An optical phase readout system and method for path-encoding weak value amplification

Abstract

The application discloses an optical phase readout system and method for path-encoding weak value amplification. A phase sensing unit encodes a physical quantity to be measured as a relative phase difference between a first coherent light field and a second coherent light field; a main signal generating unit adjusts the amplitude and / or phase relationship of the two coherent light fields and performs interference to form a main signal field at a target working point; a path-encoding reference unit adjusts the amplitude and / or phase of the two coherent light fields through a first reference path and a second reference path, and synthesizes a path-encoding reference field with a non-zero optical power, and the main signal field and the path-encoding reference field adopt different amplitude and phase combination relationships; a coherent mixing unit coherently mixes the two light fields, and a differential detection unit outputs a differential readout signal representing the physical quantity to be measured. The scheme can realize coherent differential readout of dark-end, near-dark-end or post-selection signals, and reduce the influence of detection chain saturation and common-mode noise.

Description

Technical Field

[0001] This application relates to the field of optical phase measurement and coherent optical readout technology, specifically to an optical phase readout system and method with path-coded weak value amplification. Background Technology

[0002] Optical phase readout technology converts measurable physical quantities such as angular velocity, refractive index change, displacement, temperature, strain, or pressure into phase differences between coherent optical fields, and obtains the measurement results using methods such as direct intensity detection, balanced detection, zero-difference detection, or orthogonal coherent detection. For small phase signals, increasing the detection optical power can increase the photoelectric conversion signal, but the linear dynamic range of the detector, transimpedance amplifier, and analog-to-digital converter is limited, and further increasing the optical power may cause saturation or clipping distortion.

[0003] Weak amplification or post-selection measurements utilize the near-orthogonality between pre-selected and post-selected states to enhance the response of small perturbations in selected readouts. However, some schemes rely on spatial modes, polarization modes, multimode waveguides, or complex mode conversion structures, and have low output power at the dark or near-dark ends. Direct intensity detection is also susceptible to detector noise, electronic noise, and drift.

[0004] Coherent homodyne or quadrature coherent detection can read out low-power signal fields using a reference optical field, but independent local oscillators increase the need for a light source and phase-locked structure; when the reference optical power or mixer output power is too high, it may also saturate the detector or the back-end readout chain. Therefore, a technical solution is needed that uses the same set of sensing coherent optical fields to generate an amplitude- and phase-tunable reference field, and can perform coherent differential readout with the dark end, near-dark end, or post-selected master signal field. Summary of the Invention

[0005] The technical problem to be solved by this application is: how to use a relatively simple and adjustable amplitude and phase state coherent differential readout of a low-power main signal field using a coherent reference field in dark end, near dark end, or post-selection operating states, and reduce the influence of saturation and common-mode noise on phase readout under the condition of limited dynamic range of the probe chain.

[0006] To solve the above-mentioned technical problems, this application adopts the following technical solution.

[0007] This application provides an optical phase readout system with path-coded weak amplification, including a phase sensing unit, a main signal generation unit, a path-coded reference unit, a coherent mixing unit, and a differential detection unit; the path-coded reference unit includes a first reference path and a second reference path, and at least one of the first reference path and the second reference path is provided with an adjustment unit, wherein: The phase sensing unit generates a first coherent optical field and a second coherent optical field based on the coherent probe light, and encodes the physical quantity to be measured as the relative phase difference between the two coherent optical fields; The main signal generation unit adjusts the amplitude and / or phase relationship of the two coherent optical fields and performs interference processing to generate a main signal field at the target operating point; The path-coded reference unit enables the first coherent optical field and the second coherent optical field to form a first reference optical field and a second reference optical field respectively via a first reference path and a second reference path. After adjusting the amplitude and / or phase of at least one reference optical field, they are merged to generate a path-coded reference field. The main signal field and the path coding reference field adopt different amplitude-phase combination relationships, and the path coding reference field has non-zero optical power at the target operating point; the coherent mixing unit performs coherent mixing on the main signal field and the path coding reference field; The differential detection unit performs differential detection on the output optical signal after coherent mixing to obtain a differential readout signal characterizing the physical quantity to be measured.

[0008] This application also provides an optical phase readout method for path-coded weak value amplification, including: A first coherent optical field and a second coherent optical field are generated based on coherent probe light to encode the physical quantity to be measured as the relative phase difference between the first coherent optical field and the second coherent optical field; Adjust the amplitude and / or phase relationship between the first coherent optical field and the second coherent optical field, and perform interference processing on the first coherent optical field and the second coherent optical field to generate the main signal field at the target operating point; The first coherent optical field is made to form a first reference optical field through a first reference path, and the second coherent optical field is made to form a second reference optical field through a second reference path. The amplitude and / or phase of the first reference optical field and / or the second reference optical field are adjusted and then merged to generate a path-coded reference field with non-zero optical power at the target operating point. The main signal field and the path-coded reference field adopt different amplitude and phase combination relationships. The main signal field and the path coding reference field are coherently mixed to obtain the mixed output optical signal; Differential detection is performed on the mixed-frequency output optical signal to obtain a differential readout signal characterizing the physical quantity to be measured.

[0009] Compared with directly detecting the light intensity at the dark end or near dark end, this application uses a reference field formed by encoding the same set of coherent light fields through different paths to perform coherent differential readout of the main signal field, which can obtain the in-phase component, quadrature component or selected phase projection of the phase, and suppress common mode intensity fluctuations in the coherent mixing output.

[0010] The path-encoded reference field is formed by combining the first coherent optical field and the second coherent optical field with amplitude and phase different from the main signal field, without the need for an additional independent local oscillator light source; by adjusting the reference field power, the main signal operating point and / or the input power, the detection branch can be adapted to the linear dynamic range of the detector and the back-end readout chain. Attached Figure Description

[0011] Figure 1 A schematic diagram of the composition structure of an optical phase readout system provided in this application embodiment. Figure 1 ; Figure 2 A schematic diagram of the composition structure of an optical phase readout system provided in this application embodiment. Figure 2 ; Figure 3 A schematic diagram of the composition structure of an optical phase readout system provided in this application embodiment. Figure 3 ; Figure 4 A schematic diagram of the composition structure of an optical phase readout system provided in this application embodiment. Figure 4 ; Figure 5 A schematic diagram of the composition structure of an optical phase readout system provided in this application embodiment. Figure 5 ; Figure 6 A schematic diagram of the composition structure of an optical phase readout system provided in this application embodiment. Figure 6 ; Figure 7 A schematic diagram of the composition structure of an optical phase readout system provided in this application embodiment. Figure 7 ; Figure 8 A schematic diagram of the composition structure of an optical phase readout system provided in this application embodiment. Figure 8 ; Figure 9 A schematic diagram of the composition structure of an optical phase readout system provided in this application embodiment. Figure 9 ; Figure 10 A schematic diagram illustrating the implementation process of an optical phase readout method provided in this application embodiment; Figure 11 A schematic diagram of the composition structure of a path-coded weak value amplification and readout system provided in this application embodiment; Figure 12 A schematic diagram illustrating the structural composition of a path encoding reference unit provided in an embodiment of this application; Figure 13 A schematic diagram illustrating the composition of a coherent mixing unit and a differential detection unit provided in an embodiment of this application; Figure 14This is a schematic diagram illustrating the implementation process of a weak-value amplification optical phase readout method based on a path-coded reference field, provided in an embodiment of this application.

[0012] It should be noted that the terms "first" and "second" mentioned above are only used to distinguish between different options and do not represent the degree of superiority or inferiority of the options or their priority in the implementation process. Detailed Implementation

[0013] To make the technical solution and beneficial effects of this application clearer, the embodiments of this application will be further described below with reference to the accompanying drawings. It should be understood that the embodiments described are only for illustrating this application and are not intended to limit the scope of protection of this application.

[0014] like Figure 1 As shown, the optical phase readout system 100 provided in this application embodiment includes a phase sensing unit 110, a main signal generation unit 120, a path coding reference unit 130, a coherent mixing unit 140, and a differential detection unit 150; the path coding reference unit 130 includes a first reference path 131 and a second reference path 132, and at least one of the first reference path 131 and the second reference path 132 is provided with an adjustment unit.

[0015] The phase sensing unit 110 generates a first coherent optical field 111 and a second coherent optical field 112 based on the received coherent probe light, so as to encode the physical quantity to be measured as the relative phase difference between the first coherent optical field 111 and the second coherent optical field 112.

[0016] The main signal generation unit 120 adjusts the amplitude and / or phase relationship between the first coherent optical field 111 and the second coherent optical field 112, and performs interference processing on the two coherent optical fields to generate the main signal field 121 at the target operating point.

[0017] The path coding reference unit 130 causes the first coherent optical field 111 to form a first reference optical field via the first reference path 131, and causes the second coherent optical field 112 to form a second reference optical field via the second reference path 132. After adjusting the amplitude and / or phase of at least one reference optical field by the adjustment unit, the fields are merged to generate the path coding reference field 137.

[0018] The amplitude-phase combination relationship of the two coherent optical fields in the main signal field 121 is different from the amplitude-phase combination relationship of the two reference optical fields in the path coding reference field 137, and the path coding reference field 137 has non-zero optical power at the target operating point; the coherent mixing unit 140 performs coherent mixing on the main signal field 121 and the path coding reference field 137 to obtain the mixed output optical signal.

[0019] The differential detection unit 150 performs differential detection on the mixed output optical signal to obtain a differential readout signal characterizing the physical quantity to be measured.

[0020] The phase sensing unit 110 is used to realize the conversion of the physical quantity to be measured into optical phase difference.

[0021] In some embodiments, the phase sensing unit 110 receives coherent probe light and converts physical quantities such as angular velocity, refractive index change, displacement, temperature, strain or pressure into the relative phase difference between the first coherent optical field 111 and the second coherent optical field 112.

[0022] For example, in a Mach-Zehnder interferometer sensing structure, the first coherent optical field 111 and the second coherent optical field 112 can be the output optical field of the sensing arm and the output optical field of the reference arm, respectively; in a Sagnac phase sensing structure, the two coherent optical fields can be the optical fields that return after propagating in opposite directions; in a fiber optic phase sensing structure, the two coherent optical fields can be the output optical fields after passing through different transmission paths or being subjected to different phase perturbations.

[0023] In some implementations, the phase sensing unit 110 includes a beam splitter, an optical waveguide, an optical fiber, a sensing path, and / or a beam combiner.

[0024] The phase sensing unit 110 can convert the input coherent probe light into two mutually coherent optical fields by beam splitting, path splitting, propagation in opposite directions, or transmission through different sensing arms.

[0025] For example, rotational angular velocity can cause Sagnac phase difference, and changes in strain, temperature or refractive index can cause optical path difference, thereby forming a relative phase difference between the first coherent optical field 111 and the second coherent optical field 112.

[0026] For ease of explanation, the first coherent optical field 111 and the second coherent optical field 112 can be expressed as E1=A1exp(jφ1) and E2=A2exp(jφ2), respectively, where A1 and A2 represent the amplitudes of the two coherent optical fields, φ1 and φ2 represent the phases of the two coherent optical fields, and the phase to be measured is Δφ=φ1-φ2.

[0027] The main signal generation unit 120 performs a first phase-to-phase combination of the two coherent optical fields. The main signal field 121 can be expressed as d0=a1E1+a2E2, where a1 and a2 are complex coefficients determined by the coupling ratio, loss and phase offset of the main signal generation unit 120.

[0028] By setting a1 and a2, the main signal field 121 is positioned at the dark end, near the dark end, or a preset operating point at the nominal phase to be measured. The dark end operating point corresponds to the main signal field power reaching a local minimum; the near-dark end operating point is located near the dark end and the main signal field maintains non-zero optical power; the preset operating point is the operating state determined by a preset amplitude-phase combination.

[0029] The path coding reference unit 130 performs a second phase combination on the two coherent optical fields. The path coding reference field 137 can be expressed as d1=b1E1+b2E2, where b1 and b2 are complex coefficients determined by the transmission coefficients, adjustment amounts and combination relationships of the first reference path 131 and the second reference path 132.

[0030] At the nominal operating point, the complex coefficient pair (b1, b2) is not proportional to the complex coefficient pair (a1, a2), and |d1| is greater than zero, so that the path coding reference field 137 and the main signal field 121 form different path coding results and avoid the two optical fields from degenerating into the same amplitude-phase combination.

[0031] At least one of the first reference path 131 and the second reference path 132 is provided with an adjustment unit. By adjusting the amplitude, phase, delay and / or polarization state in the reference path, b1 and / or b2 can be changed, thereby setting the power of the path coding reference field 137 and its relative phase with the main signal field 121.

[0032] The first reference path 131 and the second reference path 132 are preferably single-mode paths; the main signal field 121 and the path coding reference field 137 have the same operating frequency and spatial modes and polarization states that can interfere with each other when entering the coherent mixing unit 140.

[0033] The following explanation uses a two-path coherent optical field system consisting of a first coherent optical field 111 and a second coherent optical field 112 as an example.

[0034] The coherent mixing unit 140 is used to perform zero-difference or self-zero-difference coherent mixing between the main signal field 121 and the path coding reference field 137. The coherent mixing unit 140 may be a 90° optical mixer, a 2×2 optical coupler, a multimode interference coupler, a balanced zero-difference mixer, or an integrated coherent receiver.

[0035] The differential detection unit 150 performs differential photoelectric conversion on the phase complementary optical signal output by the coherent mixing unit 140 to suppress common mode intensity fluctuations and obtain a differential readout signal characterizing the physical quantity to be measured.

[0036] Through the above two different amplitude-phase combinations, the main signal field 121 is used to form the dark end, near-dark end, or post-selection response, and the path-coded reference field 137 is used to provide a non-zero and amplitude-phase-tunable co-source reference light; after coherent mixing, the field amplitude or field quadrature component change of the main signal field can be converted into a differential electrical signal.

[0037] In some embodiments, such as Figure 2As shown, the optical phase readout system 100 also includes a light source unit 160 and an input power adjustment unit 170. The input power adjustment unit 170 is used to adjust the power of the coherent probe light output by the light source unit 160 and send the adjusted coherent probe light to the phase sensing unit 110.

[0038] Here, the light source unit 160 is the initial light source module in the optical phase readout system 100 that provides coherent probe light. The light source unit 160 can output a laser beam with high coherence, stable wavelength and controllable optical power.

[0039] The coherent probe light refers to the coherent beam output by the light source unit 160 and used to detect the physical quantity to be measured. Before entering the phase sensing unit 110, the coherent probe light does not carry information about the physical quantity to be measured; after entering the phase sensing unit 110, the physical quantity to be measured is encoded as the relative phase difference between the two coherent light fields.

[0040] In some embodiments, after the coherent probe light output by the light source unit 160 enters the phase sensing unit, it is converted into a first coherent light field and a second coherent light field carrying the phase information to be measured through interaction with the physical quantity to be measured.

[0041] In some implementations, the light source unit 160 may be a semiconductor laser, a distributed feedback laser (DFB), a fiber laser, or an external cavity laser.

[0042] In some implementations, the light source unit 160 is mounted at the front end of the optical phase readout system, and the coherent probe light output by the light source unit is transmitted to the input power adjustment unit via an optical fiber or free-space optical path. For example, in an on-chip integrated system, the light source unit can be directly coupled to the input port of the silicon-based photonic chip; in a discrete system, the coherent probe light output by the light source unit can be guided to subsequent modules through a collimating lens and a reflector.

[0043] Using the same light source unit 160 to provide coherent probe light to the system helps to reduce the impact of frequency deviation and phase drift between multiple light sources on coherent mixing.

[0044] The input power adjustment unit 170 is an optical power control module located between the light source unit 160 and the phase sensing unit 110. The main function of the input power adjustment unit is to dynamically adjust the power of the coherent probe light entering the phase sensing unit according to the operating status of the optical phase readout system (such as detector saturation threshold, readout slope, noise level, etc.) to prevent the detector from saturating due to excessively strong signals, while optimizing readout performance.

[0045] In some implementations, the input power adjustment unit 170 may include devices such as a variable optical attenuator, an electro-optic modulator, a thermo-optic modulator, or a mechanical shutter to achieve continuous or discrete adjustment of the coherent probe optical power.

[0046] In fiber optic systems, the input power adjustment unit 170 can be a fiber-optic variable optical attenuator; in integrated photonic systems, it can be an adjustable coupler, a Mach-Zehnder intensity regulator, or a micro-ring power regulator.

[0047] The input optical power can be adjusted according to the linear range of the detector and the back-end readout chain via the input power adjustment unit 170.

[0048] In some embodiments, the main signal generation unit 120 includes a main phase adjuster and a main beam combiner. The main phase adjuster adjusts the relative phase between the first coherent optical field 111 and the second coherent optical field 112, and the main beam combiner performs beam combining interference on the adjusted two coherent optical fields to output a main signal field 121 at the target operating point.

[0049] The dark end operating point refers to the operating state in which the optical power of the main signal field 121 reaches a local minimum. For direct light intensity detection, the first-order light intensity slope at the ideal dark end is zero; this application uses coherent mixing assisted by the path-coded reference field 137 to read the changes in field amplitude or field quadrature components near the dark end.

[0050] The near-dark end operating point is located near the dark end operating point, and the main signal field 121 maintains a low and non-zero optical power, which can be a compromise between the main signal power, coherent differential readout slope and linear range.

[0051] The post-selected operating point refers to the preset operating state determined by the amplitude-phase combination of the main signal generation unit 120. The readout gain G can be defined as the ratio of the slope of the differential readout signal of this application to the slope of the reference readout scheme under the same input phase perturbation, i.e., G = ( S / φ) / ( Sref / φ), where S is the differential readout signal of this application, and Sref is the output signal of the reference readout scheme.

[0052] The main phase modulator can be a thermo-optical phase shifter, an electro-optical phase shifter, a piezoelectric fiber stretcher, or an adjustable optical path structure; the main combiner can be a directional coupler, a 2×2 optical coupler, or a multimode interference coupler.

[0053] When the phase under test undergoes a slight change near the nominal operating point, the amplitude, phase, or selected field quadrature component of the main signal field 121 changes accordingly; this change is converted into an electrical signal by coherent differential detection assisted by the path-coded reference field 137.

[0054] In some embodiments, such as Figure 3As shown, at least one of the first reference path 131 and the second reference path 132 is provided with an adjustment unit. When the first reference path 131 is provided with the first adjustment unit 133, the first adjustment unit 133 adjusts the first coherent optical field 111 to form the first reference optical field; when the second reference path 132 is provided with the second adjustment unit 134, the second adjustment unit 134 adjusts the second coherent optical field 112 to form the second reference optical field.

[0055] The first adjustment unit 133 and the second adjustment unit 134 may each include at least one of an amplitude regulator, a phase regulator, a delay regulator, and a polarization regulator.

[0056] Here, the first adjustment unit is an optical adjustment module located in the first reference path, used to actively adjust parameters such as amplitude, phase, polarization, or optical path difference of the first coherent optical field input to the first reference path.

[0057] The second adjustment unit is an optical adjustment module located in the second reference path, used to similarly control the second coherent light field input to the second reference path.

[0058] In some embodiments, the first adjustment unit 133 and the second adjustment unit 134 respectively include at least one of an amplitude regulator, a phase regulator, a delay regulator and a polarization regulator.

[0059] An amplitude modulator is a device that can change the intensity or power of an optical field, such as a variable optical attenuator, an electro-optic modulator, or a thermo-optic modulator. The function of an amplitude modulator is to control the power of the optical signal passing through the reference path to match the reference field intensity required for subsequent mixing.

[0060] A phase modulator is a device that can change the phase of an optical field, such as a Mach-Zehnder modulator, a thermo-optical phase shifter, or an electro-optical phase shifter. The function of a phase modulator is to adjust the phase delay of the light wave, thereby controlling the relative phase difference between the path coding reference field and the main signal field, and achieving phase matching during coherent mixing.

[0061] A polarization modulator is a device that can change the polarization state of an optical field, such as a waveplate, polarization controller, or integrated polarization modulator. The function of a polarization modulator is to adjust the polarization direction or ellipticity of light so that the two optical fields have compatible polarization modes during coherent mixing, thus avoiding a decrease in interference efficiency due to polarization mismatch.

[0062] The amplitude adjuster, phase adjuster, delay adjuster, and polarization adjuster can be set individually or in combination to adjust the amplitude, phase, group delay, and / or polarization state of the path-coded reference field 137.

[0063] The first adjustment unit 133 and the second adjustment unit 134 do not need to be set simultaneously. For example, the first adjustment unit 133 can be set only in the first reference path 131 to keep the second reference path 132 fixed. Alternatively, the amplitude and / or phase of the path encoding reference field 137 can be changed by adjusting the amplitude and / or phase of the first reference light field relative to the second reference light field.

[0064] In some embodiments, the first adjustment unit is built into the optical path of the first reference path, located between the first coherent optical field input end and the path combining point. The second adjustment unit is built into the optical path of the second reference path, located between the second coherent optical field input end and the path combining point.

[0065] The first adjustment unit can be a variable optical attenuator, phase modulator, amplitude modulator, thermo-optical phase shifter, electro-optical phase shifter, Mach-Zehnder modulator, tunable coupler, micro-ring modulator or a combination thereof, and is installed on the single-mode waveguide or fiber segment of the first reference path so that the first coherent optical field enters the path synthesis point after being adjusted by the first adjustment unit.

[0066] The second adjustment unit can be a variable optical attenuator, phase adjuster, thermo-optical phase shifter, electro-optical phase shifter, Mach-Zehnder modulator, tunable coupler, micro-ring adjuster or a combination thereof, and is installed on the single-mode waveguide or fiber segment of the second reference path so that the second coherent optical field enters the path synthesis point after being adjusted by the second adjustment unit.

[0067] When the first adjustment unit 133 is set only in the first reference path 131, the path coding reference field 137 can be made to meet the preset coherent mixing conditions by adjusting the amplitude or phase of the first reference optical field, such as obtaining a larger readout slope, a higher signal-to-noise ratio, or a lower equivalent phase noise.

[0068] When the second adjustment unit 134 is set only in the second reference path 132, the path coding reference field 137 can be made to meet the preset coherent mixing conditions by adjusting the amplitude or phase of the second reference optical field.

[0069] When both the first reference path 131 and the second reference path 132 are equipped with adjustment units, the amplitude and phase of the two reference optical fields can be adjusted in a coordinated manner to expand the adjustment range of the path encoding reference field 137.

[0070] In some implementations, where the first reference path includes a first adjustment unit, the first adjustment unit changes the optical power or phase of the first coherent optical field by applying controllable amplitude or phase adjustment, thereby forming a first reference optical field. The amplitude and phase states of the first reference optical field participate in determining the overall state of the path-encoded reference field.

[0071] In some embodiments, when the second reference path includes a second adjustment unit, the second adjustment unit adjusts the amplitude, phase, or delay of the second coherent optical field to form a second reference optical field. The second reference optical field and the first reference optical field are combined to form a path-coded reference field with a preset amplitude and phase state.

[0072] By setting an adjustment unit in at least one of the first reference path 131 and the second reference path 132, the relative amplitude, relative phase, relative delay and / or polarization matching state between the first reference optical field and the second reference optical field can be adjusted, thereby setting the coherent mixing conditions between the path coding reference field 137 and the main signal field 121.

[0073] In some embodiments, such as Figure 4 As shown, the coherent mixing unit 140 includes an orthogonal optical mixer 141, which includes a first mixing input and a second mixing input. The first mixing input receives the main signal field 121, and the second mixing input receives the path coding reference field 137. The orthogonal optical mixer 141 performs coherent mixing on the two optical fields and outputs in-phase forward optical signals, in-phase reverse optical signals, quadrature forward optical signals, and quadrature reverse optical signals.

[0074] The first and second mixer inputs are used to connect to the main signal field 121 and the path coding reference field 137, respectively. The quadrature optical mixer 141 can be a 90° optical mixer or an equivalent I / Q coherent mixer structure.

[0075] In-phase forward optical signals and in-phase reverse optical signals form an in-phase signal pair, while quadrature forward optical signals and quadrature reverse optical signals form a quadrature signal pair. These two signal pairs are used to obtain the in-phase and quadrature components of the phase signal, respectively.

[0076] The first and second mixing input terminals can be optical waveguide interfaces, fiber optic interfaces, or free-space optical interfaces, and ensure that the main signal field 121 and the path-coded reference field 137 satisfy coherent mixing conditions in terms of spatial mode, polarization state, and frequency.

[0077] In some implementations, the first mixer input is connected to the output of the main signal generation unit, and the second mixer input is connected to the synthesis output of the path coding reference unit. The first mixer input and the second mixer input together constitute a dual-input channel for coherent mixing.

[0078] The main signal field 121 is d0 = a1E1 + a2E2, and the path coding reference field 137 is d1 = b1E1 + b2E2. Since the two sets of complex coefficients are not proportional and d1 has non-zero optical power at the nominal operating point, the path coding reference field 137 can be used as a co-source reference light to coherently mix with the main signal field 121 at the dark end, near-dark end, or post-selected operating point.

[0079] The main signal field 121 and the path coding reference field 137 enter the 90° optical mixer from the first mixer input and the second mixer input, respectively. The 90° optical mixer outputs two pairs of phase-complementary optical signals, wherein the in-phase interference term is proportional to the cosine of the phase difference between the two optical fields, and the orthogonal interference term is proportional to the sine of the phase difference between the two optical fields.

[0080] Let the optical powers of the main signal field 121 and the path coding reference field 137 be P0 and P1, respectively, and the phase difference be φ. The four output optical powers of the ideal 90° optical mixer can be expressed as PI+=C[P0+P1+2√(P0P1)cosφ], PI-=C[P0+P1-2√(P0P1)cosφ], PQ+=C[P0+P1+2√(P0P1)sinφ] and PQ-=C[P0+P1-2√(P0P1)sinφ], where C is the scaling factor determined by the splitting relationship of the mixer.

[0081] After differentially probing the in-phase and quadrature signal pairs respectively, ΔI∝√(P0P1)cosφ and ΔQ∝√(P0P1)sinφ can be obtained. This allows for the acquisition of two quadrature phase components of the main signal field 121 relative to the path-coded reference field 137 while suppressing common DC term and common-mode intensity fluctuations.

[0082] In some embodiments, such as Figure 5 As shown, the differential detection unit 150 includes a first detector group 151 and a second detector group 152. The first detector group 151 receives in-phase forward light signals and in-phase reverse light signals and outputs in-phase differential readout signals; the second detector group 152 receives quadrature forward light signals and quadrature reverse light signals and outputs quadrature differential readout signals.

[0083] The first detector group 151 typically includes two photodetectors, which receive in-phase forward light signals and in-phase reverse light signals, respectively; the second detector group 152 typically includes two photodetectors, which receive orthogonal forward light signals and orthogonal reverse light signals, respectively.

[0084] The in-phase differential readout signal reflects the in-phase component of the phase relationship between the main signal field 121 and the path coding reference field 137, while the quadrature differential readout signal reflects the quadrature component of the phase relationship between the two optical fields.

[0085] A 90° optical mixer or equivalent I / Q coherent mixer structure generates four spatial outputs. The interference terms of the I-path forward and reverse outputs differ by 180°, the interference terms of the Q-path forward and reverse outputs differ by 180°, and the interference terms of the I-path and Q-path differ by 90°. "Orthogonal" means that the signal phase components are orthogonal; it does not require that the output optical signals have mutually perpendicular polarization states.

[0086] In some embodiments, the first detector group 151 converts the in-phase forward light signal and the in-phase reverse light signal into electrical signals, performs subtraction to eliminate common-mode noise and amplify the differential-mode signal, and finally outputs an in-phase differential readout signal, denoted as ΔI. The amplitude of the in-phase differential readout signal ΔI is directly related to the change in interference intensity caused by the phase to be measured and can be used to calculate the phase shift. The second detector group 152 performs differential processing on the orthogonal forward light signal and the orthogonal reverse light signal to output an orthogonal differential readout signal, denoted as ΔQ. Since the in-phase differential readout signal ΔI and the orthogonal differential readout signal ΔQ mathematically constitute the real and imaginary parts of the complex plane coordinate system, their combination can completely characterize the phase information and support various demodulation algorithms such as phase arctangent demodulation and linear interval slope conversion.

[0087] Understandably, in integrated photonic chips or discrete optical systems, the first detector group 151 can be located at the I-channel output of the 90° mixer, and the second detector group 152 can be located at the Q-channel output. The first detector group 151 and the second detector group 152 are connected to the back-end readout chain through independent transimpedance amplifier circuits. The separate structure of the first detector group 151 and the second detector group 152 enables the differential readout signal to have good common-mode rejection capability, effectively reducing environmental noise interference.

[0088] By using I / Q dual-channel differential detection, the in-phase and quadrature components of the phase can be obtained simultaneously for phase arctangent demodulation, phase sign discrimination, or linear interval slope conversion.

[0089] In some embodiments, such as Figure 6 As shown, the coherent mixing unit 140 includes an optical coupler 142, and the differential detection unit 150 includes a balanced detector 153. The optical coupler 142 performs coherent mixing on the main signal field 121 and the path coding reference field 137, outputting a pair of phase-complementary mixed optical signals; the balanced detector 153 performs differential detection on the pair of mixed optical signals to obtain a single-channel differential readout signal.

[0090] Here, optical coupler 142 is an optical device used for coherent mixing of the main signal field and the path-coded reference field. In one example, the optical coupler is a 2×2 coupler or an equivalent coherent mixer.

[0091] The balanced detector 153 is used to receive the output optical signal from the coherent mixer unit and to perform the subtraction operation of the two optical signals through internal circuitry, thereby obtaining the differential readout signal ΔS that is directly related to the physical quantity to be measured.

[0092] The optical coupler 142 can select a phase projection of the main signal field 121 relative to the path coding reference field 137 by setting a preset coupling ratio and phase delay, and output a pair of phase complementary mixed optical signals; the balanced detector 153 performs differential detection on the pair of mixed optical signals to obtain a single-channel differential readout signal ΔS.

[0093] The coherent mixing unit 140 can also employ a multimode interference coupler, a balanced zero-difference mixer, or an integrated coherent receiver, and the differential detection unit 150 can output an I-channel differential readout signal, a Q-channel differential readout signal, or a single-channel differential readout signal.

[0094] In this embodiment, the coherent mixing unit employs an optical coupler and outputs a pair of phase-complementary mixed optical signals. A balanced detector differentially probes these optical signals to obtain a single-channel differential readout signal characterizing the physical quantity to be measured. This structure reduces the complexity of the coherent mixing and detection hardware.

[0095] In some embodiments, such as Figure 7 As shown, the optical phase readout system 100 also includes an output processing unit 180. The output processing unit 180 receives the differential readout signal output by the differential detection unit 150 and obtains the measurement result corresponding to the physical quantity to be measured by using a preset demodulation method.

[0096] Here, the output processing unit 180 is a data processing module located after the differential detection unit 150.

[0097] Preset demodulation methods may include linear interval slope conversion, quadrature demodulation, phase arctangent calculation, lookup table calibration, or a combination thereof. The differential readout signal can be an in-phase differential readout signal ΔI, a quadrature differential readout signal ΔQ, or a single-channel differential readout signal ΔS.

[0098] The output processing unit 180 can be implemented by a field-programmable gate array, a digital signal processor, a microcontroller, or a computer, and can perform analog-to-digital conversion, filtering, calibration, and demodulation on the differential readout signal.

[0099] The differential detection unit 150 and the output processing unit 180 can be connected via an analog interface, a digital serial interface, or a parallel bus.

[0100] The output processing unit 180 can convert the differential readout signal into measurement results corresponding to angular velocity, refractive index change, displacement, temperature, strain, pressure or other physical quantities to be measured.

[0101] In some embodiments, such as Figure 8 As shown, the optical phase readout system 100 also includes a control unit 190. The control unit 190 includes a main operating point adjustment module 191 and a reference field adjustment module 192; the main operating point adjustment module 191 is used to set or maintain the target operating point of the main signal field 121, and the reference field adjustment module 192 is used to set the amplitude and phase state of the path encoding reference field 137.

[0102] The control unit 190 adjusts the main signal generation unit 120 and the path coding reference unit 130 based on the power of the detection branch, the detector saturation threshold, the readout slope, the signal-to-noise ratio, and / or the equivalent phase noise.

[0103] The main operating point adjustment module 191 and the reference field adjustment module 192 can work independently or be adjusted collaboratively according to the same control objective.

[0104] The main operating point adjustment module 191 can change the target operating point of the main signal field 121 by adjusting the driving amount of the main phase adjuster or the coupling state of the main combiner.

[0105] The main operating point adjustment module 191 can stabilize the main signal field 121 at the dark end, near the dark end, or a preset operating point based on the detector power status, readout slope, and noise parameters.

[0106] The main operating point adjustment module 191 can determine the phase offset or coupling parameters based on the differential readout signal and calibration data, and output control signals to the adjustable elements in the main signal generation unit 120.

[0107] The reference field adjustment module 192 changes the power of the path encoding reference field 137 and its relative phase with the main signal field 121 by adjusting the first adjustment unit 133 and / or the second adjustment unit 134.

[0108] The reference field adjustment module 192 can adjust the amplitude, phase, delay, or polarization state of the first reference optical field and / or the second reference optical field according to the differential readout signal, the power of the probe branch, or the quadrature error.

[0109] The reference field regulation module 192 can employ proportional-integral-derivative control, phase-locked control, scanning optimization, or model-based control strategies, and output voltage, current, or digital control quantities to the regulation unit.

[0110] The control unit 190 can be implemented by a digital signal processor, a field-programmable gate array or a microcontroller, and controls the main signal generation unit 120 and the path coding reference unit 130 through an analog or digital interface.

[0111] By coordinating the adjustment of the target operating point of the main signal field 121 and the amplitude and phase states of the path coding reference field 137, the coherent mixing output can be adapted to the linear range of the detector and the back-end readout chain.

[0112] In some embodiments, such as Figure 9 As shown, the control unit 190 also includes a power monitoring unit 193. The power monitoring unit 193 is used to monitor whether at least one of the input optical power, photocurrent, output voltage and / or back-end readout chain amplitude of each detection branch reaches a preset saturation threshold.

[0113] The power monitoring unit 193 can obtain parameters for determining saturation state through the monitoring ports, signal output terminals, transimpedance amplifier output terminals, or analog-to-digital converter output terminals of each detection branch.

[0114] Parameters used to determine saturation state may include at least one of the following: the input optical power or photocurrent of a single probe branch, the signals of multiple probe branches, the output voltage of the transimpedance amplifier, and the output code value of the analog-to-digital converter.

[0115] The preset saturation threshold is set based on the linear optical power range of the photodetector, the linear output range of the transimpedance amplifier, and / or the full-scale range of the analog-to-digital converter.

[0116] The power monitoring unit 193 can periodically or continuously sample the above parameters to determine whether any detection branch or back-end readout chain is close to or has reached saturation.

[0117] When the power monitoring unit 193 determines that the preset saturation threshold has been reached, the control unit 190 may reduce the power of the path coding reference field 137, change the target operating point of the main signal field 121, and / or reduce the coherent probe light power input to the phase sensing unit 110.

[0118] The control unit 190 prioritizes adjusting parameters that can reduce the total optical power of the detection branches, and restores each detection branch to the linear operating range while maintaining the coherent mixing phase relationship.

[0119] The control unit 190 may also include a calibration and optimization module 194 for determining the operating point, readout slope, phase zero, quadrature error and / or reference field amplitude and phase parameters.

[0120] When the system includes the input power adjustment unit 170, the control unit 190 can increase its attenuation or decrease its transmittance to reduce the total optical power borne by the detector chain.

[0121] The control unit 190 can also adjust the phase of the path encoding reference field 137 according to the coherent mixing phase or quadrature error, and adjust the gain or readout range of the differential detection unit 150 according to the detector operating state.

[0122] Before the measurement begins or during the calibration phase, the control unit 190 can set the initial parameters of each adjustable unit; during continuous measurement, it can make feedback adjustments based on the measurement results of the current sampling window or the previous sampling period.

[0123] The control unit 190 can directly output voltage, current, digital control word or other drive signals to the adjustable unit.

[0124] The control unit 190 can also send target parameters to each functional unit, and the actuators inside the functional unit will perform the corresponding adjustments.

[0125] By monitoring the power parameters of a single branch or the corresponding signal and adjusting the input power, the main signal operating point, and / or the reference field power, misjudgments caused by judging saturation solely based on differential output can be avoided.

[0126] like Figure 10 As shown, this application embodiment provides an optical phase readout method with path-coded weak value amplification, including steps S1001 to S1005: Step S1001: Generate a first coherent optical field and a second coherent optical field based on the coherent probe light, so as to encode the physical quantity to be measured as the relative phase difference between the two coherent optical fields.

[0127] Step S1002: Adjust the amplitude and / or phase relationship between the first coherent optical field and the second coherent optical field, and perform interference processing on the two coherent optical fields to generate the main signal field at the target operating point.

[0128] Step S1003: The first coherent optical field is made to form a first reference optical field through the first reference path, and the second coherent optical field is made to form a second reference optical field through the second reference path. The amplitude and / or phase of at least one reference optical field are adjusted and then merged to generate a path-coded reference field with non-zero optical power at the target operating point. The main signal field and the path-coded reference field adopt different amplitude and phase combination relationships.

[0129] Step S1004: Perform coherent mixing on the main signal field and the path coding reference field to obtain the mixed output optical signal.

[0130] Step S1005: Perform differential detection on the mixed output optical signal to obtain a differential readout signal characterizing the physical quantity to be measured.

[0131] In some embodiments, the optical phase readout system further includes a light source unit and an input power adjustment unit, and the above method further includes the following step S1011: Step S1011: The input power adjustment unit adjusts the power of the coherent probe light sent by the light source unit and sends the adjusted coherent probe light to the phase sensing unit.

[0132] In some embodiments, step S1002 above may include the following step S1021: Step S1021: Adjust the relative phase between the first coherent optical field and the second coherent optical field by the main phase adjuster, and perform beam combining interference on the two coherent optical fields by the main beam combiner, so that the main signal field is at the dark end operating point, the near dark end operating point, or the post-selected operating point.

[0133] In some embodiments, at least one of the first reference path and the second reference path is provided with an adjustment unit, and step S1003 above may include the following steps S1031 and S1032: Step S1031: When the first adjustment unit is set in the first reference path, the first coherent light field is adjusted by the first adjustment unit to form the first reference light field.

[0134] Step S1032: When the second adjustment unit is set in the second reference path, the second coherent light field is adjusted by the second adjustment unit to form the second reference light field.

[0135] In some embodiments, the first adjustment unit and the second adjustment unit respectively include at least one of an amplitude regulator, a phase regulator, a delay regulator and a polarization regulator.

[0136] In some embodiments, the coherent mixing unit includes a quadrature optical mixer, which includes a first mixing input and a second mixing input; step S1004 above may include the following step S1041: Step S1041: The quadrature optical mixer receives the main signal field through the first mixer input terminal, receives the path coding reference field through the second mixer input terminal, and performs coherent mixing on the two optical fields to output in-phase forward optical signals, in-phase reverse optical signals, quadrature forward optical signals, and quadrature reverse optical signals.

[0137] In some embodiments, the differential detection unit includes a first detector group and a second detector group, and the differential readout signal includes an in-phase differential readout signal and a quadrature differential readout signal; step S1005 above may include the following steps S1051 to S1053: Step S1051: The quadrature optical mixer outputs the in-phase forward optical signal and the in-phase reverse optical signal to the first detector group; and outputs the quadrature forward optical signal and the quadrature reverse optical signal to the second detector group; Step S1052: The first detector group performs differential detection on the in-phase forward light signal and the in-phase reverse light signal to obtain the in-phase differential readout signal; Step S1053: The second detector group performs differential detection on the orthogonal forward light signal and the orthogonal reverse light signal to obtain the orthogonal differential readout signal.

[0138] In some embodiments, the coherent mixing unit includes an optical coupler, the differential detection unit includes a balanced detector, and the differential readout signal includes a single-channel differential readout signal; Step S1004 above may include the following step S1061: Step S1061: The optical coupler performs coherent mixing of the main signal field and the path coding reference field, and outputs a pair of phase-complementary mixed optical signals.

[0139] Step S1005 above may include the following step S1062: Step S1062: The balanced detector performs differential detection on the pair of phase-complementary mixed optical signals to obtain a single-channel differential readout signal.

[0140] In some embodiments, the optical phase readout system further includes an output processing unit, and the above method may further include the following steps S1071 and S1072: Step S1071: The differential detection unit sends the differential readout signal to the output processing unit; Step S1072: The output processing unit demodulates the differential readout signal using a preset demodulation method to obtain the measurement result corresponding to the physical quantity to be measured.

[0141] In some embodiments, the optical phase readout system further includes a control unit, which includes at least a main operating point adjustment module and a reference field adjustment module. The above method may also include the following steps S1081 and S1082: Step S1081: The main operating point adjustment module adjusts the interference conditions of the main signal generation unit to set or maintain the target operating point of the main signal field.

[0142] Step S1082: The reference field adjustment module adjusts the amplitude and / or phase of the first reference optical field and / or the second reference optical field to set the amplitude and phase state of the path coding reference field.

[0143] In some embodiments, the control unit further includes at least a power monitoring unit, and the above method may further include the following step S1091: Step S1091: The power monitoring unit monitors whether at least one of the input optical power, photocurrent, output voltage, and back-end readout chain amplitude of each detection branch has reached a preset saturation threshold; if the preset saturation threshold is reached, the control unit reduces the power of the path coding reference field and / or changes the target operating point of the main signal field, and if the optical phase readout system with path coding weak value amplification includes an input power adjustment unit, it reduces the power of the coherent probe light input to the phase sensing unit.

[0144] Example 1: Path-coded weak-value amplification optical phase readout system based on I / Q differential detection.

[0145] like Figure 11 As shown, the optical phase readout system of this embodiment includes a light source unit 160, an input power adjustment unit 170, a phase sensing unit 110, a main signal generation unit 120, a path coding reference unit 130, a coherent mixing unit 140, a differential detection unit 150, an output processing unit 180, and a control unit 190.

[0146] The light source unit 160 outputs coherent light, which is then input to the phase sensing unit 110 after passing through the input power adjustment unit 170. The input power adjustment unit 170 is used to adjust the light power entering the phase sensing unit 110 so that the subsequent detector operates within a preset power range.

[0147] In this embodiment, the light source unit outputs raw coherent probe light; after passing through the input power adjustment unit, the power of this probe light is only changed, and it does not yet carry information about the physical quantity to be measured. After the probe light enters the phase sensing unit and interacts with the physical quantity to be measured, it forms a first coherent light field and a second coherent light field carrying the phase information to be measured.

[0148] Phase sensing unit 110 generates a first coherent optical field 111 and a second coherent optical field 112 based on the physical quantity to be measured. The first coherent optical field 111 and the second coherent optical field 112 have a phase difference or equivalent phase difference related to the physical quantity to be measured. The physical quantity to be measured can be angular velocity, refractive index change, displacement, temperature, strain, pressure, frequency shift, or other physical quantities that can be converted into optical phase changes. The relative phase difference between the first coherent optical field 111 and the second coherent optical field 112 contains information about the physical quantity to be measured. For example, in interferometric sensing, one beam of light passes through the sensing region carrying the phase change introduced by the physical quantity to be measured, while the other beam serves as a reference beam; the phase difference between the two beams is the phase information to be measured. Similarly, in Sagnac or other reciprocal / non-reciprocal phase sensing structures, both coherent optical fields may be acted upon, but they may produce phase changes of opposite signs or different magnitudes.

[0149] The input to the phase sensing unit 110 is coherent probe light regulated by the input power adjustment unit. The phase sensing unit 110 can convert the input probe light into two coherent optical fields by beam splitting, path splitting, clockwise or counterclockwise propagation, transmission with different arms, different resonance modes, or other coherent splitting methods.

[0150] The first coherent optical field 111 and the second coherent optical field 112 refer to two optical fields with a fixed coherence relationship output by the phase sensing unit 110. The phase difference or equivalent phase difference between the two contains information about the physical quantity to be measured. For example: In the Mach-Zehnder interferometric sensing structure, the first coherent optical field 111 can be the output optical field of the sensing arm, and the second coherent optical field 112 can be the output optical field of the reference arm. In the Sagnac phase sensing structure, the first coherent optical field 111 and the second coherent optical field 112 can be the optical fields that return after propagating clockwise and counterclockwise, respectively. In the fiber optic phase sensing structure, the first coherent optical field 111 and the second coherent optical field 112 can be two coherent output optical fields after passing through different transmission paths or different phase disturbances.

[0151] The first coherent optical field 111 and the second coherent optical field 112 are input to the main signal generation unit 120. Let the first coherent optical field 111 be E1 and the second coherent optical field 112 be E2. The main signal field 121 output by the main signal generation unit 120 is d0 = a1E1 + a2E2. By setting the complex coefficients a1 and a2, d0 can be positioned at the dark end, near the dark end, or a preset operating point at the nominal phase to be measured.

[0152] When the phase under test varies near its nominal value, the field amplitude, phase, or selected field quadrature component of d0 changes. The main signal power, readout slope, and linear range corresponding to the target operating point can be determined through calibration.

[0153] The operating point can be preset by the control unit or dynamically optimized during system operation based on detector power, saturation threshold, readout slope, or noise parameters. In practical engineering, the initial operating point is usually determined through calibration first, and then fine-tuned or maintained in a closed loop by the control unit.

[0154] like Figure 12 As shown, the first coherent optical field 111 and the second coherent optical field 112 are also input to the path coding reference unit 130. The path coding reference unit 130 includes a first reference path 131 and a second reference path 132.

[0155] The optical fields in the first reference path 131 and the second reference path 132 are combined after being adjusted by the first adjustment unit 133 and the second adjustment unit 134, respectively, to form the path-coded reference field 137, i.e., d1=b1E1+b2E2. The complex coefficients b1 and b2 are determined by the loss, coupling ratio, phase delay and adjustment amount of the two reference paths.

[0156] The first adjustment unit 133 and the second adjustment unit 134 can be adjusted in concert, or only one of them can be set. By adjusting b1 and / or b2, the complex coefficient pair (b1, b2) is made disproportionate to the complex coefficient pair (a1, a2), and d1 maintains non-zero optical power at the nominal operating point.

[0157] The path coding reference field 137 is formed by combining a first coherent optical field 111 and a second coherent optical field 112, which are from the same source as the main signal field 121, with different amplitudes and phases, thus eliminating the need for a separate local oscillator light source.

[0158] like Figure 13 As shown, the main signal field 121 is input to the coherent mixing unit 140 via the first mixing input terminal 143, and the path coding reference field 137 is input to the coherent mixing unit 140 via the second mixing input terminal 144. In this embodiment, the coherent mixing unit 140 adopts a 90° optical mixer or an equivalent I / Q coherent mixing structure.

[0159] The coherent mixer unit 140 outputs one forward output 145a, one inverted output 145b, and four forward and inverted outputs 146a and 146b, respectively. The first detector group 151 performs differential detection on the one forward output 145a and the one inverted output 145b to obtain ΔI; the second detector group 152 performs differential detection on the two forward and inverted outputs 146a and 146b, respectively, to obtain ΔQ.

[0160] The output processing unit 180 performs phase arctangent calculation, linear interval slope conversion, or table lookup calibration based on ΔI and ΔQ to obtain the measurement results corresponding to the phase to be measured and the physical quantity to be measured.

[0161] The control unit 190 includes a main operating point adjustment module 191, a reference field adjustment module 192, a power monitoring unit 193, and a calibration and optimization module 194. The control unit 190 adjusts the input power, the main signal operating point, and the amplitude and phase state of the path encoding reference field 137 based on the probe branch power, saturation threshold, readout slope, quadrature error, and / or equivalent phase noise.

[0162] The control unit 190 can periodically inject known phase disturbances, determine the current readout slope, phase zero and orthogonality error based on ΔI and ΔQ, and adjust the main phase adjuster and the first adjustment unit 133 and / or the second adjustment unit 134 accordingly.

[0163] Without saturating the detector and the back-end readout chain, the differential photoelectric conversion signal can be increased by increasing the non-zero reference power of the path coding reference field 137 and adjusting its phase; using I / Q dual-channel differential detection can also obtain the phase sign and a wider phase discrimination range.

[0164] Example 2: Path-coded weak-value amplification optical phase readout method based on single-channel balanced detection and adaptive adjustment. Figure 13 The lower right corner shows the single-channel balanced detection structure. After the main signal field 121 and the path-encoded reference field 137 are input into the 2×2 optical coupler, the single-channel differential readout signal ΔS is output by the balanced detector 153.

[0165] The flowchart of the weak-value amplification optical phase readout method based on the path-coded reference field in this embodiment is as follows: Figure 14 As shown, the steps include S1401 to S1411 as follows: Step S1401: Obtain the first coherent optical field and the second coherent optical field; The first and second coherent optical fields are generated by the phase sensing unit, and the phase difference or equivalent phase difference between them carries the phase information to be measured.

[0166] Step S1402: Generate the main signal field d0; The main signal generation unit performs interference processing on the first coherent optical field and the second coherent optical field, so that the output main signal field d0 is at the near-dark end operating point, the dark end operating point, or the post-selected operating point.

[0167] Step S1403: Generate path encoding reference field d1; The first coherent optical field or its derived optical field is input into the first reference path, and the second coherent optical field or its derived optical field is input into the second reference path. The optical fields in the first reference path and the second reference path are then combined into a path-coded reference field d1 after adjustment.

[0168] Step S1404: Adjust the amplitude and phase of the reference field; The control unit adjusts the adjustment unit in the path coding reference unit through the reference field amplitude and phase adjustment module so that the amplitude, phase or power ratio of the path coding reference field d1 meets the preset mixing conditions.

[0169] Step S1405: Perform coherent mixing and differential detection on the main signal field and the path coding reference field; The main signal field d0 and the path-coded reference field d1 are input to the coherent mixing unit, and the phase-complementary outputs after coherent mixing are input to the differential detection unit. When a single-channel balanced detection structure is used, the output is ΔS; when an I / Q detection structure is used, the outputs are ΔI and ΔQ.

[0170] Step S1406: The control unit determines whether any probe branch or back-end readout chain is close to saturation; if yes, proceed to step S1407; if no, proceed to step S1408.

[0171] Step S1407: Reduce the input optical power, reduce the path coding reference field power and / or change the main signal operating point, and return to step S1404.

[0172] When the input optical power, photocurrent, signal, transimpedance amplifier output, or analog-to-digital converter output of a single detection branch approaches a preset saturation threshold, the control unit executes step S1407.

[0173] The control unit can select and adjust the input power adjustment unit 170, the main signal generation unit 120, and / or the path coding reference unit 130 according to the adjustable units actually set in the system.

[0174] Step S1408: The control unit determines whether the readout slope, orthogonal error, or equivalent phase noise has reached the preset target; if not, proceed to step S1409; if yes, proceed to step S1410.

[0175] Step S1409: Adjust the path coding reference field power, path coding reference field phase, main signal operating point and / or coherent mixing phase, and return to step S1404.

[0176] The control unit determines the readout slope based on the differential readout signal corresponding to the known phase disturbance, and selects the corresponding adjustment amount based on the readout slope, orthogonal error, or equivalent phase noise.

[0177] Step S1410: Output the readout result of the phase to be measured; When the detector is not close to saturation and the readout slope or equivalent phase noise reaches the preset target, the readout result of the phase to be measured is output.

[0178] Step S1411: Periodically inject known phase perturbations for calibration.

[0179] Known phase perturbations can be used to determine the current readout slope, phase zero, reference field amplitude and phase state, or system drift.

[0180] When using a single-channel balanced detection structure, the system hardware complexity is lower than that of an I / Q dual-channel detection structure, making it suitable for applications where the phase change to be measured is within a preset linear range. By performing closed-loop adjustment of the input optical power, the main signal operating point, and the amplitude and phase of the path coding reference field 137, each detection branch can be kept within its linear operating range.

[0181] The choice between single-channel balanced probe and I / Q dual-channel differential probe can be made based on the application scenario. When a wider phase discrimination range or quadrature phase demodulation is required, an I / Q dual-channel differential probe can be used; when hardware simplification or small-phase linear readout near a single operating point is required, a single-channel balanced probe can be used.

[0182] Example 3: Application in Mach-Zehnder interferometer sensing structures.

[0183] In this embodiment, the phase sensing unit 110 includes a beam splitter, a sensing arm, and a reference arm. The coherent probe light is split into two paths by the beam splitter. One path passes through the sensing arm and is subjected to the physical quantity to be measured, while the other path passes through the reference arm, forming a first coherent optical field 111 and a second coherent optical field 112, respectively.

[0184] The physical quantity to be measured causes changes in the effective refractive index, geometric length, or propagation constant of the sensing arm, resulting in a phase difference to be measured between the first coherent optical field 111 and the second coherent optical field 112.

[0185] The main signal generation unit 120 performs a first phase combination on the first coherent optical field 111 and the second coherent optical field 112, so that the main signal field 121 is at the near dark end or a preset post-selected operating point.

[0186] The path coding reference unit 130 obtains reference components from the first coherent optical field 111 and the second coherent optical field 112 respectively, and performs a second phase combination through the first reference path 131 and the second reference path 132 to form a non-zero path coding reference field 137.

[0187] The coherent mixing unit 140 performs I / Q coherent mixing or single-channel coherent mixing on the main signal field 121 and the path coding reference field 137, and the differential detection unit 150 outputs ΔI, ΔQ or ΔS.

[0188] The control unit 190 can maintain the operating point of the main signal field 121 by adjusting the main phase adjuster, and maintain the preset mixing conditions by adjusting the amplitude and phase of the reference path.

[0189] This embodiment can be used to read out the Mach-Zehnder interference phase changes caused by refractive index, temperature, strain, pressure, or displacement.

[0190] Example 4: Application in Sagnac phase sensing structure.

[0191] In this embodiment, the phase sensing unit 110 includes a beam splitter / combiner and a closed sensing optical path. After being split, the coherent probe light propagates in two opposite directions along the closed sensing optical path and returns to form a first coherent optical field 111 and a second coherent optical field 112, respectively.

[0192] When the closed sensing optical path rotates or is subjected to a physical action that generates a non-reciprocal phase difference, a phase difference to be measured is formed between the first coherent optical field 111 and the second coherent optical field 112.

[0193] The main signal generation unit 120 performs a first phase combination of the two coherent optical fields, so that the main signal field 121 is at the dark end, near the dark end, or a preset selected working point.

[0194] The path coding reference unit 130 causes the two coherent optical fields to be combined in a second phase via the first reference path 131 and the second reference path 132, respectively, to form a path coding reference field 137 that is different from the main signal field 121 and has non-zero optical power.

[0195] The control unit 190 can adjust the input optical power, the main signal operating point, and the amplitude and phase of the path coding reference field 137 according to the power, readout slope, and phase zero of each detection branch.

[0196] This embodiment can be used in interferometric fiber optic gyroscopes, integrated optical gyroscopes, or other sensing systems based on Sagnac phase difference.

[0197] The above embodiments are used to illustrate the technical solutions of this application, and are not intended to limit the scope of protection of this application. Equivalent substitutions or modifications made by those skilled in the art without departing from the technical concept of this application shall fall within the scope of protection of this application.

Claims

1. An optical phase readout system with path-coded weak-value amplification, characterized in that, It includes a phase sensing unit, a main signal generation unit, a path coding reference unit, a coherent mixing unit, and a differential detection unit; The path encoding reference unit includes a first reference path and a second reference path, and at least one of the first reference path and the second reference path is provided with an adjustment unit, wherein: The phase sensing unit is used to generate a first coherent optical field and a second coherent optical field based on the received coherent probe light, so as to encode the physical quantity to be measured as the relative phase difference between the first coherent optical field and the second coherent optical field. The main signal generation unit is used to adjust the amplitude and / or phase relationship between the first coherent optical field and the second coherent optical field, and to perform interference processing on the first coherent optical field and the second coherent optical field to generate a main signal field at the target operating point. The path coding reference unit is used to make the first coherent light field form a first reference light field through the first reference path, and to make the second coherent light field form a second reference light field through the second reference path. The adjustment unit adjusts the amplitude and / or phase of the first reference light field and / or the second reference light field and then merges them to generate a path coding reference field. The amplitude and / or phase relationship between the first coherent optical field and the second coherent optical field in the main signal field is different from the amplitude and / or phase relationship between the first reference optical field and the second reference optical field in the path coding reference field, and the path coding reference field has non-zero optical power at the target operating point; the coherent mixing unit is used to coherently mix the main signal field and the path coding reference field to obtain a mixed output optical signal; The differential detection unit is used to perform differential detection on the mixed output optical signal to obtain a differential readout signal characterizing the physical quantity to be measured.

2. The system according to claim 1, characterized in that, The optical phase readout system further includes a light source unit and an input power adjustment unit, wherein: The input power adjustment unit is used to adjust the power of the coherent probe light output by the light source unit and send the adjusted coherent probe light to the phase sensing unit.

3. The system according to claim 1, characterized in that, The main signal generation unit includes a main phase adjuster and a main beam combiner, wherein: The main phase adjuster is used to adjust the relative phase between the first coherent optical field and the second coherent optical field; the main beam combiner is used to perform beam combining interference on the adjusted first coherent optical field and the second coherent optical field to output the main signal field at the target operating point; the target operating point is the dark end operating point, the near dark end operating point, or the post-selected operating point.

4. The system according to claim 1, characterized in that, The adjustment unit includes a first adjustment unit disposed on the first reference path and / or a second adjustment unit disposed on the second reference path, wherein: The first adjustment unit is used to adjust the first coherent optical field to form the first reference optical field; The second adjustment unit is used to adjust the second coherent optical field to form the second reference optical field.

5. The system according to claim 4, characterized in that, The first adjustment unit and the second adjustment unit each include at least one of an amplitude regulator, a phase regulator, a delay regulator, and a polarization regulator.

6. The system according to claim 1, characterized in that, The coherent mixing unit includes an orthogonal optical mixer, which includes a first mixing input and a second mixing input. The orthogonal optical mixer is used to receive the main signal field through the first mixer input terminal and the path coding reference field through the second mixer input terminal, and to perform coherent mixing on the main signal field and the path coding reference field to output in-phase forward optical signal, in-phase reverse optical signal, quadrature forward optical signal and quadrature reverse optical signal.

7. The system according to claim 6, characterized in that, The differential detection unit includes a first detector group and a second detector group, and the differential readout signal includes an in-phase differential readout signal and a quadrature differential readout signal; The quadrature optical mixer is further configured to output the in-phase forward optical signal and the in-phase reverse optical signal to the first detector group; and to output the quadrature forward optical signal and the quadrature reverse optical signal to the second detector group; The first detector group is used to perform differential detection on the in-phase forward light signal and the in-phase reverse light signal to obtain the in-phase differential readout signal; The second detector group is used to perform differential detection on the orthogonal forward optical signal and the orthogonal reverse optical signal to obtain the orthogonal differential readout signal.

8. The system according to claim 1, characterized in that, The coherent mixing unit includes an optical coupler, the differential detection unit includes a balanced detector, and the differential readout signal includes a single-channel differential readout signal, wherein: The optical coupler is used to coherently mix the main signal field and the path coding reference field to output a pair of phase-complementary mixed output optical signals. The balanced detector is used to differentially detect the pair of phase-complementary mixed output optical signals to obtain a single-channel differential readout signal characterizing the physical quantity to be measured.

9. The system according to claim 1, characterized in that, The optical phase readout system further includes an output processing unit, wherein: The differential detection unit is also used to send the differential readout signal to the output processing unit; The output processing unit is used to demodulate the differential readout signal using a preset demodulation method to obtain the measurement result corresponding to the physical quantity to be measured.

10. The system according to claim 1, characterized in that, The optical phase readout system further includes a control unit, which comprises a main operating point adjustment module and a reference field adjustment module, wherein: The main operating point adjustment module is used to adjust the interference conditions of the main signal generation unit in order to set or maintain the target operating point of the main signal field. The reference field adjustment module is used to adjust the amplitude and / or phase of the first reference optical field and / or the second reference optical field to set the amplitude and phase state of the path encoding reference field.

11. The system according to claim 10, characterized in that, The control unit further includes a power monitoring unit, wherein: The power monitoring unit is used to monitor whether at least one of the input optical power, photocurrent, output voltage, and back-end readout chain amplitude of each detection branch reaches a preset saturation threshold; the control unit is used to reduce the power of the path-coded reference field and / or change the target operating point of the main signal field when the preset saturation threshold is reached, and to reduce the power of the coherent probe light input to the phase sensing unit when the optical phase readout system with path-coded weak value amplification includes an input power adjustment unit.

12. An optical phase readout method for path-coded weak-value amplification, characterized in that, include: A first coherent optical field and a second coherent optical field are generated based on coherent probe light to encode the physical quantity to be measured as the relative phase difference between the first coherent optical field and the second coherent optical field; Adjust the amplitude and / or phase relationship between the first coherent optical field and the second coherent optical field, and perform interference processing on the first coherent optical field and the second coherent optical field to generate a main signal field at the target operating point; The first coherent optical field is made to form a first reference optical field via a first reference path, and the second coherent optical field is made to form a second reference optical field via a second reference path. The amplitude and / or phase of the first reference optical field and / or the second reference optical field are adjusted and then merged to generate a path-coded reference field with non-zero optical power at the target operating point. The main signal field and the path-coded reference field adopt different amplitude-phase combination relationships. The main signal field and the path coding reference field are coherently mixed to obtain a mixed output optical signal; Differential detection is performed on the mixed output optical signal to obtain a differential readout signal characterizing the physical quantity to be measured.

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