PIC chip for distributed sound wave sensing system

Abstract

The invention provides a PIC chip for a distributed sound wave sensing system, the PIC chip comprises a light source and a light source stabilizing system, and a light signal output by the light source is output to an output light path after being processed by the light source stabilizing system; a light pulse generator is arranged on the output light path; the tail part of the output light path is connected with an external optical fiber pigtail; an optical circulator on the optical fiber pigtail is arranged between the sensing optical fiber and the PIC chip, and the optical circulator inputs an optical signal returned by the sensing optical fiber to polarization equipment arranged on the PIC chip; the polarization equipment divides the optical signals input by the optical circulator into at least two paths of optical signals and transmits the two paths of optical signals to a coherent optical receiver on the PIC chip, one path of the two paths of optical signals is provided with delay, and the coherent optical receiver sends the received optical signals to an analog circuit and a digital circuit for processing. And a circuit control signal is generated and transmitted to the light pulse generator.

Description

Technical Field

[0001] The present invention belongs to the technical field of distributed optical fiber sensing, and particularly relates to a PIC chip for a distributed acoustic wave sensing system. Background Art

[0002] Distributed acoustic sensing (DAS) technology can be widely applied to fields such as seismic wave detection, oil exploration, earthquake research, intrusion detection, oil pipeline protection, geophysical observation, infrastructure integrity monitoring, structural fault location, and vehicle tracking.

[0003] A distributed acoustic sensing (DAS) system can be implemented by an optical sensing system based on a phase-sensitive optical time domain reflectometer (OTDR) for detecting local phase fluctuations caused by acoustic waves or vibrations at various positions along a sensing optical fiber, and the distance information is determined by the time of the optical pulse backscattered inside the Rayleigh backscattering (RBS). The distributed acoustic sensing (DAS) system device generally includes a sensing optical fiber, a demodulator, and a data processing unit. Traditionally, discrete optical components are used to form the demodulator in the distributed acoustic sensing (DAS) system, but this kind of demodulator is bulky, expensive, and power-consuming. Especially in the fields of portable and aerospace applications where size, weight, and power consumption are crucial, and in the Internet of Things (IoT), consumer electronics, and many other industrial applications where cost and size are the main considerations, the demodulator with too large a volume in the prior art limits the wide application of the distributed acoustic sensing system.

[0004] Therefore, it is necessary to develop a new type of distributed acoustic sensing (DAS) system that can integrate various components of the DAS demodulator on the same chip to achieve the low cost and miniaturization of the DAS system to adapt to different application fields. Summary of the Invention

[0005] The present invention provides a PIC chip for a distributed acoustic wave sensing system, which has the advantages of low cost, small size, and light weight, and can be applicable to different application fields.

[0006] Other objects and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

[0007] To achieve one or some or all of the above purposes or other purposes, a PIC chip for a distributed acoustic sensing system provided by a technical solution of the present invention includes a light source and a light source stabilization system. The optical signal output by the light source is processed by the light source stabilization system and then output to an output optical path. An optical pulse generator is arranged on the output optical path. The tail of the output optical path is connected to an external optical fiber pigtail. An optical circulator on the optical fiber pigtail is arranged between the sensing optical fiber and the PIC chip. The optical circulator inputs the optical signal returned by the sensing optical fiber to a polarization device arranged on the PIC chip. The polarization device divides the optical signal input by the optical circulator into at least two optical signals and transmits them to a coherent optical receiver on the PIC chip. A delay is set for one of the two optical signals. The coherent optical receiver sends the received optical signal to an analog circuit and a digital circuit for processing to generate a circuit control signal and transmit it to the optical pulse generator.

[0008] Between the tail of the output optical path and the external optical fiber pigtail, and between the sensing optical fiber signal input by the optical circulator and the optical signal receiving module of the PIC chip, transmission matching is performed through a mode field converter.

[0009] The optical pulse generator includes a modulator and a semiconductor optical amplifier. The circuit control signal is respectively transmitted to the modulator and the semiconductor optical amplifier.

[0010] The polarization device includes a polarization beam splitting rotator and a one-to-two optical coupler. A dual-mode optical waveguide for receiving the optical signal of the sensing optical fiber is arranged on the PIC chip. The polarization beam splitting rotator divides the optical signals of the orthogonal polarization components in the sensing optical fiber into two different optical paths and rotates the optical signal of the TM mode by 90 degrees to the TE mode. The polarization beam splitting rotator is connected to two one-to-two optical couplers. The optical signal path is divided into two pairs of two optical signals through the one-to-two optical coupler. The two pairs of two optical signals enter two coherent optical receivers for processing.

[0011] The polarization device includes a polarization controller, a polarizer and a one-to-two optical coupler. The optical circulator accesses the optical signal returned by the sensing optical fiber to the dual-mode waveguide on the PIC chip through a mode field converter. The optical signal is transmitted to the polarization controller through the dual-mode waveguide. The polarization controller is connected to a polarizer. The optical signal of the TE mode enters the optical coupler after passing through the polarizer and is divided into two optical signals. An optical delay line of 0.1 m - 10 m is placed in one of the two optical signals. The two optical signals enter the coherent optical receiver.

[0012] A 90° mixer is provided inside the coherent optical receiver for performing coherent mixing on the two split-branch signals input. The optical powers of the output signals at the Q end and the I end of the 90° mixer are proportional to the sine or cosine of the phase difference between the two input signals.

[0013] A multimode interference coupler with four input ports and four output ports is provided inside the coherent optical receiver. Two of the four input ports are used to receive the input optical signals. Two of the four output ports of the multimode interference coupler are Q ports, which are used to output a pair of output signals whose optical powers are proportional to the sine of the phase difference between the two input signals; the other two output ports of the multimode interference coupler are I ports, which are used to output a pair of output signals whose optical powers are proportional to the cosine of the phase difference between the two input signals.

[0014] A multimode interference coupler with three input ports and three output ports is provided inside the coherent optical receiver. Two input ports are used to receive the input optical signals and extract the phase difference of the input optical signals. The three output ports sequentially output three output signals whose optical powers are proportional to the sine of the phase difference of the input optical signals, the sine of the phase difference of the input optical signals plus 120 degrees, and the sine of the phase difference of the input optical signals minus 120 degrees.

[0015] A PIC chip for a distributed acoustic sensing system provided by a technical solution of the present invention. The PIC chip includes a light source and a light source stabilization system. The optical signal output by the light source is output to the output optical path after being processed by the light source stabilization system; an optical pulse generator is provided on the output optical path; the tail of the output optical path is connected to an external fiber pigtail; an optical circulator on the fiber pigtail is arranged between the sensing fiber and the PIC chip, and the optical circulator inputs the optical signal returned by the sensing fiber to a polarization device outside the PIC chip to adjust the polarization state of the input optical signal; the polarized optical signal is processed by a coupler and at least divided into two optical signals and transmitted to a coherent optical receiver on the PIC chip. One of the two optical signals is set with a delay. The coherent optical receiver sends the received optical signal to an analog circuit and a digital circuit for processing to generate a circuit control signal and transmit it to the optical pulse generator.

[0016] The polarization device includes a polarization state generator or a polarization controller that is disposed outside the PIC chip and selects and switches between a horizontal linear polarization state and a diagonal polarization state, and a polarizer connected to the polarization state generator; the optical signal processed by the polarizer is input into a PM optical coupler through a PM optical fiber, and the PM optical coupler divides the optical signal into two optical signals. A PM optical fiber delay line with a length of 1m - 20m is placed on one of the optical signals. The two PM pigtails of the PM optical coupler are connected to the optical path of the PIC chip through two mode field converters, and enter the coherent optical receiver through the optical path.

[0017] The polarization device includes a polarization beam splitter disposed outside the PIC chip. The polarization beam splitter decomposes the optical signal input by the optical circulator into two pairs of optical signals, and further decomposes them into two pairs of two-way optical signals through two fiber couplers. A delay optical fiber with a length of 0.1m - 10m is placed on one of the two-way optical signals in each pair. The two pairs of two-way optical signals are matched with the mode field converters on the PIC chip through optical fibers, and the optical signals are connected to the optical path of the PIC chip and input into two coherent optical receivers through the optical path.

[0018] The output optical fiber of the polarization beam splitter, the delay optical fiber, and the pigtails of the two fiber couplers are all PM optical fibers; the fiber coupler is a PM fiber coupler.

[0019] The optical pulse generator includes a modulator and a semiconductor optical amplifier, and the circuit control signals are respectively transmitted to the modulator and the semiconductor optical amplifier.

[0020] A PIC chip for a distributed acoustic sensing system provided by a technical solution of the present invention. The PIC chip includes a light source and a light source stabilization system. The light source stabilization system includes a micro-ring and a mirror. A part of the optical signal output by the light source is coupled into the micro-ring. A part of the optical signal in the micro-ring is coupled into the ring mirror from one side. A part of the optical signal in the ring mirror returns to the micro-ring, and a part of the optical signal enters the coherent optical receiver through the ring mirror; the optical signal output by the light source is output to the output optical path after being processed by the light source stabilization system; an optical pulse generator is disposed on the output optical path; the tail of the output optical path is connected to an external optical fiber pigtail; an optical circulator on the optical fiber pigtail is disposed between the sensing optical fiber and the PIC chip. The optical circulator inputs the optical signal returned by the sensing optical fiber into the dual-mode waveguide on the PIC chip, and transmits it to the polarization device through the dual-mode waveguide to adjust the polarization state of the input optical signal; the optical signal processed by the polarization device and a part of the optical signal coupled out by the ring mirror enter the coherent optical receiver together; the coherent optical receiver sends the received optical signal to an analog circuit and a digital circuit for processing to generate a circuit control signal and transmit it to the optical pulse generator.

[0021] The polarization device is a polarization beam splitting rotator, which outputs the TE-mode optical signal into a coherent optical receiver and inputs the TM-mode optical signal into another coherent optical receiver after rotating it by 90°; part of the optical signal coupled out by the ring mirror is divided into two optical signals by a 1×2 optical coupler and respectively enters the two coherent optical receivers.

[0022] The polarization device is a polarizer for polarization control and connecting a polarization controller. The optical signal processed by the polarization controller and the polarizer enters the coherent optical receiver together with part of the optical signal coupled out by the ring mirror.

[0023] Compared with the prior art, the beneficial effects of the present invention mainly include that the present invention designs the distributed acoustic sensing system in a packaged integrated photon chip, specifically integrates various components of the distributed acoustic sensing system modulator on the same photon integrated circuit chip, thereby realizing the low cost, small size, light weight and low power consumption of the distributed acoustic sensing system, and is applicable to a wide range of application fields.

[0024] In order to make the above and other objects, features and advantages of the present invention more obvious and understandable, the following specifically enumerates preferred embodiments and, in conjunction with the accompanying drawings, makes a detailed description as follows. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 This is a PIC chip for a distributed acoustic sensing system in Embodiment 1 of the present invention.

[0027] Figure 2 This is another PIC chip for a distributed acoustic sensing system in Embodiment 1 of the present invention.

[0028] Figure 3 This is a PIC chip for a distributed acoustic sensing system in Embodiment 2 of the present invention.

[0029] Figure 4 This is another PIC chip for a distributed acoustic sensing system in Embodiment 2 of the present invention.

[0030] Figure 5 This is a PIC chip for a distributed acoustic sensing system in Embodiment 3 of the present invention.

[0031] Figure 6 This is another PIC chip for a distributed acoustic sensing system in Embodiment 3 of the present invention.

[0032] Figure 7 This is an example of the modulator or switch device of the present invention.

[0033] Figure 8 This is a schematic diagram of the coherent optical receiver device of the present invention. Detailed implementation mode

[0034] Regarding the foregoing and other technical contents, features and effects of the present invention, they will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings. The directional terms mentioned in the following embodiments, such as: up, down, left, right, front or back, etc., are only references to the directions in the attached drawings. Therefore, the directional terms used are for illustration and not for limiting the present invention.

[0035] Embodiment 1

[0036] Embodiment 1 provides a PIC chip for a distributed acoustic sensing system. The PIC chip includes a light source and a light source stabilization system. The optical signal output by the light source is processed by the light source stabilization system and then output to the output optical path. An optical pulse generator is arranged on the output optical path. The tail of the output optical path is connected to an external optical fiber pigtail. An optical circulator on the optical fiber pigtail is arranged between the sensing optical fiber and the PIC chip. The optical circulator inputs the optical signal returned by the sensing optical fiber into a polarization device arranged on the PIC chip. The polarization device divides the optical signal input by the optical circulator into at least two optical signals and transmits them to a coherent optical receiver on the PIC chip. One of the two optical signals is set with a delay. The coherent optical receiver sends the received optical signal into an analog circuit and a digital circuit for processing to generate a circuit control signal and transmit it to the optical pulse generator.

[0037] See Figure 1 , Figure 1A PIC chip for a distributed acoustic sensing system is provided, including a light source and a light source stabilization system. The light source is a DFB laser or a DFB chip. The light source stabilization system includes an MRR micro-ring and a reflector Loopmirror. A heater Heater can be set in front of the MRR micro-ring. Part of the optical signal output by the light source is coupled into the MRR micro-ring. Part of the optical signal in the MRR micro-ring is coupled into the ring reflector Loop mirror from one side. Part of the optical signal in the ring reflector Loop mirror returns to the MRR micro-ring, and part of the optical signal enters the coherent optical receiver Coherent Receiver through the ring reflector Loop mirror. The optical signal output by the light source is processed by the light source stabilization system and then output to the output optical path. An optical pulse generator is set on the output optical path. The optical pulse generator includes a modulator Modulator (or an optical switch Switch) and a semiconductor optical amplifier (SOA). Among them, a band-pass filter BPF can be selectively placed on the output optical path. The band-pass filter can allow signals within a specific frequency range to pass through and can output signals within a certain frequency range.

[0038] The tail of the output optical path is connected to an external fiber pigtail Fiber pigtail. An optical circulator Circulator on the fiber pigtail Fiber pigtail is set between the sensing fiber fiber and the PIC chip. The optical circulator Circulator inputs the optical signal Signal from fiber returned by the sensing fiber into the polarization device set on the PIC chip. Figure 1 The polarization device set on the PIC chip substrate is a polarization beam splitting rotator PSR and two 1x2 optical couplers. The polarization beam splitting rotator splits the optical signals of the orthogonal polarization components in the sensing fiber into two different optical paths and rotates the optical signal of the TM mode by 90 degrees to the TE mode. The optical paths processed by the polarization beam splitting sensor are respectively processed by the two 1x2 optical couplers and divided into two groups of two optical signals. Each group of two optical signals enters a coherent optical receiver Coherent Receiver for processing. The coherent optical receiver sends the received optical signal into the analog circuit and the digital circuit for processing to generate a circuit control signal Switching signal and transmits it to the modulator Modulator (or the optical switch Switch) and the semiconductor optical amplifier (SOA) respectively, so as to control the modulator Modulator (or the optical switch Switch) and the semiconductor optical amplifier (SOA).

[0039] Among them Figure 1The PIC chip for a distributed acoustic sensing system, between the tail of the output optical path on the PIC chip and the fiber pigtail outside the PIC chip, and between the fiber pigtail of the optical circulator and the PIC chip, for transmitting the optical signal to the polarization beam splitting rotator, the dual-mode waveguide (which supports the transmission of optical signals in both the transverse electric mode TE and the transverse magnetic mode TM) is transmitted through a mode spot converter SSC for transmission matching. The mode spot converter SSC is used to match the mode field diameter of the chip output light and the output fiber pigtail.

[0040] Figure 2 Another PIC chip for a distributed acoustic sensing system in Embodiment 1 is given. Figure 2 The PIC chip for a distributed acoustic sensing system in Figure 1 is basically similar to the PIC chip in Figure 2 The polarization device provided on the PIC chip substrate in Figure 1 includes a polarization controller, a polarizer, and a 1*2 optical coupler. The optical circulator accesses the optical signal returned by the sensing fiber into the dual-mode waveguide on the PIC chip through the mode spot converter SSC. The optical signal is transmitted through the dual-mode waveguide to the polarization controller, and the polarization controller is connected to a polarizer. The TE-mode optical signal enters the 1*2 optical coupler after passing through the polarizer, and the TE-mode optical signal is split into two optical signals. One of the optical signals is provided with an optical delay line of 0.1 m - 10 m, and the two optical signals finally enter the coherent optical receiver for further processing. The final processing steps are the same as

[0041] Embodiment 2

[0042] Embodiment 2 provides a PIC chip for a distributed acoustic sensing system. The PIC chip includes a light source and a light source stabilization system. The optical signal output by the light source is processed by the light source stabilization system and then output to an output optical path. An optical pulse generator is arranged on the output optical path. The tail of the output optical path is connected to an external fiber pigtail. An optical circulator on the fiber pigtail is arranged between the sensing fiber and the PIC chip. The optical circulator inputs the optical signal returned by the sensing fiber to a polarization device outside the PIC chip to adjust the polarization state of the input optical signal. The polarized optical signal is processed by a coupler and divided into at least two optical signals for transmission to a coherent optical receiver on the PIC chip. A delay is set for one of the two optical signals. The coherent optical receiver sends the received optical signal to an analog circuit and a digital circuit for processing to generate a circuit control signal and transmit it to the optical pulse generator.

[0043] The biggest difference between Embodiment 2 and Embodiment 1 is that the polarization device in Embodiment 2 is arranged outside the PIC chip, and at the same time, the polarization device arranged outside the PIC chip in Embodiment 2 is also different from that in Embodiment 1. The polarization device in Embodiment 1 is integrated on the substrate and needs to be realized by semiconductor manufacturing processes, with relatively high requirements for production and manufacturing. While in Embodiment 2, the external polarization device facilitates manufacturing.

[0044] For the specific structure of the PIC chip in Embodiment 2, this embodiment takes Figure 3 and Figure 4 as an example for illustration. Refer to Figure 3 , Figure 3 A PIC chip for a distributed acoustic sensing system is provided, including a light source and a light source stabilization system. The light source is a DFB laser or a DFB chip. The light source stabilization system includes an MRR micro-ring and a reflection mirror (Loop mirror). A heater (Heater) can be arranged in front of the MRR micro-ring. Part of the optical signal output by the light source is coupled into the MRR micro-ring. Part of the optical signal in the MRR micro-ring is coupled into the ring-shaped reflection mirror (Loop mirror) from one side. Part of the optical signal in the ring-shaped reflection mirror (Loop mirror) returns to the MRR micro-ring, and part of the optical signal enters the coherent optical receiver (Coherent Receiver) through the ring-shaped reflection mirror (Loop mirror). The optical signal output by the light source is processed by the light source stabilization system and then output to an output optical path. An optical pulse generator is arranged on the output optical path. The optical pulse generator includes a modulator (Modulator or optical switch) and a semiconductor optical amplifier (SOA). A band-pass filter (BPF) can be optionally placed on the output optical path. The band-pass filter allows signals within a specific frequency range to pass through and can output signals within a certain frequency range.

[0045] The tail of the output optical path is connected to an external sensing optical fiber. An optical circulator of the external sensing optical fiber is arranged between the sensing optical fiber and the PIC chip. The optical circulator inputs the optical signal returned by the sensing optical fiber into a polarization device arranged outside the PIC chip.

[0046] The external polarization device is a polarization state generator PSG 2-state(0° / 45°) or a polarization controller that switches between a horizontal linear polarization (0°) and a diagonal polarization (45°) state arranged outside the PIC chip, or a polarizer connected to the polarization state generator PSG 2-state(0° / 45°) or the polarization controller;

[0047] The optical signal processed by the polarizer is input into a PM optical coupler through a PM optical fiber. The PM optical coupler divides the optical signal into two optical signals. A 1m - 20m PM optical fiber delay line is placed on one of the optical signals. The two PM pigtails of the PM optical coupler are connected to the optical path of the PIC chip through two spot size converters SSC, and enter the coherent optical receiver through the optical path for further processing. The subsequent processing steps are exactly the same as those in the first embodiment and will not be elaborated here.

[0048] Figure 4 Another PIC chip for a distributed acoustic wave sensing system with a polarization device arranged outside the PIC chip is given. The specific polarization device includes a polarization beam splitter PBS arranged outside the PIC chip. The polarization beam splitter PBS decomposes the optical signal input by the optical circulator into two pairs of optical signals, and further decomposes them into two pairs of two optical signals through two fiber couplers (C1 and C2). A 0.1m - 10m delay optical fiber is placed on one of the two optical signals in each pair. The two pairs of two optical signals are matched with the spot size converter on the PIC chip through the optical fiber, and the optical signal is connected to the optical path of the PIC chip and input into two coherent optical receivers (Coherent Receiver1 and Coherent Receiver2) through the optical path. The subsequent processing steps are the same as those in the first embodiment and will not be elaborated.

[0049] As an alternative embodiment, the output optical fiber of the polarization beam splitter, the delay optical fiber, and the pigtails of the two fiber couplers are all PM optical fibers; the fiber coupler is a PM fiber coupler.

[0050] Embodiment Three

[0051] Embodiment 3 provides a PIC chip for a distributed acoustic sensing system. The PIC chip includes a light source and a light source stabilization system. The light source stabilization system includes a microring and a mirror. A part of the optical signal output by the light source is coupled into the microring. A part of the optical signal in the microring is coupled into the ring mirror from one side. A part of the optical signal in the ring mirror returns to the microring, and a part of the optical signal enters the coherent optical receiver through the ring mirror. The optical signal output by the light source is processed by the light source stabilization system and then output to the output optical path. An optical pulse generator is arranged on the output optical path. The tail of the output optical path is connected to an external optical fiber pigtail. An optical circulator on the optical fiber pigtail is arranged between the sensing optical fiber and the PIC chip. The optical circulator inputs the optical signal returned by the sensing optical fiber into a dual-mode waveguide on the PIC chip and transmits it through the dual-mode waveguide to a polarization device to adjust the polarization state of the input optical signal. The optical signal processed by the polarization device and a part of the optical signal coupled out by the ring mirror enter the coherent optical receiver together. The coherent optical receiver sends the received optical signal to an analog circuit and a digital circuit for processing to generate a circuit control signal and transmit it to the optical pulse generator.

[0052] The difference between Embodiment 3 and Embodiment 1 and Embodiment 2 lies in that Embodiment 3 uses a part of the optical signal coupled out from the light source and the optical signal returned by the sensing optical fiber processed by the polarization device for beat frequency processing.

[0053] See specifically Figure 5 and Figure 6 , Figure 5 For the provided PIC chip for a distributed acoustic sensing system, the polarization device is a polarization beam splitting rotator. The polarization beam splitting rotator outputs the TE-mode optical signal to one coherent optical receiver and rotates the TM-mode optical signal by 90° and inputs it into another coherent optical receiver. A part of the optical signal coupled out by the ring mirror is split into two optical signals through a 1x2 optical coupler and enters the two coherent optical receivers respectively.

[0054] Figure 6 For the provided PIC chip for a distributed acoustic sensing system, the polarization device is a polarization controller and a polarizer connected to the polarization controller. The optical signal processed by the polarization controller and the polarizer and a part of the optical signal coupled out by the ring mirror enter the coherent optical receiver together.

[0055] Figure 5 and Figure 6 The polarization devices of the devices in

[0056] As an optional implementation manner in the above three groups of embodiments, for examples of the modulator or optical switch device in the above three groups of embodiments, seeFigure 7 , which shows examples of three different modulator / switching devices that can be used in Figure 1 . Figure 7 a is a standard Mach-Zehnder modulator (MZM) device, which may not be able to achieve a sufficiently high ER on its own to meet the requirements of DAS, because the slight differences in the coupling ratios of the two couplers and the slight differences in the transmission losses between the two branches make it difficult for the power in the upper and lower branches of the MZM modulator to be exactly the same.

[0057] Figure 7 b is a High Extinction Ratio Mach-Zehnder modulator (MZM), in which a Mach-Zehnder interferometer (MZI) is placed before the MZM. The MZI can act as an adjustable coupler, which can be achieved by adjusting the relative phase between the two arms of the MZI. An adjustable phase shifter can be thermally tuned by applying a current to the resistor in one of the arms to ensure the optimization of the Extinction Ratio (ER) of the MZM.

[0058] Finally, Figure 7 c is a modulator made of multiple microrings, which is used to achieve a high Extinction Ratio (ER). These devices can be implemented on a thin-film lithium niobate (TFLN) or silicon-on-insulator (SOI) platform.

[0059] As an alternative implementation in the above three groups of embodiments, the structure of the coherent optical receiving receiver in the above three groups of embodiments is as Figure 8 shown, Figure 8 a shows a 90° mixer, and the outputs of its Q and I ports are respectively proportional to the sine and cosine of the phase difference between the two inputs :

[0060]

[0061] where A i and B i (i = 1, 2, 3, 4) are constants.

[0062] In various implementations, the hardware design can be used to meet the following conditions: A i = A j = A, B i = B j = B, in which case the phase difference between the two input signals can be expressed as:

[0063]

[0064] Figure 8b shows a coherent optical receiver composed of a 4×4 multimode interference (MMI) coupler, where two of the four input ports are used to generate a pair of Q ports whose phases are sinusoidally proportional to the phases between the two input signals, and a pair of I ports whose phases are cosine-functionally proportional to the phases between the two input signals, as described in the above equations (1a) to (1e).

[0065] Figure 8 c shows a coherent optical receiver equipped with a 3x3 MMI coupler, where two input ports are used to input two optical signals to extract their phase difference, and the optical powers of the three output ports can be expressed as:

[0066]

[0067] The above has introduced in detail a PIC chip for a distributed acoustic sensing system provided by the present invention. Specific examples are used in this article to elaborate on the structure and working principle of the present invention. The description of the above embodiments is only used to help understand the method and core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A PIC chip for a distributed acoustic wave sensing system, characterized in that: The PIC chip includes a light source and a light source stabilization system. The light signal output by the light source is processed by the light source stabilization system and then output to the output light path. An optical pulse generator is provided on the output optical path; The tail of the output optical path is connected to an external optical fiber pigtail; The optical circulator on the optical fiber pigtail is arranged between the sensing optical fiber and the PIC chip, and the optical circulator inputs the optical signal returned by the sensing optical fiber to the polarization device arranged on the PIC chip; The polarization device divides the optical signal input by the optical circulator into at least two optical signals and transmits them to the coherent optical receiver on the PIC chip. One of the two optical signals is delayed. The coherent optical receiver sends the received optical signal to the analog circuit and the digital circuit for processing to generate a circuit control signal and transmit it to the optical pulse generator.

2. The PIC chip for a distributed acoustic wave sensing system according to claim 1, characterized in that: Transmission matching is performed between the tail of the output optical path and the external optical fiber pigtail, and between the sensing optical fiber signal input by the optical circulator and the optical signal receiving module of the PIC chip through a spot mode converter.

3. The PIC chip for a distributed acoustic wave sensing system according to claim 1, characterized in that: The optical pulse generator includes a modulator and a semiconductor optical amplifier, and the circuit control signal is transmitted to the modulator and the semiconductor optical amplifier respectively.

4. The PIC chip for a distributed acoustic wave sensing system according to claim 1, characterized in that: The polarization device includes a polarization beam splitter and a one-to-two optical coupler, and the PIC chip is provided with a dual-mode optical waveguide for receiving an input sensing fiber optical signal; The polarization beam splitter rotator divides the optical signal of the orthogonal polarization components in the sensing optical fiber into two different optical paths, and rotates the optical signal of the TM mode by 90 degrees to the TE mode; The polarization beam splitter rotator is connected to two one-to-two optical couplers, and the optical signal path is divided into two pairs of two-path optical signals through the one-to-two optical couplers. The two pairs of two-path optical signals enter two coherent optical receivers for processing.

5. The PIC chip for a distributed acoustic wave sensing system according to claim 1, characterized in that: The polarization device includes a polarization controller, a polarizer, and a one-to-two optical coupler; The optical circulator connects the optical signal returned by the sensing optical fiber to the dual-mode waveguide on the PIC chip via a mode spot converter, and the optical signal is transmitted to the polarization controller via the dual-mode waveguide. The polarization controller is connected to a polarizer, and the TE mode optical signal enters the optical coupler after passing through the polarizer, and the TE mode optical signal is divided into two optical signals, one of which is placed with a 0.1m-10m optical delay line, and the two optical signals enter the coherent optical receiver.

6. The PIC chip for a distributed acoustic wave sensing system according to claim 4, characterized in that: The coherent optical receiver is provided with a 90° mixer for coherently mixing the two input split branch signals. The optical power of the output signals at the Q end and the I end of the 90° mixer is proportional to the sine or cosine of the phase difference between the two input signals.

7. The PIC chip for a distributed acoustic wave sensing system according to claim 4, characterized in that: A multimode interference coupler having four input ports and four output ports is arranged in the coherent optical receiver, two of the four input ports are used to receive input optical signals, and two of the four output ports of the multimode interference coupler are Q ports, which are used to output a pair of output signals whose optical power is in sinusoidal proportion to the phase difference between the two input signals; The other two output ports of the multimode interference coupler are I ports, which are used to output a pair of output signals whose optical power is in cosine proportion to the phase difference between the two input signals.

8. The PIC chip for a distributed acoustic wave sensing system according to claim 4, characterized in that: The coherent optical receiver is provided with a multimode interference coupler having three input ports and three output ports, wherein the two input ports are used to receive input optical signals and extract the phase difference of the input optical signals, and the three output ports sequentially output three output signals whose optical powers are in a sinusoidal proportion to the phase difference of the input optical signals, in a sinusoidal proportion to the phase difference of the input optical signals plus 120 degrees, and in a sinusoidal proportion to the phase difference of the input optical signals minus 120 degrees.

9. A PIC chip for a distributed acoustic wave sensing system, characterized in that: The PIC chip includes a light source and a light source stabilization system. The light signal output by the light source is processed by the light source stabilization system and then output to the output light path. An optical pulse generator is provided on the output optical path; The tail of the output optical path is connected to an external optical fiber pigtail; The optical circulator on the optical fiber pigtail is arranged between the sensing optical fiber and the PIC chip, and the optical circulator inputs the optical signal returned by the sensing optical fiber to the polarization device outside the PIC chip to adjust the polarization state of the input optical signal; The polarization-processed optical signal is processed by a coupler and divided into at least two optical signals, which are transmitted to the coherent optical receiver on the PIC chip. One of the two optical signals is delayed. The coherent optical receiver sends the received optical signal to an analog circuit and a digital circuit for processing to generate a circuit control signal and transmit it to the optical pulse generator.

10. The PIC chip for a distributed acoustic wave sensing system according to claim 9, characterized in that: The polarization device includes a polarization state generator or polarization controller arranged outside the PIC chip for selectively switching between horizontal linear polarization and diagonal polarization states, and a polarizer connected to the polarization state generator; The optical signal processed by the polarizer is input to the PM optical coupler via the PM optical fiber. The PM optical coupler divides the optical signal into two optical signals, one of which is placed on a 1m-20m PM optical fiber delay line. The two PM pigtails of the PM optical coupler are connected to the optical path of the PIC chip via two spot mode converters and enter the coherent optical receiver via the optical path.

11. The PIC chip for a distributed acoustic wave sensing system according to claim 9, characterized in that: The polarization device includes a polarization beam splitter arranged outside the PIC chip, the polarization beam splitter decomposes the optical signal input by the optical circulator into two pairs of optical signals, and further decomposes it into two pairs of two-way optical signals through two optical fiber couplers, one optical signal of each pair of two-way optical signals is placed in a 0.1m-10m delay optical fiber, the two pairs of two-way optical signals are matched with the mode spot converter on the PIC chip through the optical fiber, and the optical signal is connected to the optical path of the PIC chip, and is input into two coherent optical receivers through the optical path.

12. The PIC chip for a distributed acoustic wave sensing system according to claim 11, characterized in that: The output fiber of the polarization beam splitter, the delay fiber, and the pigtails of the two fiber couplers are all PM fibers; The optical fiber coupler is a PM optical fiber coupler.

13. The PIC chip for a distributed acoustic wave sensing system according to claim 9, characterized in that: The optical pulse generator includes a modulator and a semiconductor optical amplifier, and the circuit control signal is transmitted to the modulator and the semiconductor optical amplifier respectively.

14. A PIC chip for a distributed acoustic wave sensing system, characterized in that: The PIC chip includes a light source and a light source stabilization system, the light source stabilization system includes a micro-ring and a reflector, part of the light signal output by the light source is coupled into the micro-ring, part of the light signal in the micro-ring is coupled into the annular reflector from one side, part of the light signal in the annular reflector returns to the micro-ring, and part of the light signal enters the coherent optical receiver through the annular reflector; The optical signal output by the light source is processed by the light source stabilization system and then output to the output optical path; An optical pulse generator is provided on the output optical path; The tail of the output optical path is connected to an external optical fiber pigtail; The optical circulator on the optical fiber pigtail is arranged between the sensing optical fiber and the PIC chip, and the optical circulator inputs the optical signal returned by the sensing optical fiber into the dual-mode waveguide on the PIC chip, and transmits the optical signal to the polarization device through the dual-mode waveguide to adjust the polarization state of the input optical signal; The optical signal processed by the polarization device and part of the optical signal coupled out by the ring reflector enter the coherent optical receiver; The coherent optical receiver sends the received optical signal to the analog circuit and the digital circuit for processing to generate a circuit control signal and transmit it to the optical pulse generator.

15. The PIC chip for a distributed acoustic wave sensing system according to claim 14, characterized in that: The polarization device is a polarization beam splitter rotator, which outputs a TE mode optical signal to a coherent optical receiver and rotates a TM mode optical signal by 90° before inputting it into another coherent optical receiver; Part of the optical signal coupled out by the annular reflector is divided into two optical signals through a one-to-two optical coupler and enters two coherent optical receivers respectively.

16. The PIC chip for a distributed acoustic wave sensing system according to claim 14, characterized in that: The polarization device is a polarization control and a polarizer connected to the polarization controller. The optical signal processed by the polarization controller and the polarizer enters the coherent optical receiver together with part of the optical signal coupled out by the annular reflector.

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