CN111623892B - Adaptive optical fiber type Mach-Zehnder interferometer for time-varying random signal measurement - Google Patents

Adaptive optical fiber type Mach-Zehnder interferometer for time-varying random signal measurement Download PDF

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CN111623892B
CN111623892B CN202010460999.3A CN202010460999A CN111623892B CN 111623892 B CN111623892 B CN 111623892B CN 202010460999 A CN202010460999 A CN 202010460999A CN 111623892 B CN111623892 B CN 111623892B
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phase
optic
optical fiber
electro
signal
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CN111623892A (en
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刘芳
张勇
杨迎
徐钏
陈鹏程
王刘
杨嘉欣
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Nanjing Tech University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
    • G01J2009/0226—Fibres
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
    • G01J2009/0249—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods with modulation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
    • G01J2009/028—Types
    • G01J2009/0288—Machzehnder

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Instruments For Measurement Of Length By Optical Means (AREA)
  • Optical Communication System (AREA)

Abstract

The invention discloses a self-adaptive optical fiber type Mach-Zehnder interferometer for measuring time-varying random signals, wherein laser emitted by a laser is coupled into an optical fiber by an optical fiber collimator and is transmitted to an electro-optic amplitude modulator by the optical fiber, a signal emitted by a first signal generator is input to the electro-optic amplitude modulator, one end of a first optical fiber beam splitter receives the signal emitted by the electro-optic amplitude modulator, the other end of the first optical fiber beam splitter outputs two paths of signals, one path of signal is converged to a second optical fiber beam splitter by a first electro-optic phase modulator and a first phase shifter in sequence, the other path of signal is converged to a second optical fiber beam splitter by a second electro-optic phase modulator and a second phase shifter in sequence, the first electro-optic phase modulator also receives the signal emitted by the second signal generator, the output signal of the second optical fiber beam splitter outputs two paths of signals by a balance detector, and one path of signal is fed back to the first phase shifter, the other path is fed back to the second electro-optical phase modulator through a second phase-locked loop. Compared with other modes, the estimation precision of the time-varying random phase is higher.

Description

Adaptive optical fiber type Mach-Zehnder interferometer for time-varying random signal measurement
Technical Field
The invention relates to the field of quantum precision measurement, in particular to a self-adaptive optical fiber type Mach-Zehnder interferometer for measuring time-varying random phase signals.
Background
Quantum precision measurement is an important research direction in the fields of physics and optics today. Optical frequency and phase measurement has hitherto been one of the measurement techniques with the highest measurement accuracy among all physical quantities. In the field of precision measurement, measurement of a lot of physical quantities is summarized as measurement of phases, so that an interferometer becomes the most common experimental device in precision measurement and plays a vital role in basic scientific research and practical engineering application. For example, the measurement of the gravitational wave is based on the principle of optical michelson interferometer, so that the optical phase caused by the time-space variation in the generalized relativity theory can be precisely measured. In addition, physical quantities such as refractive index and length can be precisely measured by using the laser interference principle, and the measurement precision is high by using the coherence property of laser.
At present, the precision of quantum precision measurement is higher and higher, and measurable physical quantities are quite wide, however, two problems still exist in the precision measurement: 1. quantum measurement is mainly based on a free space system, and future informatization is rapidly developed to require a miniaturized and practical optical system; 2. the quantum precision measurement mainly focuses on the measurement of a fixed signal, but the tracking research on a random signal and a real-time signal is less, and the research on the latter is very important in a practical application system.
The patent "an optical fiber type adaptive balanced homodyne measurement system for measuring time-varying phase signal" is a time-varying phase signal tracking device based on an optical fiber system, however, the limit of the balanced homodyne detection measurement device adopted by the system to the optical power of the signal can not further improve the phase estimation precision, and the number of injected photons is about-106The minimum phase estimate variance only reaches 0.03.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problem of insufficient estimation precision in the prior art, the invention provides the self-adaptive optical fiber type Mach-Zehnder interferometer for measuring the time-varying random signal, which can measure the time-varying random signal and has higher estimation precision.
The technical scheme is as follows: the invention relates to a self-adaptive optical fiber Mach-Zehnder interferometer for time-varying random signal measurement, which comprises a laser, an optical fiber collimator, a first signal generator, an electro-optic amplitude modulator, a first optical fiber beam splitter, a first electro-optic phase modulator, a first phase shifter, a second electro-optic phase modulator, a second phase shifter, a second optical fiber beam splitter, a balance detector, a second signal generator, a first phase-locked loop and a second phase-locked loop, wherein laser emitted by the laser is coupled into an optical fiber through the optical fiber collimator and is transmitted to the electro-optic amplitude modulator through the optical fiber, a signal emitted by the first signal generator is input to the electro-optic amplitude modulator, one end of the first optical fiber beam splitter receives the signal emitted by the electro-optic amplitude modulator, the other end of the first optical fiber beam splitter outputs two paths of signals, and one path of signals sequentially passes through the first electro-optic phase modulator and the first phase shifter and is converged to the second optical fiber beam splitter, the other path of the signal is converged to a second optical fiber beam splitter through a second electro-optic phase modulator and a second phase shifter in sequence, the first electro-optic phase modulator also receives a signal sent by a second signal generator, an output signal of the second optical fiber beam splitter outputs two paths of signals through a balance detector, one path of the signal is fed back to the first phase shifter through the first phase-locked loop, and the other path of the signal is fed back to the second electro-optic phase modulator through a second phase-locked loop.
Further, the first phase-locked loop comprises a Proportional Integral Derivative (PID) controller and a high-voltage amplifier, and the balance detector, the PID controller, the high-voltage amplifier and the first phase shifter are connected in sequence.
Further, the second phase-locked loop comprises a third signal generator, a phase-locked amplifier, a kalman filter and a proportional controller, the balance detector, the phase-locked amplifier, the kalman filter, the proportional controller and the second electro-optic phase modulator are sequentially connected, and the third signal generator is connected to the phase-locked amplifier.
Further, the laser is used for outputting free space type continuous wave narrow linewidth 1064nm laser. The first signal generator is for generating a 2.5MHz drive signal. The second signal generator is for generating a time-varying random signal. The third signal generator is used for generating a reference signal. The electro-optic amplitude modulator, the first electro-optic phase modulator and the second electro-optic phase modulator are all of waveguide type, and the first phase shifter and the second phase shifter are all of optical fiber type.
Further, the balanced detector is composed of two photodiodes with the same gain response, and is used for performing photocurrent subtraction according to the light power received by each photodiode and outputting the light power.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: 1, an all-fiber Mach-Zehnder interferometer suitable for random phase estimation is established, and a signal sensing unit and a signal feedback unit are respectively additionally arranged on two arms of the interferometer. The two arms of the interferometer are loss matched and a polarization maintaining optical fiber device is adopted. 2, in laser interferenceIn a linear Gaussian system for phase measurement, a first-order low-pass filter and a proportional amplifier are adopted to form a Kalman filter, and a random phase estimation loop is established and gives an optimal phase estimation value under the minimum variance. And 3, constructing a low-frequency low-gain slow loop by adopting a proportional-integral-derivative device, and offsetting interferometer phase drift caused by environmental disturbance such as vibration, temperature and the like. Meanwhile, the method locks the phase difference of two arms of the interferometer to pi/2 to obtain the maximum phase measurement sensitivity. And 4, amplitude modulation is carried out on the input state of the optical fiber interferometer by adopting a modulation transfer technology, and the detection signal is demodulated to a low-frequency band, so that low-frequency phase measurement is realized. And 5, an optical balance detection technology is adopted in the aspect of signal detection, and the detection means can offset common-mode noise in the photoelectric system, so that the phase tracking precision is further improved. 6. Compared with the prior art, the method can greatly improve the number of injected photons at the input end of the interferometer to 3.7 multiplied by 1010The absolute accuracy of the random phase estimation is improved.
Drawings
FIG. 1 is a schematic structural diagram of an embodiment of the present invention;
FIG. 2 is a time domain diagram of time varying random phase estimation;
fig. 3 is a schematic diagram of random phase tracking variance as a function of photon number.
Detailed Description
As shown in fig. 1, the present embodiment provides an adaptive optical fiber mach-zehnder interferometer for time-varying random signal measurement, which includes a laser 1, an optical fiber collimator 2, an electro-optical amplitude modulator 3, a first signal generator 4, a first optical fiber splitter 5, a second signal generator 6, a first electro-optical phase modulator 7, a first phase shifter 8, a second electro-optical phase modulator 9, a second phase shifter 10, a second optical fiber splitter 11, a balanced detector 12, a first phase-locked loop, and a second phase-locked loop. The electro-optical amplitude modulator 3, the first electro-optical phase modulator 7 and the second electro-optical phase modulator 9 are all of waveguide type, and the first phase shifter 8 and the second phase shifter 10 are all of optical fiber type.
The laser 1 outputs laser with a 1064nm narrow linewidth of free space type continuous wave, the emitted laser is coupled into an optical fiber by an optical fiber collimator 2 and is transmitted to a waveguide type electro-optic amplitude modulator 3 through the optical fiber, a first signal generator 4 provides a 2.5MHz driving signal and loads the driving signal to the waveguide type electro-optic amplitude modulator 3, amplitude modulation of an optical field is achieved, and the modulated laser is incident into a first optical fiber beam splitter 5.
The first optical fiber beam splitter 5, the first electro-optic phase modulator 7, the first phase shifter 8, the second electro-optic phase modulator 9, the second optical fiber type phase shifter 10 and the second optical fiber beam splitter 11 jointly form an optical fiber type Mach-Zehnder interferometer for tracking and measuring time-varying random phases. The first optical fiber beam splitter 5 and the second optical fiber beam splitter 11 are both 50/50 optical fiber beam splitters, one of two paths of laser output by the first optical fiber beam splitter 5 enters the first electro-optic phase modulator 7, and the other path enters the first electro-optic phase modulator 9. The second signal generator 6 outputs a time-varying random signal which is applied as a modulation signal to the first electro-optical phase modulator 7, and the first electro-optical phase modulator 7 modulates the phase of the laser signal according to the time-varying random signal, thereby loading the phase information of the time-varying random signal into the laser signal and outputting the laser signal carrying the phase of the time-varying random signal. The first phase shifter 8 is an actuator of a first phase-locked loop, which adjusts the phase of the laser carrying random phase information according to the signal fed back by the high-voltage amplifier, and the dynamic adjustment range of the device is large, which can compensate the phase drift caused by environmental disturbance and lock the phase difference of two arms of the interferometer to pi/2. The second electro-optical phase modulator 9 receives the other path of signal output by the first fiber beam splitter 5, and adaptively adjusts the phase of the input laser signal according to the phase estimation signal output by the proportional controller 18. The second fiber-type phase shifter 10 has the same structure as the first phase shifter 8 and is used for loss matching of both arms of the interferometer. The beams from the two arms of the interferometer are interfered at the second fiber beam splitter 11, and then the interference signal is split into two paths with the splitting ratio of 50/50 and is detected and received by the balanced detector 12.
The balance detector 12 is used for detecting laser interference signals, and is composed of two photodiodes with the same gain response, and performs photocurrent subtraction according to the light power received by each photodiode and outputs the photocurrent subtraction, so that common mode noise of an optoelectronic system is deducted, and the detection precision is improved.
The first phase-locked loop and the second phase-locked loop are respectively used for controlling the relative phase difference between two arms of the Mach-Zehnder interferometer and capturing estimated phase information. The first phase-locked loop comprises a proportional integral derivative PID controller 13 and a high-voltage amplifier 14, the first phase-locked loop feeds back to the first optical fiber type phase shifter 8 through the proportional integral derivative PID controller 13 and the high-voltage amplifier 14 according to a direct current signal output by the balance detector 12, so that a low-frequency and low-gain feedback control loop is formed, the loop is used for counteracting interferometer phase drift caused by environmental disturbance such as vibration, temperature and the like, and meanwhile, the method locks the phase difference of two arms of the interferometer to pi/2 to obtain the maximum phase measurement sensitivity. The second phase-locked loop comprises a third signal generator 15, a phase-locked amplifier 16, a kalman filter 17 and a proportional controller 18, the second phase-locked loop demodulates the alternating current signal output by the balanced detector 12 through the phase-locked amplifier 16 to obtain a photocurrent error signal containing phase estimation information, wherein the third signal generator 15 provides a reference signal to the phase-locked amplifier 16, the kalman filter 17 and the proportional controller 18 jointly act on the photocurrent error signal to perform filtering estimation, the signal is fed back to the second electro-optic phase modulator 9 and is simultaneously output to an oscilloscope 19, and an optimal phase estimation value of minimum estimation variance is obtained by adjusting the gain of the proportional controller 18.
The experiment of this example was verified, and the results are shown in fig. 2 and 3. Fig. 2 is a time domain diagram of time varying random phase estimation, and the time varying random signal in fig. 2(a) is a 3kHz bandwidth random signal generated by white noise generated by the second signal generator 6 through a low pass filter. Fig. 2(b) shows the estimation result output by the proportional controller 18 after kalman filtering, and it can be seen that the phase estimation method according to the present invention has a good effect. Fig. 3 is a graph of experimental results of phase estimation variance as a function of injected photon count. In the experiment, under different photon numbers, the mean square error of tracking is measured and calculated, the Kalman filtering gain is adjusted, and the optimal tracking variance is recorded. The number of photons reaches 3.7 multiplied by 10 in the experiment10The tracking variance reaches 2.5 multiplied by 10-5. It can be seen that the phase estimation accuracy of the present invention is very high.

Claims (9)

1. An adaptive fiber-optic mach-zehnder interferometer for time-varying random signal measurement, characterized by: the laser phase-locked loop based on the electro-optic amplitude modulator comprises a laser, an optical fiber collimator, a first signal generator, an electro-optic amplitude modulator, a first optical fiber beam splitter, a first electro-optic phase modulator, a first phase shifter, a second electro-optic phase modulator, a second phase shifter, a second optical fiber beam splitter, a balance detector, a second signal generator, a first phase-locked loop and a second phase-locked loop, wherein laser emitted by the laser is coupled into an optical fiber through the optical fiber collimator and is transmitted to the electro-optic amplitude modulator through the optical fiber, a signal emitted by the first signal generator is input to the electro-optic amplitude modulator, one end of the first optical fiber beam splitter receives the signal emitted by the electro-optic amplitude modulator, the other end of the first optical fiber beam splitter outputs two paths of signals, one path of signals sequentially passes through the first electro-optic phase modulator and the first phase shifter and is converged to the second optical fiber beam splitter, and the other path of, The second phase shifter converges to a second optical fiber beam splitter, the first electro-optic phase modulator also receives a signal sent by a second signal generator, an output signal of the second optical fiber beam splitter outputs two paths of signals through a balance detector, one path of signals is fed back to the first phase shifter through the first phase-locked loop, and the other path of signals is fed back to the second electro-optic phase modulator through a second phase-locked loop.
2. The adaptive fiber-optic mach-zehnder interferometer for time-varying random signal measurement according to claim 1, characterized in that: the first phase-locked loop comprises a Proportional Integral Derivative (PID) controller and a high-voltage amplifier, and the balance detector, the PID controller, the high-voltage amplifier and the first phase shifter are sequentially connected.
3. The adaptive fiber-optic mach-zehnder interferometer for time-varying random signal measurement according to claim 1, characterized in that: the second phase-locked loop comprises a third signal generator, a phase-locked amplifier, a Kalman filter and a proportional controller, the balance detector, the phase-locked amplifier, the Kalman filter, the proportional controller and the second electro-optic phase modulator are sequentially connected, and the third signal generator is connected to the phase-locked amplifier.
4. The adaptive fiber-optic mach-zehnder interferometer for time-varying random signal measurement according to claim 1, characterized in that: the laser is used for outputting free space type continuous wave narrow linewidth 1064nm laser.
5. The adaptive fiber-optic mach-zehnder interferometer for time-varying random signal measurement according to claim 1, characterized in that: the first signal generator is for generating a 2.5MHz drive signal.
6. The adaptive fiber-optic mach-zehnder interferometer for time-varying random signal measurement according to claim 1, characterized in that: the second signal generator is for generating a time-varying random signal.
7. The adaptive fiber-optic mach-zehnder interferometer for time-varying random signal measurement according to claim 1, characterized in that: the balance detector is composed of two photodiodes with the same gain response, and is used for outputting light current subtraction according to the light power received by each photodiode.
8. The adaptive fiber-optic mach-zehnder interferometer for time-varying random signal measurement according to claim 3, characterized in that: the third signal generator is used for generating a reference signal.
9. The adaptive fiber-optic mach-zehnder interferometer for time-varying random signal measurement according to claim 1, characterized in that: the electro-optic amplitude modulator, the first electro-optic phase modulator and the second electro-optic phase modulator are all of waveguide type, and the first phase shifter and the second phase shifter are all of optical fiber type.
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