CN115980914A - On-chip integrated wavelength division multiplexer and chip - Google Patents

Abstract

The application discloses an on-chip integrated wavelength division multiplexer and a chip. The on-chip integrated wavelength division multiplexer includes a first-level multiplexing module and a second-level multiplexing module. The first-level multiplexing module has multiple input ports and two output ports, the second-stage multiplexing module has two input ports and one output port, and the two output ports of the first-stage multiplexing module are respectively multiplexed with the second-stage multiplexing module Optical coupling with the corresponding input port of the module; wherein, the bandwidth of each flat-top wavelength division multiplexing structure in the first-level multiplexing module covers the center wavelength of the incident light respectively received by its two input ports plus the preset The frequency band range corresponding to the offset threshold. The technical solution of the present application can make the flat-top band bandwidth of the two first-stage combined optical signals generated by the first-stage multiplexing module wider, thereby avoiding the crosstalk between adjacent channels caused by the central wavelength shift caused by various factors problem, without any feedback regulation, which improves work efficiency and reduces device loss.

Description

On-chip integrated wavelength division multiplexer and chip

technical field

The present application relates to the technical field of optical communication, in particular to an on-chip integrated wavelength division multiplexer and chip.

Background technique

In high-speed and large-capacity optical communication, wavelength division multiplexing (Wavelength Division Multiplexing, WDM) is an effective means to increase the capacity of optical communication. At the same time, combined with photonic integrated chips, it can effectively reduce the size of devices and improve the system The integration level, the key devices are wavelength division multiplexing device (MUX) and wavelength division multiplexing device (DEMUX).

As shown in Figure 1, taking four-channel wavelength division multiplexing as an example, the wavelength division multiplexer based on the cascaded Mach-Zehnder interferometer (MZI) structure in the existing silicon optical chip consists of three parallel and Cascade-connected Mach-Zehnder interferometers 10' constitute, wherein each Mach-Zehnder interferometer 10' includes two 2×2 3dB couplers 11' and two connecting arms 12', a monitoring probe device 13', one of the connecting arms is an adjustable phase shift arm (indicated by a dotted line in the figure). The above-mentioned existing wavelength division multiplexer needs to be combined with the monitoring detector 13' to adjust the adjustable phase-shift arms of the cascaded Mach-Zehnder interferometers 10' when in use, which causes the adjustment process to be inconvenient. consumes more. In addition, the optical bandwidth of the 3dB coupler 11' is limited, therefore, multiple cascaded Mach-Zehnder interferometers 10' have multiple 3dB couplers 11' in the optical path of the wavelength division multiplexer, which significantly reduces the wavelength division Multiplexer performance.

The ideal wavelength division multiplexing device should be purely passive and does not need to be adjusted. However, the optical waveguide device in the silicon-based wavelength division multiplexer will be affected by the width, inclination angle change, and silicon waveguide thickness change caused by the processing technology. and temperature changes, etc., resulting in the shift of the center wavelength of the silicon-based wavelength division multiplexing device, thus, the shift of the center wavelength of the existing silicon-based wavelength division multiplexing device will cause the difference between the optical signals of adjacent channels crosstalk occurs.

Contents of the invention

The purpose of this application is to provide an on-chip integrated wavelength division multiplexer and chip, which is used to improve the crosstalk problem between optical signals of adjacent channels, and has the advantages of low power consumption and large optical bandwidth.

According to one aspect of the present application, an on-chip integrated wavelength division multiplexer is provided, which includes a first-stage multiplexing module and a second-stage multiplexing module, the first-stage multiplexing module has a plurality of input ports and two output ports, the second-level multiplexing module has two input ports and one output port, and the two output ports of the first-level multiplexing module are respectively corresponding to the input of the second-level multiplexing module Port optical coupling; the first-level multiplexing module includes at least two flat-top wavelength division multiplexing structures, each of which has two input ports and one output port, wherein each of the flat-top wavelength division multiplexing structures The bandwidth of the flat-top wavelength division multiplexing structure covers the frequency band range corresponding to the center wavelength of the incident light respectively received by its two input ports plus a preset offset threshold.

According to an embodiment of the present application, the first-stage multiplexing module multiplexes the incident lights with the same polarization state received by the multiple input ports to generate two first-stage multiplexed optical signals, and The two first-stage combined optical signals are respectively input to the corresponding input ports of the second-stage multiplexing module, and the second-stage multiplexed module combines the two first-stage combined optical signals received by its two input ports. performing multiplexing on the optical signals to generate a second-stage multiplexed optical signal, wherein the second-stage multiplexed optical signal includes a first group of optical wave components and a second group of optical wave components, and the first group of optical wave components and the second group of optical wave components have different polarization states; the second-stage multiplexing module performs polarization multiplexing on the first group of light wave components and the second group of light wave components. .

According to an embodiment of the present application, when the λ1, λ2, λ3...λn wavelength-divided optical signals with predetermined wavelength intervals are input to the multiple input ports of the first-stage multiplexing module, where n≥4, And n is an even number; for each of the flat-topped wavelength division multiplexing structures, an incident optical signal of an odd channel is input from an input port of the flat-topped wavelength division multiplexing structure, and from the flat-topped wavelength division multiplexing structure The other input port inputs the incident optical signal of the even channel.

According to an embodiment of the present application, the at least two flat-top wavelength division multiplexing structures are composed of any combination of the following structures: multiple cascaded Mach-Zehnder interference structures, arrayed waveguide grating structures, etched diffraction grating structures , a combined structure composed of a mode multiplexer and a multimode Bragg grating, and a reverse Bragg grating directional coupler structure.

According to an embodiment of the present application, the on-chip integrated wavelength division multiplexer is a silicon-based wavelength division multiplexer.

According to an embodiment of the present application, the difference between the central wavelengths of the incident light received by the two input ports of each of the flat top wavelength division multiplexing structures is greater than a preset wavelength difference threshold.

According to an embodiment of the present application, the on-chip integrated wavelength division multiplexer further includes a coupling structure connected to the output port of the second-stage multiplexing module for multiplexing the second-stage The second stage multiplexed optical signal output by the output port of the module is coupled with an external optical fiber array to output the multiplexed optical signal.

According to an embodiment of the present application, the second-stage multiplexing module is a polarization rotation beam splitter, and the polarization rotation beam splitter combines the two received first-stage combined optical signals into The polarization states of the first set of lightwave components and the second set of lightwave components.

According to an embodiment of the present application, the polarization rotating beam splitter includes a through-waveguide and a cross-waveguide, a through-port and a cross-port respectively connecting the through-waveguide and the cross-waveguide, and a mode conversion structure connected to the through-waveguide; The through waveguide and the cross waveguide form a mode multiplexing structure; the through port and the cross port both include a wedge-shaped structure in which a strip waveguide is transformed into a ridge waveguide; and the mode conversion structure is a double-layer wedge-shaped mode conversion structure.

According to an embodiment of the present application, the second-stage multiplexing module is a polarization beam combiner, and the on-chip integrated wavelength division multiplexer further includes a polarization rotator, and the input port of the polarization rotator is connected to the first An output port of the multiplexing module is optically coupled to receive light output from the output port, and an output port of the polarization rotator is optically coupled to an input port of the polarization beam combiner to output to the polarization beam combiner light, wherein the polarization beam combiner is used to combine two received light beams with different polarization states into one light beam, and the polarization rotator is used to change the polarization state of the received light beams; wherein the polarization rotation The detector changes the original polarization state of the received light beam to a polarization state perpendicular to the original polarization state.

According to an embodiment of the present application, the second-level multiplexing module is a polarization beam combiner, and the on-chip integrated wavelength division multiplexer further includes at least one polarization rotator, and for each polarization rotator, its input The port is used to receive one path of incident light, and its output port is optically coupled to the input port of one of the at least two flat-topped wavelength division multiplexing structures, so as to output light to the flat-topped wavelength division multiplexing structure, wherein, The polarization beam combiner is used to combine two received light beams with different polarization states into one light beam, and the polarization rotator is used to change the polarization state of the received light beams, and is changed by the at least one polarization rotator The light of the polarization state is output by only one output port of the first-stage multiplexing module; wherein each of the polarization rotators changes the original polarization state of the received light beam to a polarization state perpendicular to the original polarization state .

According to an embodiment of the present application, each of the flat-top wavelength division multiplexing structures includes at least two 1dB flat-tops, wherein each 1dB flat-top is a wavelength range corresponding to the optical attenuation range of 1dB, and each 1dB flat-top The wavelength range corresponding to the top is greater than 20 nanometers.

According to an embodiment of the present application, the distance between two adjacent 1 dB flat tops of the same flat top wavelength division multiplexing structure is less than 5 nanometers.

According to an embodiment of the present application, among the at least two flat-top wavelength division multiplexing structures, the wavelength range corresponding to the 1dB flat-top in one of the flat-top wavelength division multiplexing structures is the same as the flat-top wavelength range of the other one. The wavelength ranges corresponding to the 1dB flat top in the division multiplexing structure partially overlap.

According to still another aspect of the present application, a chip is provided, and the chip includes the on-chip integrated wavelength division multiplexer described in any one of the foregoing embodiments.

In the on-chip integrated wavelength division multiplexer and chip provided by the embodiment of the present application, the bandwidth of each flat-top wavelength division multiplexing structure in the first-level multiplexing module can cover the incident signals respectively received by its two input ports. The central wavelength of the light plus the frequency band corresponding to the preset offset threshold, thus making the flat-top band bandwidth of the two first-stage multiplexed optical signals generated by the first-stage multiplexing module wider, which can cover various The problem of crosstalk between adjacent channels caused by the shift of the center wavelength caused by factors has realized the multiplexing of incident optical signals of different wavelengths; in addition, the first-level multiplexing module and the second-level multiplexing module do not need to Any feedback regulation improves work efficiency, reduces device loss, and helps reduce the sensitivity of the on-chip integrated wavelength division multiplexer to waveguide width, waveguide height, and waveguide inclination.

Description of drawings

The technical solutions and other beneficial effects of the present application will be apparent through the detailed description of the specific embodiments of the present application below in conjunction with the accompanying drawings.

Fig. 1 is the structural representation of the MZI type on-chip integrated wavelength division multiplexer in the existing silicon light chip;

Figure 2a is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by an embodiment of the present application;

FIG. 2b is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by another embodiment of the present application;

FIG. 2c is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by another embodiment of the present application;

FIG. 3 is a schematic structural diagram of a polarization rotating beam splitter (PSR) in an embodiment of the present application;

Figures 4a-4e are schematic diagrams of multiple implementations of a flat-top wavelength division multiplexing structure formed by using multiple cascaded Mach-Zehnder interference structures in the embodiment of the present application;

FIG. 5 is a schematic diagram of using an arrayed waveguide grating structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application;

6 is a schematic diagram of using an etched diffraction grating structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application;

7 is a schematic diagram of a flat-top wavelength division multiplexing structure using a combined structure composed of a mode multiplexing device and a multimode Bragg grating in an embodiment of the present application;

8 is a schematic diagram of using an inverted Bragg grating directional coupler structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application;

Fig. 9 is a simulated spectrum diagram of a flat-top wavelength division multiplexing structure composed of any combination of multiple cascaded Mach-Zehnder interference structures, arrayed waveguide grating structures, and etched diffraction grating structures in an embodiment of the present application;

Fig. 10 is the spectrogram of the beam near the central wavelength of 1291nm in the spectrogram shown in Fig. 9;

Figure 11 is a set of light waves generated by using a flat-top wavelength division multiplexing structure composed of a combined structure composed of a mode multiplexer and a multimode Bragg grating, and an arbitrary combination of an inverted Bragg grating directional coupler structure in an embodiment of the present application The simulated spectrogram of the component;

Figure 12 is another group of light waves generated by the flat-top wavelength division multiplexing structure composed of any combination of mode multiplexers and multimode Bragg gratings and any combination of inverse Bragg grating directional coupler structures in the embodiment of the present application The simulated spectrogram of the component;

FIG. 13 is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided in another embodiment of the present application;

FIG. 14 is a schematic structural diagram of a polarization rotator (PR) in the on-chip integrated wavelength division multiplexer shown in FIG. 13;

FIG. 15 is a schematic structural diagram of a polarization beam combiner (PBC) in the on-chip integrated wavelength division multiplexer shown in FIG. 13;

FIG. 16 is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by another embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Apparently, the described embodiments are only some of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts belong to the scope of protection of this application.

The terms "first" and "second" herein are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of said features. In the description of the present application, "plurality" means two or more, unless otherwise specifically defined.

In the description of this application, it should be noted that unless otherwise specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected, or electrically connected, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction of two components relation. Those of ordinary skill in the art can understand the specific meanings of the above terms in this application according to specific situations.

The following disclosure provides many different implementations or examples for implementing different structures of the present application. To simplify the disclosure of the present application, components and arrangements of specific examples are described below. Of course, they are examples only and are not intended to limit the application. Furthermore, the present application may repeat reference numerals and/or reference letters in various instances, such repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and/or arrangements discussed.

2a-2c are schematic structural diagrams of an on-chip integrated wavelength division multiplexer provided by an embodiment of the present application, and FIG. 3 is a schematic structural diagram of a polarization rotating beam splitter in an embodiment of the present application.

Referring to FIG. 2 a - FIG. 2 c and FIG. 3 , an embodiment of the present application provides an on-chip integrated wavelength division multiplexer 1000 , which includes a first-stage multiplexing module 100 and a second-stage multiplexing module 200 . The first stage multiplexing module 100 has a plurality of input ports and two output ports, the second stage multiplexing module 200 has two input ports and one output port, all of the first stage multiplexing module 100 The two output ports are optically coupled to the corresponding input ports of the second-level multiplexing module 200; multiplexing to generate two first-stage multiplexed optical signals, and input the two first-stage multiplexed optical signals to corresponding input ports of the second-stage multiplexing module 200 . The second-stage multiplexing module 200 multiplexes the two first-stage multiplexed optical signals received by its two input ports to generate a second-stage multiplexed optical signal, wherein the second-stage multiplexed optical signal A first set of lightwave components and a second set of lightwave components are included, the first set of lightwave components and the second set of lightwave components have different polarization states. The first stage multiplexing module 100 is composed of at least two flat top wavelength division multiplexing structures (110, 120), each of which has two input ports and a flat top wavelength division multiplexing structure (110, 120). output port, wherein the bandwidth of each flat-top wavelength division multiplexing structure (110, 120) covers the center wavelength of the incident light received by its two input ports plus the preset offset threshold corresponding to frequency range.

In the on-chip integrated wavelength division multiplexer provided in this embodiment, the bandwidth of each flat-top wavelength division multiplexing structure in the first-stage multiplexing module can cover the center of the incident light received by its two input ports respectively. The frequency band range corresponding to the wavelength plus the preset offset threshold, thus making the flat-top band bandwidth of the two first-stage multiplexing optical signals generated by the first-stage multiplexing module wider, which can cover the bandwidth caused by various factors The resulting center wavelength shift causes the adjacent channel crosstalk problem. In addition, the first-level multiplexing module and the second-level multiplexing module do not need any feedback adjustment during the working process, which improves work efficiency and reduces device loss. And it is beneficial to reduce the sensitivity of the on-chip integrated wavelength division multiplexer to changes in waveguide width, waveguide height, waveguide inclination angle and surrounding environment temperature.

The structure and working mechanism of the on-chip integrated wavelength division multiplexer 1000 will be further described in detail below with reference to FIGS. 2 a to 3 .

Referring to Fig. 2a, illustratively, in this embodiment, take λ1, λ2, λ3, λ4 (the wavelengths are arranged from small to large) four-wavelength on-chip integrated wavelength division multiplexer as an example, the on-chip integrated wavelength division multiplexer The multiplexer 1000 includes a first-level multiplexing module 100 and a second-level multiplexing module 200. The first-level multiplexing module 100 is composed of at least two flat-top wavelength division multiplexing structures (110, 120) connected in parallel. The secondary multiplexing module 200 is an integrated polarization rotating beam splitter. In this embodiment, each of the flat-top wavelength division multiplexing structures 110 has two input ports and one output port, and the polarization rotating beam splitter 200 includes two input ports and one output port, and the two The two output ports of the flat-top wavelength division multiplexing structure 110 are respectively connected to the two input ports of the polarization rotating beam splitter 200 for optical coupling; the output ports of the polarization rotating beam splitter 200 are used for output synthesis beam.

Specifically, the two incident optical signals of λ1 and λ3 are input by two input ports of a flat-top wavelength division multiplexing structure 110, and the two incident optical signals of λ2 and λ4 are input by another flat-top wavelength division multiplexing structure 120. Two input ports are input, and the flat-top band bandwidth of each said flat-top wavelength division multiplexing structure (110, 120) can cover the central wavelength of the incident light received by its two input ports respectively plus the preset The frequency band range corresponding to the offset threshold, that is, the bandwidth of the flat-top wavelength division multiplexing structure 110 is greater than λ1 ± Δλ and λ3 ± Δλ, and the bandwidth of the flat-top wavelength division multiplexing structure 120 is greater than λ2 ± Δλ and λ4 ± Δλ (where Δλ is the passband width required by the system for the on-chip integrated wavelength division multiplexing device), to realize the multiplexing of incident optical signals of different wavelengths, due to the wide bandwidth of the flat-top wavelength division multiplexing structure 110, each flat-top The wavelength division multiplexing structure can transmit two beams with a large difference in center wavelength, so it can tolerate the difference between adjacent channels caused by the center wavelength shift caused by the waveguide width, waveguide inclination angle, waveguide height and temperature changes. Crosstalk problem.

The above-mentioned on-chip integrated wavelength division multiplexer is a silicon-based wavelength division multiplexer, which includes a silicon-based substrate, and a first-level multiplexing module 100 and a second-level multiplexing module 200 are arranged on the silicon-based substrate; It may be an on-chip integrated wavelength division multiplexer structure based on other substrates, and the present invention is not limited here.

When inputting λ1, λ2, λ3...λn wavelength-divided optical signals with predetermined wavelength intervals into the multiple input ports of the first-stage multiplexing module, where n≥4, and n is an even number; for each In the flat-top wavelength division multiplexing structure, incident optical signals of odd channels are input from one input port of the flat-top wavelength division multiplexing structure, and even-numbered channels are input from another input port of the flat-top wavelength division multiplexing structure incident light signal. That is to say, λ1 and λ3 are respectively input into two input ports of the flat-topped WDM structure for multiplexing, and λ2 and λ4 are respectively input into two input ports of the other flat-topped WDM structure for multiplexing , adopting this misplaced multiplexing method can make the difference between the central wavelengths of the incident light received by the two input ports of each of the flat top wavelength division multiplexing structures (110, 120) larger, by This prevents crosstalk effects between adjacent bands within the same channel.

The difference between the central wavelengths of the incident light received by the two input ports of each of the flat top wavelength division multiplexing structures (110, 120) is greater than a preset wavelength difference threshold. Taking four (λ1, λ2, λ3, λ4) wavelength-divided optical signals as an example, the wavelength difference between λ1 and λ2 is greater than or equal to 20nm, the wavelength difference between λ3 and λ4 is greater than or equal to 20nm, and λ1 and λ3 The wavelength difference between λ2 and λ4 is greater than or equal to 40nm, and the wavelength difference between λ2 and λ4 is greater than or equal to 40nm. Of course, the difference between the central wavelengths of the incident light received by the two input ports of each flat-top wavelength division multiplexing structure (110, 120) can also be set according to actual application conditions.

It should be noted that, in this embodiment, for each flat-top wavelength division multiplexing structure, the loss at the center wavelength λ0 of the on-chip integrated wavelength division multiplexing device constituted by it is small, and the loss in the range of λ0 ± Δλ near the center wavelength The loss compared to the center wavelength is less than 1dB. Among them, λ0±Δλ is called the 1dB flat-top range of the channel. Wherein, each 1dB flat-top is a wavelength range corresponding to an optical attenuation range of 1dB, and each 1dB flat-top in the flat-top wavelength division multiplexing structure corresponds to a wavelength range larger than 20 nanometers. In the same flat-top wavelength division multiplexing structure, there is a certain distance between the wavelength ranges corresponding to two adjacent 1dB flat-tops. The wavelength ranges corresponding to some 1dB flat-tops in the two flat-top multiplexing structures will overlap. Specifically, as shown in FIG. 11 and FIG. 12 , FIG. 11 may represent a spectrum diagram of one of the top-hat wave multiplexing structures. It can be seen from the figure that it has at least two 1dB flat tops (the flat part of the horizontal axis in the figure). The center wavelength of the wavelength corresponding to one 1dB flat top is 1291 nanometers, and the center wavelength of the wavelength corresponding to the other 1dB flat top is 1331 nanometers. Each 1dB plateau corresponds to a wavelength range of approximately 40 nanometers (the width of the flat portion in the figure). Fig. 12 can represent the spectrum diagram of another top-hat wave multiplexing structure. It can be seen from the figure that it also has at least two 1dB tops. One 1dB flat top corresponds to a center wavelength of 1271 nm, and the other 1dB flat top corresponds to a center wavelength of 1311 nm. Each 1dB plateau corresponds to a wavelength range of about 40 nanometers. In the wavelength range corresponding to the 1dB flat-top of the two flat-top WDM structures, the 1dB flat-top ranges corresponding to the center wavelength 1271 nm and the center wavelength 1291 nm partly overlap, and the center wavelength 1291 nm and the center wavelength 1311 nm correspond to The 1dB flat-top ranges of 1311nm and 1331nm center wavelengths partly overlap. However, since these central wavelengths are cross-distributed in different flat-top multiplexing structures, the wavelength ranges corresponding to the 1 dB flat-top range of these central wavelengths can be staggered, so that the function of multiplexing can be realized. In addition, two adjacent 1dB flat-tops of the same flat-top multiplexing structure can be separated by a predetermined distance, so as to improve the multiplexing effect and the tolerance of the absorption process. Preferably, the predetermined distance of the interval may be less than 5 nanometers. It should be noted that, in this embodiment, the interval between two adjacent 1dB flat-tops refers to the distance between the edges of the two 1dB flat-tops, not the distance between the centers of the two 1dB flat-tops.

It should be understood that, as shown in FIG. 2c, when the λ1, λ2, λ3, λ4...λ7, λ8 wavelength-divided optical signals with predetermined wavelength intervals and arranged in ascending order of wavelength are input to the first-stage multiplexing module, When there are multiple input ports, similarly, adopt the dislocation multiplexing mode, input the incident optical signal of odd channels from one input port of the flat top wavelength division multiplexing structure, and input the incident optical signal from the other input port of the flat top wavelength division multiplexing structure One input port inputs incident optical signals of even channels. For example, input λ1 and λ5 into two input ports of one of the flat-topped wavelength division multiplexing structures for multiplexing, and input λ3 and λ7 into two input ports of the other flat-topped wavelength division multiplexing structure for multiplexing , and subsequently, the multiplexed λ1/λ5 and the multiplexed λ3/λ7 are respectively input to the two input ports of the same flat-top wavelength division multiplexing structure for multiplexing, thereby obtaining λ1/λ3/ Combined wave of λ5/λ7. Input λ2 and λ6 into two input ports of the flat-topped wavelength division multiplexing structure for multiplexing, and input λ4 and λ8 into the two input ports of the other flat-topped wavelength division multiplexing structure for multiplexing, and then , the combined λ2/λ6 and the combined λ4/λ8 are respectively input to the two input ports of the same flat-top wavelength division multiplexing structure for multiplexing, thereby obtaining λ2/λ4/λ6/ Synthesis of λ8. It can be understood that the above-mentioned multiplexing method uses a flat-top wavelength division multiplexing structure to first combine every two of the eight channels into four channels, and then combine the four channels of light waves into two channels to reach the polarization rotating beam splitter, and then the polarization rotating beam splitter Rotate the beam splitter to perform polarization multiplexing; in other embodiments, four of the eight optical signals (λ1/λ3/λ5/λ7) can also be combined into one through a flat-top wavelength division multiplexing structure, and the other four ( λ2/λ4/λ6/λ8) are combined into one path through another flat-top wavelength division multiplexing structure, and then the combined light of these two flat-top wavelength division multiplexing structures is combined into one path through a polarization rotating beam splitter. In addition, when more λ1, λ2, λ3, λ4...λn wavelength-divided optical signals with predetermined wavelength intervals are input to the multiple input ports of the first-stage multiplexing module, n>8, and n is an even number, it can be realized based on the same dislocation combining method, which will not be repeated here.

As shown in Figure 3, the polarization rotating beam splitter (Polarization Split Rotator, PSR) 210 in the present embodiment comprises straight-through waveguide 211 and crossover waveguide 212, connects through-port 213 and crossover port 214 of straight-through waveguide 211 and crossover waveguide 212 respectively , and the mode conversion structure 215 connected to the through-waveguide 211 . Here, the through waveguide 211 and the cross waveguide 212 form a mode multiplexing structure, and the through port 213 and the cross port 214 both include a strip waveguide-to-ridge waveguide wedge-shaped structure, which serves as the input port of the polarization rotating beam splitter. The mode conversion structure 215 is a double-layer wedge-shaped mode conversion structure, which serves as the output port of the polarization rotating beam splitter and outputs the combined optical signal.

As shown in Figure 2a-Figure 3, in the optical signals of four wavelengths λ1, λ2, λ3, λ4 (arranged from small to large wavelengths), λ1 and λ3 are respectively formed by one of the two flat-top WDM structures. The two input ports of the top-top wavelength division multiplexing structure 110 are input, and the first-stage combined optical signal composed of λ1±Δλ/λ3±Δλ is output after being multiplexed by the flat-top wavelength division multiplexing structure 110; λ2 and λ4 are respectively It is input from two input ports of another flat-topped wavelength division multiplexing structure 120 in the two flat-topped wavelength division multiplexing structures, and the output is composed of λ2±Δλ/λ4 after being combined by the flat-topped wavelength division multiplexing structure 120 The first stage multiplexed optical signal composed of ±Δλ. It should be noted that the above four incident optical signals λ1, λ3, λ2 and λ4 are all linearly polarized light and have the same polarization state, assuming that they are all linearly polarized light in TE0 (Transverse Electric mode, transverse electric mode) mode, After the two flat-top wavelength division multiplexing structures ( 110 , 120 ) respectively perform multiplexing, the output first-stage multiplexed optical signal is still combined beam linearly polarized light in TE0 mode. The two first-stage multiplexed optical signals (i.e., the λ1±Δλ/λ3±Δλ optical signal after the multiplexing and the λ2±Δλ/λ4±Δλ optical signal after the multiplexing) composed of the combined linearly polarized light of the TE0 mode are respectively composed of The through-port 213 and the cross-port 214 of the above-mentioned integrated polarization rotating beam splitter (PSR) 210 are input, and enter the through-waveguide 211 and the cross-waveguide 212 respectively. The polarization state of the λ2±Δλ/λ4±Δλ optical signal entering the straight-through waveguide 211 remains unchanged, and the λ2±Δλ/λ4±Δλ optical signal in the TE0 mode is still output after passing through the mode conversion structure 215; the λ1±Δλ optical signal entering the cross waveguide 212 The /λ3±Δλ optical signal is coupled into the straight-through waveguide 211, and is mode-multiplexed with the optical signal in the straight-through waveguide 211. The mode of the λ1±Δλ/λ3±Δλ optical signal is converted from the TE0 mode to the TE1 (higher-order) mode. The conversion structure 215 is transformed into a TM0 (Transverse Magnetic mode, transverse magnetic mode) mode (that is, the polarization state changes) and synthesizes a bundle of lines including the TE0+TM0 mode with the λ2±Δλ/λ4±Δλ optical signal of the TE0 mode in the original straight-through waveguide 211 polarized light output.

Further, as shown in FIG. 2b, the on-chip integrated wavelength division multiplexer 1000 also includes a coupling structure 300, and the coupling structure 300 is connected to the output port of the second-stage multiplexing module 200 for connecting the The output port of the second-stage multiplexing module 100 is coupled with the combined optical signal (second-stage multiplexed optical signal) outputted by the output port of the second-stage multiplexing module 100 to an external optical fiber array, so as to input the optical signal to be modulated and convert the modulated optical signal to the external optical fiber array. The signal is output, which has high coupling efficiency and can reduce the loss of the entire optical path. Specifically, the coupling structure 300 may be a low polarization-dependent loss edge coupler (low PDL edge coupler).

4a-4e are schematic diagrams of various implementations of using multiple cascaded Mach-Zehnder interference structures to form a flat-top wavelength division multiplexing structure in the embodiment of the present application. As shown in FIG. 4a-FIG. 4e, 121-125 in the diagrams represent each different implementation of the flat-top wavelength division multiplexing structure. In this embodiment, in order to make the first-stage multiplexed optical signal output by each of the flat-topped wavelength division multiplexing structures 110 an approximately rectangular waveform, each of the flat-topped wavelength division multiplexing structures 110 is It is designed as a digital filter, which is composed of at least two cascaded Mach-Zehnder interference structures (MZI), assuming that the digital filter is denoted as A, and the 2*2 coupler is denoted as B , the phase shift arm is expressed as C, then B and C can be synthesized into A, and the numerical value of the splitting ratio on the coupler and the phase shift on the phase shift arm represent the coefficients in front of B and C, how much A cascaded MZI represents how many orders of approximation. Exemplarily, in the single Mach-Zehnder interference structure (MZI) in Figure 4a-Figure 4e, the number 0.5 means that the splitting ratio of the cross port of the 2*2 3-dB coupler is 0.5, that is, the output of one port is 0.5 , the output of the other port is 0.5; the number 0.29 means that the splitting ratio of the 2*2 coupler cross port is 0.29, that is, the output of one port is 0.29, and the output of the other port is 0.71; the number 0.08 means the 2*2 coupler cross port The splitting ratio is 0.08, that is, the output of one port is 0.08, and the output of the other port is 0.92; the rest of the numbers represent the same analogy, and we will not give examples here. In addition, ΔL corresponds to the length of the waveguide where light is transmitted on the upper and lower phase shift arms of a single Mach-Zehnder interference structure (MZI); Lπ corresponds to the length of light traveling on the upper and lower phase shift arms of a single Mach-Zehnder interference structure (MZI) Transmission produces a waveguide length that is phase shifted by π. Finally, an approximately rectangular waveform can be synthesized, which realizes widening the flat-top band bandwidth of each flat-top wavelength division multiplexing structure 110, so that it can cover the incident light respectively received by its two input ports. The frequency band range corresponding to the center wavelength plus the preset offset threshold.

By designing each flat-top wavelength division multiplexing structure as a form of digital filter, the flat-top bandwidth of each flat-top wavelength division multiplexing structure 110 can be widened so that it can tolerate the waveguide width , waveguide inclination angle, waveguide height and temperature changes caused by the center wavelength shift problem, and no need to set any feedback adjustment, not only improves the work efficiency, but also reduces the device loss.

FIG. 5 is a schematic diagram of using an arrayed waveguide grating structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application. As shown in Figure 5, in this embodiment, each of the flat-top wavelength division multiplexing structures is composed of an arrayed waveguide grating structure, and the arrayed waveguide grating structure (Array Waveguide Gratings, AWG) 130 includes a plurality of arrayed waveguides 131 (also referred to as a waveguide channel), the arrayed waveguide 131 adopts a linear waveguide structure. Exemplarily, the number of channels of the arrayed waveguide 131 is 6, of course, it can also be other numbers, which is not limited in this patent. Specifically, the arrayed waveguide grating structure 130 is fabricated on a silicon-on-insulator (Silicon On Insulator, SOI) material using an etching process. The SOI material includes a top layer of silicon, a buried oxide layer of silicon dioxide, and a substrate silicon. The thickness of the top layer of silicon is 220nm, the arrayed waveguide 131 and other structures can be formed on the top layer of silicon by etching, and the etching depth is, for example, 220nm. During operation, the two incident optical signals λ1 and λ3 are phase-modulated by multiple arrayed waveguides 131 in the arrayed waveguide grating structure 130 to synthesize a bundle of first-stage multiplexed optical signals (λ1/λ3). Similarly, the two incident optical signals λ2 and λ4 are synthesized into a first-stage multiplexed optical signal (λ2/λ4) after phase modulation by multiple arrayed waveguides 131 in the arrayed waveguide grating structure 130 . Using the arrayed waveguide grating structure 130 to form a flat-top wavelength division multiplexing structure can also widen the flat-top wavelength band bandwidth of the flat-top wavelength division multiplexing structure, so that it can cover the incident light respectively received by its two input ports. The frequency band range corresponding to the central wavelength plus the preset offset threshold, and compared to the flat-top wavelength division multiplexing structure composed of multiple cascaded Mach-Zehnder interferometer structures, the above-mentioned array grating structure 130 has It has the advantages of compact structure, small size, low insertion loss, narrow wavelength division multiplexing interval and low process difficulty.

FIG. 6 is a schematic diagram of using an etched diffraction grating structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application. As shown in FIG. 6, in this embodiment, each of the flat top wavelength division multiplexing structures is formed by an etched diffraction grating structure. Exemplarily, the etched diffraction grating structure 140 includes an input waveguide (141, 142) , an output waveguide 143, a Rowland circle 144, and a concave grating 145. The interior of the Rowland circle 144 is a free propagation area, and the reflective surface of the concave grating 145 is composed of multiple sub-curved surfaces (not shown in the figure), and the multiple sub-curved surfaces can realize the decomplexing of optical signals use. Wherein, both the input waveguide (141, 142) and the output waveguide 143 are arranged on the Rowland circle 144. When working, the two incident optical signals λ1 and λ3 generate two input mode spots after passing through the interior of the Rowland circle 144, and then the two input mode spots enter the free propagation area of the Rowland circle 144 and propagate, incident on the reflection of the concave grating 145 surface, after being reflected and focused by the concave grating 145, a bundle of first-stage multiplexed optical signals (λ1/λ3) is output from the output waveguide 143. Similarly, after the two incident optical signals λ2 and λ4 pass through the interior of the Rowland circle 144, two input mode spots are generated, and then the two input mode spots enter the free propagation area of the Rowland circle 144 to propagate, and are incident on the reflection of the concave grating 145 surface, after being reflected and focused by the concave grating 145, a bundle of first-stage multiplexed optical signals (λ2/λ4) is output from the output waveguide 143. The above-mentioned flat-top wavelength division multiplexing structure composed of the etched diffraction grating structure 140 can also widen the flat-top wavelength band bandwidth of the flat-top wavelength division multiplexing structure, so that it can cover the signals received by its two input ports respectively. The central wavelength of the incident light plus the frequency band corresponding to the preset offset threshold, and the above-mentioned etched diffraction grating structure 140 is relatively multiple In terms of structure, the requirements for processing accuracy are low, the overall integration is high, the size of the output waveguide is relatively small, and the overall size is more optimized.

FIG. 7 is a schematic diagram of a flat-top wavelength division multiplexing structure using a combined structure composed of a mode multiplexing device and a multimode Bragg grating in an embodiment of the present application. As shown in FIG. 7 , in this embodiment, each of the flat top wavelength division multiplexing structures 110 is composed of a combined structure of a mode multiplexing device 151 and a multimode Bragg grating 152, wherein the mode multiplexing device 151 For making the input light incident into the multimode Bragg grating 152, the mode multiplexing device 151 includes a first port, a second port and a third port, and the first port and the second port are respectively used for input or output For optical signals, the third port is connected to the output port of the multimode Bragg grating 152 . During operation, two incident optical signals λ1 and λ3 (both in TE0 mode, for example) are respectively input to the first port of the mode multiplexer 151 and to the input port of the multimode Bragg grating 152, for example, After the incident optical signal of wavelength λ3 (such as TE0 mode) passes through the multimode Bragg grating 152 and the mode multiplexer 151, the polarization state mode of the incident optical signal of wavelength λ3 (TE0) does not change in any way, directly It exits from the second port of the mode multiplexer 151; and the incident optical signal (for example, TE0 mode) of the wavelength of λ1 passes through the mode multiplexer 151 and is converted into the light of the TE1 mode or a higher order mode and is transmitted from the The third port of the mode multiplexer 151 is incident into the multimode Bragg grating 152, and is converted into the TE0 mode after being reflected by the multimode Bragg grating 152, and then the optical signal of the wavelength λ1 passes through the TE0 mode After the mode multiplexer 151 is output from the second port of the mode multiplexer 151, after the optical signal of the λ1 wavelength of the TE0 mode is combined with the optical signal of the λ3 wavelength of the TE0 mode, the output first-stage multiplexed signal (λ1/λ3), which is still linearly polarized light in TE0 mode. Similarly, two incident optical signals λ2 and λ4 (both in TE0 mode, for example) are respectively input to the first port of the mode multiplexer 151 and input to the input port of the multimode Bragg grating 152. Similarly, the After the incident optical signal of wavelength λ4 (for example, TE0 mode) passes through the multimode Bragg grating 152 and the mode multiplexer 151, the polarization state mode of the optical signal of wavelength λ4 (TE0) does not change in any way, directly from the The second port of the mode multiplexer 151 exits; and the incident optical signal (such as TE0 mode) of the λ2 wavelength passes through the mode multiplexer 151 and is converted into the TE1 mode or the light of a higher order mode is multiplexed from the mode The third port of the device 151 is incident into the multi-mode Bragg grating 152, and after being reflected by the multi-mode Bragg grating 152, it is transformed into a TE0 mode, and then the optical signal of wavelength λ2 is multiplexed in the TE0 mode through the mode After the mode multiplexer 151 is output from the second port of the mode multiplexer 151, after the optical signal of the λ2 wavelength of the TE0 mode is combined with the optical signal of the λ4 wavelength of the TE0 mode, the output first-stage multiplexed signal (λ2/λ4 ), which is still linearly polarized light in TE0 mode. The above-mentioned flat-top wavelength division multiplexing structure using a combined structure composed of a mode multiplexing device and a multimode Bragg grating can also widen the flat-top wavelength band bandwidth of the flat-top wavelength division multiplexing structure, so that it can cover two The frequency band range corresponding to the center wavelength of the incident light received by the input ports plus the preset offset threshold.

FIG. 8 is a schematic diagram of using an inverted Bragg grating directional coupler structure as a flat-top wavelength division multiplexing structure in an embodiment of the present application. As shown in FIG. 8, in this embodiment, each of the flat top wavelength division multiplexing structures 110 is composed of a reverse Bragg grating directional coupler structure, and the reverse Bragg grating directional coupler 160 includes a first reverse A Bragg grating directional coupling structure 161 and a second inverse Bragg grating directional coupling structure 162 . During operation, two incident light signals λ1 and λ3 (both in TE mode, for example) are respectively input from the forward port of the second reverse Bragg grating directional coupling structure 162 and the reverse port of the first reverse Bragg grating directional coupling structure 161, Since the λ3 wavelength optical signal is input from the reverse port of the first inverse Bragg grating directional coupling structure 161, the first inverse Bragg grating directional coupling structure 161 has no effect on the λ3 wavelength optical signal (TE), The λ3 wavelength optical signal is directly emitted from the forward port of the first reversed Bragg grating directional coupling structure 161; Port input, so the second reversed Bragg grating directional coupling structure 162 acts on the λ1 wavelength optical signal (TE), and the λ1 wavelength optical signal is input from the forward port of the second reversed Bragg grating directional coupling structure 162 Afterwards, it will run into the first reverse Bragg grating directional coupling structure 161 near the center position of the second reverse Bragg grating directional coupling structure 162, and from the first reverse Bragg grating directional coupling structure 161 output at the forward port, so that the two incident optical signals λ1(TE) and λ3(TE) have a certain optical path difference, and finally the optical signal λ3 output at the forward port of the first reversed Bragg grating directional coupling structure 161 (TE) and the optical signal λ1(TE) are converged and coupled to generate the first-stage multiplexed optical signal (λ1(TE)/λ3(TE)). Similarly, based on the above-mentioned same setting method, the optical signal λ4 (TE) input at the reverse port of the first reverse Bragg grating directional coupling structure 161 and the optical signal λ4 (TE) input at the second reverse Bragg grating directional coupling structure 162 The optical signal λ2(TE) input to the forward port finally generates the second-stage combined optical signal (λ2(TE)/λ4(TE )). The flat-top wavelength division multiplexing structure using the reverse Bragg grating directional coupler structure can also widen the flat-top wavelength band bandwidth of the flat-top wavelength division multiplexing structure, so that it can cover the signals received by its two input ports respectively. The center wavelength of the incident light plus the frequency band range corresponding to the preset offset threshold.

Optionally, in other embodiments of the present application, the at least two flat-top wavelength division multiplexing structures are composed of any combination of the following structures: multiple cascaded Mach-Zehnder interference structures, arrayed waveguide grating structures, Etched diffraction grating structure, combined structure of mode multiplexer and multimode Bragg grating, reversed Bragg grating directional coupler structure.

Fig. 9 is a simulated spectrum diagram of a flat-top wavelength division multiplexing structure composed of any combination of multiple cascaded Mach-Zehnder interference structures, arrayed waveguide grating structures, and etched diffraction grating structures in an embodiment of the present application. FIG. 10 is a spectrum diagram of light beams whose center wavelength is around 1291 nm in the spectrum diagram shown in FIG. 9 .

When the first-stage multiplexing module 100 is composed of any combination of the plurality of cascaded Mach-Zehnder interference structures, the arrayed waveguide grating structure and the etched diffraction grating structure, the final generated total The simulated spectrum diagram of FIG. 9 is shown in FIG. 9, wherein, a flat-top wavelength division multiplexing structure realizes channels (channels) whose center wavelengths are respectively 1271nm/1311nm wavelength (Wavelength) in TE (Transverse Electric mode, transverse electric mode) polarization mode Another flat-top wavelength division multiplexing structure uses TM (Transverse Magnetic mode, transverse magnetic mode) polarization mode to realize the sharing of channels with center wavelengths of 1291nm/1331nm wavelength (Wavelength). The finally generated second-stage multiplexing signal includes a first group of light wave components and a second group of light wave components, wherein the first group of light wave components and the second group of light wave components have different polarization states.

Exemplarily, in Fig. 10, the flat-top band bandwidth of the optical channel corresponding to the center wavelength of 1291nm is close to 34nm, therefore, even if the corresponding wavelength division multiplexing structure is affected by factors such as waveguide width, height, inclination angle and temperature change The light beam with a central wavelength of 1291nm is shifted to the long wavelength band (redshift) or to the short wavelength band (blue shift), which can also ensure that the light beam is in a flat region within the range of the central wavelength of 1291nm±6nm. That is to say, the first-stage multiplexed optical signal generated in the optical channel (channel) can tolerate the influence of factors such as waveguide width, height, inclination angle and temperature changes on the central wavelength shift, reducing the influence on the waveguide width, height or inclination angle. sensitivity.

Figure 11 is a set of light waves generated by using a flat-top wavelength division multiplexing structure composed of a combined structure composed of a mode multiplexer and a multimode Bragg grating, and an arbitrary combination of an inverted Bragg grating directional coupler structure in an embodiment of the present application The simulation spectrogram of the component, Fig. 12 is the flat top wavelength division multiplexing that adopts the combination structure that is formed by mode multiplexer and multimode Bragg grating, the arbitrary combination of reverse Bragg grating directional coupler structure in one embodiment of the present application A simulated spectrum plot of another set of light wave components generated by the structure.

In Figure 11, the bandwidth of the flat-top band of the beam path with a center wavelength of 1291nm is greater than 12nm, which can ensure that the center wavelength is 1291nm ± 6nm in the flat area, and the bandwidth of the flat-top band of the beam path with a center wavelength of 1331nm It is also greater than 12nm, which can ensure that the center wavelength is in the range of 1331nm±6nm to be a flat region. In Fig. 12, the bandwidth of the flat-top band of the beam path with a central wavelength of 1271nm is greater than 12nm, which can ensure a flat area within the range of the central wavelength of 1271nm±6nm, and the bandwidth of the flat-top band of the beam path with a central wavelength of 1311nm is greater than 12nm, which can ensure that the center wavelength is 1311nm ± 6nm in the range of flat areas. Therefore, even if the corresponding flat-top WDM structure is affected by factors such as waveguide width, height, inclination, and temperature changes, the central wavelength band shifts to the long band (red shift) or shifts to the short band (blue shift) ), and it can also ensure that they are flat regions within the range of the central wavelength ±6nm. That is to say, the first-stage multiplexed optical signal generated in the optical channel can tolerate the influence of factors such as waveguide width, height, inclination angle and temperature changes on the central wavelength shift, reducing the impact of the flat-top wavelength division multiplexing structure on the waveguide width, Altitude or inclination sensitivity.

FIG. 13 is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided in another embodiment of the present application,

FIG. 14 is a schematic structural diagram of a polarization rotator (PR) in the on-chip integrated wavelength division multiplexer shown in FIG. 13;

FIG. 15 is a schematic structural diagram of a polarization beam combiner (PBC) in the on-chip integrated wavelength division multiplexer shown in FIG. 13 .

As shown in Figure 13, different from the preceding embodiments, in this embodiment, the second-level multiplexing module in the on-chip integrated wavelength division multiplexer 2000 is a polarization beam combiner (Polarization Beam Combiner, PBC) 230, The on-chip integrated wavelength division multiplexer 2000 also includes a polarization rotator (polarizationrotator, PR) 220, the input port of the polarization rotator 220 is optically coupled to an output port of the first multiplexing module 100, to receive the The light output from the output port, the output port of the polarization rotator 220 is optically coupled to an input port of the polarization beam combiner 230 to output light to the polarization beam combiner 230, wherein the polarization beam combiner 230 is used to combine two received light beams with different polarization states into one light beam, and the polarization rotator 220 is used to change the polarization state of the received light beams.

Exemplarily, the first-stage multiplexing module 100 has a plurality of input ports and two output ports; the polarization beam combiner 230 includes two input ports and one output port; the first-stage multiplexing module 100 The two output ports of the polarization beam combiner 230 are respectively connected to the two input ports; the multi-path incident optical signals (λ1, λ2, λ3, λ4 (the wavelengths are arranged from small to large)) with the same polarization state are respectively sent to the A plurality of input ports of the first-stage multiplexing module 100 are input, and after the multiplexing of the first-stage multiplexing module 100, the two output ports of the first-stage multiplexing module 100 output two first-stage Among the multiplexed optical signals, one path is directly optically coupled to an input port of the polarization beam combiner 230, so as to input the first-stage multiplexed optical signal to an input port of the polarization beam combiner 230; The polarization rotator 220 is optically coupled to the other input port of the polarization beam combiner 230, so as to optically couple the light beam after the polarization state of the first-stage multiplexed optical signal is rotated by 90° by the polarization rotator 220 to the other input port of the polarization beam combiner 230, and finally through the polarization beam combiner 230, a second-stage combined optical signal with two polarization states perpendicular to each other is output, wherein the second-stage combined optical signal A first set of lightwave components and a second set of lightwave components are included, the first set of lightwave components and the second set of lightwave components have different polarization states.

Optionally, the polarization rotator (PR) 220 and the polarization beam combiner (PBC) 230 may also be silicon-based polarization rotators (PR) and silicon-based polarization beam combiners (PBC).

As shown in FIG. 14 , in this embodiment, the polarization rotator 220 is used to change the original polarization state of the received light beam to a polarization state perpendicular to the original polarization state. The polarization rotator (PR) 220 includes a ridge waveguide 221 and a part of the planar waveguide 222 on one side of the ridge waveguide 221 . Wherein, the ridge waveguide 221 includes a first wedge structure 221a, a linear structure 221b and a second wedge structure 221c connected in sequence. The first wedge-shaped structure 221a is used as the input end of the polarization rotator 220, and its width gradually narrows along the optical path until it is flush with and connected to the linear structure 221b; the width of the second wedge-shaped structure 221c gradually widens along the optical path until it is in line with the external light waveguide connection. Part of the planar waveguide 222 has a height lower than that of the ridge waveguide 221 and includes a third wedge structure 222 a and a fourth wedge structure 222 b located on the same side of the ridge waveguide 221 and connected to each other. The third wedge-shaped structure 222a is close to the side of the first wedge-shaped structure 221a, the fourth wedge-shaped structure 222b is close to the side of the linear structure 221b, the tip of the third wedge-shaped structure 222a is close to the side of the wider end of the first wedge-shaped structure 221a, the fourth wedge-shaped structure The tip of the second wedge-shaped structure 221c is adjacent to the narrower end of the second wedge-shaped structure 221c. Linearly polarized light is incident from the wider end of the first wedge-shaped structure 221a of the ridge waveguide 221, and in the section of the first wedge-shaped structure 221a and the linear structure 221b, the light mode is distributed into the ridge waveguide 221 and the planar waveguide 222, so that its polarization state is rotated , the polarization state has been rotated by 90 degrees when incident on the second wedge-shaped structure 221c, and then coupled into the external optical waveguide through the second wedge-shaped structure 221c. In other embodiments, the polarization rotator-beam combiner (PSR) shown in Figure 3 can also be used as the polarization rotator. The linearly polarized light is incident from the cross port, coupled to the straight-through waveguide through the cross waveguide, and finally output through the mode conversion structure The polarization state of linearly polarized light is rotated by 90 degrees.

As shown in FIG. 15 , in this embodiment, the polarization beam combiner 230 is composed of three identical mode conversion couplers, and each mode conversion coupler includes a single-mode access waveguide and a multi-mode bus waveguide. Wherein, the first mode conversion coupler 231 and the second mode conversion coupler 232 are connected in parallel and located at the input end of the polarization beam combiner 230 . The single-mode access waveguide 231a of the above-mentioned first mode conversion coupler 231 and the single-mode access waveguide 232a of the second mode conversion coupler 232 are respectively connected to the output end of the polarization rotator 220 and a flat-top wavelength division multiplexing structure 110. output. The third mode conversion coupler 233 cascades the above two mode conversion couplers 231, 232, and the multimode bus waveguide 233b of the third mode conversion coupler 233 is connected to the output end of the multimode bus waveguide 231b of the first mode conversion coupler 231 , the single-mode access waveguide 233a of the third mode conversion coupler 233 is connected to the output end of the single-mode access waveguide 232a of the second mode conversion coupler 232 . In this embodiment, the polarization beam combiner 230 composed of three mode conversion couplers combined with the polarization rotator 220 is used to pair the two first channels with the same linear polarization state output by the two flat top wavelength division multiplexing structures 110. Polarized beam combining is performed on the multiplexed optical signals to reduce crosstalk. Moreover, since the mode conversion coupler has the characteristics of low loss and large bandwidth, the optical loss is further reduced, and the optical bandwidth of the device is improved.

Fig. 16 is a schematic structural diagram of an on-chip integrated wavelength division multiplexer provided by another embodiment of the present application. As shown in Fig. 16, different from the foregoing embodiments, the second-stage multiplexing module 200 in this embodiment is Polarization beam combiner (Polarization Beam Combiner, PBC) 230, described on-chip integrated wavelength division multiplexer 3000 also includes at least one polarization rotator (polarization rotator, PR) 220, for each described polarization rotator 220, its input The port is used to receive one of the incident light, and its output port is optically coupled with the input port of one of the at least two flat-topped wavelength division multiplexing structures 110, so as to output light to the flat-topped wavelength division multiplexing structure 110, Wherein, the polarization beam combiner 230 is used to combine two received light beams with different polarization states into one light beam, and the polarization rotator 220 is used to change the polarization state of the received light beams, and the The light whose polarization state is changed by at least one polarization rotator 220 is only output from one output port of the first-stage multiplexing module 100 .

Exemplarily, in this embodiment, the first-stage multiplexing module 100 has multiple input ports and two output ports; the polarization beam combiner 230 includes two input ports and one output port; the flat The two output ports of the top broadband wavelength division multiplexing combination structure 100 are respectively connected to the two input ports of the polarization beam combiner 230; for each of the polarization rotators 220, its output port is used to receive one incident light, For changing the polarization state of the received light beam, at least two incident optical signals are respectively optically coupled to the input port of one of the flat-top wavelength division multiplexing structures 110 through the corresponding polarization rotator 220, through the The polarization rotator 220 rotates the polarization states of the at least two incident optical signals by 90° and then couples them to an input port of the on-chip integrated wavelength division multiplexer 110 of the flat top broadband, and then the flat top wavelength division The output port of the multiplexing structure 110 outputs the first-stage multiplexed optical signal after multiplexing; at least two incident optical signals are directly incident on an input port of the flat-topped wavelength division multiplexing structure 110, and then the flat-topped wave The output port of the division multiplexing structure 110 outputs the first-stage multiplexed optical signal after multiplexing, because the polarization modes of the two first-stage multiplexed optical signals output by the two output ports of the first-stage multiplexing module 100 are different , so after being combined by the polarization beam combiner 230, a combined optical signal with two mutually perpendicular polarization states (second-stage combined optical signal) is output.

The present application also proposes a chip, which includes the on-chip integrated wavelength division multiplexer described in any one of the foregoing embodiments.

In the on-chip integrated wavelength division multiplexer and chip provided by the embodiment of the present application, the bandwidth of each flat-top wavelength division multiplexing structure in the first-level multiplexing module can cover the bandwidth received by its two input ports respectively. The central wavelength of the incident light plus the frequency band corresponding to the preset offset threshold, so that each flat-top wavelength division multiplexing structure can transmit two beams with a large difference in central wavelength, thereby overcoming the problems caused by various factors. The problem of crosstalk between adjacent channels caused by the central wavelength shift; and the first-level multiplexing module and the second-level multiplexing module do not need any feedback adjustment during the working process, which improves the work efficiency, reduces device loss, and has It is beneficial to reduce the sensitivity of the on-chip integrated wavelength division multiplexer to changes in waveguide width, waveguide height, waveguide inclination angle and surrounding environment temperature.

In the foregoing embodiments, the descriptions of each embodiment have their own emphases, and for parts not described in detail in a certain embodiment, reference may be made to relevant descriptions of other embodiments.

The on-chip integrated wavelength division multiplexer and the chip provided by the application have been described in detail above in conjunction with the embodiments. In this paper, specific examples have been used to illustrate the principles and implementation methods of the application. The descriptions of the above embodiments are only used to help Understand the technical solution and its core idea of the present application; those skilled in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or The replacement does not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.

Claims (15)

1. a kind of on-chip integrated wavelength division multiplexer, it is characterized in that, described wavelength division multiplexer comprises first-level multiplexing module and second-level multiplexing module, and described first-level multiplexing module has a plurality of input port and two output ports, the second-level multiplexing module has two input ports and one output port, and the two output ports of the first-level multiplexing module are respectively connected to the second-level multiplexing module The corresponding input port is optically coupled; The first-stage multiplexing module includes at least two flat-topped wavelength division multiplexing structures, each of which has two input ports and one output port, wherein each of the flat-topped wavelength division multiplexing structures has two input ports and one output port. The bandwidth of the division multiplexing structure covers the frequency band range corresponding to the center wavelength of the incident light respectively received by its two input ports plus a preset offset threshold. 2. The on-chip integrated wavelength division multiplexer according to claim 1, wherein the first stage multiplexing module multiplexes the incident light with the same polarization state received by the multiple input ports to Generate two first-stage multiplexed optical signals, and input the two first-stage multiplexed optical signals to corresponding input ports of the second-stage multiplexing module, and the second-stage multiplexed module sends the two The two first-stage multiplexed optical signals received at the input port are multiplexed to generate a second-stage multiplexed optical signal, wherein the second-stage multiplexed optical signal includes a first group of light wave components and a second group of light wave components, The first group of light wave components and the second group of light wave components have different polarization states; the second stage multiplexing module performs polarization multiplexing on the first group of light wave components and the second group of light wave components. 3. on-chip integrated wavelength division multiplexer according to claim 2, is characterized in that, When inputting λ1, λ2, λ3...λn wavelength-divided optical signals with predetermined wavelength intervals into the multiple input ports of the first-stage multiplexing module, where n≥4, and n is an even number , the λ1, λ2, λ3... and n are arranged in sequence according to the order of wavelength; Input the incident optical signal of the odd channel from the input port of one of the at least two flat top wavelength division multiplexing structures, and input the even channel from the input port of the other of the at least two flat top wavelength division multiplexing structures incident light signal. 4. on-chip integrated wavelength division multiplexer according to claim 3, is characterized in that, the difference between the central wavelength of the incident light that two input ports of each described flat top wavelength division multiplexing structure receives greater than the preset wavelength difference threshold. 5. The on-chip integrated wavelength division multiplexer according to claim 1, wherein said at least two flat-top wavelength division multiplexing structures are formed by any combination of the following structures: a plurality of cascaded Mach-Zehnder An interference structure, an arrayed waveguide grating structure, an etched diffraction grating structure, a combined structure composed of a mode multiplexer and a multimode Bragg grating, and a reverse Bragg grating directional coupler structure. 6. The on-chip integrated wavelength division multiplexer according to claim 1, characterized in that the on-chip integrated wavelength division multiplexer is a silicon-based wavelength division multiplexer. 7. on-chip integrated wavelength division multiplexer according to claim 1, is characterized in that, described wavelength division multiplexer also comprises coupling structure, and described coupling structure is connected with the output port of described second stage multiplexing module , for coupling the second-stage multiplexed optical signal output from the output port of the second-stage multiplexing module with an external optical fiber array, so as to output the multiplexed optical signal. 8. The on-chip integrated wavelength division multiplexer according to any one of claims 1-7, wherein the second-level multiplexing module is a polarization rotating beam splitter, and the polarization rotating beam splitter will The received two paths of first-level multiplexed optical signals are multiplexed into the first group of light wave components and the second group of light wave components with mutually perpendicular polarization states. 9. The on-chip integrated wavelength division multiplexer according to claim 8, wherein the polarization rotating beam splitter comprises a straight-through waveguide and a cross waveguide, a through-port and a cross-port connecting the straight-through waveguide and the cross waveguide respectively , and a mode conversion structure connected to the straight-through waveguide; the straight-through waveguide and the cross waveguide form a mode multiplexing structure; the through-port and the cross-port both include a strip waveguide-to-ridge waveguide wedge-shaped structure; the mode conversion structure A mode-transformation structure for a double-layered wedge. 10. The on-chip integrated wavelength division multiplexer according to any one of claims 1-7, wherein the second-level multiplexing module is a polarization beam combiner, and the wavelength division multiplexer also includes A polarization rotator, the input port of the polarization rotator is optically coupled to an output port of the first multiplexing module to receive the light output from the output port, and the output port of the polarization rotator is combined with the polarization One input port of the device is optically coupled to output light to the polarization beam combiner, wherein the polarization beam combiner is used to combine two received beams with different polarization states into one beam, and the polarization rotation The polarization rotator is used to change the polarization state of the received light beam; wherein, the polarization rotator changes the original polarization state of the received light beam to a polarization state perpendicular to the original polarization state. 11. The on-chip integrated wavelength division multiplexer according to any one of claims 1-7, wherein the second-level multiplexing module is a polarization beam combiner, and the wavelength division multiplexer also includes At least one polarization rotator, for each of the polarization rotators, its input port is used to receive one of the incident light, and its output port is connected to the input port light of one of the at least two flat top wavelength division multiplexing structures Coupling to output light to the flat-top wavelength division multiplexing structure, wherein the polarization beam combiner is used to combine two received beams with different polarization states into one beam, and the polarization rotator is used to change the received beam The polarization state of the received light beam, and the light whose polarization state is changed by the at least one polarization rotator is only output by one output port of the first-stage multiplexing module; wherein, each of the polarization rotators will receive the The original polarization state of the light beam is changed to a polarization state perpendicular to said original polarization state. 12. The on-chip integrated wavelength division multiplexer according to any one of claims 1-7, wherein each said flat top wavelength division multiplexing structure comprises at least two 1dB flat tops, wherein each The 1dB flat top is the wavelength range corresponding to the light attenuation range of 1dB, and the wavelength range corresponding to each 1dB flat top is greater than 20 nanometers. 13. The on-chip integrated wavelength division multiplexer according to claim 12, characterized in that the interval between two adjacent 1 dB flat tops of the same flat top wavelength division multiplexing structure is less than 5 nanometers. 14. The on-chip integrated wavelength division multiplexer according to claim 12 is characterized in that, in the at least two flat-top wavelength division multiplexing structures, the 1dB flat-top in the flat-top wavelength division multiplexing structure of one of them The corresponding wavelength range partially overlaps with the wavelength range corresponding to the 1dB flat top in the other flat top wavelength division multiplexing structure. 15. A chip, characterized by comprising the on-chip integrated wavelength division multiplexer according to any one of claims 1-12.

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