Measuring device, measuring method and detection equipment

Abstract

The present disclosure provides a measurement device, comprising: a beam splitter for splitting an input laser into a reference optical signal and a measurement optical signal; the measurement optical signal is reflected by the to-be-measured target to form a reflection optical signal; the optical interference coupler comprises at least two input ports and a plurality of output ports, and the reference optical signal and the reflected optical signal enter the interference coupler from the two input ports respectively; the interference coupler enables the reference light signal to interfere with the emission light signal to obtain N paths of light intensity signals output by the N output ports, and the N paths of light intensity signals have the same phase difference; wherein N is an integer not less than 2; the photoelectric detector is used for converting the N paths of light intensity signals into N paths of electric signals; and the feedback control module is used for adjusting the input laser according to the light intensity information carried by the at least two paths of electric signals so as to lock the interference points of the reference light signal and the reflected light signal. The invention further provides a measuring method and detection equipment.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of measurement, in particular to a measurement device, a measurement method and a detection equipment. BACKGROUND

[0002] In the application background of precision measurement, microsystem regulation and complex structure monitoring, high-fidelity acquisition and dynamic tracking of low-frequency weak vibration signals are becoming increasingly important. Especially in the low-frequency band of 1Hz to several thousand Hz, the key physical processes such as structure resonance response, environmental disturbance monitoring and biological signal perception often exhibit micro-amplitude and long-term vibration, which puts higher requirements on the sensitivity and stability of the measurement device. Optical interference measurement technology has been widely used in micro-nano displacement detection and vibration monitoring due to its non-contact, high resolution and anti-electromagnetic interference advantages. However, in the low-frequency measurement scene, the optical interference measurement device is easily affected by factors such as light source wavelength drift, temperature fluctuation and polarization disturbance, resulting in slow and significant drift of the output phase, and then causing strong 1 / f noise. This low-frequency phase instability will seriously interfere with the identification and reconstruction of weak signals, causing baseline fluctuation and cumulative error, and then limiting the minimum detectable vibration and practical application ability of the system. SUMMARY

[0003] The present disclosure provides a measurement device, a measurement method and a detection equipment using the measurement device.

[0004] In a first aspect, the present disclosure provides a measurement device, comprising: a beam splitter for splitting an input laser into a reference light signal and a measurement light signal; the measurement light signal forms a reflected light signal after being reflected by a target to be measured; an optical interference coupler comprising at least two input ports and a plurality of output ports, the reference light signal and the reflected light signal enter the interference coupler from two input ports respectively; the interference coupler causes the reference light signal and the reflected light signal to interfere, obtaining N light intensity signals output by N output ports respectively, the N light intensity signals have the same phase difference between them; wherein N is an integer not less than 2; a photodetector for converting the N light intensity signals into N electrical signals; a feedback control module for adjusting the input laser according to the light intensity information carried by at least two electrical signals to lock the interference point of the reference light signal and the reflected light signal.

[0005] In some embodiments, the beam splitter, the optical interference coupler, the photodetector and the feedback control module are integrated on a chip; the measurement device further comprises an optical waveguide system, which constitutes the light path of the reference light signal, the measurement light signal, the reflected light signal and the light intensity signal on the chip.

[0006] In some embodiments, the measuring device further comprises an on-chip laser, which is controlled by the feedback control module to fine-tune the input laser.

[0007] In some embodiments, the measuring device further comprises an on-chip electro-optical modulator, which is controlled by the feedback control module to adjust the input laser.

[0008] In some embodiments, the measuring device further comprises a signal output module, which obtains interference information according to the N electrical signals and outputs.

[0009] In some embodiments, the feedback control module comprises: a comparison submodule, which obtains the difference between any two of the electrical signals; a calculation submodule, which obtains a digital control quantity according to the difference using a predetermined control algorithm; a conversion submodule, which converts the digital control quantity into an analog voltage signal; and an output submodule, which generates a control signal according to the analog voltage signal to drive the laser to fine-tune the input signal or to control the electro-optical modulator to adjust the input signal.

[0010] In some embodiments, the optical interference coupler comprises an N×N optical coupler.

[0011] In a second aspect, the embodiments of the present disclosure provide a measuring method, characterized in that comprising: dividing an input laser into a reference light signal and a measurement light signal; the measurement light signal forms a reflected light signal after being reflected by a target to be measured; causing the reference light signal to interfere with the reflected light signal to obtain N light intensity signals, the N light intensity signals having the same phase difference; wherein N is an integer not less than 2; converting the N light intensity signals into N electrical signals; and adjusting the input laser according to the light intensity information carried by at least two of the electrical signals to lock the interference point of the reference light signal and the reflected light signal.

[0012] In some embodiments, the measuring method further comprises: obtaining interference information according to the N electrical signals and outputting.

[0013] In a third aspect, the embodiments of the present disclosure provide a detection device comprising the measuring device according to the first aspect of the embodiments of the present disclosure.

[0014] The measuring device, the measuring method and the detection equipment applying the measuring device of the embodiments of the present disclosure can realize dynamic self-locking of the interference working point without relying on external reference light or spectrum scanning based on the characteristics that the phase difference between the output ports of the optical interference coupler is equal, and further realize high-fidelity, real-time measurement and stable-state tracking of the low-frequency weak vibration signal, thereby constructing a self-stable phase demodulation mechanism without reference signal and calibration process, which well suppresses the low-frequency drift of the interference system and significantly improves the measurement stability and signal-to-noise ratio performance of the measuring device and the detection equipment in the low-frequency band. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A schematic block diagram of a measuring device according to an embodiment of the present disclosure.

[0016] Figure 2 A schematic block diagram of a measuring device according to another embodiment of the present disclosure.

[0017] Figure 3 A schematic block diagram of a measuring device according to still another embodiment of the present disclosure.

[0018] Figure 4 A schematic diagram of a phase self-locking mechanism according to an embodiment of the present disclosure.

[0019] Figure 5 A schematic structural block diagram of a feedback control module of a measuring device according to an embodiment of the present disclosure.

[0020] Figure 6 A schematic block diagram of a specific example of a measuring device according to an embodiment of the present disclosure.

[0021] Figure 7 A schematic block diagram of another specific example of a measuring device according to an embodiment of the present disclosure.

[0022] Figure 8 A schematic block diagram of another specific example of a measuring device according to an embodiment of the present disclosure.

[0023] Figure 9 A schematic block diagram of another specific example of a measuring device according to an embodiment of the present disclosure.

[0024] Figure 10 A schematic flowchart of a measuring method according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0025] In order for those skilled in the art to better understand the technical solutions of the present disclosure, the technical solutions of the present disclosure are described in detail below with reference to the drawings.

[0026] Example embodiments will be described more fully hereinafter with reference to the accompanying drawings; this Example embodiments may, however, be embodied in different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0027] In the case of no conflict, each embodiment of the disclosure and each feature in the embodiment can be combined with each other.

[0028] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0030] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an overly literal or overly formal sense unless expressly so defined herein.

[0031] The existing optical interference measurement device generally exists the key technical difficulties such as serious phase drift and 1 / f noise dominant in the low frequency band. 1 / f noise is a low-frequency noise whose noise power is inversely proportional to frequency. Since 1 / f noise cannot be filtered out, it is an important limiting factor that hinders the realization of high-quality performance in precision measurement applications. In some related technologies, in order to obtain high-stability interference output, it is often necessary to rely on frequency spectrum scanning, spectrum demodulation, or use a tunable laser for fine control. However, these schemes generally have problems such as complex system, response delay, and dependence on external control.

[0032] The embodiments of the present disclosure aim to solve the problems of continuous strong 1 / f noise caused by factors such as wavelength drift of the light source, temperature fluctuation, and polarization disturbance, and propose a measurement device.

[0033] The embodiments of the present disclosure provide a measurement device, such as Figure 1As shown, the measuring device includes: a beam splitter 2, which splits the input laser into a reference light signal and a measurement light signal; the measurement light signal is reflected by the target to form a reflected light signal; an optical interference coupler 5, including at least two input ports and multiple output ports, wherein the reference light signal and the reflected light signal enter the interference coupler from the two input ports respectively; the interference coupler causes the reference light signal to interfere with the emitted light signal, thereby obtaining N light intensity signals output from the N output ports respectively, wherein the N light intensity signals have the same phase difference; wherein N is an integer not less than 2; a photodetector 6, which converts the N light intensity signals into N electrical signals; and a feedback control module 7, which adjusts the input laser according to the light intensity information carried by at least two electrical signals to lock the interference point between the reference light signal and the reflected light signal.

[0034] In some embodiments, the optical interference coupler 5 is an N×N optical coupler, such as a 2×2, 3×3, or 4×4 optical coupler. This N×N optical coupler is used to interfere the optical signals of the reference arm and the measurement arm, and generates N optical intensity signals (I1, I2, ..., I...) at the output. N N optical intensity signals (I1, I2, ..., I N The phase difference between the two phases is fixed at 2π / N, which is used to construct the phase reconstruction model.

[0035] Suppose the expression for the nth output signal of the coupler is as follows:

[0036]

[0037] Where φ is the optical interference phase, A is the light intensity amplitude, and B is the DC drift of the light intensity.

[0038] To achieve stability of the interference phase point during long-term system operation, using I n with I n+1 For example, when I n =I n+1 At that time, it can be seen from the above formula that:

[0039]

[0040] Where k is a positive integer, the system operating point is locked at k. etc.

[0041] In some embodiments, the beam splitter 2, the optical interference coupler 5, the photodetector 6, and the feedback control module 7 are integrated on the chip; the measurement device also includes an optical waveguide system, which forms the optical path for the reference optical signal, the measurement optical signal, the reflected optical signal, and the light intensity signal to propagate on the chip.

[0042] In some embodiments, the measurement device further comprises an on-chip laser, which is controlled by the feedback control module to fine-tune the input laser.

[0043] In some embodiments, the measurement device further comprises an on-chip electro-optical modulator, which is controlled by the feedback control module to modulate the input laser.

[0044] In some embodiments, the measurement device further comprises a signal output module to obtain the interference information from the N electrical signals and output.

[0045] Suppose the nth output signal of the coupler is expressed as follows:

[0046]

[0047] where φ is the optical interference phase, A is the light intensity amplitude, and B is the DC drift of the light intensity. The N light intensity signals constitute a cosine phase set with φ as the central parameter. The value of φ can be decoupled by algebraic reconstruction or vector projection, and then the low-frequency vibration signal is inverted.

[0048] In some embodiments, the feedback control module comprises:

[0049] a comparison submodule to obtain the difference between any two electrical signals;

[0050] a calculation submodule to obtain a digital control quantity using a predetermined control algorithm according to the difference;

[0051] a conversion submodule to convert the digital control quantity into an analog voltage signal;

[0052] an output submodule to generate a control signal according to the analog voltage signal to drive the laser to fine-tune the input signal or to control the electro-optical modulator to modulate the input signal.

[0053] In some embodiments, the optical interference coupler comprises an NxN optical coupler, such as a 2x2 optical coupler, a 3x3 optical coupler, or a 4x4 optical coupler.

[0054] Figure 2A schematic block diagram of a measurement device 10A according to an embodiment of the present disclosure is shown. The measurement device 10A comprises: a beam splitter 2 which divides the input laser from a light source into a reference light signal and a measurement light signal; an optical interference coupler 5 comprising at least two input ports and a plurality of output ports, the reference light signal directly entering the optical interference coupler 5 from one input port, the measurement light signal forming a reflected light signal after being reflected by a target to be measured 4 and entering the optical interference coupler 5 from another input port, wherein N is an integer not less than 2; a photodetector which converts N light intensity signals into N electrical signals; and a feedback control module 7 which adjusts the input laser according to the light intensity information carried by the at least two electrical signals to lock the interference point of the reference light signal and the reflected light signal.

[0055] Based on the inherent phase difference characteristics between the light intensity signals output by the output ports of the optical interference coupler 5, the present disclosure can achieve dynamic self-locking of the interference working point without relying on external reference light or spectrum scanning, thereby achieving high-fidelity, real-time measurement and stable-state tracking of low-frequency weak vibration signals, and thus constructing a self-stabilized phase demodulation mechanism without a reference signal and a calibration process. The mechanism effectively suppresses the low-frequency drift of the interference system and significantly improves the measurement stability and signal-to-noise ratio performance of the measurement device in the low-frequency band.

[0056] Figure 3 A measurement device 10B according to another embodiment of the present disclosure is shown. The measurement device is a self-stabilized optical interference measurement device suitable for an integrated photonic chip platform.

[0057] Embodiments of the present disclosure also aim to solve the problem that measurement devices are difficult to miniaturize for integration into a photonic chip platform, and are particularly unsuitable for deployment in large-scale array sensor networks or on-chip sensor systems.

[0058] With the development of integrated photonics technology, more and more sensor systems are beginning to shift to silicon-based photonic chip platforms, with the expectation of taking advantage of the high integration, low power consumption and scalability of the platforms to construct a new generation of miniaturized vibration measurement devices. Some related technologies are difficult to miniaturize and integrate, and are particularly unsuitable for deployment in large-scale array sensor networks or on-chip sensor systems. Moreover, in the process of on-chip integration, the optical waveguide interference structure is more sensitive to process errors and thermal disturbances, and how to achieve low-frequency stable interference demodulation and automatic working point locking in an on-chip sensor has become a key challenge restricting its performance.

[0059] Therefore, there is a need for an interference measurement device that is compact in structure and suitable for an integrated photonic chip (waveguide) platform, does not require pre-calibration, and has an endogenous phase stabilization mechanism. The device can achieve high-fidelity, real-time measurement and stable-state tracking of low-frequency weak vibration signals without relying on external reference light or spectrum scanning.

[0060] To address the aforementioned problems in the prior art, this disclosure provides a measurement device 10B according to another embodiment. The system includes: a laser unit 1, a beam splitter 2, an output optical path 3, a target under test 4, an optical interference coupler 5, a photodetector 6, a feedback control module 7, and a signal output unit 8. Wherein, N is an integer not less than 2; in some preferred embodiments, N is 3 or 4. The measurement device can be at least partially integrated into a photonic chip platform and is suitable for real-time stable measurement of weak vibration signals.

[0061] Laser unit 1 is used to couple stable, continuous light output from the laser into the photonic chip platform. In some preferred embodiments, the laser is a distributed feedback laser (DFB) with good wavelength frequency stability. In some embodiments, the laser can be combined with an electro-optic modulator in the photonic chip platform to achieve phase or wavelength fine-tuning.

[0062] The measurement device includes a reference arm and a measurement arm. The beam splitter 2 is used to split the input laser into a reference optical signal propagating through the reference arm and a measurement optical signal propagating through the measurement arm. In some embodiments, the beam splitter 2 may include an on-chip Y-branch waveguide, a multimode interferometer (MMI) beam splitter, etc.

[0063] The reference arm is connected to the optical interference coupler 5 to maintain a fixed optical path. The measuring arm guides the measurement light signal to the target 4 through the output light path 3 to sense the minute optical path disturbances caused by external low-frequency vibrations.

[0064] The optical interference coupler 5 is a multi-port interference coupling structure. In some preferred embodiments, the optical interference coupler 5 adopts an on-chip multimode interference (MMI) structure or a cross waveguide structure.

[0065] In some embodiments, the optical interference coupler 5 is an N×N optical coupler, such as a 2×2, 3×3, or 4×4 optical coupler. This N×N optical coupler is used to interfere the optical signals of the reference arm and the measurement arm, and generates N optical intensity signals (I1, I2, ..., I...) at the output. N N optical intensity signals (I1, I2, ..., I N The phase difference between the two phases is fixed at 2π / N, which is used to construct the phase reconstruction model.

[0066] The photodetector 6 is preferably a photodetector array, correspondingly disposed after each output port of the optical interference coupler 5, for converting each light intensity signal into an electrical signal. In some embodiments, the photodetector 6 may be an integrated photodiode array integrated into a photonic chip platform. In some embodiments, the optical interference coupler 5 can be coupled to an external high-speed photodetector 6 via a chip to achieve signal acquisition.

[0067] The feedback control module 7 performs feedback control based on the difference between any two of the N light intensity signals obtained from the optical interference coupler 5 to fine-tune the wavelength of the input laser, thereby realizing the closed-loop self-stabilization function of the measurement device 10B.

[0068] The signal output unit 8 is used to collect, process and output the optical phase or displacement response signal obtained after final demodulation, and can be connected to an upper system through a data interface for subsequent monitoring, analysis and identification tasks.

[0069] The above modules or units of the measurement device 10B of the present disclosure can be integrated on a silicon-based, silicon nitride or other photonic platform, and the overall structure is compact, suitable for large-scale layout, multi-channel array expansion and low-power embedded deployment, and particularly suitable for low-frequency weak vibration real-time detection application scenarios in complex environments. Moreover, the measurement device 10B of the present disclosure is based on the inherent phase difference characteristics between the output ports of the optical interference coupler, and constructs an on-chip self-stabilized phase demodulation mechanism without reference signal and calibration process, which suppresses the low-frequency drift of the interference system from the source, and realizes the realizability, low-frequency measurement stability and signal-to-noise ratio performance of the system on the integrated photonic chip platform.

[0070] Regarding the direct phase demodulation and automatic locking mechanism without external reference optical signal proposed in the present disclosure, Figure 4 The principle diagram of the phase self-locking mechanism of the present disclosure is shown.

[0071] Assuming that the nth output signal expression of the coupler is as follows:

[0072]

[0073] where φ is the optical interference phase, A is the light intensity amplitude, and B is the DC drift of the light intensity. The N light intensity signals constitute a cosine phase set with φ as the center parameter, and the value of φ can be decoupled by algebraic reconstruction or vector projection, thereby realizing the inversion of the low-frequency vibration signal.

[0074] In addition, in order to realize the stability of the interference phase point during the long-term operation of the system, the present disclosure constructs a locking strategy based on the output symmetry. Taking I n and I n+1 as examples, when I n = I n+1 , it can be known from the above formula that:

[0075]

[0076] where k is a positive integer, and the system operating point is locked at and the like.

[0077] The control measurement device 10B keeps detecting I n -In+1 the feedback error signal, the closed-loop controller drives the laser current to make the light source wavelength adjust in real time, and automatically pull the interference point back to the target position so that I n = I n+1 , and the immunity of the interference system to disturbances is achieved.

[0078] Referring to Figure 4 It can be seen that, under the disturbance condition, the measuring device 10B can automatically control the interference point to be stably controlled at a given phase position, and suppress low-frequency phase drift. The control principle of this method is clear, the algorithm convergence is strong, and the hardware interface is simple, which is suitable for different order coupler systems and has migration application ability in integrated photon chip platform.

[0079] It can be seen that the measuring device 10B of the embodiment of the disclosure fully utilizes the inherent 2π / N phase difference relationship between the output ports of the optical interference coupler, and proposes a self-stable phase demodulation mechanism without external reference light or spectrum scanning. By constructing a multi-channel interference output model with symmetry or cosine characteristics, the real optical phase caused by low-frequency weak vibration is directly decoupled and reconstructed, and high-resolution and real-time measurement output is realized. The demodulation and locking mechanism of the disclosure is suitable for various coupler structures, including 2x2, 3x3 and 4x4, etc., has good universality and expansibility, is convenient to deploy in different platforms, and is especially suitable for implementation on integrated photon chip platform.

[0080] Due to the above characteristics of the measuring device of the disclosure, it is suitable for detection tasks of various low-frequency micro-vibration signals, and due to its high sensitivity, strong stability and easy integration, it can be widely applied to the following scenes: in the fields of structural health monitoring, bridge and tunnel state evaluation, precision instrument vibration analysis, etc., for detecting low-frequency micro-displacement or disturbance, meeting the long-term continuous monitoring demand; in sound information acquisition and acoustic vibration communication terminal, for extracting vibration information such as structure sound and voice signal, suitable for intelligent terminal, edge device, vibration perception module and other scenes; in integrated photon chip platform and microsystem, for constructing on-chip vibration sensor, micro-detection node and multi-channel interference network, improving system integration and deployment flexibility; the system can also be combined with other electronic, optical or algorithm modules, and applied to industrial detection, environmental monitoring, biological signal detection, underwater acoustic vibration perception and other composite technology fields.

[0081] Figure 5 A schematic structural block diagram of the feedback control module 7 of the measuring device 10B of the embodiment of the disclosure is shown. As Figure 5As shown, the feedback control module 7 includes a comparison submodule 701, a calculation submodule 702, a digital-to-analog conversion submodule 703, and an output submodule 704. The comparison submodule 701 obtains the difference between any two of the interference output signals from the optical interference coupler 5. The calculation submodule 702 outputs an adjustment instruction according to a preset control method; in some embodiments, the preset control method includes PID (proportional-integral-derivative control), sliding mode control, etc. The digital-to-analog conversion submodule 703 converts the digital control quantity into an analog voltage signal. The output submodule 704 generates a control voltage to drive the laser, achieving fine tuning of the laser wavelength. The control process is continuously performed by the feedback control module 7, forming a complete closed-loop structure, without the need for pre-calibration or spectral scanning, to obtain good real-time performance and stability.

[0082] The measurement device 10B realizes the following working process by means of the optical interference coupler 5 and the feedback control module 7: the vibration signal causes structural displacement, thereby forming an interference phase difference, which causes the N-channel output of the optical interference coupler 5 to output N light intensity signals with a 2π / N phase difference, and the feedback control module 7 performs phase demodulation and difference feedback control to dynamically adjust the wavelength of the laser, thereby keeping the interference point stable and keeping the phase output stable.

[0083] The measurement device 10B of the embodiments of the present disclosure introduces a closed-loop feedback control strategy while adopting the optical interference coupler for automatic locking of the interference working point, and calculates the difference between any two of the interference outputs in real time and uses it as a feedback variable to drive the laser, and adjusts the wavelength or phase of the laser stably through a PID control method, etc., to realize automatic locking and long-term stable maintenance of the interference working point, effectively resisting the influence of slow-changing factors such as wavelength drift and polarization disturbance, without the need for pre-calibration and manual intervention.

[0084] Reference will be made to the following Figures 6-9 Some specific examples of the measurement device with self-stabilization capability constructed based on an integrated photonic chip platform according to the present disclosure are described in detail.

[0085] Figure 6 A specific example of the measurement device 10C according to the embodiments of the present disclosure is provided.

[0086] As Figure 6As shown, the measurement device 10C includes a laser unit 1, a first beam splitter 2a, a second beam splitter 2b, a target to be measured 4, an optical interference coupler 5, a photodetector 6, a feedback control module 7, and the like; wherein the laser unit 1 is a laser diode, which is coupled to the first beam splitter 2a through a first fiber coupler 11a; the first beam splitter 2a and the second beam splitter 2b can be on-chip 1x2 beam splitters; the second beam splitter 2b is coupled to the target to be measured 4 through a second fiber coupler 11b; the optical interference coupler 5 is a 4x4 multimode interference (MMI) coupler; the 4x4 multimode interference coupler is coupled to the photodetector 6 through a third fiber coupler 11c; and the feedback control module 7 can be a control module using a PID control method.

[0087] When the measurement device 10C is in operation, the input laser of the laser unit 1 is coupled to the inside of the chip through the input waveguide, and is divided into a reference arm and a measurement arm by the first beam splitter 2a. The measurement arm is connected to a microstructure (such as a pressure-sensitive film, a micro-cantilever, etc.) that can respond to external vibration disturbance, and the reflected measurement light and the reference light interfere in the 4x4 multimode interference coupler, and four light intensity signals I1, I2, I3, I4 with a phase difference of π / 2 are obtained at the output end.

[0088] After the four signals are collected by the photodetector 6, the interference phase φ is obtained by using a cosine fitting or an algebraic reconstruction algorithm. At the same time, the system calculates I2-I4 as an error signal in real time, which is input to the feedback control module 7 after D / A conversion to drive the DFB laser current, so as to realize the fine adjustment of the laser wavelength, thereby enabling the system to stably operate near the target interference point (such as ), and realizing the automatic locking and long-term stable maintenance of the working point.

[0089] The measurement device 10C of the present disclosure fully utilizes the inherent 2π / N phase difference relationship between the output ports of the optical interference coupler, and proposes a self-stable phase demodulation mechanism without external reference light or spectrum scanning. By constructing a multi-channel interference output model with symmetry or cosine characteristics, the real optical phase caused by low-frequency weak vibration is directly decoupled and reconstructed, and high-resolution and real-time measurement output is realized. In addition, the measurement device 10C of the present disclosure only relies on a fixed-wavelength laser and a conventional photodetector, without the need for a tunable laser, a spectrometer or a complex phase locking device, and further realizes the on-chip packaging, array deployment and high integration of the embedded sensing system by using the multi-channel interference structure in the integrated photonics chip platform, so that the system structure is simple, the power consumption is low, the decoupling is strong, and the engineering applicability is strong.

[0090] Figure 7 A specific example of the measurement device 10D of the present embodiment.

[0091] As shown in FIG. 10D, the measurement device 10D includes a laser unit 1, a first beam splitter 2a, a second beam splitter 2b, a target to be measured 4, an optical interference coupler 5, a photodetector 6, a feedback control module 7, and the like; wherein the laser unit 1 is a laser diode, which is coupled to the first beam splitter 2a through a first fiber coupler 11a; the first beam splitter 2a and the second beam splitter 2b can be on-chip 1x2 beam splitters; the second beam splitter 2b is coupled to the target to be measured 4 through a second fiber coupler 11b; the optical interference coupler 5 is a 4x4 multimode interference (MMI) coupler; the 4x4 multimode interference coupler is coupled to the photodetector 6 through a third fiber coupler 11c; and the feedback control module 7 can be a control module using a PID control method. Figure 7As shown, the measurement device 10D includes a laser unit 1, a first beam splitter 2a, a second beam splitter 2b, a target to be measured 4, an optical interference coupler 5, a photodetector 6, a feedback control module 7, and the like; wherein the laser unit 1 is a laser diode, which is coupled to the first beam splitter 2a through a first fiber coupler 11a; the first beam splitter 2a and the second beam splitter 2b are on-chip 1x2 beam splitters; the second beam splitter 2b is coupled to the target to be measured 4 through a second fiber coupler 11b; the optical interference coupler 5 is a 3x3 multimode interference coupler; the 3x3 multimode interference coupler is coupled to the photodetector 6 through a third fiber coupler 11c; and the feedback control module 7 can be a control module using a PID control method.

[0092] When the measurement device 10D is in operation, the input laser of the laser unit 1 is coupled to the inside of the chip through an input waveguide, and is divided into a reference arm and a measurement arm by the first beam splitter 2a. The measurement arm is connected to a microstructure (such as a pressure-sensitive film, a micro-cantilever, or the like) that can respond to external vibration disturbance, and the reflected measurement light and the reference light interfere with each other in the 3x3 multimode interference coupler, so that three light intensity signals I1, I2, and I3 with a phase difference of 2π / 3 are obtained at the output end, and there is a fixed phase difference between them

[0093] After the three signals are collected by the photodetector 6, the interference phase φ is obtained by using a cosine fitting or an algebraic reconstruction algorithm. At the same time, the system calculates I2-I3 as an error signal in real time, which is input to the feedback control module 7 after D / A conversion, to drive the DFB laser current, so as to realize the fine adjustment of the laser wavelength, so that the system can stably operate near the target interference point (such as ), and realize automatic locking and long-term stable maintenance of the working point.

[0094] The measurement device 10D uses a 3x3 multimode interference coupler with a more compact structure as an interference output unit, which further reduces the system area and complexity while maintaining the self-stabilization control capability.

[0095] Figure 8 A specific example of the measurement device 10E of the embodiments of the present disclosure. The measurement device 10E is an interference measurement device with full-chip self-stabilization capability, that is, the complete on-chip integration of the laser and the optical path is realized.

[0096] As shown in FIG. 10E, the measurement device 10E includes a laser unit 1, a first beam splitter 2a, a second beam splitter 2b, a target to be measured 4, an optical interference coupler 5, a photodetector 6, a feedback control module 7, and the like; wherein the laser unit 1 is a laser diode, which is coupled to the first beam splitter 2a through a first fiber coupler 11a; the first beam splitter 2a and the second beam splitter 2b are on-chip 1x2 beam splitters; the second beam splitter 2b is coupled to the target to be measured 4 through a second fiber coupler 11b; the optical interference coupler 5 is a 3x3 multimode interference coupler; the 3x3 multimode interference coupler is coupled to the photodetector 6 through a third fiber coupler 11c; and the feedback control module 7 can be a control module using a PID control method. Figure 8As shown, the measurement device 10E includes a laser unit 1, a first beam splitter 2a, a second beam splitter 2b, a target to be measured 4, an optical interference coupler 5, a photodetector 6, a feedback control module 7, and the like; wherein the laser unit 1 is an on-chip laser integrated on a photonic chip platform by means of hetero-integration or bonding; the first beam splitter 2a and the second beam splitter 2b are on-chip 1x2 beam splitters; the optical interference coupler 5 is a 4x4 multimode interference coupler; the photodetector 6 is an on-chip photodetector integrated on the photonic chip platform; and the feedback control module 7 can be a control module using a PID control method.

[0097] The input laser of the laser unit 1 is directly injected into the first beam splitter 2a to divide into a reference arm and a measurement arm. The measurement arm waveguide is connected to the target to be measured 4 or an integrated micro device on the chip. The reflected measurement light and the reference light interfere in the 4x4 MMI coupler, and the output port provides four light intensity signals with a phase difference of π / 2.

[0098] The measurement device 10E integrates both the laser unit 1 and the target to be measured 4 on the photonic chip platform, without the need for external lasers and packaged interference paths, and has a higher overall implementation degree, which is conducive to forming a high-integration, self-packaging and low-power on-chip sensor array system.

[0099] Figure 9 This is a specific example of the measurement device 10F of the embodiments of the present disclosure. The measurement device 10F implements an alternative control method without adjusting the wavelength of the laser, which is suitable for the case where the frequency of the laser is fixed but the system needs to have self-stabilization control capability.

[0100] As shown in FIG. 10F, Figure 9 The measurement device 10F includes a power supply 10, a laser unit 1, a first beam splitter 2a, a second beam splitter 2b, a target to be measured 4, an optical interference coupler 5, a photodetector 6, a feedback control module 7, and the like; and the measurement device 10F further introduces an on-chip integrated phase modulator 9 in the interference path, which is, for example, an electro-optical modulator such as a Mach-Zehnder modulator or an acousto-optic modulator, and the modulator is used to finely adjust the phase of the reference arm or the measurement arm. The second beam splitter 2b of the measurement arm is coupled to the target to be measured 4 through a fiber coupler 11. The output signal still uses an NxN multimode interference coupler to provide a multi-channel interference signal, and the difference between two channels of light intensity is extracted as a feedback control input.

[0101] The feedback control module 7 adjusts the driving voltage of the phase modulator 9 according to the error signal of the two light intensity signals to replace the adjustment of the current or voltage of the laser unit 1, so as to realize the position locking and dynamic state keeping of the interference point. The measurement device 10F of the embodiments of the present disclosure expands the diversity of the control path, and is suitable for the integrated photonic chip platform of silicon nitride, indium phosphide and the like which does not have a wavelength-regulated laser source.

[0102] Figure 10 A schematic flowchart of a measurement method according to an embodiment of the present disclosure. The measurement method comprises:

[0103] S110, dividing input laser into a reference light signal and a measurement light signal; the measurement light signal forms a reflected light signal after being reflected by a target to be measured;

[0104] S120, causing the reference light signal to interfere with the reflected light signal to obtain N light intensity signals, the N light intensity signals having the same phase difference therebetween; wherein N is an integer not less than 2;

[0105] S130, converting the N light intensity signals into N electrical signals;

[0106] S140, adjusting the input laser according to light intensity information carried by at least two of the electrical signals to lock the interference point of the reference light signal and the reflected light signal.

[0107] In some embodiments, the measurement method further comprises: obtaining interference information according to the N electrical signals and outputting.

[0108] An embodiment of the present disclosure provides a detection device comprising a measurement device according to an embodiment of the present disclosure.

[0109] Example embodiments have been disclosed herein and, although the use of specific terms is expressly used herein, they are intended in the sense only of general descriptive purpose and should not be taken as limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics or / and elements described in connection with a particular embodiment can be used in conjunction with other embodiments without departing from the scope of the present disclosure, unless otherwise explicitly stated. Therefore, those skilled in the art will understand that various changes in form and detail can be made without departing from the scope of the present disclosure as set forth in the appended claims.

Claims

1. A measuring device, characterized in that The measurement device comprises: a beam splitter, which divides input laser into a reference light signal and a measurement light signal; the measurement light signal forms a reflected light signal after being reflected by a target to be measured; an optical interference coupler, which comprises at least two input ports and a plurality of output ports, the reference light signal and the reflected light signal enter the interference coupler from two input ports respectively; the interference coupler causes the reference light signal and the reflected light signal to interfere, obtaining N light intensity signals output by N output ports respectively, the N light intensity signals have the same phase difference; wherein N is an integer not less than 2; a photodetector, which converts the N light intensity signals into N electrical signals; a feedback control module, which adjusts the input laser according to the light intensity information carried by at least two electrical signals, so as to lock the interference point of the reference light signal and the reflected light signal.

2. The measuring device of claim 1, wherein, The beam splitter, the optical interference coupler, the photodetector and the feedback control module are integrated on a chip; the measurement device further comprises an optical waveguide system, which constitutes the optical path of the reference light signal, the measurement light signal, the reflected light signal and the light intensity signal on the chip.

3. The measuring device of claim 2, wherein, The measurement device further comprises a laser integrated on the chip, which is controlled by the feedback control module to provide the input laser.

4. The measuring device of claim 2, wherein, The measurement device further comprises an electro-optical modulator integrated on the chip, which is controlled by the feedback control module to adjust the input laser.

5. The measuring device of claim 2, wherein, The measurement device further comprises a signal output module, which obtains interference information according to the N electrical signals and outputs.

6. The measuring device according to any one of claims 1 to 5, characterized in that The feedback control module comprises: a comparison submodule, which obtains the difference between any two electrical signals; a calculation submodule, which obtains a digital control quantity by using a predetermined control algorithm according to the difference; a conversion submodule, which converts the digital control quantity into an analog voltage signal; an output submodule, which generates a control signal according to the analog voltage signal, so as to drive the laser to provide the input signal or control the electro-optical modulator to adjust the input signal.

7. The measuring device according to any one of claims 1 to 5, characterized in that The optical interference coupler comprises an N×N optical coupler.

8. A method of measurement, characterized by, The measurement method comprises: dividing input laser into a reference light signal and a measurement light signal; the measurement light signal forms a reflected light signal after being reflected by a target to be measured; causing the reference light signal and the reflected light signal to interfere, obtaining N light intensity signals, the N light intensity signals have the same phase difference; wherein N is an integer not less than 2; converting the N light intensity signals into N electrical signals; adjusting the input laser according to the light intensity information carried by at least two electrical signals, so as to lock the interference point of the reference light signal and the reflected light signal.

9. The measurement method according to claim 8, characterized in that, The measurement method further comprises: obtaining interference information according to the N electrical signals and outputting.

10. A detection device, characterized by The measurement device comprises the measurement device according to any one of claims 1 to 7.

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