阅读说明：本技术 一种基于硅基波导光栅可调谐波分复用系统的无中断调控方法 (uninterrupted regulation and control method based on silicon-based waveguide grating tunable wavelength division multiplexing system ) 是由 余辉 王肖飞 江晓清 杨建义 于 2019-10-09 设计创作，主要内容包括：本发明公开了一种基于硅基波导光栅可调谐波分复用系统的无中断调控方法。该系统基于硅基波导光栅实现,包括多级可调谐滤波器级联,每一级可调谐滤波器由两级相同的布拉格光栅滤波器级联构成,相邻两级可调谐滤波器之间通过单模波导连接,在每级可调谐滤波器中第一级布拉格光栅滤波器、第二级布拉格光栅滤波器及第二弯曲波导上均分别覆盖有金属电极；通过调控金属电极的电压既可以调控每级可调谐滤波器的下载通道的通断。本发明的调控方法当调节任意一级滤波器的工作波长时对其他级滤波器不产生影响,可以实现无中断调控。且本发明采用平面集成光波导工艺制作,一次刻蚀完成,易制作,成本低,损耗小,性能好。(The invention discloses a uninterrupted regulation and control method based on a silicon-based waveguide grating tunable wavelength division multiplexing system, which is realized based on a silicon-based waveguide grating and comprises a multistage tunable filter cascade, wherein each -stage tunable filter is formed by cascading two identical Bragg grating filters, the adjacent two stages of tunable filters are connected through a single-mode waveguide, the -stage Bragg grating filter, the second-stage Bragg grating filter and the second curved waveguide in each stage of tunable filter are respectively covered with a metal electrode, and the on-off of a download channel of each stage of tunable filter can be regulated and controlled by regulating and controlling the voltage of the metal electrode.)

1, an uninterrupted regulation and control method based on a silica-based waveguide grating tunable wavelength division multiplexing system, which is characterized in that the tunable wavelength division multiplexing system is realized based on silica-based waveguide grating, and comprises a multistage tunable filter cascade, each -stage tunable filter is formed by cascading two stages of same Bragg grating filters, a download end of a -stage Bragg grating filter is connected with an input end of a second-stage Bragg grating filter through a -th curved waveguide, an add end of a -stage Bragg grating filter is connected with a straight-through end of the second-stage Bragg grating filter through a second curved waveguide, the download end of the second-stage Bragg grating filter is used as a download channel of the tunable filter, the straight-through end of a -stage Bragg grating filter in a front -stage tunable filter is connected with an input end of a -stage Bragg grating filter in a -stage tunable filter through a single-mode waveguide, and metal electrodes are respectively covered on a -stage Bragg grating filter, the second-stage Bragg grating filter and;

the uninterrupted regulation and control method is characterized in that the central wavelength of the two-stage Bragg grating filter is regulated and controlled by regulating and controlling the voltage of the metal electrodes on the th Bragg grating filter and the second Bragg grating filter in the -stage tunable filter, so that the difference of the central wavelengths of the two-stage Bragg grating filters is larger than the bandwidth of the Bragg grating filter, the downloading channel of the two-stage tunable filter is closed without influencing other cascaded tunable filters, then the voltage of the metal electrodes on the th Bragg grating filter and the second Bragg grating filter is regulated and controlled to enable the central wavelengths of the two-stage Bragg grating filters to be the same, the corresponding downloading channel returns to normal work, and uninterrupted regulation and control is.

2. The hitless tuning and control method based on a silica-based waveguide grating tunable wavelength division multiplexing system of claim 1, wherein: the Bragg grating filter adopts a grating auxiliary filter or a multimode waveguide grating filter.

3, tunable WDM system with hitless tuning, characterized in that the system structure of claim 1 is used.

Technical Field

The invention relates to uninterrupted regulation and control methods for a tunable wavelength division multiplexing system, mainly relates to a silica-based waveguide grating filter, and particularly relates to uninterrupted regulation and control methods for a tunable wavelength division multiplexing system based on silica-based waveguide grating.

Background

In recent years, with the rapid development of integrated photonics, silicon-based integrated photonic devices have become important research directions, in the field of silicon-based integrated photonic devices, silicon-based waveguide grating devices are receiving more and more attention, and a great deal of results are obtained for the research on the aspects of the theory, formation mechanism, manufacturing method, application and the like of silicon-based waveguide gratings, and the silicon-based waveguide grating devices have the application field of breadth by combining the characteristics of simple structure, easy integration, compatibility of the manufacturing process and the existing mature CMOS (complementary metal oxide semiconductor) process and the like.

Based on the advantages of large refractive index difference, low loss, low cost, compatible manufacturing process with CMOS process and the like of silicon materials, the current exploration of an uninterrupted tunable wavelength division multiplexing system also obtains -defined results, for example, the tunable wavelength division multiplexing system based on a micro-ring structure guarantees the stability of adjacent channels through the thermo-optic effect of the micro-ring, although the uninterrupted of each channel can be realized, the micro-ring filter has the limitation of FSR, which results in the limitation of bandwidth tuning range, and the micro-ring can cause the phase change in the adjusting process, so that the tunable wavelength division multiplexing system has many limitations in practical application.

Disclosure of Invention

The invention aims to provide uninterrupted regulation and control methods based on a silicon-based waveguide grating tunable wavelength division multiplexing system, which have the advantages of simple structure, simple process, small insertion loss and no interruption of each channel signal, and the silicon-based waveguide grating-based wavelength division multiplexing system has no limitation of FSR (frequency selective response), large tuning range, box-shaped filter spectral lines which can improve the utilization rate of frequency spectrum, can regulate the phase change of signals through an annular structure, and does not influence the phase of the signals when regulating each -level filter, so the uninterrupted regulation and control method provided for the silicon-based waveguide grating tunable wavelength division multiplexing system has great research significance.

In order to achieve the purpose of the invention, the invention adopts the technical scheme that:

an uninterrupted regulation and control method based on a silica-based waveguide grating tunable wavelength division multiplexing system, wherein the tunable wavelength division multiplexing system is realized based on silica-based waveguide gratings and comprises a multistage tunable filter cascade, each -stage tunable filter is formed by cascading two identical bragg grating filters, the download end of the -stage bragg grating filter is connected with the input end of the second-stage bragg grating filter through a -th curved waveguide, the add end of the -stage bragg grating filter is connected with the through end of the second-stage bragg grating filter through a second curved waveguide, the download end of the second-stage bragg grating filter is used as a download channel of the tunable filter, the through end of the -stage bragg grating filter in the front -stage tunable filter is connected with the input end of the -stage bragg grating filter in the -stage tunable filter through a single-mode waveguide, and metal electrodes are respectively covered on the -stage bragg grating filter, the second-stage bragg grating filter and the second curved waveguide;

the uninterrupted regulation and control method is characterized in that the central wavelength of the two-stage Bragg grating filter is regulated and controlled by regulating and controlling the voltage of the metal electrodes on the th Bragg grating filter and the second Bragg grating filter in the -stage tunable filter, so that the difference of the central wavelengths of the two-stage Bragg grating filters is larger than the bandwidth of the Bragg grating filter, the downloading channel of the two-stage tunable filter is closed without influencing other cascaded tunable filters, then the voltage of the metal electrodes on the th Bragg grating filter and the second Bragg grating filter is regulated and controlled to enable the central wavelengths of the two-stage Bragg grating filters to be the same, the corresponding downloading channel returns to normal work, and uninterrupted regulation and control is.

The Bragg grating filter adopts a grating auxiliary filter or a multimode waveguide grating filter.

According to the technical scheme, a metal electrode covered on a bent waveguide is used for achieving the purpose of adjusting the signal phase, for each -level tunable filter, the voltage of the metal electrode on a -level Bragg grating filter in the filter is fixed, the voltage of the metal electrode on another -level Bragg grating filter is increased, the central wavelength of the Bragg grating filter can be moved due to the thermal effect of silicon materials, when the central wavelength difference corresponding to the two-level Bragg grating filter is larger than the bandwidth of the single-level Bragg grating filter, the corresponding channel of the filter in the whole wavelength division multiplexing system can be closed, the central wavelength of the filter can be moved to the same position by respectively adjusting the voltage of the two-level Bragg grating filter, namely the working wavelength of any -level tunable filter can be adjusted without influence on other-level tunable filters, and uninterrupted adjustment can be achieved.

The invention has the beneficial effects that:

1) the Bragg grating filter is adopted for separating the grating reflection signals, so that the tolerance is large, and the insertion loss is small;

2) the invention is based on the silica-based waveguide grating filter, has large tolerance, and the bandwidth adjusting range is not limited by FSR, thus realizing the filter which can meet different bandwidth requirements;

3) the invention adopts a cascade mode of two-stage Bragg grating filters, and covers a metal electrode on the Bragg grating filters, and the position of the central wavelength of each channel can be adjusted by applying different voltages to the metal electrode;

4) the cascade mode between the two stages of Bragg grating filters is realized by the curved waveguide, and sections of the curved waveguide are covered with metal electrodes for realizing the phase adjustment of signals;

5) the invention can realize the uninterrupted regulation and control in the multi-channel wavelength division multiplexing system, and the normal use of other channels is not influenced in the regulation and control process of the channel, thereby greatly improving the flexibility of the wavelength division multiplexing system.

6) The manufacturing process of the invention is compatible with the traditional CMOS process, is finished by times of etching, and has the advantages of low cost, good performance, small loss, simple structure, easy manufacture and large-scale production potential.

Drawings

Fig. 1 is a schematic diagram of the whole structure of the tunable wavelength division multiplexing system based on the silica-based waveguide grating.

Fig. 2 is a schematic diagram of the structure of a tunable filter of every stages.

FIG. 3 is a schematic diagram of a system of the present invention employing a multimode waveguide grating filter;

fig. 4 is a schematic diagram of the structure of a bragg grating filter (grating assist type).

FIG. 5 is a schematic of the uninterrupted conditioning process of the present invention.

In the figure, 1, an input single-mode waveguide, 2, a Bragg grating filter, 3, a metal electrode, 4, a single-mode connection waveguide, 5, an output single-mode waveguide, 6, an th curved waveguide, 7, a third curved waveguide, 8, a single-mode output waveguide, 9, a second curved waveguide, 10, a metal electrode, 11, an input end, 12, a th-level single-mode waveguide grating, 13, a through end, 14, a download end, 15, a second-level single-mode waveguide grating, 16 and an add end.

Detailed Description

The invention is further described with reference to the drawings.

As shown in fig. 1 and 2, the wavelength division multiplexer of the present invention is implemented based on a silica-based waveguide grating, and includes a cascade of multiple tunable filters, each -level tunable filter is formed by cascading bragg grating filters with the same two levels, the bragg grating filters may be grating-assisted filters or multimode waveguide grating filters, for example, the grating-assisted filters are used in the examples of fig. 1 and 2, and the multimode waveguide grating filters are used in the example of fig. 3.

Each -level tunable filter comprises two Bragg grating filters (grating auxiliary filters) with completely same structures, a -th curved waveguide 6, a second curved waveguide 9 and a third curved waveguide 7, each -level grating auxiliary filter comprises an input end 11, a -th monomode waveguide grating 12, a through end 13, a download end 14, a second monomode waveguide grating 15 and an add end 16, an input signal in each -level grating auxiliary filter is coupled to the second monomode waveguide grating 15 through the input end and the -th monomode waveguide grating 12 and is output from the download end 14, an input monomode waveguide 1 is connected to the input end of an -level grating auxiliary filter in a -level tunable filter 634-level tunable filter, the input monomode waveguide 1 is used for inputting a signal, finally, the through end of an -level grating auxiliary filter in an -level tunable filter is connected to an output monomode waveguide 5, a download end of a -level Bragg grating filter in each level tunable filter is connected to the input end of the second-level Bragg grating filter through a -curved waveguide grating auxiliary filter, a second-level Bragg grating filter -level tunable filter is connected to the input end of the second monomode waveguide grating filter through a curved waveguide grating filter, the second curved waveguide grating filter, the download end of the second monomode grating auxiliary filter is connected to the second monomode waveguide grating filter, the second monomode waveguide grating filter is connected to the input end of the second tunable filter, the second curved waveguide grating filter, the second tunable filter is connected to the second monomode waveguide grating auxiliary grating filter, the second curved waveguide grating filter, the;

the working principle of the invention is as follows:

the center wavelength of each -stage filter is in ranges, and the center wavelength can be adjusted in ranges by adjusting the voltage of the metal electrode.

The grating auxiliary filter comprises two single-mode waveguide gratings (TE)₀The signal enters th single-mode waveguide grating to satisfy phase matching condition (n)₀₁+n₀₂) The wavelength of/2 ═ lambda/lambda will be back-coupled to TE₀And the signal is output from the second single-mode waveguide grating. In the formula n₀₁Is th single-mode waveguide grating TE₀Mode effective index, n₀₂For the second single-mode waveguide grating TE₀The mode effective refractive index, λ is the resonant wavelength, and Λ is the grating tooth period.

When the voltages of the metal electrodes on the two-stage grating auxiliary type filters are different, the two-stage grating auxiliary type filters work at different resonant wavelength positions, when the difference of the central wavelengths of the two-stage grating auxiliary type filters is larger than the bandwidth, the transmission spectral lines of the two-stage grating auxiliary type filters do not overlap, signals downloaded from the th-stage grating auxiliary type filter do not couple when passing through the second-stage grating auxiliary type filter, the signals are directly input to the add end of the th-stage grating auxiliary type filter through the through end of the second-stage grating auxiliary type filter, and the signals are output from the through end of the th-stage grating auxiliary type filter through the coupling action of the th-stage grating auxiliary type filter.

The filters of different stages according to the present invention work at different central wavelengths, as shown in fig. 5state1, 2, and 3, the central wavelengths of the download channels of the two-stage tunable filter of fig. 5 are located at the wavelength λ respectively₁、λ₂When the central wavelength position of the th-order tunable filter needs to be adjusted, firstly, the voltage of the th-order grating auxiliary filter 17 in the order of tunable filter is fixed, then the applied voltage of the -order grating auxiliary filter 18 is increased (or decreased), and after the voltage is applied to the metal electrode according to joule's law, heat energy is generated, and further the temperature is increased, and through the thermo-optical effect of silicon, the refractive index of the silicon material is related to the temperature, and in the temperature range of 300-:

the thermo-optic coefficient of the silicon material measured at room temperature (300K) is 1.8 multiplied by 10^-4。

The thermo-optic effect of silicon causes the refractive index of silicon to change such that its center wavelength (in terms of (n)₀₁+n₀₂) λ/Λ,/2 ═ n₀₁、n₀₂Changes occur and Λ remains the same only in relation to the structure), the wavelength changes), when the difference of the center wavelengths of the two-stage grating auxiliary filter in the th-stage tunable filter is larger than the bandwidth of the single-stage grating auxiliary filter, the down-loading end of the stage tunable filter is in the off state, the stage filter is turned off, as shown in fig. 5state 2, the bandwidth of the filter is determined by the structure of the grating:

where L is the total length of the bragg grating, k is the grating coupling coefficient, Λ is the grating tooth period, and λ is the center wavelength (note that -like wavelength variation is small relative to the magnitude of the wavelength, such as a wavelength variation of ten nanometers or twenty nanometers is already large, but the wavelength value is around 1550 nanometers, so the wavelength variation is small compared to the wavelength value itself, and the effect of the variation on the bandwidth is substantially negligible, i.e. the bandwidth of the filter is determined only by the structure)

In order to adjust the center wavelength of the tunable filter, the voltage applied to the th grating auxiliary filter 17 is correspondingly increased (or decreased) to be the same as the voltage applied to the second grating auxiliary coupler 18, so that the spectral lines of the two grating auxiliary couplers are completely overlapped, as shown in fig. 5state 3₁And λ₂And λ₂And λ₃The wavelength difference of the single-stage grating auxiliary filter is larger than the bandwidth of the single-stage grating auxiliary filter, so that the uninterrupted adjustment of the channel is realized.

The wavelength division multiplexing system is realized based on silicon-based waveguide grating, and the process flow can adopt standard insulating layersSilicon On Insulator (SOI) material, wherein the SOI material is composed of substrate Si and substrate SiO₂And top silicon with thickness of 220nm, substrate SiO₂May be 2 μm. After the surface of the SOI wafer is cleaned, the silicon oxide is deposited by adopting a Plasma Enhanced Chemical Vapor Deposition (PECVD) method as a mask in the photoetching part, and a required 220nm waveguide pattern is formed by utilizing deep ultraviolet exposure. And etching the top layer silicon by adopting ion beam assisted free radical etching (ICP) dry etching. A protective layer of silicon dioxide of about 2 μm is then deposited over the waveguide layer. The width of the single-mode waveguide of the grating auxiliary filter is 600nm and 400nm respectively, the size of the grating teeth determines the position of the central wavelength, for example, the size of the grating teeth is 40nm and 20nm, the grating period is 312nm, and the duty ratio is 0.5.