguide width and waveguide spacing are both not less than the minimum fabrication linewidth. It can be understood that by connecting the helical ring waveguide 5 after the straight waveguide 4 to form an anti-reflection zone, port reflection is effectively eliminated, achieving low return loss without the need for an external isolator, thus improving optical transmission efficiency and quality.
[0038] For ease of design, the main waveguide 1, coupling waveguide 2 and straight waveguide 4 in this embodiment can all be designed in an axisymmetric shape, and the two coupling waveguides 2 and the two curved waveguides 3 can be arranged in an axisymmetric manner.
[0039] Furthermore, the straight waveguide 4 and the main waveguide 1 have the same width at their connection points; the straight waveguide 4 and the helical ring waveguide 5 have the same width at their connection points. The curved waveguide 3 and the coupling waveguide 2 have the same width at their connection points.
[0040] It is worth noting that the design of equal width at the waveguide connection is mainly to achieve a smooth transition of optical field modes, avoiding impedance mismatch and mode mismatch caused by abrupt width changes, thereby effectively reducing the reflection and scattering loss of optical signals at the connection interface; ensuring that optical energy can be transmitted efficiently and stably between different waveguide structures, maintaining the adiabatic transmission characteristics of the optical field, not only reducing the insertion loss of the device and improving the beam splitting and combining efficiency, but also ensuring the stability and consistency of device performance within the target communication band, helping to achieve ultra-wide bandwidth beam splitting and combining functions and low return loss.
[0041] In summary, the beam splitter / combiner of this application includes a main waveguide 1, two coupling waveguides 2, and two curved waveguides 3. The width of the main waveguide 1 in the directional coupling region varies along a set curve. The two coupling waveguides 2 are symmetrically arranged on both sides of the main waveguide 1 along the axial direction, and the width of each coupling waveguide 2 in the directional coupling region varies synchronously with the set curve. Each of the two curved waveguides 3 is connected to one coupling waveguide 2. The set curve is configured by setting multiple parameterized points along the propagation direction in the directional coupling region to define the boundary shape of the main waveguide 1, calculating the gradient of the influence of the boundary shape on the optical transmission performance in the target communication band, iteratively optimizing the position of the parameterized points along the gradient descent direction, and connecting the optimized parameterized points to form the set curve.
[0042] Therefore, this application designs the boundary curves of the main waveguide and the coupled waveguide using a parameterized optimization method based on gradient descent. This enables precise optimization of the optical transmission performance within the target communication band, allowing the waveguide structure to achieve a more ideal optical field distribution and energy coupling characteristics within that band. This significantly improves the transmission performance and functional stability of the beam splitter / combiner within the target communication band.
[0043] The second aspect of this application provides a method for using a beam splitter / combiner.
[0044] In one embodiment, reference is made to Figure 5 , Figure 5 This is a flowchart illustrating one embodiment of the method for using the beam splitter / combiner described in this application. Figure 5 As shown, the method of using the beam splitter / combiner includes: S1. The incident light is input through the main waveguide 1 and coupled into the two coupling waveguides 2; S2. The light coupled to the coupling waveguide 2 is output through the corresponding bent waveguide 3 to split the bandwidth.
[0045] Steps S1 and S2 above achieve bandwidth splitting. To effectively eliminate port reflections, in one embodiment, the method further includes: The beam splitter also includes a straight waveguide 4, one end of which is connected to the main waveguide 1, and the other end is connected to a reflection suppression terminal structure. The light from the main waveguide 1 is input to the reflection suppression terminal structure through the straight waveguide 4.
[0046] Specifically, the incident light enters from the left end of the beam splitter and enters the main waveguide 1. In the directional coupling region, it is symmetrically coupled into two coupling waveguides 2. The light in one coupling waveguide 2 exits through a bent waveguide 3, and the light in the other coupling waveguide 2 exits through another bent waveguide 3, achieving ultra-wide bandwidth beam splitting. The light in the main waveguide 1 enters the helical ring waveguide 5 through the axisymmetric straight waveguide 4, and is ultimately dissipated to avoid reflection.
[0047] To achieve bandwidth aggregation, see [link to relevant documentation]. Figure 6 As shown, in one embodiment, it further includes: S3. Incident light is input through two curved waveguides 3 and transmitted to the corresponding two coupled waveguides 2. S4. Optical light is coupled into the main waveguide 1 through two coupled waveguides 2 to achieve bandwidth combining.
[0048] Specifically, the incident light is input from the right end of the beam splitter and combiner, and enters two curved waveguides 3 respectively. The light in one curved waveguide 3 is incident into one coupling waveguide 2, and the light in the other curved waveguide 3 is incident into another coupling waveguide 2. The light in the two coupling waveguides 2 gradually couples into the main waveguide 1 during propagation, and finally outputs from the left end of the main waveguide 1, realizing ultra-wide bandwidth beam combining.
[0049] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.
[0050] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0051] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A beam splitter / combiner, characterized in that, The beam splitter / combiner includes: Main waveguide (1), the width of which varies along a set curve in the directional coupling region; Two coupling waveguides (2) are symmetrically arranged on both sides of the main waveguide (1) along the axial direction of the main waveguide (1), and the width of each coupling waveguide (2) in the directional coupling region changes synchronously with the set curve; Two curved waveguides (3), each of the curved waveguides (3) is connected to one of the coupled waveguides (2); The set curve is configured as follows: By setting multiple parameterized points along the propagation direction in the directional coupling region to define the boundary shape of the main waveguide (1), the gradient of the influence of the boundary shape on the optical transmission performance in the target communication band is calculated, the position of the parameterized points is iteratively optimized along the gradient descent direction, and the optimized parameterized points are connected to form the set curve.
2. The beam splitter / combiner as described in claim 1, characterized in that, Also includes: A straight waveguide (4) is connected at one end to the main waveguide (1) and at the other end to a reflection suppression terminal structure.
3. The beam splitter / combiner as described in claim 2, characterized in that: The reflection suppression terminal structure is a helical ring waveguide (5).
4. The beam splitter / combiner as described in claim 3, characterized in that: The straight waveguide (4) and the main waveguide (1) have the same width at the connection point; The straight waveguide (4) and the helical ring waveguide (5) have the same width at the connection point.
5. The beam splitter / combiner as described in claim 1, characterized in that: The curved waveguide (3) and the coupled waveguide (2) have the same width at the connection point.
6. The beam splitter / combiner as described in claim 1, characterized in that: The set curve is formed by connecting the parameterized points at the optimal position using an interpolation method that satisfies the condition of continuous differentiability.
7. The beam splitter / combiner as described in claim 6, characterized in that: The set curve is formed by connecting multiple segments of continuously differentiable function curves, including circular curves, Euler curves, or cubic function curves.
8. A method of using the beam splitter / combiner as described in claim 1, characterized in that, The method of using the beam splitter / combiner includes: The incident light is input through the main waveguide (1) to couple into the two coupling waveguides (2); The light coupled to the coupling waveguide (2) is output through the corresponding curved waveguide (3) to split the bandwidth.
9. The method of using the beam splitter / combiner as described in claim 8, characterized in that, Also includes: The beam splitter also includes a straight waveguide (4), one end of which is connected to the main waveguide (1), and the other end is connected to a reflection suppression terminal structure; The light in the main waveguide (1) is input to the reflection suppression terminal structure through the straight waveguide (4).
10. The method of using the beam splitter / combiner as described in claim 9, characterized in that, Also includes: Incident light is input through the two curved waveguides (3) respectively and transmitted to the corresponding two coupled waveguides (2). Optical light is coupled into the main waveguide (1) through the two coupled waveguides (2) to achieve bandwidth combining.