A high-performance 3x3 coupler and PGC fusion improved demodulation method and device

Abstract

The application discloses a high-performance 3*3 coupler and PGC fusion improved demodulation method and device, wherein an initial measured interference signal is divided into three initial to-be-measured signals through a 3*3 coupler, the three initial to-be-measured signals are operated, and then a frequency multiplication signal of two carrier signals and a corresponding sinusoidal frequency multiplication signal are introduced, so that all useless high-order harmonic components of the three initial to-be-measured signals are filtered out after passing through a low-pass filter, and the influence of carrier phase delay, light intensity disturbance and modulation depth on a demodulation result is eliminated through certain mathematical calculation. The application not only eliminates the influence of light intensity disturbance, carrier phase delay and modulation depth, but also improves the detection sensitivity of a tiny signal and the anti-interference ability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of signal demodulation, and particularly relates to a high-performance 3*3 coupler and PGC fusion improved demodulation method and device. BACKGROUND

[0002] The 3*3 coupler demodulation method has many advantages such as high sensitivity, low signal loss, high adaptability and strong anti-interference ability, and the phase generation carrier (PGC) demodulation technology has many advantages such as large dynamic range, high sensitivity and strong signal fidelity, so the two algorithms are widely used in high-precision and high-anti-interference measurement of distributed optical fiber sensors, hydrophones, interferometers and other instruments and equipment. The 3*3 coupler demodulation method is to realize phase demodulation by introducing a 3*3 coupler with a 120° phase difference between two arms and combining an interference structure; and the PGC demodulation technology is to suppress low-frequency noise by introducing a high-frequency carrier modulation signal, and then restore the original signal to be measured after operation, which is mainly divided into arctangent (PGC-Arctan) algorithm and differential cross multiplication (PGC-DCM) algorithm.

[0003] However, the 3*3 coupler demodulation method is limited by its structure and other factors, and the output signal is easy to be disturbed by light intensity or polarization fading, so that the three-way output phase does not constitute 120°, and the demodulation effect is poor; and the differential cross multiplication algorithm and the arctangent algorithm are very sensitive to light intensity disturbance, carrier phase delay and modulation depth fluctuation. In addition, since the arctangent algorithm is to divide the two-way quadrature components after mixing by a low-pass filter to obtain the tangent value, and then restore the signal to be measured by arctangent operation, this method can only work in the interval of (-90°, 90°), and will produce a jump at the boundary of the interval, so that the signal outside the interval is difficult to demodulate.

[0004] ​In order to improve the demodulation accuracy of the demodulation result, and at the same time improve the sensitivity of the system to the detection of small signals and the anti-interference of the demodulation algorithm, generally only the structure of the sensing system can be upgraded or improved in hardware or the operation derivation process can be improved. Most of the existing improved algorithms can only eliminate the influence of some factors, for example, the improved phase carrier PGC demodulation method in the invention with publication number CN110411334B eliminates the influence of carrier phase delay and solves the problem that the interference signal is out of synchronization with the frequency multiplication signal due to analog-to-digital conversion; In the article "An improved PGC demodulation algorithm for optical fiber interferometers with insensitive to carrier phase delay and modulation depth" in 2022, an improved algorithm based on PGC-DCM is proposed to eliminate the influence of carrier phase delay and at the same time compensate the modulation depth, and there are few methods that can eliminate the three factors at the same time. In view of this problem, the invention with publication number CN118353539A proposes a high-performance phase generation carrier demodulation method and device, but this invention can eliminate the influence of three disturbance factors at the same time, but it does not consider the detection sensitivity of small signals and anti-interference problems. SUMMARY

[0005] In order to solve the problem that the existing demodulation technology is difficult to eliminate the influence of light intensity interference, carrier phase delay and modulation depth at the same time, and at the same time enhance the detection ability of small signals, improve the demodulation accuracy and system stability, the present application proposes a high-performance 3×3 coupler and PGC fusion improved demodulation method and device. The 3×3 coupler and PGC fusion improved demodulation method is used to demodulate the measured signal from the three initial interference signals, which not only eliminates the influence of light intensity interference, carrier phase delay and modulation depth on the demodulation result, but also amplifies the small signal by introducing the 3×3 coupler structure, improves the detection sensitivity of small signals and the accuracy of phase demodulation, and enhances the anti-interference performance. It can be widely used in perimeter security, track monitoring, large-scale building health monitoring and other fields.

[0006] Technical scheme:

[0007] In a first aspect, the present application discloses a high-performance 3×3 coupler and PGC fusion improved demodulation method, which comprises the following steps:

[0008] The initial measured interference signal is output as three signals I1(t), I2(t) and I3(t) through a 3×3 coupler, wherein:

[0009] The first measured interference signal I1(t) is divided into two paths after passing through the first DC filter, and the two paths are mixed with one frequency and two frequency of the carrier signal respectively, and the low frequency filter is used to filter the two mixed signals to obtain the first filter signal L1 and the second filter signal L2;

[0010] The second measured interference signal I2(t) is divided into three paths after passing through the second DC filter, one path is directly filtered by the low-pass filter to obtain the third filter signal L3, and the other two paths are mixed with one frequency and two frequency of the carrier signal respectively, and the low-pass filter is used to filter the two mixed signals to obtain the fourth filter signal L4 and the fifth filter signal L5;

[0011] The third measured interference signal I3(t) is divided into two paths after passing through the third DC filter, and the two paths are mixed with one frequency and two frequency of the carrier signal respectively, and the low frequency filter is used to filter the two mixed signals to obtain the sixth filter signal L6 and the seventh filter signal L7;

[0012] S2. The first filter signal L1 is added to the sixth filter signal L6, and then squared, and the square of the fourth filter signal L4 is added to obtain the first carrier-free phase delay square signal S1. The second filter signal L2 is added to the seventh filter signal L7, and then squared, and the square of the fifth filter signal L5 is added to obtain the second carrier-free phase delay square signal S2.

[0013] S3. The first carrier-free phase delay square signal S1 and the second carrier-free phase delay square signal S2 are subjected to square root operation respectively to obtain the first carrier-free phase delay signal K1 and the second carrier-free phase delay signal K2. The first carrier-free phase delay signal K1 is derived with respect to time t to obtain the first operation result D1. The second carrier-free phase delay signal K2 is added to the third filter signal L3 to obtain the second operation result D2. The third operation result D3 is obtained by dividing the first operation result D1 by the second operation result D2.

[0014] S4. The third operation result D3 is multiplied by 2 / C to obtain the modulation depth elimination signal V.

[0015] S5. The modulation depth elimination signal V is subjected to integral operation, and after filtering out high frequency noise, the measured signal phase signal is obtained.

[0016] Further, in step S1, the three initial measured interference signals I1(t), I2(t) and I3(t) output by the 3×3 coupler are:

[0017]

[0018] In the formula, m is the amplitude of the light intensity disturbance, ωn is the angular frequency of the light intensity perturbation, t is time, A is the DC component of the light intensity, B is the amplitude of the initial interference signal, C is the modulation depth, ω c is the angular frequency of the carrier modulation signal, θ is the carrier phase delay, is the phase signal of the signal to be measured at time t;

[0019] The expressions of the first filter signal L1 and the second filter signal L2 are respectively:

[0020]

[0021] In the formula, J1(C) is a first-order Bessel function, and J2(C) is a second-order Bessel function;

[0022] The expressions of the third filter signal L3, the fourth filter signal L4, and the fifth filter signal L5 are respectively:

[0023]

[0024] In the formula, J0(C) is a zero-order Bessel function;

[0025] The expressions of the sixth filter signal L6 and the seventh filter signal L7 are respectively:

[0026]

[0027] Further, in step S2, the expressions of the first carrierless phase delay square signal S1 and the second carrierless phase delay square signal S2 are respectively:

[0028]

[0029] Further, in step S3, the expressions of the first carrierless phase delay signal K1 and the second carrierless phase delay signal K2 are respectively:

[0030]

[0031] The expressions of the first operation result D1, the second operation result D2, and the third operation result D3 are respectively:

[0032]

[0033] Further, in step S4, the expression of the modulation depth influence elimination signal V is:

[0034]

[0035] The application discloses a high-performance 3*3 coupler and PGC fusion improved demodulation device.

[0036] The output end of the first DC filter divides the signal into two paths to enter the mixing filter module; the output end of the second DC filter divides the signal into three paths, one of which enters the third low-pass filter, and the other two enter the mixing filter module; the output end of the third DC filter divides the signal into two paths to enter the mixing filter module; the third low-pass filter module is used for filtering high-frequency components of the input signal to obtain a third filtered signal L3; the mixing filter module is used for mixing and filtering high-frequency components of six input signals to obtain a first filtered signal L1, a second filtered signal L2, a fourth filtered signal L4, a fifth filtered signal L5, a sixth filtered signal L6 and a seventh filtered signal L7.

[0037] The input end of the carrier phase delay elimination module is connected with the output end of the mixing filter module, which is used for adding the first filtered signal L1 and the sixth filtered signal L6, squaring the sum, adding the square of the fourth filtered signal L4 to obtain a first carrier phase delay elimination square signal S1, adding the second filtered signal L2 and the seventh filtered signal L7, squaring the sum, and adding the square of the fifth filtered signal L5 to obtain a second carrier phase delay elimination square signal S2.

[0038] The input end of the light intensity disturbance elimination module is connected with the output end of the third low-pass filter and the carrier phase delay elimination module, respectively, and the first carrier phase delay elimination square signal S1 and the second carrier phase delay elimination square signal S2 are subjected to square root operation to obtain a first carrier phase delay elimination signal K1 and a second carrier phase delay elimination signal K2, wherein the first carrier phase delay elimination signal K1 is derived with respect to time t to obtain a first operation result D1, the second carrier phase delay elimination signal K2 and the third filtered signal L3 are added to obtain a second operation result D2, and the first operation result D1 is divided by the second operation result D2 to obtain a third operation result D3.

[0039] The input end of the modulation depth elimination module is connected with the output end of the light intensity disturbance elimination module, which is used for multiplying the third operation result D3 by 2 / C to obtain a modulation depth elimination signal V.

[0040] The input end of the integration module is connected with the output end of the modulation depth elimination module, which is used for restoring a demodulation signal.

[0041] The input end of the high-pass filter module is connected with the output end of the integration module, and is used for filtering low-frequency noise signals in the demodulation signal.

[0042] Further, the mixing filter module comprises a first multiplier, a second multiplier, a third multiplier, a fourth multiplier, a fifth multiplier, a sixth multiplier, a digital frequency synthesizer, a first low-pass filter, a second low-pass filter, a fourth low-pass filter, a fifth low-pass filter, a sixth low-pass filter and a seventh low-pass filter.

[0043] One input end of the first multiplier and the second multiplier is connected with a first DC filter, and the other input end is connected with a one-frequency reference signal output end and a two-frequency reference signal output end of the digital frequency synthesizer respectively, for mixing two signals filtered by DC and two frequency signals; one input end of the third multiplier and the fourth multiplier is connected with a second DC filter, and the other input end is connected with a one-frequency sine signal output end and a two-frequency sine signal output end of the digital frequency synthesizer respectively, for mixing two signals filtered by DC and two frequency signals; one input end of the fifth multiplier and the sixth multiplier is connected with a third DC filter, and the other input end is connected with a one-frequency reference signal output end and a two-frequency reference signal output end of the digital frequency synthesizer respectively, for mixing two signals filtered by DC and two frequency signals.

[0044] The output ends of the first multiplier, the second multiplier, the third multiplier, the fourth multiplier, the fifth multiplier and the sixth multiplier are connected with the input ends of the first low-pass filter, the second low-pass filter, the fourth low-pass filter, the fifth low-pass filter, the sixth low-pass filter and the seventh low-pass filter respectively, for low-pass filtering six mixed signals to obtain six filtered signals of the phase of the to-be-tested signals, and the output ends of the first low-pass filter, the second low-pass filter, the fourth low-pass filter, the fifth low-pass filter, the sixth low-pass filter and the seventh low-pass filter are connected with the carrier phase delay elimination module.

[0045] Further, the carrier phase delay elimination module comprises a first adder, a second adder, a third adder, a fourth adder, a first squarer, a second squarer, a third squarer and a fourth squarer.

[0046] The first input end of the first adder is connected with the output end of the first low-pass filter, the second input end is connected with the output end of the sixth low-pass filter, and the output end is connected with the input end of the first squarer; the first input end of the second adder is connected with the output end of the second low-pass filter, the second input end is connected with the output end of the seventh low-pass filter, and the output end is connected with the input end of the third squarer; the output end of the first squarer is connected with the first input end of the third adder; the input end of the second squarer is connected with the output end of the fourth low-pass filter, and the output end is connected with the second input end of the third adder; the output end of the third squarer is connected with the first input end of the fourth adder; the input end of the fourth squarer is connected with the output end of the fifth low-pass filter, and the output end is connected with the second input end of the fourth adder.

[0047] The output ends of the third adder and the fourth adder are connected with the light intensity disturbance elimination module.

[0048] Further, the light intensity disturbance elimination module comprises a first square root generator, a second square root generator, a fifth adder, a first differentiator and a first divider.

[0049] The input end of the first square root generator is connected with the output end of the third adder; the input end of the second square root generator is connected with the output end of the fourth adder; the input end of the first differentiator is connected with the output end of the first square root generator, and the output end is connected with the first input end of the first divider; the first input end of the fifth adder is connected with the output end of the third low-pass filter, the second input end is connected with the output end of the second square root generator, and the output end is connected with the second input end of the first divider.

[0050] The output end of the first divider is connected with the modulation depth influence elimination module.

[0051] Further, the modulation depth influence elimination module comprises a first constant unit and a seventh multiplier.

[0052] The first input end of the seventh multiplier is connected with the first constant unit, the second input end is connected with the output end of the first divider, and the output end is connected with the input end of the integration module.

[0053] The output end of the integration module is connected with the high-pass filter module.

[0054] Beneficial effects:

[0055] The high-performance 3*3 coupler and PGC fusion improved demodulation method and device of the application, the initial measured interference signal is divided into three initial measured signals by 3*3 coupler, the three initial measured signals are operated, the frequency multiplication signal of two carrier signals and the corresponding sinusoidal frequency multiplication signal are introduced, so that the three initial measured signals will filter out all the useless high harmonic components after passing through the low-pass filter, and the influence of carrier phase delay, light intensity disturbance and modulation depth on the demodulation result is eliminated through certain mathematical calculation; the application not only eliminates the influence of light intensity interference, carrier phase delay and modulation depth on the demodulation result, but also amplifies the small signal by introducing 3*3 coupler structure, improves the detection sensitivity and phase demodulation accuracy of the small signal, enhances the anti-interference performance, and can be widely applied in perimeter security, track monitoring, large-scale building health monitoring and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 It is the structure diagram of the high-performance 3*3 coupler and PGC fusion improved demodulation device of the application.

[0057] Figure 2 It is the flow chart of the high-performance 3*3 coupler and PGC fusion improved demodulation method of the application.

[0058] Figure 3 It is the demodulation result diagram of the application when the initial measured signal amplitude is 1.5 rad and the frequency is 500 Hz.

[0059] Figure 4 It is the demodulation result diagram of the application under different modulation depths.

[0060] Figure 5 It is the demodulation result diagram of the application under different light intensity disturbances (amplitude, frequency are different).

[0061] Figure 6 It is the demodulation result diagram of the application under different carrier phase delays.

[0062] Figure 7 It is the demodulation result diagram of the application when the initial measured signal amplitude is 0.1 rad and the frequency is 500 Hz. DETAILED DESCRIPTION

[0063] The following examples can make the professional technical personnel more fully understand the application, but do not limit the application in any way.

[0064] Reference Figure 2 The embodiment discloses a high-performance 3*3 coupler and PGC fusion improved demodulation method, which comprises the following steps:

[0065] S1. The initial measured interference signal is output through a 3x3 coupler to three signals, which are collected by a data acquisition card after being detected by a photoelectric detector, and are I1(t), I2(t) and I3(t) respectively, the expressions of which are as follows, which contain three different influencing factors of light intensity disturbance, modulation depth and carrier phase delay:

[0066] The first path:

[0067] The second path:

[0068] The third path:

[0069] In the formula, m is the amplitude of the light intensity disturbance, ω n is the angular frequency of the light intensity disturbance, t is the time, A is the light intensity direct current component, B is the amplitude of the initial interference signal, C is the modulation depth, ω c is the angular frequency of the carrier modulation signal, θ is the carrier phase delay, is the phase signal of the signal to be measured at t;

[0070] The first measured interference signal I1(t) is divided into two paths after passing through the first direct current filter, and is mixed with one frequency and two frequencies of the carrier signal respectively, and then both paths are filtered by a low-pass filter to obtain two filtered signals, which are the first filtered signal L1 and the second filtered signal L2;

[0071]

[0072] In the formula, J1(C) is a first-order Bessel function, and J2(C) is a second-order Bessel function;

[0073] The second measured interference signal I2(t) is divided into three paths after passing through the second direct current filter, one of which is directly filtered by a low-pass filter to obtain a filtered signal, which is the third filtered signal L3, and the other two are mixed with one frequency and two frequencies of the carrier signal respectively, and then both paths are filtered by a low-pass filter to obtain two filtered signals, which are the fourth filtered signal L4 and the fifth filtered signal L5;

[0074]

[0075] In the formula, J0(C) is a zero-order Bessel function;

[0076] The third measured interference signal I3(t) is divided into two paths after passing through the third direct current filter, and is mixed with one frequency and two frequencies of the carrier signal respectively, and then both paths are filtered by a low-pass filter to obtain two filtered signals, which are the sixth filtered signal L6 and the seventh filtered signal L7;

[0077]

[0078] S2. Eliminate carrier phase delay

[0079] Square the first filter signal L1 and the sixth filter signal L6 after adding them together, and then add the square of the fourth filter signal L4 to obtain the first carrier phase delay square signal S1. Square the second filter signal L2 and the seventh filter signal L7 after adding them together, and then add the square of the fifth filter signal L5 to obtain the second carrier phase delay square signal S2.

[0080]

[0081] S3. Eliminate light intensity disturbance

[0082] Take the square root operation on the first carrier phase delay square signal S1 and the second carrier phase delay square signal S2 respectively, thereby obtaining the first carrier phase delay signal K1 and the second carrier phase delay signal K2. Derive the first carrier phase delay signal K1 with respect to time t to obtain the first operation result D1. Add the second carrier phase delay signal K2 and the third filter signal L3 to obtain the second operation result D2. Divide the first operation result D1 by the second operation result D2 to obtain the third operation result D3.

[0083]

[0084] The expressions of the first operation result D1, the second operation result D2, and the third operation result D3 are respectively:

[0085]

[0086] S4. Eliminate modulation depth influence

[0087] Multiply the third operation result D3 by 2 / C to obtain the modulation depth elimination signal V.

[0088]

[0089] S5. Integrate the modulation depth elimination signal V to filter out high-frequency noise and obtain the measured signal phase signal

[0090] In this embodiment, the effective bandwidth BW of the carrier frequency effective = 2f m , f m is the highest frequency of the carrier signal. The bandwidth BW of the low-pass filter LP = f cut to ensure that the required signal can pass through, and the cutoff frequency f cut is usually selected as f cut ≥ fmax where f max is the highest frequency of the signal to be measured. As a preferred solution, in order to ensure that the filter can retain the main component of the signal, f cut = 2f max or f cut = f max + Δf, Δf is to ensure that the filter has sufficient bandwidth to cover the characteristics of the signal. For example, the sampling rate is set to 200 kHz, the signal to be measured is set to 500 Hz, the amplitude is set to 2 rad, and the carrier signal frequency is set to 10 kHz. According to the above parameters, it can be judged that the effective bandwidth of the carrier frequency is 60 kHz, the low-pass filter bandwidth is specified as 1 kHz, and the FIR low-pass filter with Hamming window is selected to realize it.

[0091] Referring to Figure 1 , the embodiment discloses a high-performance 3*3 coupler and PGC fusion improved demodulation device, which comprises a first DC filter, a second DC filter, a third DC filter, a third low-pass filter, a frequency mixing filter module, a carrier phase delay elimination module, an optical intensity disturbance elimination module, a modulation depth influence elimination module, an integration module and a high-pass filter module.

[0092] The output end of the first DC filter divides the signal into two paths entering the frequency mixing filter module; the output end of the second DC filter divides the signal into three paths, one path entering the third low-pass filter, and the other two paths entering the frequency mixing filter module; the output end of the third DC filter divides the signal into two paths entering the frequency mixing filter module.

[0093] The output end of the third low-pass filter is connected to the optical intensity disturbance elimination module for filtering out high-frequency components of the initial measured interference signal entering; the output end of the frequency mixing filter module is connected to the carrier phase delay elimination module for mixing the six input signals filtered by the DC filter and filtering out high-frequency components; the output end of the carrier phase delay elimination module is connected to the optical intensity disturbance elimination module for eliminating the carrier phase delay in the demodulation signal; the output end of the optical intensity disturbance elimination module is connected to the modulation depth influence elimination module for eliminating the optical intensity disturbance in the demodulation signal; the output end of the modulation depth influence elimination module is connected to the integration module for eliminating the influence of the modulation depth on the demodulation signal; the output end of the integration module is connected to the high-pass filter module for restoring the demodulation signal; and the high-pass filter module is used for filtering out low-frequency noise signals in the demodulation signal.

[0094] The frequency mixing filter module of the embodiment comprises a first multiplier to a sixth multiplier, a digital frequency synthesizer, a first low-pass filter, a second low-pass filter, a fourth low-pass filter, a fifth low-pass filter, a sixth low-pass filter and a seventh low-pass filter.

[0095] The input end I of the first multiplier, the second multiplier is connected with the first DC filter, the input end II is connected with the one frequency reference signal output end, the two frequency reference signal output end of the digital frequency synthesizer respectively, for mixing two signals which have passed through DC filtering with two frequency signals; the input end I of the third multiplier, the fourth multiplier is connected with the second DC filter, the input end II is connected with the one frequency sine signal output end, the two frequency sine signal output end of the digital frequency synthesizer respectively, for mixing two signals which have passed through DC filtering with two frequency signals; the input end I of the fifth multiplier, the sixth multiplier is connected with the third DC filter, the input end II is connected with the one frequency reference signal output end, the two frequency reference signal output end of the digital frequency synthesizer respectively, for mixing two signals which have passed through DC filtering with two frequency signals.

[0096] The output end of the first multiplier, the second multiplier, the third multiplier, the fourth multiplier, the fifth multiplier and the sixth multiplier is connected with the input end of the first low pass filter, the second low pass filter, the fourth low pass filter, the fifth low pass filter, the sixth low pass filter and the seventh low pass filter respectively, for low pass filtering operation to six mixed signals, obtaining six filter signals of the phase of the signals to be measured, and the output end of the first low pass filter, the second low pass filter, the fourth low pass filter, the fifth low pass filter, the sixth low pass filter and the seventh low pass filter is connected to the carrier phase delay elimination module.

[0097] The carrier phase delay elimination module of the embodiment comprises a first adder, a second adder, a third adder, a fourth adder, a first squarer, a second squarer, a third squarer and a fourth squarer.

[0098] The input end I of the first adder is connected with the output end of the first low pass filter, the input end II is connected with the output end of the sixth low pass filter, and the output end is connected with the input end of the first squarer; the input end I of the second adder is connected with the output end of the second low pass filter, the input end II is connected with the output end of the seventh low pass filter, and the output end is connected with the input end of the third squarer; the output end of the first squarer is connected with the input end I of the third adder; the input end of the second squarer is connected with the output end of the fourth low pass filter, and the output end is connected with the input end II of the third adder; the output end of the third squarer is connected with the input end I of the fourth adder; the input end of the fourth squarer is connected with the output end of the fifth low pass filter, and the output end is connected with the input end II of the fourth adder; the output end of the third adder and the fourth adder is connected with the light intensity disturbance elimination module.

[0099] The light intensity disturbance elimination module of the embodiment comprises a first square root device, a second square root device, a fifth adder, a first differentiator and a first divider.

[0100] The input end of the first square root device is connected with the output end of the third adder; the input end of the second square root device is connected with the output end of the fourth adder; the input end of the first differentiator is connected with the output end of the first square root device, and the output end is connected with the input end I of the first divider; the input end I of the fifth adder is connected with the output end of the third low pass filter, the input end II is connected with the output end of the second square root device, and the output end is connected with the input end II of the first divider; the output end of the first divider is connected with the elimination of modulation depth influence module.

[0101] The elimination of modulation depth influence module of the embodiment comprises a first constant unit and a seventh multiplier.

[0102] The input end I of the seventh multiplier is connected with the first constant unit, the input end II is connected with the output end of the first divider, and the output end is connected with the input end of the integration module.

[0103] The output end of the integration module is connected with the high pass filter module, and the low frequency noise is filtered through the high pass filter module to obtain the phase to be measured.

[0104] In order to verify the beneficial effects of the present application, the inventors use the aforementioned high-performance 3*3 coupler and PGC fusion improved demodulation method and device to make the following embodiments:

[0105] Embodiment 1

[0106] The initial signal to be measured is set to 1.5 rad, the frequency is set to 500 Hz, the carrier modulation signal frequency is set to 20 kHz, the modulation depth is set to 2 rad, the sampling rate is set to 200 kHz, the light intensity DC component is 1 rad, the interference signal amplitude is 1 rad, the signal to be measured is shown in (a) of Figure 3 , and the demodulation result is shown in (b) of Figure 3 , and it can be seen from Figure 3 that the 3*3 coupler and PGC fusion improved demodulation method and device of the present application can restore the signal to be measured.

[0107] Embodiment 2

[0108] The initial signal to be measured is set to 1.5 rad, the frequency is set to 200 Hz, the carrier modulation signal frequency is set to 20 kHz, the sampling rate is set to 200 kHz, the light intensity DC component is 1 rad, the interference signal amplitude is 1 rad, and the modulation depth is set to 1.5 rad, 2.37 rad, 2.63 rad and 3.6 rad, respectively, the signal to be measured is shown in (a) of Figure 4 , and the demodulation result is shown in (b) of Figure 4 , and it can be seen from Figure 4 that the 3*3 coupler and PGC fusion improved demodulation method and device of the present application are not sensitive to the change of modulation depth C.

[0109] Embodiment 3

[0110] Set the initial to-be-measured signal amplitude as 1.5 rad, the frequency as 200 Hz, the carrier modulation signal frequency as 20 kHz, the modulation depth as 2 rad, the sampling rate as 200 kHz, the light intensity DC component as 1 rad, the interference signal amplitude as 1 rad, the light intensity disturbance amplitude as 1 rad and 2 rad, the frequency as 10 Hz and 20 Hz, the to-be-measured signal as shown in (a) of Figure 5 , and the demodulation result as shown in (b) of Figure 5 , it can be seen from Figure 5 that the 3*3 coupler and PGC fusion improved demodulation method and device are not affected by the light intensity disturbance.

[0111] Example 4

[0112] Set the initial to-be-measured signal amplitude as 1.5 rad, the frequency as 200 Hz, the carrier modulation signal frequency as 20 kHz, the modulation depth as 2 rad, the sampling rate as 200 kHz, the light intensity DC component as 1 rad, the interference signal amplitude as 1 rad, the carrier phase delay as 23°, 67° and 114° respectively, the to-be-measured signal as shown in (a) of Figure 6 , and the demodulation result as shown in (b) of Figure 6 , it can be seen from Figure 6 that the 3*3 coupler and PGC fusion improved demodulation method and device can eliminate the influence of the carrier phase delay on the demodulation result.

[0113] Example 5

[0114] Set the initial to-be-measured signal amplitude as 0.1 rad, the frequency as 500 Hz, the carrier modulation signal frequency as 20 kHz, the modulation depth as 2 rad, the sampling rate as 200 kHz, the light intensity DC component as 1 rad, the interference signal amplitude as 1 rad, the to-be-measured signal as shown in (a) of Figure 7 , and the demodulation result as shown in (b) of Figure 7 , it can be seen from Figure 7 that the 3*3 coupler and PGC fusion improved demodulation method and device can restore the to-be-measured signal.

[0115] In summary, the high-performance 3*3 coupler and PGC fusion improved demodulation method and device obtain a relationship formula not containing the light intensity disturbance, the carrier phase delay and the modulation depth, can determine the to-be-measured signal phase, and finally restores the phase signal not affected by the above three factors, and can effectively improve the phase demodulation precision and the demodulation stability.

[0116] The above are only preferred embodiments of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiments. Any technical scheme falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled in the art, some improvements and refinements without departing from the principles of the present application shall be considered as the protection scope of the present application.

Claims

1. A high-performance 3x3 coupler and PGC fusion improved demodulation method, characterized by, The demodulation method comprises the following steps: The initial measured interference signal is output as three signals I1(t), I2(t) and I3(t) through a 3*3 coupler, wherein: The first measured interference signal I1(t) is divided into two signals after passing through a first DC filter, the two signals are mixed with a carrier signal of one frequency and two frequencies respectively, and low-frequency filters are used to filter the two mixed signals to obtain a first filtered signal L1 and a second filtered signal L2; The second measured interference signal I2(t) is divided into three signals after passing through a second DC filter, one signal is directly filtered by a low-pass filter to obtain a third filtered signal L3, and the other two signals are mixed with a carrier signal of one frequency and two frequencies respectively, and the two mixed signals are filtered by low-pass filters to obtain a fourth filtered signal L4 and a fifth filtered signal L5; The third measured interference signal I3(t) is divided into two signals after passing through a third DC filter, the two signals are mixed with a carrier signal of one frequency and two frequencies respectively, and low-frequency filters are used to filter the two mixed signals to obtain a sixth filtered signal L6 and a seventh filtered signal L7; S2. The first filtered signal L1 is added to the sixth filtered signal L6, and then squared, and the square of the fourth filtered signal L4 is added to obtain a first carrier-free phase delay square signal S1, and the second filtered signal L2 is added to the seventh filtered signal L7, and then squared, and the square of the fifth filtered signal L5 is added to obtain a second carrier-free phase delay square signal S2; S3. The first carrier-free phase delay square signal S1 and the second carrier-free phase delay square signal S2 are respectively subjected to square root operation to obtain a first carrier-free phase delay signal K1 and a second carrier-free phase delay signal K2, wherein the first carrier-free phase delay signal K1 is derived with respect to time t to obtain a first operation result D1, the second carrier-free phase delay signal K2 is added to the third filtered signal L3 to obtain a second operation result D2, and the first operation result D1 is divided by the second operation result D2 to obtain a third operation result D3; S4. The third operation result D3 is multiplied by 2 / C to obtain a modulation depth elimination signal V; S5. The signal V eliminating the influence of modulation depth is integrated to obtain the phase signal of the signal to be measured after filtering out high frequency noise 2. The high performance 3x3 coupler and PGC fusion improved demodulation method according to claim 1, wherein, In step S1, the three initial measured interference signals I1(t), I2(t) and I3(t) output by the 3*3 coupler are respectively: where m is the amplitude of the light intensity perturbation, ω n is the angular frequency of the light intensity perturbation, t is time, A is the DC component of the light intensity, B is the amplitude of the initial interference signal, C is the modulation depth, ω c is the angular frequency of the carrier modulation signal, θ is the carrier phase delay, is the phase signal of the signal to be measured at time t; The expressions of the first filtered signal L1 and the second filtered signal L2 are respectively: In the formula, J1(C) is a first-order Bessel function, and J2(C) is a second-order Bessel function; The expressions of the third filtered signal L3, the fourth filtered signal L4 and the fifth filtered signal L5 are respectively: In the formula, J0(C) is a zero-order Bessel function; The expressions of the sixth filtered signal L6 and the seventh filtered signal L7 are respectively:

3. The high performance 3x3 coupler and PGC fusion improved demodulation method according to claim 1, characterized in that, In step S2, the expressions of the first carrier-free phase delay square signal S1 and the second carrier-free phase delay square signal S2 are respectively:

4. The high performance 3x3 coupler and PGC fusion improved demodulation method of claim 1, wherein, In step S3, the expressions of the first carrier-free phase delay signal K1 and the second carrier-free phase delay signal K2 are respectively: The expression of the first operation result D1, the second operation result D2 and the third operation result D3 is respectively:

5. The high performance 3x3 coupler and PGC fusion improved demodulation method of claim 1, wherein, In step S4, the expression of the elimination modulation depth influence signal V is:

6. A high-performance 3x3 coupler and PGC fusion improved demodulation device, characterized in that, The demodulation device comprises a first DC filter, a second DC filter, a third DC filter, a third low-pass filter, a mixed frequency filtering module, an elimination carrier phase delay module, an elimination light intensity disturbance module, an elimination modulation depth influence module, an integration module and a high-pass filtering module; The output end of the first DC filter divides the signal into two paths to enter the mixed frequency filtering module; the output end of the second DC filter divides the signal into three paths, one path enters the third low-pass filter, and the other two paths enter the mixed frequency filtering module; The output end of the third DC filter divides the signal into two paths to enter the mixed frequency filtering module; the third low-pass filtering module is used for filtering high-frequency components of the input signal to obtain a third filtered signal L3; The mixed frequency filtering module is used for mixing and filtering high-frequency components of six input signals to obtain a first filtered signal L1, a second filtered signal L2, a fourth filtered signal L4, a fifth filtered signal L5, a sixth filtered signal L6 and a seventh filtered signal L7; The input end of the elimination carrier phase delay module is connected with the output end of the mixed frequency filtering module, and is used for adding the first filtered signal L1 and the sixth filtered signal L6, squaring the sum, adding the square of the fourth filtered signal L4 to obtain a first carrier phase delay square signal S1, adding the second filtered signal L2 and the seventh filtered signal L7, squaring the sum, and adding the square of the fifth filtered signal L5 to obtain a second carrier phase delay square signal S2; The input end of the elimination light intensity disturbance module is connected with the output end of the third low-pass filter and the elimination carrier phase delay module, and is used for performing square root operation on the first carrier phase delay square signal S1 and the second carrier phase delay square signal S2 to obtain a first carrier phase delay signal K1 and a second carrier phase delay signal K2, wherein the first carrier phase delay signal K1 is derived with respect to time t to obtain a first operation result D1, the second carrier phase delay signal K2 is added to the third filtered signal L3 to obtain a second operation result D2, and the third operation result D3 is obtained by dividing the first operation result D1 by the second operation result D2; The input end of the elimination modulation depth influence module is connected with the output end of the elimination light intensity disturbance module, and is used for multiplying the third operation result D3 by 2 / C to obtain an elimination modulation depth influence signal V; The input end of the integration module is connected with the output end of the elimination modulation depth influence module, and is used for restoring a demodulation signal; The input end of the high-pass filtering module is connected with the output end of the integration module, and is used for filtering low-frequency noise signals in the demodulation signal.

7. The high performance 3x3 coupler and PGC fusion improved demodulation device according to claim 6, characterized in that, The mixed frequency filtering module comprises a first multiplier, a second multiplier, a third multiplier, a fourth multiplier, a fifth multiplier, a sixth multiplier, a digital frequency synthesizer, a first low-pass filter, a second low-pass filter, a fourth low-pass filter, a fifth low-pass filter, a sixth low-pass filter and a seventh low-pass filter; One of the inputs of the first multiplier and the second multiplier is connected to the first DC filter, and the other input is connected to the one frequency reference signal output and the two frequency reference signal output of the digital frequency synthesizer respectively, for mixing the two DC filtered signals with the two frequency signals; one of the inputs of the third multiplier and the fourth multiplier is connected to the second DC filter, and the other input is connected to the one frequency sine signal output and the two frequency sine signal output of the digital frequency synthesizer respectively, for mixing the two DC filtered signals with the two frequency signals; one of the inputs of the fifth multiplier and the sixth multiplier is connected to the third DC filter, and the other input is connected to the one frequency reference signal output and the two frequency reference signal output of the digital frequency synthesizer respectively, for mixing the two DC filtered signals with the two frequency signals. The outputs of the first multiplier, the second multiplier, the third multiplier, the fourth multiplier, the fifth multiplier and the sixth multiplier are connected to the inputs of the first low-pass filter, the second low-pass filter, the fourth low-pass filter, the fifth low-pass filter, the sixth low-pass filter and the seventh low-pass filter respectively, for low-pass filtering the six mixed signals to obtain the filtered signals of the six to-be-measured signal phases, and the outputs of the first low-pass filter, the second low-pass filter, the fourth low-pass filter, the fifth low-pass filter, the sixth low-pass filter and the seventh low-pass filter are connected to the carrier phase delay elimination module.

8. The high performance 3x3 coupler and PGC fusion improved demodulation device according to claim 6, wherein, The carrier phase delay elimination module comprises a first adder, a second adder, a third adder, a fourth adder, a first squarer, a second squarer, a third squarer and a fourth squarer. The first input of the first adder is connected to the output of the first low-pass filter, the second input is connected to the output of the sixth low-pass filter, and the output is connected to the input of the first squarer; the first input of the second adder is connected to the output of the second low-pass filter, the second input is connected to the output of the seventh low-pass filter, and the output is connected to the input of the third squarer; the output of the first squarer is connected to the first input of the third adder; the input of the second squarer is connected to the output of the fourth low-pass filter, and the output is connected to the second input of the third adder; the output of the third squarer is connected to the first input of the fourth adder; the input of the fourth squarer is connected to the output of the fifth low-pass filter, and the output is connected to the second input of the fourth adder; The outputs of the third adder and the fourth adder are connected to the light intensity disturbance elimination module.

9. The high performance 3x3 coupler and PGC fusion improved demodulation device according to claim 6, wherein, The light intensity disturbance elimination module comprises a first square root device, a second square root device, a fifth adder, a first differentiator and a first divider. The input end of the first square root device is connected with the output end of the third adder; the input end of the second square root device is connected with the output end of the fourth adder; the input end of the first differentiator is connected with the output end of the first square root device, and the output end is connected with the first input end of the first divider; the first input end of the fifth adder is connected with the output end of the third low pass filter, the second input end is connected with the output end of the second square root device, and the output end is connected with the second input end of the first divider; The output end of the first divider is connected with the elimination of modulation depth influence module.

10. The high performance 3x3 coupler and PGC fusion improved demodulation device according to claim 6, wherein, The elimination of modulation depth influence module comprises a first constant unit and a seventh multiplier; The first input end of the seventh multiplier is connected with the first constant unit, the second input end is connected with the output end of the first divider, and the output end is connected with the input end of the integration module; The output end of the integration module is connected with the high pass filter module.

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