A Brillouin optical time domain analyzer chip and system

Abstract

This invention relates to a Brillouin optical time-domain analyzer chip and system, comprising: a light source selection and distribution unit, a probe light generation unit, a pump light generation unit, a light detection unit, an optical signal port, and an electrical signal port; external light source and laser signals are input through the optical signal port and respectively input to the probe light generation unit and the pump light generation unit through the light source selection and distribution unit; the probe light generation unit includes an IQ modulator and a filter based on a dual parallel Mach-Zehnder modulator structure; the pump light generation unit includes two cascaded intensity modulators based on a Mach-Zehnder modulator structure and a polarization controller; the light detection unit includes a photodetector for receiving the probe light input. Compared with the prior art, this invention integrates the core optoelectronic devices of the Brillouin optical time-domain analyzer sensing system onto a silicon photonics chip, effectively achieving temperature sensing while maintaining high performance, meeting application requirements.

Description

Technical Field

[0001] This invention relates to fiber optic sensing technology, and in particular to a Brillouin optical time domain analyzer chip and system. Background Technology

[0002] Brillouin optical time-domain analyzers (OTDAs) are high-performance distributed sensing technologies widely used for quasi-static monitoring of variables such as temperature and strain. Their sensing range can reach tens of kilometers, even exceeding 100 kilometers, with spatial resolution down to several meters. These advantages have led to their widespread application in structural health monitoring, geological engineering monitoring, and other fields. However, current Brillouin OTDAs are typically composed of discrete optoelectronic devices, resulting in large size, heavy weight, and high cost, thus limiting the wider application of this technology.

[0003] The development of photonic integration technology has opened up new opportunities for fiber optic sensing systems, not only driving the miniaturization of fiber optic sensors but also effectively reducing costs. In the fields of single-point and quasi-distributed sensing systems, integrated fiber Bragg grating sensors based on silicon-on-insulator (SOI) or indium phosphide (InP) platforms have been successfully implemented, demonstrating their application potential in wearable sensors. Furthermore, there are already integrated examples of optical frequency domain reflectometers and phase-sensitive optical time domain reflectometers based on Rayleigh backscattering. However, in the field of Brillouin sensors, although there have been attempts to integrate Brillouin optical time domain reflectometers on the indium phosphide platform, effective sensing results have not yet been obtained. For Brillouin optical time domain analyzers, system integration is still in its early stages and has not yet been explored in depth. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a Brillouin optical time domain analyzer chip and system.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] As a first aspect of the present invention, a Brillouin optical time domain analyzer chip is provided, comprising: a light source selection and allocation unit, a probe light generation unit, a pump light generation unit, a light detection unit, an optical signal port, and an electrical signal port;

[0007] The signals from the external light source and the laser are input through the optical signal port and then connected to the light source selection and distribution unit via polarization beam splitters.

[0008] The light source selection and distribution unit includes a light source selection switch and a beam splitter. The output of the light source selection and distribution unit is connected to the input of the probe light generation unit and the pump light generation unit, respectively.

[0009] The probe light generation unit includes an IQ modulator and a filter based on a dual parallel Mach-Zehnder modulator structure; the output of the probe light generation unit is connected to an optical signal port for output.

[0010] The pump light generation unit includes a cascaded first intensity modulator and second intensity modulator based on a Mach-Zehnder modulator structure, as well as a polarization controller; the output of the pump light generation unit is connected to an optical signal port for output.

[0011] The optical detection unit includes a photodetector connected to the optical signal port for receiving probe light input.

[0012] As a preferred technical solution, the optical signal port includes a first optical signal port and a second optical signal port;

[0013] The first optical signal port includes an external light source input port, a test output port, a probe light output port, a pump light output port, and a scattering signal input port; the second optical signal port includes a laser chip input port.

[0014] The external light source input port is connected to the input of the first polarization beam splitter, and the output of the first polarization beam splitter is connected to the first input of the light source selection switch.

[0015] The laser chip input port is connected to the input of the second polarization beam splitter 122, and the output of the second polarization beam splitter is connected to the second input of the light source selection switch;

[0016] The first output of the light source selection switch is connected to the test output port, and the second output of the light source selection switch 123 is connected to the beam splitter input.

[0017] The first output of the beam splitter is connected to the input of the IQ modulator, the output of the IQ modulator is connected to the input of the filter, and the output of the filter is connected to the probe light output port.

[0018] The second output of the beam splitter is connected to the input of the first intensity modulator, the output of the first intensity modulator is connected to the input of the second intensity modulator, the output of the second intensity modulator is connected to the input of the polarization controller, and the output of the polarization controller is connected to the pump light output port.

[0019] The scattering signal input port is connected to the input of the photodetector.

[0020] As a preferred technical solution, the first optical signal port and the second optical signal port adopt a cantilever beam edge coupler, and the silicon substrate under the buried oxide layer is removed;

[0021] The first optical signal port and the second optical signal port are located at the edge of the chip. The first optical signal port is fixed to the fiber array by UV adhesive curing, providing a standard interface for the connection of external optical devices.

[0022] As a preferred technical solution, the electrical signal port includes a pulse signal input port group, a microwave signal input port group, a tuning and bias signal input port group, and a received signal output port;

[0023] The pulse signal input port group is connected to the drive terminals of the first intensity modulator and the second intensity modulator;

[0024] The microwave signal input port group is connected to the drive terminal of the IQ modulator;

[0025] The tuning and bias signal input port group includes a light source selection switch, a beam splitter, an IQ modulator, a filter, a first intensity modulator, a second intensity modulator and a polarization controller operating point tuning input terminal, as well as an IQ modulator, a first intensity modulator, a second intensity modulator and a photodetector bias point input terminal;

[0026] The signal receiving output port includes the output port of the photodetector.

[0027] As a preferred technical solution, in the light source selection and allocation unit:

[0028] The light source selection switch is based on an interferometer structure, including two multimode interference couplers and a thermo-optical phase shifter. By adjusting the thermo-optical phase shifter, the input laser from either the external light source input port or the laser chip input port can be selected as the light source for subsequent links.

[0029] The beam splitter is based on an interferometer structure and consists of two multimode interference couplers and a thermo-optical phase shifter. The phase difference between the two arms is adjusted by the thermo-optical phase shifter, thereby achieving the adjustment of any beam splitting ratio. The beam splitter splits the incident light into two beams, one of which enters the probe light generation unit and the other enters the pump light generation unit.

[0030] As a preferred technical solution, the IQ modulator is a dual flat Mach-Zehnder type electro-optic modulator, which includes two identically designed sub-Mach-Zehnder type electro-optic modulators. The modulator electrodes are in the form of traveling wave electrodes. A thermal phase shifter is provided on the modulation arm of the main modulator and the modulation arm of the sub-modulator to add an additional phase shift to the optical signal.

[0031] The tuning signal input port of the IQ modulator receives the tuning signal and is set to operate in carrier-suppressed single-sideband modulation mode, while retaining the -1st order sideband; the bias signal input port of the IQ modulator receives the bias voltage, so that both sub-Mach-Zehnder electro-optic modulators are set at the carrier suppression point.

[0032] The two arms of the sub-modulator of the IQ modulator have a phase difference of 180°, and the upper and lower arms of the main modulator have a phase difference of 90°. They are driven by a set of microwave signals with the same power and a 90° phase difference.

[0033] As a preferred technical solution, the filter uses an upload / download type microring structure, with a hot electrode deposited above the ring waveguide; the passband center of the microring filter is aligned with the single-sideband signal emitted after modulation by the IQ modulator.

[0034] As a preferred technical solution, the first intensity modulator and the second intensity modulator are Mach-Zehnder type electro-optic modulators. The modulator electrodes are in the form of traveling wave electrodes. A thermal phase shifter is provided on the modulation arm of the modulator to add an additional phase shift to the optical signal. The bias signal input terminal of the modulator receives the bias voltage to realize the bias of the modulator PN junction.

[0035] The first and second intensity modulators perform pulse generation functions. Both the first and second intensity modulators receive tuning signals and are set to the null operating point. The pulse signal input port receives pulse signals.

[0036] As a preferred technical solution, the polarization controller includes two Mach-Zehnder interferometer structures with thermo-optical phase shifters and a deflection-rotation beam combiner.

[0037] As a second aspect of the present invention, a Brillouin optical time domain analyzer is provided, comprising the Brillouin optical time domain analyzer chip as described above;

[0038] The laser module provides continuous single-frequency laser light and connects to the external light source input port of the Brillouin optical time domain analyzer chip.

[0039] The optical amplification and optical transmission unit includes an optical isolator, an optical amplifier, and an optical circulator; the input of the optical amplifier is connected to the pump light output port of the Brillouin optical time domain analyzer, and the output of the optical amplifier is connected to port 1 of the optical circulator; the input of the optical isolator is connected to the probe light output port of the Brillouin optical time domain analyzer chip, and the output of the optical isolator is connected to the beginning of the sensing fiber; port 3 of the optical circulator is connected to the scattering signal input port of the Brillouin optical time domain analyzer.

[0040] The drive and control circuit includes a pulse signal generation unit, a microwave signal generation unit, a tuning and bias signal generation unit, a receiving signal conditioning unit, and a signal acquisition unit. The output of the pulse signal generation unit is connected to the pulse signal input port group of the Brillouin optical time-domain analyzer chip; the output of the microwave signal generation unit is connected to the microwave signal input port group of the Brillouin optical time-domain analyzer chip; the output of the tuning and bias signal generation unit is connected to the tuning and bias signal input port group; the input of the receiving signal conditioning unit is connected to the receiving signal output port of the Brillouin optical time-domain analyzer chip; and the output of the receiving signal conditioning unit is connected to the input of the signal acquisition unit.

[0041] The signal processing unit executes the demodulation algorithm program of the Brillouin optical time domain analyzer;

[0042] The sensing fiber is connected to port 2 of the optical circulator at its tail end.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1) This invention integrates the core optoelectronic components of a Brillouin optical time-domain analyzer onto a miniaturized chip, significantly reducing the instrument's size, weight, and cost while maintaining excellent system performance. This not only allows the Brillouin optical time-domain analyzer to be used more widely in traditional application areas but also better meets the demands of fields such as aerospace, the Internet of Things, and consumer electronics regarding mechanical size, hardware cost, mass production cost, and ease of use.

[0045] 2) The probe light generation unit of this invention is driven by a microwave radio frequency signal to perform single-sideband modulation. It employs an IQ modulator based on a dual flat Mach-Zehnder electro-optic modulator and a bandpass filter with a micro-ring structure. The IQ modulator operates in carrier-suppressed single-sideband modulation mode and retains the -1st order sideband. Both of its sub-Mach-Zehnder electro-optic modulators operate at the carrier suppression point. The bandwidth of the IQ modulator is >30GHz, far exceeding the requirements of a Brillouin optical time-domain analyzer. The passband center of the micro-ring filter is aligned with the single-sideband signal emitted after modulation by the IQ modulator to further filter out spurious frequencies and improve the sideband suppression ratio. By combining the IQ modulator and the micro-ring filter, a cleaner single-sideband signal can be obtained.

[0046] 3) In this invention, the pump light generation unit is driven by a pulse signal and consists of two cascaded intensity modulators based on a Mach-Zehnder modulator structure and a polarization controller. The modulator electrodes are traveling-wave electrodes, and the bias signal input terminal of the modulator receives a bias voltage to bias the modulator's PN junction. At a bias voltage of -3V, the bandwidth of the two intensity modulators can reach 30GHz. The cascading of the intensity modulators improves the extinction ratio of the generated pulse signal, achieving a static extinction ratio >45dB and a dynamic extinction ratio >40dB for the generated pump light, meeting the extinction ratio requirements of the Brillouin optical time-domain analyzer.

[0047] 4) The light source selection and distribution unit of the present invention has advantages in size and cost compared with discrete devices, and has tunability to enhance the robustness of the system; the probe light generation unit can improve the sideband suppression ratio of the generated single-sideband signal by using an IQ modulator and a micro-ring-based bandpass filter, thereby generating a higher quality single-sideband signal; the pump light generation unit can generate pulsed light with a high extinction ratio that meets the requirements of the Brillouin optical time domain analyzer by using cascaded Mach-Zehnder modulators. Compared with the use of two cascaded Mach-Zehnder modulator modules in discrete devices, the integrated scheme effectively reduces costs.

[0048] 5) The chip manufacturing of this invention is compatible with CMOS processes, and the integrated devices are all based on standard and conventional process flows, possessing the potential for large-scale production and significantly reducing costs. Chip design can fully utilize the well-proven mature device libraries and design standards in existing integrated manufacturing platforms, significantly shortening the design cycle and reducing design difficulty and failure risk. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the Brillouin optical time-domain analyzer chip structure of the present invention;

[0050] Figure 2 This is a structural diagram of one embodiment of the integrated polarization controller of the present invention;

[0051] Figure 3 This is a structural diagram of the sensing system based on the Brillouin optical time-domain analyzer chip of the present invention;

[0052] Figure 4 This is a measured performance curve of the sensing system of the present invention;

[0053] The diagram shows the following components: 1. Brillouin optical time-domain analyzer chip; 111. First optical signal port; 112. Second optical signal port; 121. First polarization beamsplitter; 122. Second polarization beamsplitter; 123. Light source selection switch; 124. Beamsplitter; 131. IQ modulator; 132. Filter; 141. First intensity modulator; 142. Second intensity modulator; 143. Polarization controller; 15. Photodetector; 2. Laser module; 31. Optical isolator; 32. Optical amplifier; 33. Optical circulator; 41. Pulse signal generation unit; 42. Microwave signal generation unit; 43. Tuning and bias signal generation unit; 44. Received signal conditioning unit; 45. Signal acquisition unit; 5. Signal processing unit; 6. Sensing fiber. Detailed Implementation

[0054] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0055] Example 1

[0056] like Figure 1 As shown, this embodiment provides a Brillouin optical time domain analyzer chip, including: a light source selection and allocation unit, a probe light generation unit, a pump light generation unit, a light detection unit, an optical signal port, and an electrical signal port.

[0057] The light source selection and distribution unit includes a light source selection switch 123 and an adjustable beam splitter 124.

[0058] The probe light generation unit includes an IQ modulator 131 and a filter 132. The IQ modulator 131 is based on a dual parallel Mach-Zehnder modulator structure with a modulation bandwidth >12GHz; the filter 132 is based on a micro-ring structure and is a bandpass filter.

[0059] The pump light generation unit includes a cascaded first intensity modulator 141 and a second intensity modulator 142 based on a Mach-Zehnder modulator structure, and a polarization controller 143.

[0060] The optical detection unit is a photodetector 15.

[0061] The optical signal ports include a first optical signal port 111 and a second optical signal port 112. The first optical signal port 111 includes an external light source input port, a test output port, a probe light output port, a pump light output port, and a scattering signal input port; the second optical signal port 112 includes a laser chip input port.

[0062] The various optoelectronic devices of the Brillouin optical time-domain analyzer chip are connected via integrated silicon waveguides. The external light source input port is connected to the input of the first polarization beamsplitter 121, and the output of the first polarization beamsplitter 121 is connected to the first input of the light source selection switch 123. The laser chip input port is connected to the input of the second polarization beamsplitter 122, and the output of the second polarization beamsplitter 122 is connected to the second input of the light source selection switch 123. The first output of the light source selection switch 123 is connected to the test output port, and the second output of the light source selection switch 123 is connected to the input of the beamsplitter 124. The first output of beam splitter 124 is connected to the input of IQ modulator 131, the output of IQ modulator 131 is connected to the input of filter 132, and the output of filter 132 is connected to the probe light output port; the second output of beam splitter 124 is connected to the input of first intensity modulator 141, the output of first intensity modulator 141 is connected to the input of second intensity modulator 142, the output of second intensity modulator 142 is connected to the input of polarization controller 143, and the output of polarization controller 143 is connected to the pump light output port; the scattering signal input port is connected to the input of photodetector 15.

[0063] The electrical signal ports include pulse signal input port group, microwave signal input port group, tuning and bias signal input port group, and receive signal output port.

[0064] The pulse signal input port group is connected to the driving terminals of the first intensity modulator 141 and the second intensity modulator 142; the microwave signal input port group is connected to the driving terminal of the IQ modulator 131; the operating point tuning input terminals of the light source selection switch 123, beam splitter 124, IQ modulator 131, filter 132, first intensity modulator 141, second intensity modulator 142, and polarization controller 143, and the bias point input terminals of IQ modulator 131, first intensity modulator 141, second intensity modulator 142, and photodetector 15 constitute the tuning and bias signal input port group; the output of photodetector 15 constitutes the receiving signal output port.

[0065] In this embodiment, both the first optical signal port 111 and the second optical signal port 112 are cantilever beam edge couplers. The silicon substrate beneath the buried oxide layer is removed in its implementation to overcome the light leakage problem caused by the limited thickness of the buried oxide layer, thereby improving coupling efficiency. The optical signal ports are placed at the chip edge, and the first optical signal port 111 is fixed to the fiber array by UV adhesive curing, providing a standard interface for connecting external optical devices.

[0066] In this embodiment, the light source selection switch 123 is based on an interferometer structure and consists of two 2×2 multimode interferometric couplers and a thermo-optical phase shifter. Adjusting the thermo-optical phase shifter allows selection of the input laser from either the external light source input port or the laser chip input port as the light source for subsequent links.

[0067] In this embodiment, the adjustable beam splitter 124 is based on an interferometer structure and consists of two 2×2 multimode interferometric couplers and a thermo-optical phase shifter. The phase difference between the two arms can be adjusted via the thermo-optical phase shifter, thereby achieving arbitrary beam splitting ratio adjustment. Compared to commercially available optical beam splitters 124 with fixed beam splitting ratios used in typical discrete systems, this integrated beam splitter 124 allows for flexible adjustment of the beam splitting ratio, thus enhancing the system's adjustment margin. The adjustable beam splitter 124 splits the incident light into two beams: one enters the probe light generation unit, and the other enters the pump light generation unit.

[0068] In this embodiment, the IQ modulator 131 is a dual-flat Mach-Zehnder electro-optic modulator, consisting of two identically designed sub-Mach-Zehnder electro-optic modulators. The modulator electrodes are in the form of traveling-wave electrodes. Each sub-modulator has a thermal phase shifter on its modulation arm to add an additional phase shift to the optical signal. In addition to the thermal phase shifter on the sub-modulator's modulation arm, a thermal phase shifter also exists on the arm of the main modulator. The modulator is based on carrier dispersion. The bias signal input terminal of the IQ modulator 131 receives a bias voltage that biases both sub-Mach-Zehnder electro-optic modulators to the same state. At a bias voltage of -3V, the bandwidth of the IQ modulator 131 is >30GHz, far exceeding the requirements of a Brillouin optical time-domain analyzer.

[0069] IQ modulation supports multiple modulation formats. In this embodiment, the IQ modulator 131 operates in carrier-suppressed single-sideband modulation mode, retaining a -1st-order sideband. To operate in this mode, the tuning signal input port of the IQ modulator 131 receives a suitable tuning signal and sets it to the corresponding operating point. Both sub-Mach-Zehnder electro-optic modulators are set at the carrier-suppressed point, with a 180° phase difference between the two arms of the sub-modulators, and a 90° phase difference is introduced between the upper and lower arms of the main modulator. A set of microwave signals with the same power and a 90° phase difference is generated by the microwave signal generation unit 42 to drive the IQ modulator 131. The frequency of the microwave signals is between 10 GHz and 12 GHz.

[0070] In this embodiment, filter 132 uses an upload / download type microring structure to achieve bandpass filter functionality. A thermal electrode is deposited above the ring waveguide to support active tuning.

[0071] In this embodiment, the passband center of the micro-loop filter is aligned with the single-sideband signal emitted after modulation by the IQ modulator 131, in order to further filter out spurious frequencies and improve the sideband rejection ratio. By combining the IQ modulator 131 and the micro-loop filter, a cleaner single-sideband signal can be obtained.

[0072] In this embodiment, the first intensity modulator 141 and the second electro-optic modulator are Mach-Zehnder type electro-optic modulators. The modulator electrodes are in the form of traveling wave electrodes, and a thermal phase shifter is provided on the modulation arm of the modulator to add an additional phase shift to the optical signal. The modulator is based on the carrier dispersion effect. The bias signal input terminal of the modulator receives a bias voltage to bias the PN junction of the modulator. At a bias voltage of -3V, the bandwidth of the first intensity modulator 141 and the second intensity modulator 142 is >30GHz.

[0073] In this embodiment, the first intensity modulator 141 and the second intensity modulator 142 perform pulse generation. Both the first intensity modulator 141 and the second intensity modulator 142 receive tuning signals and are set to the null operating point. The pulse signal input port receives the pulse signal. Cascading the intensity modulators can improve the extinction ratio of the generated pulse signal to meet the extinction ratio requirements of the Brillouin optical time domain analyzer. In this embodiment, the static extinction ratio is >45dB, and the dynamic extinction ratio is >40dB.

[0074] In this embodiment, the structure of the polarization controller 143 is as follows: Figure 2 As shown, it consists of two Mach-Zehnder interferometer structures with thermo-optical phase shifters and a deflection-rotation beam combiner. Polarization switching can be achieved by adjusting the first-stage thermo-optical phase shifter, and polarization scrambling can be achieved by jointly adjusting the first and second-stage thermo-optical phase shifters.

[0075] In this embodiment, the photodetector 15 is a germanium-silicon photodetector 15, which is achieved by doping on a silicon waveguide and epitaxial growth of germanium.

[0076] Example 2

[0077] like Figure 3 As shown, this embodiment also provides a Brillouin optical time domain analyzer system, including:

[0078] The Brillouin optical time-domain analyzer chip as described in Example 1;

[0079] Laser module 2 provides continuous single-frequency laser light and connects to the external light source input port of Brillouin optical time domain analyzer chip 1;

[0080] The optical amplification and optical transmission unit includes an optical isolator 31, an optical amplifier 32, and an optical circulator 33; wherein the input of the optical amplifier 32 is connected to the pump light output port of the Brillouin optical time domain analyzer, and the output of the optical amplifier 32 is connected to port 1 of the optical circulator 33; the input of the optical isolator 31 is connected to the probe light output port of the Brillouin optical time domain analyzer chip 1, and the output of the optical isolator 31 is connected to the beginning of the sensing fiber 6; and port 3 of the optical circulator 33 is connected to the scattering signal input port of the Brillouin optical time domain analyzer.

[0081] The drive and control circuit includes a pulse signal generation unit 41, a microwave signal generation unit 42, a tuning and bias signal generation unit 43, a receiving signal conditioning unit 44, and a signal acquisition unit 45. The output of the pulse signal generation unit 41 is connected to the pulse signal input port group of the Brillouin optical time-domain analyzer chip 1; the output of the microwave signal generation unit 42 is connected to the microwave signal input port group of the Brillouin optical time-domain analyzer chip 1; the output of the tuning and bias signal generation unit 43 is connected to the tuning and bias signal input port group; the input of the receiving signal conditioning unit 44 is connected to the receiving signal output port of the Brillouin optical time-domain analyzer chip 1; and the output of the receiving signal conditioning unit 44 is connected to the input of the signal acquisition unit 45.

[0082] Signal processing unit 5 executes the demodulation algorithm program of the Brillouin optical time domain analyzer;

[0083] The end of the sensing fiber 6 is connected to port 2 of the optical circulator 33.

[0084] The Brillouin optical time-domain analyzer chip and Brillouin optical time-domain analyzer sensing system in this embodiment support multiple modulation and demodulation schemes. Preferably, a single-pulse scheme is used in this example. The system settings are as follows:

[0085] Laser module 2 provides 1550nm single-frequency continuous light, which enters Brillouin optical time-domain analyzer chip 1 through an external light source input port. First, the light source selection switch 123 selects the input light of laser module 2 as the light source for subsequent chip links by adjusting the thermal phase shifter. The adjustable beam splitter 124 splits the light into two beams at a certain ratio, one beam enters the probe light generation unit, and the other beam enters the pump light generation unit.

[0086] In the probe light generation unit, the IQ modulator 131 is set to carrier-suppressed single-sideband mode and driven by the signal generated by the microwave signal generation unit 42. The microwave signal generation unit 42 includes a microwave signal transmitter, an RF amplifier, and a 90° hybrid coupler; the output of the microwave signal generator is connected to the input of the RF amplifier, and the output of the RF amplifier is connected to the input of the 90° hybrid coupler. The RF signal generated by the microwave signal generation unit 42 drives the IQ modulator 131 to perform single-sideband modulation, with the modulation frequency scanning from 10.725 GHz to 10.975 GHz in 2 MHz steps. The single-sideband signal output by the IQ modulator 131 is further filtered by a micro-loop filter 132 to remove spurious frequencies, thereby obtaining a higher quality single-sideband signal. Continuous probe light is emitted through the probe light output port of the Brillouin optical time-domain analyzer chip 1, passes through the optical isolator 31, and enters the sensing fiber 6 from the other end.

[0087] In the pump light generation unit, two cascaded Mach-Zehnder modulators are biased at the null point and driven by a signal generated by the pulse signal generation unit 41. The pulse signal generation unit 41 is an arbitrary signal generator that produces a pulse sequence with a pulse width of 50 ns and a period of 270 μs, driving the on-chip cascaded first intensity modulator 141 and second intensity modulator 142. The polarization controller 143 can adjust the polarization state of the output pulse through the configuration of the thermal phase shifter. The modulated pump pulse is emitted from the pump light output port of the Brillouin optical time domain analyzer chip 1, amplified by the erbium-doped fiber amplifier, and then enters the sensing fiber 6 through the optical circulator 33. The sensing fiber 6 is a 25 km G.652.D single-mode fiber. The signal light carrying stimulated Brillouin scattering enters the chip from port 3 of the optical circulator 33 through the scattering signal input port of the Brillouin optical time domain analyzer chip 1 and is received by the on-chip photodetector 15.

[0088] The current signal output by the photodetector 15 is processed by the receiving signal conditioning unit 44. The receiving signal conditioning unit 44 is a transimpedance amplifier circuit with a bandwidth of approximately 200MHz, which converts the current signal generated by the on-chip electro-optic modulator into a voltage signal.

[0089] The output signal of the receiving signal conditioning unit 44 is acquired by the signal acquisition unit 45. The signal acquisition unit 45 is an acquisition card that records 1000 time-domain trajectories at each frequency scan point.

[0090] Temperature sensing experiments were conducted using the Brillouin optical time-domain analyzer system built based on this implementation method. Figure 4 The diagram shows the Brillouin frequency shift distribution of the demodulated 25km sensing fiber 6. The inset shows a magnified view near the fiber end, clearly demonstrating the Brillouin frequency shift caused by the 60℃ hotspot. The experiment illustrates that the Brillouin optical time-domain analyzer in this embodiment can effectively achieve temperature sensing, meeting application requirements.

[0091] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A Brillouin optical time-domain analyzer chip, characterized in that, include: The light source selection and distribution unit, the probe light generation unit, the pump light generation unit, the light detection unit, the optical signal port, and the electrical signal port; The optical signal port includes a first optical signal port (111) and a second optical signal port (112); the first optical signal port (111) includes an external light source input port, a test output port, a probe light output port, a pump light output port, and a scattering signal input port; the second optical signal port (112) includes a laser chip input port; The signals from the external light source and the laser are input through the optical signal port and then connected to the light source selection and distribution unit via polarization beam splitters. The light source selection and distribution unit includes a light source selection switch (123) and a beam splitter (124). The output of the light source selection and distribution unit is connected to the input of the probe light generation unit and the pump light generation unit, respectively. The probe light generation unit includes an IQ modulator (131) and a filter (132) based on a dual parallel Mach-Zehnder modulator structure; the output of the probe light generation unit is connected to an optical signal port for output. The IQ modulator (131) is a dual flat Mach-Zehnder type electro-optic modulator, which includes two identical sub-Mach-Zehnder type electro-optic modulators. The modulator electrodes are in the form of traveling wave electrodes. A thermal phase shifter is provided on the modulation arm of the main modulator and the modulation arm of the sub-modulator to add an additional phase shift to the optical signal. The tuning signal input port of the IQ modulator (131) receives the tuning signal and is set to operate in carrier-suppressed single-sideband modulation mode, while retaining the -1st order sideband; the bias signal input port of the IQ modulator (131) receives the bias voltage, so that both sub-Mach-Zehnder electro-optic modulators are set at the carrier suppression point; the phase difference between the two arms of the sub-modulators of the IQ modulator (131) is 180°. The upper and lower arms of the main modulator introduce 90° The phase difference is driven by a set of microwave signals with the same power and a 90° phase difference; The filter (132) uses an upload / download type microring structure with a hot electrode deposited above the ring waveguide; the passband center of the microring filter is aligned with the single-sideband signal emitted after modulation by the IQ modulator (131); The pump light generation unit includes a cascaded first intensity modulator (141) and second intensity modulator (142) based on a Mach-Zehnder modulator structure, as well as a polarization controller (143); the output of the pump light generation unit is connected to an optical signal port for output. The first intensity modulator (141) and the second intensity modulator (142) are Mach-Zehnder type electro-optic modulators. The modulator electrodes are in the form of traveling wave electrodes. A thermal phase shifter is provided on the modulation arm of the modulator to add an additional phase shift to the optical signal. The bias signal input terminal of the modulator receives the bias voltage to realize the bias of the modulator PN junction. The first intensity modulator (141) and the second intensity modulator (142) perform pulse generation function. Both the first intensity modulator (141) and the second intensity modulator (142) receive the tuning signal and are set to the null operating point. The pulse signal input port receives the pulse signal. The optical detection unit includes a photodetector (15) connected to the optical signal port for receiving probe light input.

2. The Brillouin optical time-domain analyzer chip according to claim 1, characterized in that, The external light source input port is connected to the input of the first polarization beam splitter (121), and the output of the first polarization beam splitter (121) is connected to the first input of the light source selection switch (123); the laser chip input port is connected to the input of the second polarization beam splitter (122), and the output of the second polarization beam splitter (122) is connected to the second input of the light source selection switch (123); the first output of the light source selection switch (123) is connected to the test output port, and the second output of the light source selection switch (123) is connected to the input of the beam splitter (124); the first output of the beam splitter (124) is connected to the IQ modulator (…). The input of IQ modulator (131) is connected to the input of filter (132), and the output of filter (132) is connected to the probe light output port; the second output of beam splitter (124) is connected to the input of first intensity modulator (141), the output of first intensity modulator (141) is connected to the input of second intensity modulator (142), the output of second intensity modulator (142) is connected to the input of polarization controller (143), and the output of polarization controller (143) is connected to the pump light output port; the scattering signal input port is connected to the input of photodetector (15).

3. The Brillouin optical time-domain analyzer chip according to claim 2, characterized in that, The first optical signal port (111) and the second optical signal port (112) adopt cantilever beam edge couplers and remove the silicon substrate under the buried oxide layer; The first optical signal port (111) and the second optical signal port (112) are located at the edge of the chip. The first optical signal port (111) is fixed to the fiber array by UV adhesive curing, providing a standard interface for the connection of external optical devices.

4. The Brillouin optical time-domain analyzer chip according to claim 1, characterized in that, The electrical signal ports include a pulse signal input port group, a microwave signal input port group, a tuning and bias signal input port group, and a receive signal output port; The pulse signal input port group is connected to the drive terminals of the first intensity modulator (141) and the second intensity modulator (142); The microwave signal input port group is connected to the drive terminal of the IQ modulator (131); The tuning and bias signal input port group includes the operating point tuning input terminals of the light source selection switch (123), beam splitter (124), IQ modulator (131), filter (132), first intensity modulator (141), second intensity modulator (142) and polarization controller (143), as well as the bias point input terminals of IQ modulator (131), first intensity modulator (141), second intensity modulator (142) and photodetector (15); The signal receiving output port includes the output port of the photodetector (15).

5. A Brillouin optical time-domain analyzer chip according to claim 1, characterized in that, In the light source selection and allocation unit: The light source selection switch (123) is based on an interferometer structure and includes two multimode interference couplers and a thermo-optical phase shifter. By adjusting the thermo-optical phase shifter, the input laser of either the external light source input port or the laser chip input port can be selected as the light source for the subsequent link. The beam splitter (124) is based on an interferometer structure and consists of two multimode interference couplers and a thermo-optical phase shifter. The phase difference between the two arms is adjusted through the thermo-optical phase shifter, thereby achieving the adjustment of any beam splitting ratio. The beam splitter (124) splits the incident light into two beams, one of which enters the probe light generation unit and the other enters the pump light generation unit.

6. A Brillouin optical time-domain analyzer chip according to claim 1, characterized in that, The polarization controller (143) includes two Mach-Zehnder interferometer structures with thermo-optical phase shifters and a deflection-rotation beam combiner.

7. A Brillouin optical time-domain analyzer sensing system, characterized in that, Includes the Brillouin optical time-domain analyzer chip as described in any one of claims 1-6; Laser module (2) provides continuous single-frequency laser and connects to the external light source input port of Brillouin optical time domain analyzer chip (1); The optical amplification and optical transmission unit includes an optical isolator (31), an optical amplifier (32), and an optical circulator (33); wherein the input of the optical amplifier (32) is connected to the pump light output port of the Brillouin optical time domain analyzer, and the output of the optical amplifier (32) is connected to port 1 of the optical circulator (33); the input of the optical isolator (31) is connected to the probe light output port of the Brillouin optical time domain analyzer chip (1), and the output of the optical isolator (31) is connected to the beginning of the sensing fiber (6); and port 3 of the optical circulator (33) is connected to the scattering signal input port of the Brillouin optical time domain analyzer. The drive and control circuit includes a pulse signal generation unit (41), a microwave signal generation unit (42), a tuning and bias signal generation unit (43), a receiving signal conditioning unit (44), and a signal acquisition unit (45); wherein, the output of the pulse signal generation unit (41) is connected to the pulse signal input port group of the Brillouin optical time domain analyzer chip (1), the output of the microwave signal generation unit (42) is connected to the microwave signal input port group of the Brillouin optical time domain analyzer chip (1), the output of the tuning and bias signal generation unit (43) is connected to the tuning and bias signal input port group, the input of the receiving signal conditioning unit (44) is connected to the receiving signal output port of the Brillouin optical time domain analyzer chip (1), and the output of the receiving signal conditioning unit (44) is connected to the input of the signal acquisition unit (45); The signal processing unit (5) executes the demodulation algorithm program of the Brillouin optical time domain analyzer; The end of the sensing fiber (6) is connected to port 2 of the optical circulator (33).

Images