阅读说明：本技术 一种双y分支光波导相位调制器 (double-Y-branch optical waveguide phase modulator ) 是由 田自君 杨千泽 闫应星 徐鎏婧 于 2020-12-15 设计创作，主要内容包括：本发明公开了一种双Y分支光波导相位调制器,包括依次连接的光源、相位调制器芯片和光纤环,所述相位调制器芯片还依次连接有光电探测器和信号处理电路,所述相位调制器芯片包括衬底以及制作在该衬底上的第一Y分支光波导、第二Y分支光波导和基波导,所述第一Y分支光波导的输出端与所述基波导的一端连接,所述基波导的另一端与所述第二Y分支光波导的输入端连接；所述第一Y分支光波导的输出端相对于所述第二Y分支光波导的输入端在垂直于光信号传播的方向上偏移取值范围为100μm～4000μm的距离d,以使得在第一Y分支光波导合束点产生的辐射模从相位调制器芯片的端面辐射出去,以此来消除辐射模在光路中耦合形成的串扰和噪声问题。(The invention discloses a double-Y-branch optical waveguide phase modulator, which comprises a light source, a phase modulator chip and an optical fiber ring which are sequentially connected, wherein the phase modulator chip is also sequentially connected with a photoelectric detector and a signal processing circuit; the output end of the first Y-branch optical waveguide is shifted by a distance d with a value range of 100-4000 micrometers in a direction perpendicular to the propagation direction of the optical signal relative to the input end of the second Y-branch optical waveguide, so that a radiation mode generated at a beam junction point of the first Y-branch optical waveguide is radiated from the end face of the phase modulator chip, and the problems of crosstalk and noise caused by coupling of the radiation mode in an optical path are solved.)

1. A dual Y-branch optical waveguide phase modulator, characterized by: the phase modulator chip comprises a substrate, and a first Y-branch optical waveguide, a base waveguide and a second Y-branch optical waveguide which are manufactured on the substrate, wherein the first Y-branch optical waveguide is provided with a first input end, a second input end and an output end, the second Y-branch optical waveguide is provided with an input end, a first output end and a second output end, the output end of the first Y-branch optical waveguide is connected with one end of the base waveguide, the other end of the base waveguide is connected with the input end of the second Y-branch optical waveguide, the first Y-branch optical waveguide is used for receiving optical signals, and the base waveguide is used for transmitting the optical signals received by the first Y-branch optical waveguide to the second Y-branch optical waveguide, the second Y-branch optical waveguide is used for splitting an optical signal transmitted by the fundamental waveguide and transmitting the split optical signal to the optical fiber ring; the output end of the first Y-branch optical waveguide is offset relative to the input end of the second Y-branch optical waveguide by a distance d with a value range of 100-4000 micrometers in a direction perpendicular to the propagation direction of the optical signal; and the second Y-branch optical waveguide is provided with a modulation electrode, the modulation electrode is connected with the signal processing circuit, and the modulation electrode is used for carrying out phase modulation on an optical signal on the second Y-branch optical waveguide.

2. The dual Y-branch optical waveguide phase modulator of claim 1 wherein: the first input end of the first Y-branch optical waveguide is connected with the output end of the light source, the first input end is used for accessing an optical signal, and the second input end of the first Y-branch optical waveguide is connected with the photoelectric detector.

3. The dual Y-branch optical waveguide phase modulator of claim 1 wherein: the optical fiber ring is provided with a first port and a second port, a first output end of the second Y-branch optical waveguide is connected with the first port of the optical fiber ring, and a second output end of the second Y-branch optical waveguide is connected with the second port of the optical fiber ring.

4. The dual Y-branch optical waveguide phase modulator of claim 1 wherein: the fundamental wave is guided to be a raised cosine function curve.

5. The dual Y-branch optical waveguide phase modulator of claim 1 wherein: the optical fiber ring is a polarization-maintaining optical fiber ring.

6. The dual Y-branch optical waveguide phase modulator of claim 1 wherein: the modulation electrode is a push-pull modulation electrode.

Technical Field

The invention relates to the technical field of phase modulators, in particular to a double-Y-branch optical waveguide phase modulator.

Background

The optical fiber gyroscope is an angular rate sensing instrument based on the Sagnac phase shift effect, and has a series of advantages of all-solid-state structure, small volume, electromagnetic interference resistance, high precision, long service life and the like. Fig. 1 is a schematic diagram of an existing optical fiber gyroscope, the optical fiber gyroscope is composed of a light source, a coupler, a Y waveguide, a polarization-maintaining fiber ring, a photodetector and a signal processing circuit, optical elements are connected in a pigtail fusion mode to form a closed light path, and a circuit part adopts a full-digital closed-loop detection scheme. When the polarization maintaining fiber ring rotates at an angular rate omega relative to the inertial space, two lines of light waves transmitted along the positive direction and the negative direction of the polarization maintaining fiber ring respectively experience different optical paths to generate a Sagnac phase difference phi, the signal processing circuit introduces a modulation signal on the Y waveguide phase modulator to offset the Sagnac phase difference phi caused by the rotation of the fiber ring, and the angular rate information of the system rotating relative to the inertial space can be obtained by detecting the modulation signal.

In order to improve the optical path integration level of the fiber optic gyroscope and simplify the optical path adjustment process, a scheme of adopting a double-Y-branch optical waveguide phase modulator to replace a combination of an optical fiber coupler and a Y-waveguide phase modulator in an original optical path is provided in the industry. However, when the double-Y-branch optical waveguide phase modulator is applied to a fiber optic gyroscope, the input light is split for the first time at the beam combining point of the first Y-branch optical waveguide, approximately half of the optical signal after the first splitting continues to propagate forward along the fundamental waveguide, and is split again at the splitting point of the second Y-branch optical waveguide and then transmitted into the optical fiber ring, and the other half of the optical signal after the first light splitting is radiated into the substrate to form an asymmetric radiation mode, the radiation mode propagates forwards in the substrate, when the radiation mode propagates to the splitting point at the second Y-branch optical waveguide, a part of the radiation mode will be coupled back into the second Y-branch optical waveguide, and a parasitic phase difference is generated at both branches of the second Y-branch optical waveguide, the phase difference is very sensitive to temperature, crosstalk and noise can be formed in an optical path, and the zero-offset stability of the fiber optic gyroscope is further influenced.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a double-Y branch optical waveguide phase modulator to solve the problem of noise introduced by radiation mode coupling in the existing double-Y branch optical waveguide modulator.

In order to solve the above problems, the present invention provides a dual Y-branch optical waveguide phase modulator, comprising a light source, a phase modulator chip and an optical fiber ring connected in sequence, wherein the phase modulator chip is further connected in sequence with a photodetector and a signal processing circuit, the phase modulator chip comprises a substrate, and a first Y-branch optical waveguide, a second Y-branch optical waveguide and a fundamental waveguide fabricated on the substrate, the first Y-branch optical waveguide has a first input end, a second input end and an output end, the second Y-branch optical waveguide has an input end, a first output end and a second output end, the output end of the first Y-branch optical waveguide is connected with one end of the fundamental waveguide, the other end of the fundamental waveguide is connected with the input end of the second Y-branch optical waveguide, the first Y-branch optical waveguide is used for receiving optical signals, the fundamental waveguide is used for transmitting optical signals received by the first Y-branch optical waveguide to the second Y-branch optical waveguide, the second Y-branch optical waveguide is used for splitting an optical signal transmitted by the fundamental waveguide and transmitting the split optical signal to the optical fiber ring; the output end of the first Y-branch optical waveguide is offset relative to the input end of the second Y-branch optical waveguide by a distance d with a value range of 100-4000 micrometers in a direction perpendicular to the propagation direction of the optical signal; and the second Y-branch optical waveguide is provided with a modulation electrode, the modulation electrode is connected with the signal processing circuit, and the modulation electrode is used for carrying out phase modulation on an optical signal on the second Y-branch optical waveguide.

Further, a first input end of the first Y-branch optical waveguide is connected to an output end of the light source, the first input end is used for accessing an optical signal, and a second input end of the first Y-branch optical waveguide is connected to the photodetector.

Furthermore, the optical fiber ring has a first port and a second port, a first output end of the second Y-branch optical waveguide is connected to the first port of the optical fiber ring, and a second output end of the second Y-branch optical waveguide is connected to the second port of the optical fiber ring.

Further, the fundamental wave is a raised cosine function curve.

Further, the optical fiber ring is a polarization-maintaining optical fiber ring.

Further, the modulation electrode is a push-pull modulation electrode.

The invention has the beneficial effects that: the output end of the first Y-branch optical waveguide is deviated from the input end of the second Y-branch optical waveguide by a distance of 100-4000 micrometers in a direction vertical to the propagation direction of the optical signal, the first Y-branch optical waveguide and the second Y-branch optical waveguide are connected through a section of fundamental waveguide with a raised cosine function curve, when the optical signal is transmitted forward along the first Y-branch optical waveguide, nearly half of the optical signal is transmitted forward along the fundamental waveguide to the second Y-branch optical waveguide at the beam combining point of the first Y-branch optical waveguide, and meanwhile, nearly half of the optical signal is radiated into the substrate to form a radiation mode and is transmitted forward along the substrate Therefore, the problems of crosstalk and noise caused by coupling of radiation modes in the optical path are solved.

Drawings

Fig. 1 is a schematic diagram of an operation of a conventional optical fiber gyro.

Fig. 2 is a schematic structural diagram of a preferred embodiment of a dual Y-branch optical waveguide phase modulator according to the present invention.

Detailed Description

The invention will be further explained with reference to the drawings.

In the description of the present invention, unless otherwise specified and limited, it is to be noted that the term "connected" is to be interpreted broadly, and may be, for example, a mechanical connection or an electrical connection, or a communication between two elements, or may be a direct connection or an indirect connection through an intermediate medium, and a specific meaning of the term may be understood by those skilled in the art according to specific situations.

Fig. 2 is a structural diagram of a preferred embodiment of a dual Y-branch optical waveguide phase modulator according to the present invention. The double-Y-branch optical waveguide phase modulator comprises a light source 1, a phase modulator chip 2 and an optical fiber ring 3 which are sequentially connected, wherein the phase modulator chip 2 is further sequentially connected with a photoelectric detector 4 and a signal processing circuit 5. The light source 1 is used for generating an optical signal and transmitting the optical signal to the phase modulator chip 2; the phase modulator chip 2 is used for splitting an optical signal and transmitting the split optical signal to the optical fiber ring 3; two optical signals in the optical fiber ring 3 are transmitted in the optical fiber ring 3 along opposite directions and then return to the phase modulator chip 2 again to generate interference and form interference signals, wherein the optical fiber ring 3 is a polarization maintaining optical fiber ring; the photoelectric detector 4 is used for detecting the intensity change of the interference signal; the signal processing circuit 5 performs phase modulation on the optical signal on the phase modulator chip 2 according to the detection result of the photodetector 4 to offset the phase difference introduced by the rotation of the optical fiber ring 3 relative to the inertial space, so as to calculate the corresponding angular rate.

The phase modulator chip 2 includes a substrate 21, and a first Y-branch optical waveguide 22, a fundamental waveguide 23, and a second Y-branch optical waveguide 24 formed on the substrate 21. The substrate 21 is preferably a lithium niobate crystal material. The first Y-branch optical waveguide 22 is configured to receive an optical signal, the base waveguide 23 is configured to transmit the optical signal received by the first Y-branch optical waveguide 22 to a second Y-branch optical waveguide 24, and the second Y-branch optical waveguide 24 is configured to split the optical signal transmitted by the base waveguide 23 and transmit the split optical signal to the optical fiber ring 3.

The first Y-branch optical waveguide 22 has a first input end 221, a second input end 222, and an output end 223; the first input end 221 is connected to an output end of the light source 1, and the first input end 221 is used for receiving an optical signal; the second input end 222 is connected to the photodetector 4, and the second input end 222 is configured to transmit an intensity variation signal, which is formed by interference of two optical signals on two optical waveguides of the second Y-branch optical waveguide 24, to the photodetector 4; the output end 223 of the first Y-branch optical waveguide 22 is connected to one end of the base waveguide 23, and the output end 223 is used for transmitting an optical signal to the base waveguide 23. The second Y-branch optical waveguide 24 has an input 241, a first output 242, and a second output 243; the input end 241 of the second Y-branch optical waveguide 24 is connected to the other end of the fundamental waveguide 23, and the input end 241 is used for receiving an optical signal transmitted by the fundamental waveguide 23; the optical fiber ring 3 has a first port 31 and a second port 32, the first output end 242 of the second Y-branch optical waveguide 24 is connected to the first port 31 of the optical fiber ring 3, the second output end 243 of the second Y-branch optical waveguide 24 is connected to the second port 32 of the optical fiber ring 3, and the first output end 242 and the second output end 243 are used for transmitting optical signals to the optical fiber ring 3.

The output 223 of the first Y-branch optical waveguide 22 is offset from the input 241 of the second Y-branch optical waveguide 24 by a distance of 100 to 4000 μm in a direction perpendicular to the direction of optical signal propagation; the optical signal enters the first Y-branch optical waveguide 22 from the first input end 221 and is split by approximately 3dB at the beam-combining point of the first Y-branch optical waveguide 22, then, nearly half of the optical signal propagates forward along the base waveguide 23 to the second Y-branch optical waveguide 24, and the other nearly half of the optical signal radiates into the substrate 21 to form a radiation mode and propagates forward along the substrate 21 and finally radiates out from the end face of the phase modulator chip 2, so that a part of the radiation mode at the beam-splitting point of the second Y-branch optical waveguide 24 is prevented from being re-coupled into the second Y-branch optical waveguide 24 to generate a parasitic phase difference, thereby eliminating the noise problem caused by radiation mode coupling. The base waveguide 23 is a raised cosine function curve to reduce the optical signal transmission loss introduced by bending in the base waveguide 23.

The second Y-branch optical waveguide 24 is provided with a modulation electrode 25, the modulation electrode 25 is connected to the signal processing circuit 5, the modulation electrode 25 is used for performing phase modulation on an optical signal on the second Y-branch optical waveguide 24, and the modulation electrode 25 is a push-pull modulation electrode. The signal processing circuit 5 introduces a modulation signal to the modulation electrode 25 according to the detection result of the photodetector 4 to perform phase modulation on the optical signal on the second Y-branch optical waveguide 24, so that the refractive indexes of the two branch optical waveguides on the second Y-branch optical waveguide 24 change, and further the optical signals in the two branch optical waveguides on the second Y-branch optical waveguide 24 generate a phase difference during transmission to cancel the phase difference introduced by the rotation of the optical fiber ring 3 relative to the inertial space.

The working principle of the invention is as follows:

an optical signal generated by the light source 1 enters the first Y-branch optical waveguide 22 through the first input end 221 of the first Y-branch optical waveguide 22, the optical signal is split by approximately 3dB for the first time at the beam combining point of the first Y-branch optical waveguide 22, wherein approximately half of the optical signal propagates along the base waveguide 23 to reach the second Y-branch optical waveguide 24, and is split for the second time at the beam splitting point of the second Y-branch optical waveguide 24, and two optical signals split by the second Y-branch optical waveguide 24 are transmitted along two branch optical waveguides of the second Y-branch optical waveguide 24 respectively.

The optical signal transmitted along the upper side branch optical waveguide in the second Y-branch optical waveguide 24 sequentially enters the optical fiber ring 3 through the first output end 242 of the second Y-branch optical waveguide 24 and the first port 31 of the optical fiber ring 3, is transmitted along the optical fiber ring 3, and is then transmitted to the lower side branch optical waveguide of the second Y-branch optical waveguide 24 sequentially through the second port 32 of the optical fiber ring 3 and the second output end 243 of the second Y-branch optical waveguide 24; the optical signal transmitted along the lower branch optical waveguide in the second Y-branch optical waveguide 24 sequentially enters the optical fiber ring 3 through the second output end 243 of the second Y-branch optical waveguide 24 and the second port 32 of the optical fiber ring 3, is transmitted along the optical fiber ring 3, and is then sequentially transmitted to the upper branch optical waveguide of the second Y-branch optical waveguide 24 through the first port 31 of the optical fiber ring 3 and the first output end 242 of the second Y-branch optical waveguide 24. Two optical signals returned to the two branch optical waveguides of the second Y-branch optical waveguide 24 through the optical fiber ring 3 interfere at the junction point of the second Y-branch optical waveguide 24 and generate an interference signal, which sequentially enters the first Y-branch optical waveguide 22 through the input end 241 of the second Y-branch optical waveguide 24, the fundamental waveguide 23 and the output end 223 of the first Y-branch optical waveguide 22, and enters the photodetector through the second input end 222 of the first Y-branch optical waveguide 22, the photodetector 4 detects the intensity variation of the interference signal and transmits the detection result to the signal processing circuit 5, the signal processing circuit 5 applies a voltage to the modulation electrode 25 according to the detection result transmitted by the photodetector 4 to cancel the phase difference introduced by the rotation of the optical fiber ring 3 with respect to the inertial space, the rotation angle rate of the optical fiber ring 3 relative to the inertial space can be calculated according to the voltage signal applied to the modulation electrode 25 by the signal processing circuit 5.

The other nearly half of the optical signal after the first splitting is radiated into the substrate 21 to form a radiation mode, and since the output end 223 of the first Y-branch optical waveguide 22 is shifted by a corresponding distance in the direction perpendicular to the propagation direction of the optical signal with respect to the input end 241 of the second Y-branch optical waveguide 24, so that the radiation mode propagates forward in the substrate 21 and finally radiates out from the end face of the phase modulator chip 2, a part of the radiation mode is prevented from being re-coupled into the second Y-branch optical waveguide 24 at the splitting point of the second Y-branch optical waveguide 24, thereby eliminating the crosstalk and noise problems caused by the radiation mode coupling in the optical path.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures made by using the contents of the present specification and the drawings can be directly or indirectly applied to other related technical fields, and are within the scope of the present invention.