On-chip integrated dual-mode bidirectional switchable add / drop multiplexer and preparation method thereof
By designing an on-chip integrated dual-mode bidirectional switchable add/drop multiplexer, the problems of insufficient unidirectional transmission and mode switching capabilities of traditional multiplexers are solved, and miniaturized, low-loss and low-crosstalk bidirectional transmission and multi-mode multiplexing are achieved, improving the performance and adaptability of optical communication systems.
Patent Information
- Application Number
- CN202411653775.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-19
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2044-11-19
AI Technical Summary
In existing optical communication systems, traditional multiplexers have problems such as unidirectional transmission, weak mode switching capability, large size, low integration, high loss and large crosstalk, which limit their application and system performance in full-duplex communication systems.
An on-chip integrated dual-mode bidirectional switchable add/drop multiplexer was designed. It uses a silicon substrate and SiO2 material, and includes a reverse mode conversion unit, a bidirectional mode coupler, and a curved waveguide. CMOS processing technology is used to achieve miniaturization and low-cost manufacturing, supporting bidirectional transmission and mode switching.
It realizes bidirectional transmission and multi-mode multiplexing functions, reduces manufacturing difficulty and cost, improves system flexibility and integration, and enhances signal transmission quality and system stability.
Smart Images
Figure CN119644507B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of integrated photonics, in particular to an on-chip integrated dual-mode bidirectional switchable add / drop multiplexer and a preparation method thereof. Background Art
[0002] With the rapid development of information technology, the demand for optical communication systems is increasing, placing higher demands on multiplexers, a key component in optical communication systems. Multiplexers are an important component of optical communication networks, used to integrate multiple optical signals into the same optical fiber for transmission, thereby improving the transmission efficiency and bandwidth utilization of optical fibers. Although traditional single-mode multiplexers have met the needs of early optical communication systems to a certain extent, their transmission capacity and flexibility have gradually become insufficient in the face of growing data transmission volume. To overcome these problems, researchers have begun to explore dual-mode or multi-mode multiplexing technologies, hoping to improve the overall performance of the system by increasing the number of transmission modes.
[0003] However, existing mode multiplexers have some significant limitations. First, traditional multiplexers typically only support unidirectional transmission and cannot achieve bidirectional communication, which limits their application in full-duplex communication systems. Second, most mode multiplexers have weak mode switching capabilities, making it difficult to flexibly switch between different modes, resulting in poor system adaptability when dealing with different application scenarios. In addition, existing multiplexers are large in size and have low integration, which is not conducive to the realization of miniaturized and low-cost optical communication systems. Finally, traditional multiplexers have high losses and large crosstalk, which affects the quality of signal transmission and the stability of the system. Summary of the Invention
[0004] The purpose of the present invention is to provide an on-chip integrated dual-mode bidirectional switchable add / drop multiplexer and a preparation method thereof. The multiplexer can support bidirectional transmission and can flexibly switch between different modes. It has the advantages of small package size, low loss, low crosstalk, low manufacturing difficulty, and large process tolerance.
[0005] The present invention is achieved in that:
[0006] An on-chip integrated dual-mode bidirectional switchable add / drop multiplexer comprises a silicon-based substrate, a buried oxide layer disposed on the silicon-based substrate, a silicon waveguide layer disposed on the buried oxide layer, and an upper cladding layer covering the buried oxide layer and encapsulating the silicon waveguide layer; the buried oxide layer and the upper cladding layer are both made of SiO2 material;
[0007] The core design of the silicon waveguide layer lies in the reverse mode conversion unit located in the center of the bus waveguide. Furthermore, bidirectional mode couplers are symmetrically arranged on either side of the bus waveguide, each of which is connected to a curved waveguide at both ends. These curved waveguides are further connected to corresponding optical switches.
[0008] Furthermore, the silicon waveguide layer includes a bus waveguide, which has a long straight waveguide structure. A reverse mode conversion unit is provided in the central area of the bus waveguide, and the reverse mode conversion unit is composed of two rows of gratings along the direction of the bus waveguide, with the two rows of gratings offset by half a period. The grating period first increases linearly, then remains uniform, and then decreases linearly. The grating size first increases linearly, then remains uniform, and then decreases linearly. Two bidirectional mode couplers are symmetrically provided on the same side of the bus waveguide, each of which has a long straight waveguide structure and is parallel and arranged in parallel with the bus waveguide. The two bidirectional mode couplers correspond to the bus waveguides at both ends of the reverse mode conversion unit respectively. The two ends of each bidirectional mode coupler are respectively connected to a curved waveguide, which is connected to an optical switch. The bus waveguide, bidirectional mode coupler, curved waveguide and optical switch are all made of silicon. The reverse mode conversion unit is made of SiO2 material.
[0009] Preferably, in the above solution, the width of the bus waveguide should be greater than the bidirectional mode couplers on both sides.
[0010] Preferably, in the above solution, the bus waveguide width is 0.8-1.5 μm.
[0011] Preferably, in the above solution, the width of the bidirectional mode couplers on both sides is 0.4-0.55 μm.
[0012] Preferably, in the above solution, the distance between the bus waveguide and the bidirectional mode coupler is 100-200 nm.
[0013] Preferably, in the above solution, the heights of the bus waveguide, the bidirectional mode coupler, the bent waveguide, the reverse mode conversion unit and the optical switch are all 220 nm.
[0014] Preferably, in the above solution, the bus waveguide, the bidirectional mode coupler, the bent waveguide, the reverse mode conversion unit and the optical switch are manufactured at one time.
[0015] Preferably, in the above solution, the grating period of the reverse mode conversion unit adopts a chirped design, wherein the period first increases linearly, then remains uniform, and finally decreases linearly.
[0016] Preferably, in the above solution, the grating size of the reverse mode conversion unit adopts an apodization design, and its length first increases linearly, then remains uniform, and finally decreases linearly.
[0017] Preferably, in the above solution, the grating duty cycle of the reverse mode conversion unit is 0.5.
[0018] Preferably, in the above solution, all waveguides are made of silicon-on-insulator material.
[0019] Preferably, in the above solution, SiO2 material is filled in the reverse mode conversion unit when the upper cladding layer is manufactured.
[0020] Preferably, in the above solution, the optical switch can be formed using the principle of Mach-Zehnder Interferometer (MZI).
[0021] Preferably, in the above solution, the four curved waveguides are all bent in a direction away from the bus waveguide.
[0022] In the above solution, the preparation method of the on-chip integrated dual-mode bidirectional switchable add / drop multiplexer includes the following steps:
[0023] a. Preparing a buried oxide layer of SiO2 material on a silicon-based substrate;
[0024] b. placing a mask on the buried oxide layer, wherein the mask is designed with a specific pattern;
[0025] c. preparing a silicon waveguide layer at a position corresponding to the mask on the buried oxide layer;
[0026] d. Remove the mask and prepare an upper cladding layer of SiO2 material on the buried oxide layer. The upper cladding layer wraps the silicon waveguide layer to form an on-chip integrated dual-mode bidirectional switchable add / drop multiplexer.
[0027] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:
[0028] 1. Improved functionality: With the auxiliary control of the reverse mode conversion unit and the optical switch, the present invention better realizes the new function of the dual-mode bidirectional switchable add / drop multiplexer. Compared with many previous designs, it has more flexibility and improves on-chip integration.
[0029] 2. Ease of manufacturing and enhanced reliability. The waveguide structures used in this invention, including bus waveguides, bidirectional mode couplers, and curved waveguides, all have characteristic dimensions at the micron or submicron level. This effectively reduces the equipment precision requirements during the photonic device manufacturing process, thereby simplifying the manufacturing process and improving the reliability and stability of the device.
[0030] 3. Excellent design flexibility, easy operation, and strong scalability. The input / output ports can be flexibly arranged on both sides of the four curved waveguides and the bus waveguide. This not only increases layout freedom but also enables efficient conversion between multiple modes, including TE0 to TE1 and TE0 to TE2, by finely adjusting the specific parameters of the reverse mode conversion unit and the optical switch. This design greatly enriches the system's functionality and significantly improves its ability to meet the needs of diverse application scenarios, demonstrating outstanding versatility and adaptability.
[0031] 4. Compact structure, easy fabrication, and significant cost-effectiveness. This invention utilizes SOI (silicon-on-insulator) materials with a high refractive index difference to achieve device miniaturization and integration. Furthermore, based on inexpensive and mature CMOS processing technology, it not only simplifies the production process but also significantly reduces production costs, showing broad application prospects in the field of integrated photonics.
[0032] 5. Multifunctionality. The present invention is not only applicable to the multiplexing of multiple modes (TE0 and TE1 / TE0 and TE2), but also can realize the multiplexing function of polarization states under the same structure, thereby greatly enriching its application potential in various optical communication systems. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 3 is a schematic diagram of the planar (top view) structure of the silicon waveguide layer in an embodiment of the present invention.
[0034] Figure 2 yes Figure 1 Schematic diagram of the structure of the reverse mode conversion unit.
[0035] Figure 3 Figure 2 shows the transmission spectra of an embodiment of the present invention within the wavelength range of 1500 to 1600 nm. Specifically, (a) and (b) show the transmission spectra observed at the download end (Port A / B), respectively, when the TE0 or TE1 mode is input through the bus waveguide. (c) shows the transmission spectra observed at the upload end (right side of the bus waveguide), when the TE0 mode is input through different ports (Port a / b) of the optical switch.
[0036] Figure 4 This is the field evolution of the embodiment of the present invention when the wavelength is set to 1550nm, where (a) and (b) correspond to the downloading situation, and (c) and (d) correspond to the uploading situation.
[0037] In the figure: 1. Bus waveguide; 2. Bidirectional mode coupler; 3. Bend waveguide; 4. Reverse mode conversion unit; 5. Optical switch. DETAILED DESCRIPTION
[0038] The present invention relates to an on-chip integrated dual-mode bidirectional switchable add / drop multiplexer designed to process TE0 and TE1 mode optical signals. The system supports bidirectional transmission and mode conversion of TE0 and TE1 mode optical signals input from the left side of the bus waveguide and TE0 mode optical signals input from Port 2. This silicon-based multiplexer not only has excellent technical performance, but also demonstrates great potential in practical applications. Through careful design, the multiplexer achieves bidirectional input capability, supporting the effective transmission of optical signals in both directions; at the same time, it also has powerful multi-mode multiplexing capabilities, making it possible to simultaneously process optical signals of different modes, thereby greatly improving the flexibility and efficiency of the system. In addition, the present invention takes into account low manufacturing difficulty and high process tolerance, which lays a solid foundation for large-scale production and practical deployment.
[0039] The working principle and features of the present invention are described in detail below with reference to the accompanying drawings. The embodiments given are only used to explain the present invention and are not used to limit the scope of the present invention.
[0040] like Figure 1 As shown, the present invention provides an on-chip integrated dual-mode bidirectional switchable add / drop multiplexer. The key design point of the multiplexer structure lies in the silicon waveguide layer. The specific structure of the silicon waveguide layer is as follows: a reverse mode conversion unit 4 is set in the central area of the bus waveguide 1, and bidirectional mode couplers 2 are arranged at both ends of the same side of the bus waveguide 1, and each bidirectional mode coupler 2 is connected to a curved waveguide 3 at both ends, and the curved waveguide 3 is further connected to the corresponding optical switch 5. The bus waveguide 1, the reverse mode conversion unit 4, the bidirectional mode coupler 2, the curved waveguide 3 and the optical switch 5 together constitute the silicon waveguide layer. Below the silicon waveguide layer is a buried oxide layer, above it is an upper cladding layer, and below the buried oxide layer is a silicon-based substrate. The buried oxide layer and the upper cladding layer are both made of SiO2 material.
[0041] The bus waveguide 1 is a long, straight waveguide structure. The reverse mode conversion unit 4 is composed of two rows of aperture gratings arranged side by side in the center region of the bus waveguide 1, along the direction of the bus waveguide 1. The bidirectional mode coupler 2 is also a long, straight waveguide structure and is parallel to the bus waveguide 1. The bidirectional mode coupler near the input end of the bus waveguide 1 is denoted as the first bidirectional mode coupler, and the bidirectional mode coupler near the output end of the bus waveguide 1 is denoted as the second bidirectional mode coupler. The four curved waveguides are all curved away from the bus waveguide 1. The curved waveguides are similar to 90° curved waveguides. When the first bidirectional mode coupler is connected to the curved waveguides at both ends, it corresponds to the area between the input end of the bus waveguide 1 and the reverse mode conversion unit 4. When the second bidirectional mode coupler is connected to the curved waveguides at both ends, it corresponds to the area between the output end of the bus waveguide 1 and the reverse mode conversion unit 4.
[0042] The two rows of hole-shaped grating structures of the reverse mode conversion unit 4 are as follows Figure 2 As shown in Figure 2, the two rows of gratings are offset by half a period, meaning the apertures on one row correspond to the blank space between two adjacent gratings on the other row. The grating period is chirped, initially increasing linearly, then remaining uniform, and finally decreasing linearly. The gratings can have either circular or square apertures. Figure 2 The gratings are rectangular, with the long side of the rectangle oriented in the direction of bus waveguide 1. The grating length in each row is apodized, increasing linearly, then remaining uniform, and finally decreasing linearly. The grating width remains constant, and the grating duty cycle is 0.5.
[0043] The bus waveguide 1, the bidirectional mode coupler 2, the bent waveguide 3 and the optical switch 5 are all made of silicon-on-insulator materials, while the reverse mode conversion unit 4 is made of SiO2 material.
[0044] It should be noted that the bus waveguide 1, bidirectional mode coupler 2, curved waveguide 3, reverse mode conversion unit 4 and optical switch 5 are manufactured at one time, so when making the mask, it is necessary to set specific patterns in the corresponding positions in advance. Figure 1 For the structure, when manufacturing the silicon waveguide layer, the mask plate has a blocking portion at the grating position corresponding to the reverse mode conversion unit 4, and Si is not formed in this blocking portion. Subsequently, when manufacturing the upper cladding layer, SiO2 material is filled in this area, thereby forming a reverse mode conversion unit of SiO2 material.
[0045] In the embodiment of the present invention, the height of the silicon waveguide layer is 220 nm, that is, the heights of the bus waveguide 1 , the bidirectional mode coupler 2 , the bent waveguide 3 , the reverse mode conversion unit 4 and the optical switch 5 are all 220 nm.
[0046] In this embodiment of the present invention, the bus waveguide 1 has a width of 0.8-1.5 μm, while the bidirectional mode coupler 2 and curved waveguide 3 have widths of 0.4-0.55 μm. This design allows for better mode coupling. The spacing between the bus waveguide 1 and the bidirectional mode coupler 2 is 100-200 nm. The optical switch 5 can be formed using the principles of a Mach-Zehnder interferometer (MZI).
[0047] In the embodiment of the present invention, the input optical signal is TE0 or TE1, and its wavelength range is 1500nm-1600nm.
[0048] The simulation results of this embodiment are as follows Figure 3 As shown. Figure 3Simulation results (a) and (b) show the transmission spectra of the two modes at the downstream end (Ports A / B) obtained by selecting TE0 or TE1 input in bus waveguide 1. Meanwhile, (c) shows the corresponding transmission spectra at the upstream end (to the right of bus waveguide 1) obtained by inputting TE0 into curved waveguide 3 (Ports a / b).
[0049] Figure 4 The field evolution characteristics of the TE0 and TE1 mode optical signals input from both sides of the bus waveguide at a wavelength of 1550nm are shown in this embodiment. Specifically, the transmission characteristics of the optical signal in this embodiment mainly include the following two situations:
[0050] 1. When a TE0 or TE1 mode optical signal is input into bus waveguide 1 from the left, the TE0 mode optical signal first enters the reverse mode conversion unit 4, where reverse coupling occurs and converts it to TE1 mode. The TE1 mode optical signal then continues to propagate to the bidirectional mode coupler 2 region, where mode coupling occurs, coupling the TE1 mode in bus waveguide 1 to the waveguide below, converting it to TE0 mode. This TE0 mode optical signal is then transmitted through the curved waveguide 3, ultimately arriving at Port A. On the other hand, for a directly input TE1 mode optical signal, it is directly coupled to the waveguide below in the bidirectional mode coupler 2 region and similarly converted to TE0 mode. It is then transmitted through the curved waveguide 3, ultimately arriving at Port B. Whether outputting a TE0 mode optical signal from Port A or Port B, it is further guided to the optical switch 5, ultimately arriving at Port 1.
[0051] 2. When a TE0 mode optical signal is input into optical switch 5 from Port 2, it is selectively routed to either Port a or Port b for output, and then enters curved waveguide 3. If a TE0 mode optical signal is input into curved waveguide 3 from Port a, it is directly coupled into bus waveguide 1 through bidirectional mode coupler 2, converted to TE1 mode, and then reaches reverse mode conversion unit 4, where reverse coupling occurs, converting it back to TE0 mode and ultimately outputting from the right side of bus waveguide 1. On the other hand, when a TE0 mode optical signal is input into curved waveguide 3 from Port b, it is also directly coupled into the bus waveguide through bidirectional mode coupler 2, converting to TE1 mode. However, it does not undergo conversion by reverse mode conversion unit 4 and is directly output from the right side of bus waveguide 1.
[0052] The grating design of the reverse mode conversion unit 4 in this embodiment complies with the phase matching condition in the coupled mode theory, and its phase matching formula can be given by the following formula:
[0053]
[0054] In formula (1), β 前 and β 后 are the propagation constants of the forward mode and the backward mode respectively, m is the number of stages and is usually 1, and Λ is the period.
[0055] The above content details the implementation method of an on-chip integrated dual-mode bidirectional switchable up / down multiplexer. The reverse mode conversion unit used in the present invention includes a highly flexible Bragg grating. This design allows the conversion from TE2 mode to TE0 mode by appropriately adjusting the grating structure (period and size) while keeping the overall system architecture basically unchanged, thereby constructing a function that can support TE2 and TE0 dual-mode bidirectional switchable up / down multiplexing. Compared with the mode multiplexer in the prior art, the solution of the present invention exhibits significantly better scalability.
[0056] The waveguide coupler provided by this invention demonstrates excellent multiplexing performance, boasting advantages such as small package size, low loss, low crosstalk, easy manufacturing, and wide process tolerances. It can be flexibly applied in fields such as optical communications and integrated photonics. The technical solution and the resulting optical signal transmission characteristics significantly surpass those of existing related devices.
[0057] The contents described in the embodiments of this specification are merely an enumeration of the implementation forms of the inventive concept. The scope of protection of the present invention should not be regarded as limited to the specific forms described in the embodiments. The scope of protection of the present invention also extends to equivalent technical means that can be thought of by those skilled in the art based on the inventive concept.
Claims
1. An on-chip integrated dual-mode bidirectional switchable add / drop multiplexer, comprising a silicon-based substrate, a buried oxide layer disposed on the silicon-based substrate, a silicon waveguide layer disposed on the buried oxide layer, and an upper cladding layer covering the buried oxide layer and encapsulating the silicon waveguide layer; the buried oxide layer and the upper cladding layer are both made of SiO2 material; wherein: The silicon waveguide layer includes a bus waveguide, which has a long straight waveguide structure. A reverse mode conversion unit is arranged in the central area of the bus waveguide. The reverse mode conversion unit is composed of two rows of gratings along the direction of the bus waveguide, and the two rows of gratings are offset by half a period. The grating period first increases linearly, then remains uniform, and then decreases linearly. The grating size first increases linearly, then remains uniform, and then decreases linearly. Two bidirectional mode couplers are symmetrically arranged on the same side of the bus waveguide, each of which has a long straight waveguide structure and is parallel to and arranged in parallel with the bus waveguide. The two bidirectional mode couplers correspond to the bus waveguides at both ends of the reverse mode conversion unit respectively. The two ends of each bidirectional mode coupler are respectively connected to a curved waveguide, which is connected to an optical switch. The bus waveguide, bidirectional mode coupler, curved waveguide and optical switch are all made of silicon. The reverse mode conversion unit is made of SiO2 material.
2. The on-chip integrated dual-mode bidirectional switchable add / drop multiplexer according to claim 1, wherein: The width of the bus waveguide is greater than the width of the bidirectional mode coupler.
3. The on-chip integrated dual-mode bidirectional switchable add / drop multiplexer according to claim 2, wherein: The bus waveguide width is 0.8-1.5 μm, and the bidirectional mode coupler width is 0.4-0.55 μm.
4. The on-chip integrated dual-mode bidirectional switchable add / drop multiplexer according to claim 1, wherein: The spacing between the bus waveguide and the bidirectional mode coupler is 100-200 nm.
5. The on-chip integrated dual-mode bidirectional switchable add / drop multiplexer according to claim 1, wherein: The height of the bus waveguide, bidirectional mode coupler, curved waveguide, reverse mode conversion unit and optical switch is 220nm.
6. The on-chip integrated dual-mode bidirectional switchable add / drop multiplexer according to claim 1, wherein: The grating duty cycle of the reverse mode conversion unit is 0.
5.
7. The on-chip integrated dual-mode bidirectional switchable add / drop multiplexer according to claim 1, wherein: The optical switch is formed using the principle of Mach-Zehnder interferometer.
8. The on-chip integrated dual-mode bidirectional switchable add / drop multiplexer according to claim 1, wherein: The bus waveguide, bidirectional mode coupler, curved waveguide, reverse mode conversion unit and optical switch are manufactured at one time.
9. The on-chip integrated dual-mode bidirectional switchable add / drop multiplexer according to claim 1, wherein: The four curved waveguides are all bent in a direction away from the bus waveguide.
10. A method for preparing the on-chip integrated dual-mode bidirectional switchable add / drop multiplexer according to any one of claims 1 to 9, characterized in that: The steps include: a. Preparing a buried oxide layer of SiO2 material on a silicon-based substrate; b. placing a mask on the buried oxide layer, wherein the mask is designed with a specific pattern; c. preparing a silicon waveguide layer at a position corresponding to the mask on the buried oxide layer; d. Remove the mask and prepare an upper cladding layer of SiO2 material on the buried oxide layer. The upper cladding layer wraps the silicon waveguide layer to form an on-chip integrated dual-mode bidirectional switchable add / drop multiplexer.