A Polarization-Multiplexed M-Z and Sagnac Composite Interferometer

Abstract

The present invention discloses a polarization multiplexing based M-Z and Sagnac composite interferometer. The composite interferometer includes an input light source, a polarizer, a circulator, a first coupler, a first polarization beam splitter, a second polarization beam splitter, a first phase modulator, a first optical fiber loop, a first detector, a second detector, a second phase modulator, a second optical fiber loop, a third optical fiber loop, a second coupler, a third detector and a fourth detector, a first signal processing unit, a second signal processing unit, a computer, a first electrical wire, a second electrical wire, a first data transmission line and a second data transmission line. In the present invention, PBS devices are added to both arms of a polarization-maintaining Mach-Zehnder interferometer to form a loop between the two arms, thereby realizing the multiplexing of a Sagnac interferometer and a Mach-Zehnder interferometer. After being combined with a disk-type acceleration probe, the interferometer can simultaneously measure acceleration and angular velocity.

Description

Technical Field

[0001] The invention belongs to the field of optical fiber interferometer measurement and relates to an interferometer, in particular to a Mach-Zehnder and Sagnac composite interferometer based on polarization multiplexing. Background Art

[0002] Seismic waves are the only physical waves that can penetrate the interior of the earth's medium. As a manifestation of the drastic changes in the earth's internal energy, they are one of the most serious disasters that cause loss of human life and property. As a vector mechanical wave, seismic waves contain not only three independent translational components but also three independent rotational components in terms of spatial dimension. To fully describe and analyze seismic waves, it is necessary to obtain accurate full-dimensional seismic wave information. The fiber optic gyroscope based on the Sagnac interferometer has a high angular velocity resolution; the vibration meter based on the Mach-Zehnder interferometer has a high acceleration resolution. The Mach-Zehnder and Sagnac composite interferometer based on polarization multiplexing can measure angular velocity and acceleration simultaneously in the same optical path. Facing the urgent need for seismic wave information acquisition, the composite fiber interferometer has broad development prospects due to its multi-parameter sensing mechanism.

[0003] Regarding the measurement of the rotational component of seismic motion, as early as 1996, A. Castellani and Z. Zembaty pointed out that near the earthquake source, the ratio of the rotational component to the translational component of seismic motion is relatively high, indicating that the rotational component of seismic motion is of great significance for predicting the dynamic response of seismic waves (Castellani A, Zembaty Z. Comparison between earthquake rotation spectra obtained by different experimental sources[J]. Engineering structures, 1996, 18(8): 597 - 603.). In 1997, GE Stedman of the University of Canterbury proposed using a ring laser gyroscope to measure the rotational component of seismic motion with high precision (Stedman GE. Ring-laser tests of fundamental physics and geophysics[J]. Reports on progress in physics, 1997, 60(6): 615.); in 2000, the team of G E Stedman at the University of Canterbury used a large ring laser gyro to detect the horizontal and vertical rotational components of teleseismic surface waves and body waves (Pancha A, Webb T H, Stedman G E, et al. Ring laser detection of rotations from teleseismic waves[J]. Geophysical Research Letters, 2000, 27(21): 3553 - 3556.). In 2013, C. Clivati of the National Institute of Metrology of Italy proposed an optical fiber gyroscope based on the Sagnac effect and implemented on a multiplexed telecommunication optical fiber network. Their loop covers an area of 20 square kilometers. This Sagnac interferometer can detect signals greater than 10 -8 (rad / s) / Hz 1 / 2 , but due to its complex structure and extremely high requirements for the installation site, the large ring laser gyro cannot be widely installed.

[0004] For the measurement of the translational component of seismic motion, Yang Jun et al. from Harbin Engineering University have proposed a variety of fiber optic strain measurement schemes. Such as an ultra-short baseline compliant cylinder structure fiber optic displacement sensor and fiber optic strain gauge (CN102927914B), a short baseline differential laser strain gauge (CN102927924B), and an ultra-short baseline differential disk type fiber optic displacement sensor and fiber optic strain gauge (CN102927913B). The above patents describe the use of a Michelson interferometer to measure the translational component of seismic waves, with a strain measurement resolution of 10 -11 ~10 -12 ε, and a dynamic range greater than 180 dB. However, none of the above three strain gauges can measure the angular velocity generated by seismic waves. In 2016, Yang Jun from Harbin Engineering University disclosed a rotational seismic wave measurement device based on a compound interferometer (CN106125131B). This patent combines a traditional fiber optic gyro (Sagnac interferometer) with a Michelson interferometer, multiplexes the two interferometers in the optical path, reduces the volume of the measurement device, and increases the measurement function at the same time. The angular velocity measurement resolution of the fiber optic gyro is 10 -9 rad / s. However, because the Sagnac interferometer and the Michelson interferometer share the same sensing arm, the crosstalk between the two interferometers is relatively large. In the same year, Yang Jun et al. from Harbin Engineering University disclosed an inclinometer based on a compound interferometer structure (CN106441226B). This patent designs a compound interferometer optical path structure, multiplexes two Mach-Zehnder interferometers, a Michelson interferometer, and a Sagnac interferometer in the optical path, greatly reducing the volume and manufacturing cost of the inclinometer and improving the system integration. In 2020, Yuan Yonggui et al. from Harbin Engineering University proposed a single-source Michelson-Sagnac compound dual-polarization fiber optic interferometer (CN111426856A). This interferometer combines a fiber optic gyro and a Michelson fiber optic interferometer, multiplexes the two fiber optic interferometers on the sensing arm and the polarization-maintaining axis, can measure acceleration and angular velocity simultaneously, and suppresses the influence of environmental temperature changes on acceleration measurement. However, this compound interferometer has the disadvantage of relatively large signal crosstalk between the two interferometers. Summary of the Invention

[0005] In order to simultaneously measure acceleration and angular velocity, eliminate the polarization fading phenomenon, and reduce the signal crosstalk between the measurements of the two parameters, the present invention provides a polarization multiplexing-based M-Z and Sagnac composite interferometer. The present invention adds a polarization beam splitter (PBS) device to both arms of a polarization-maintaining Mach-Zehnder interferometer to form a loop between the two arms, thereby realizing the multiplexing of a Sagnac interferometer and a Mach-Zehnder interferometer. Moreover, after being combined with a disk-type acceleration probe, this interferometer can simultaneously measure acceleration and angular velocity.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] A polarization multiplexing-based M-Z and Sagnac composite interferometer includes a light source module, a composite interferometer sensing optical path module, and a host computer signal processing module, wherein:

[0008] The light source module includes an input light source and a polarizer;

[0009] The composite interferometer sensing optical path module includes a circulator, a first coupler, a first polarization beam splitter, a second polarization beam splitter, a first phase modulator, a first optical fiber loop, a first detector, a second detector, a second phase modulator, a second optical fiber loop, a third optical fiber loop, a second coupler, a third detector, and a fourth detector;

[0010] The host computer signal processing module includes a first signal processing unit, a second signal processing unit, a computer, a first electric wire, a second electric wire, a first data transmission line, and a second data transmission line;

[0011] The input light source is connected to the f1 port of the polarizer, the f2 port of the polarizer is connected to the a1 port of the circulator to form a 45-degree polarization-maintaining optical fiber solder joint, and the a3 port of the circulator is connected to the first detector; the a2 port of the circulator is connected to the b1 port of the first coupler, the b2 port of the first coupler is connected to the second detector, the b3 port of the first coupler is connected to the c1 port of the first polarization beam splitter, the c3 port of the first polarization beam splitter is connected to the first phase modulator, the first phase modulator is connected to the first optical fiber loop, the b4 port of the coupler is connected to the d1 port of the second polarization beam splitter, and the d3 port of the second polarization beam splitter is connected to the first optical fiber loop; the c2 port of the first polarization beam splitter is connected to the second phase modulator, the second phase modulator is connected to the second optical fiber loop, the d2 port of the second polarization beam splitter is connected to the third optical fiber loop, the e1 port of the second coupler is connected to the second optical fiber loop, the e2 port of the second coupler is connected to the third optical fiber loop, the e3 port of the second coupler is connected to the third detector, and the e4 port of the second coupler is connected to the fourth detector; the first detector and the second detector are connected to the first signal processing unit through the first electric wire, the first signal processing unit is connected to the computer through the first data transmission line, the third detector and the fourth detector are connected to the second signal processing unit through the second electric wire, and the second signal processing unit is connected to the computer through the second data transmission line.

[0012] A method for measuring acceleration and angular velocity using the above-mentioned Mach-Zehnder and Sagnac composite interferometer based on polarization multiplexing includes the following steps:

[0013] Step 1: The light emitted by the input light source becomes polarized light after passing through the polarizer, enters the fast axis and slow axis of the polarization-maintaining optical fiber through the 45-degree polarization-maintaining optical fiber solder joint, and the polarized light of the fast and slow axes is divided into two paths by the first coupler after passing through the circulator;

[0014] Step 2: The polarized light of the fast and slow axes of the two paths is respectively divided into fast-axis light and slow-axis light after passing through the first polarization beam splitter and the second polarization beam splitter;

[0015] Step 3: One path of the slow-axis light passes through the first phase modulator, then through the first fiber optic loop, then through the second polarization beam splitter, and enters the first coupler. Another path of the slow-axis light passes through the first fiber optic loop, then through the first polarization beam splitter, and enters the first coupler. The two paths of slow-axis light form the two sensing optical signals of the Sagnac fiber interferometer. The two sensing optical signals converge and interfere at the first coupler. The interference signal is divided into two paths by the first coupler. One path passes through the circulator and reaches the first detector, and the other path reaches the second detector. The differential interference optical signal is detected by the first detector and the second detector respectively and converted into differential interference electrical signals. The differential interference electrical signals are transmitted by the first electrical wire to the first signal processing unit, and then transmitted to the computer through the first data transmission line for carrier phase demodulation to obtain the angular velocity signal;

[0016] Step 4: One path of the fast-axis light passes through the second phase modulator and enters the second coupler through the second fiber optic loop. Another path of the fast-axis light passes through the third fiber optic loop and enters the second coupler. The two paths of fast-axis light form the two sensing optical signals of the Mach-Zehnder fiber interferometer. The two sensing optical signals converge and interfere at the second coupler. The interference signal is divided into two paths by the second coupler, and is detected by the third detector and the fourth detector respectively and converted into differential interference electrical signals. The differential interference electrical signals are transmitted by the second electrical wire to the second signal processing unit, and then transmitted to the computer through the second data transmission line for carrier phase demodulation to obtain the acceleration signal.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) By using an optical path multiplexing structure, the Mach-Zehnder fiber interferometer and the Sagnac interferometer share the input light source. The optical path structure is simple, the sensing area is flexible to change, and the system manufacturing cost is low.

[0019] (2) It is easy to combine with a disk-type acceleration probe, and can measure the acceleration and angular velocity in seismic waves simultaneously. Compared with traditional single-component sensors, the function is more comprehensive.

[0020] (3) Separating the gyroscope loop and the strain-sensitive loop between two polarization beam splitters can reduce the crosstalk between the two sensing fiber optic loops.

[0021] (4) Using a polarization-maintaining fiber optic path can eliminate the polarization fading phenomenon.

[0022] (5) By differentially detecting the interference optical signals of the Mach-Zehnder fiber interferometer and the Sagnac interferometer, the influence of the DC optical intensity drift on the measurement system can be eliminated. Description of the Drawings

[0023] Figure 1It is a schematic diagram of the principle of a polarization multiplexing Mach-Zehnder and Sagnac composite interferometer;

[0024] Figure 2 It is a schematic diagram of the combination principle of the fiber optic loop of the Mach-Zehnder interferometer and the disk-type acceleration probe;

[0025] Figure 3 It is a schematic structural diagram of the combination of the fiber optic loop of the Mach-Zehnder interferometer and the disk-type acceleration probe;

[0026] Figure 4 It is a schematic diagram of the combination principle of the fiber optic loop of the Sagnac interferometer and the disk-type acceleration probe;

[0027] Figure 5 It is a schematic diagram of the solder joint of the 45-degree polarization-maintaining fiber; Specific implementation manners

[0028] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the protection scope of the present invention.

[0029] The present invention provides a polarization multiplexing M-Z and Sagnac composite interferometer, as Figure 1 shown. The main body of the composite interferometer is divided into three parts: a light source module 1, a composite interferometer sensing optical path module 2, and a host computer signal processing module 3, where:

[0030] The light source module 1 includes an input light source 11 and a polarizer 12;

[0031] The composite interferometer sensing optical path module 2 includes a circulator 211, a first coupler 212, a first polarization beam splitter 213, a second polarization beam splitter 214, a first phase modulator 215, a first fiber optic loop 216, a first detector 217, a second detector 218, a second phase modulator 221, a second fiber optic loop 222, a third fiber optic loop 223, a second coupler 224, a third detector 225, and a fourth detector 226;

[0032] The host computer signal processing module 3 includes a first signal processing unit 31, a second signal processing unit 32, a computer 33, a first electric wire 34, a second electric wire 37, a first data transmission line 35, and a second data transmission line 36;

[0033] The input light source 11 is connected to the f1 port of the polarizer 12. The f2 port of the polarizer 12 is connected to the a1 port of the circulator 211 to form a 45-degree polarization-maintaining fiber optic solder joint 13. The a3 port of the circulator 211 is connected to the first detector 217. The a2 port of the circulator 211 is connected to the b1 port of the first coupler 212. The b2 port of the first coupler 212 is connected to the second detector 218. The b3 port of the first coupler 212 is connected to the c1 port of the first polarization beam splitter 213. The c3 port of the first polarization beam splitter 213 is connected to the first phase modulator 215. The first phase modulator 215 is connected to the first fiber optic loop 216. The b4 port of the coupler 212 is connected to the d1 port of the second polarization beam splitter 214. The d3 port of the second polarization beam splitter 214 is connected to the first fiber optic loop 216. The c2 port of the first polarization beam splitter 213 is connected to the second phase modulator 221. The second phase modulator 221 is connected to the second fiber optic loop 222. The d2 port of the second polarization beam splitter 214 is connected to the third fiber optic loop 223. The e1 port of the second coupler 224 is connected to the second fiber optic loop 222. The e2 port of the second coupler 224 is connected to the third fiber optic loop 223. The e3 port of the second coupler 224 is connected to the third detector 225. The e4 port of the second coupler 224 is connected to the fourth detector 226. The first detector 217 and the second detector 218 are connected to the first signal processing unit 31 through the first electric wire 34. The first signal processing unit 31 is connected to the computer 33 through the first data transmission line 35. The third detector 225 and the fourth detector 226 are connected to the second signal processing unit 32 through the second electric wire 37. The second signal processing unit 32 is connected to the computer 33 through the second data transmission line 36.

[0034] In the present invention, the polarizer 12, the circulator 211, the first coupler 212, the first polarization beam splitter 213, the second polarization beam splitter 214, the first fiber optic loop 216, the second fiber optic loop 222, the third fiber optic loop 223 and the second coupler 224 are all polarization-maintaining fiber optic devices.

[0035] In the present invention, the 45-degree polarization-maintaining fiber optic solder joint 13 axially welds the f2 port of the polarizer 12 and the a1 port of the circulator 211 at 45 degrees.

[0036] In the present invention, the Mach-Zehnder fiber optic interferometer and the Sagnac fiber optic interferometer share the input light source 11, the first coupler 212, the first polarization beam splitter 213 and the second polarization beam splitter 214.

[0037] In the present invention, the first optical fiber loop 216 and the disk-type acceleration probe are combined as the sensing arm of the Sagnac fiber interferometer to measure the angular velocity; the second optical fiber loop 222, the third optical fiber loop 223 and the disk-type acceleration probe are combined as the sensing arm of the Mach-Zehnder fiber interferometer to measure the acceleration.

[0038] In the present invention, the interference optical signals of the Mach-Zehnder fiber interferometer are output from the two output ends (e3 port and e4 port) of the second coupler 224, and the photodetectors (the third detector 225 and the fourth detector 226) perform differential detection on the interference optical signals of the Mach-Zehnder fiber interferometer; the interference optical signals of the Sagnac fiber interferometer are output from the two output ends (b1 port and b2 port) of the first coupler 212, and one of the differential signals enters the circulator 211, and the photodetectors (the first detector 217 and the second detector 218) perform differential detection on the interference optical signals of the Sagnac fiber interferometer. The photodetectors perform differential detection on the interference optical signals of the two fiber interferometers, which can eliminate the influence of the DC light intensity drift on the measurement system and reduce the noise.

[0039] In the present invention, the light is divided into fast-axis light and slow-axis light through the first polarization beam splitter 213 and the second polarization beam splitter 214. The slow-axis light is input into the Sagnac fiber interferometer formed by the first optical fiber loop 216, and the fast-axis light is input into the Mach-Zehnder fiber interferometer formed by the second optical fiber loop 222 and the third optical fiber loop 223. The separation of the fast and slow axes of the light can reduce the signal crosstalk between the angular velocity sensitive loop (the first optical fiber loop 216) and the acceleration sensitive loop (the second optical fiber loop 222, the third optical fiber loop 223).

[0040] The specific measurement process of the above Mach-Zehnder and Sagnac composite interferometer based on polarization multiplexing is as follows:

[0041] Step 1: The light emitted by the input light source 11 becomes polarized light after passing through the polarizer 12, enters the fast axis and slow axis of the polarization-maintaining fiber through the 45-degree polarization-maintaining fiber solder joint 13, and the polarized light of the fast and slow axes is divided into two paths by the first coupler 212 after passing through the circulator 211.

[0042] Step 2: The polarized light of the fast and slow axes of the two paths is respectively divided into fast-axis light and slow-axis light after passing through the first polarization beam splitter 213 and the second polarization beam splitter 214.

[0043] Step 3: One path of the slow-axis light passes through the first phase modulator 215, then through the first fiber optic loop 216, then through the second polarization beam splitter 214, and enters the first coupler 212. Another path of the slow-axis light passes through the first fiber optic loop 216, then through the first polarization beam splitter 213, and enters the first coupler 212. The two paths of slow-axis light form the two sensing optical signals of the Sagnac fiber interferometer. The two sensing optical signals converge and interfere at the first coupler 212. The interference signal is divided into two paths by the first coupler 212. One path passes through the circulator 211 and reaches the first detector 217, and the other path reaches the second detector 218. The differential interference optical signal is detected by the first detector 217 and the second detector 218 respectively and converted into a differential interference electrical signal. The differential interference electrical signal is transmitted to the first signal processing unit 31 through the first electrical wire 34, and then transmitted to the computer 33 through the first data transmission line 35 for carrier phase demodulation, so as to obtain the angular velocity signal.

[0044] Step 4: One path of the fast-axis light passes through the second phase modulator 221, then through the second fiber optic loop 222, and enters the second coupler 224. Another path of the fast-axis light passes through the third fiber optic loop 223 and enters the second coupler 224. The two paths of fast-axis light form the two sensing optical signals of the Mach-Zehnder fiber interferometer. The two sensing optical signals converge and interfere at the second coupler 224. The interference signal is divided into two paths by the second coupler 224, and is detected by the third detector 225 and the fourth detector 226 respectively and converted into a differential interference electrical signal. The differential interference electrical signal is transmitted to the second signal processing unit 32 through the second electrical wire 37, and then transmitted to the computer 33 through the second data transmission line 36 for carrier phase demodulation, so as to obtain the acceleration signal. This optical path structure realizes the simultaneous differential detection of acceleration and angular velocity.

[0045] The combined schematic diagram of the fiber optic loop of the Mach-Zehnder interferometer and the disk-type acceleration probe is as Figure 2 shown, and the structural schematic diagram is as Figure 3 shown. The second fiber optic loop 222 and the third fiber optic loop 223 are bonded to the upper and lower sides of the elastic disk 41. When the probe housing 43 is subjected to an acceleration, the mass block 42 drives the elastic disk 41 to move axially. The fiber optic loops on both sides of the elastic disk 41 are respectively stretched and compressed, causing the phase difference of the optical signals of the two fiber optic loops of the Mach-Zehnder fiber interferometer to change, and the interference light intensity will change and be detected by the photodetector, so that the external acceleration can be calculated.

[0046] The external modulation of the optical signal of the Mach-Zehnder fiber interferometer is performed by using the second phase modulator 221. The expressions of the interference optical signals detected by the third detector 225 and the fourth detector 226 are:

[0047]

[0048] where I R and I S are the light intensities, and is the optical path difference. A more commonly used expression of the above formula is:

[0049]

[0050] where A is the DC component of the light intensity, B is the AC component, C is the phase modulation depth, ω0 is the carrier signal frequency, is the measured signal.

[0051] After carrier phase demodulation of the interference optical signal of the Mach-Zehnder fiber interferometer, we get:

[0052]

[0053] Equation (3) is the expression of the phase to be measured.

[0054] The combined schematic diagram of the fiber optic loop of the Sagnac interferometer and the disk-type acceleration probe is as shown in Figure 4 Figure []. The first fiber optic loop 216 is bonded to both sides of the elastic disk 51. When the probe housing 53 rotates around the axis at an angular velocity ω, the mass block 52 drives the elastic disk 51 to rotate around the axis at an angular velocity ω. The fiber optic loops on both sides of the elastic disk 51 are respectively stretched and compressed, causing a change in the phase difference between the optical signals of the two fiber optic loops of the Sagnac fiber interferometer, and the interference light intensity will change and be detected by the photodetector, so that the external angular velocity can be deduced. Using the Sagnac fiber interferometer formed by the first fiber optic loop 216 to measure the rotational angular velocity, when the probe rotates around the axis at an angular velocity ω, the phase difference between the two optical signals of the Sagnac fiber interferometer during interference is:

[0055]

[0056] where A is the total area enclosed by the two fiber optic loops, λ is the wavelength of light, c is the speed of light, and ω is the angular velocity. The measurement of the angular velocity ω is the measurement of the output phase difference of the Sagnac fiber interferometer. The modulation and demodulation methods of the interference optical signal of the Sagnac fiber interferometer are the same as those of the interference optical signal of the Mach-Zehnder fiber interferometer.

[0057] The Sagnac fiber interferometer and the Mach-Zehnder fiber interferometer are separated between the first polarization beam splitter 213 and the second polarization beam splitter 214. Compared with other composite fiber interferometers, the crosstalk between the signals of the Sagnac fiber interferometer and the Mach-Zehnder fiber interferometer in the present invention is less.

[0058] Embodiment:

[0059] The present embodiment will be described below in conjunction with specific parameters:

[0060] In this embodiment, the polarization multiplexed Mach-Zehnder and Sagnac composite interferometer is as Figure 1 shown, and the device selection and parameters are as follows:

[0061] (1) The input light source 11 is an ASE broadband light source with a central wavelength of 1550 nm, a half spectral width greater than 45 nm, and a power of 10 mW;

[0062] (2) The circulator 211 has a central wavelength of 1550 nm, an insertion loss less than 1 dB, a minimum isolation of 40 dB per channel, a maximum crosstalk of 50 dB, a polarization mode dispersion of 0.1 ps, a three-port structure, and a rated power of 500 mW;

[0063] (3) The first coupler 212 has an operating wavelength of 1550 nm and a splitting ratio of 50% / 50%; the second coupler 224 has an operating wavelength of 1550 nm and a splitting ratio of 50% / 50%;

[0064] (4) The first optical fiber loop 216 has an operating wavelength of 1550 nm, a loop crosstalk < -18 dB, a loop attenuation < 0.3 dB / km, an inner diameter of 50 mm, an outer diameter of 80 mm, and a fiber length of 300 m; the second optical fiber loop 222 has an operating wavelength of 1550 nm, a loop crosstalk < -18 dB, a loop attenuation < 0.3 dB / km, an inner diameter of 50 mm, an outer diameter of 80 mm, and a fiber length of 300 m; the third optical fiber loop 223 has an operating wavelength of 1550 nm, a loop crosstalk < -18 dB, a loop attenuation < 0.3 dB / km, an inner diameter of 50 mm, an outer diameter of 80 mm, and a fiber length of 300 m;

[0065] (5) The first phase modulator 215 is a cylindrical piezoelectric ceramic ring wound with an optical fiber, having a resonant frequency of 2000 Hz, a resonant resistance less than 200 ohms, a capacitance of 50 nF ± 30%, a ring thickness of 1 mm, a ring height of 10 mm, a ring outer diameter of 20 mm, and a 1 m long optical fiber wound on the piezoelectric ceramic ring and bonded with a strong adhesive; the second phase modulator 221 is a cylindrical piezoelectric ceramic ring wound with an optical fiber, having a resonant frequency of 2000 Hz, a resonant resistance less than 200 ohms, a capacitance of 50 nF ± 30%, a ring thickness of 1 mm, a ring height of 10 mm, a ring outer diameter of 20 mm, and a 1 m long optical fiber wound on the piezoelectric ceramic ring and bonded with a strong adhesive;

[0066] (6) The polarizer 12 has a central wavelength of 1550 nm, a bandwidth of ±30 nm, an insertion loss of 0.4 dB, an extinction ratio of 30 dB, and a maximum withstand power of 300 mW;

[0067] (7) The central wavelength of the first polarization beam splitter 213 is 1550 nm, the bandwidth is ±40 nm, the insertion loss is 0.4 dB, and the maximum power it can withstand is 300 mW; the central wavelength of the second polarization beam splitter 214 is 1550 nm, the bandwidth is ±40 nm, the insertion loss is 0.4 dB, and the maximum power it can withstand is 300 mW.

[0068] The sensing probe of the interferometer is as Figures 2 - 4 shown, and the device selection and structure are as follows:

[0069] (1) The mass blocks 42 and 52 are cube-shaped heavy objects with a mass of 100 g, made of steel material, with uniform mass distribution, no internal defects, and a thermal expansion coefficient less than 0.9×10 -10 / °C;

[0070] (2) The thickness of the elastic disks 41 and 51 is 1 mm, the inner diameter is 10 mm, the outer diameter is 110 mm, and the material is a copper alloy disk with good flexibility and uniform mass distribution;

[0071] (3) The probe housings 43 and 53 are cylinders, made of aluminum alloy, with a height of 80 mm and an outer diameter of 120 mm;

[0072] (4) The first optical fiber loop 216 is bonded to the upper side of the elastic disk 51 with a strong glue; the second optical fiber loop 222 and the third optical fiber loop 223 are bonded to the upper and lower sides of the elastic disk 41 with a strong glue, and the two optical fiber loops are centered and aligned vertically.

[0073] The 45-degree polarization-maintaining optical fiber solder joint 13 is as Figure 5 shown, and this solder joint axially welds the f2 port of the polarizer 12 and the a1 port of the circulator 211 at 45 degrees.

Claims

1. A polarization multiplexing based M-Z and Sagnac composite interferometer, characterized in that The composite interferometer includes a light source module, a composite interferometer sensing optical path module, and a host computer signal processing module, where: The light source module includes an input light source and a polarizer; The composite interferometer sensing optical path module includes a circulator, a first coupler, a first polarization beam splitter, a second polarization beam splitter, a first phase modulator, a first optical fiber loop, a first detector, a second detector, a second phase modulator, a second optical fiber loop, a third optical fiber loop, a second coupler, a third detector, and a fourth detector; The host computer signal processing module includes a first signal processing unit, a second signal processing unit, a computer, a first electric wire, a second electric wire, a first data transmission line, and a second data transmission line; The input light source is connected to the f1 port of the polarizer, the f2 port of the polarizer is connected to the a1 port of the circulator to form a 45-degree polarization-maintaining optical fiber solder joint, the a3 port of the circulator is connected to the first detector; the a2 port of the circulator is connected to the b1 port of the first coupler, the b2 port of the first coupler is connected to the second detector, the b3 port of the first coupler is connected to the c1 port of the first polarization beam splitter, the c3 port of the first polarization beam splitter is connected to the first phase modulator, the first phase modulator is connected to the first optical fiber loop, the b4 port of the coupler is connected to the d1 port of the second polarization beam splitter, the d3 port of the second polarization beam splitter is connected to the first optical fiber loop; the c2 port of the first polarization beam splitter is connected to the second phase modulator, the second phase modulator is connected to the second optical fiber loop, the d2 port of the second polarization beam splitter is connected to the third optical fiber loop, the e1 port of the second coupler is connected to the second optical fiber loop, the e2 port of the second coupler is connected to the third optical fiber loop, the e3 port of the second coupler is connected to the third detector, the e4 port of the second coupler is connected to the fourth detector; the first detector and the second detector are connected to the first signal processing unit through the first electric wire, the first signal processing unit is connected to the computer through the first data transmission line, the third detector and the fourth detector are connected to the second signal processing unit through the second electric wire, and the second signal processing unit is connected to the computer through the second data transmission line.

2. The M-Z and Sagnac composite interferometer based on polarization multiplexing according to claim 1, characterized in that The polarizer, circulator, first coupler, first polarization beam splitter, second polarization beam splitter, first optical fiber loop, second optical fiber loop, third optical fiber loop, and second coupler are all polarization-maintaining optical fiber devices.

3. The polarization multiplexing based M-Z and Sagnac composite interferometer according to claim 1, wherein The 45-degree polarization-maintaining optical fiber solder joint axially welds the f2 port of the polarizer and the a1 port of the circulator at 45 degrees.

4. The polarization multiplexing based M-Z and Sagnac composite interferometer according to claim 1, characterized in that The first optical fiber loop combined with the disk-type acceleration probe can be used as the sensing arm of the Sagnac fiber interferometer to measure the angular velocity.

5. The polarization multiplexing based M-Z and Sagnac compound interferometer according to claim 4, characterized in that The first optical fiber loop is bonded to both sides of the elastic disk of the disk-type acceleration probe.

6. The polarization multiplexing based M-Z and Sagnac compound interferometer according to claim 4, wherein The interference optical signal of the Sagnac fiber interferometer is output from the b1 port and b2 port of the first coupler, and one of the differential signals enters the circulator, and the first detector and the second detector perform differential detection on the interference optical signal of the Sagnac fiber interferometer.

7. The polarization multiplexing based M-Z and Sagnac compound interferometer according to claim 1, wherein The second optical fiber loop and the third optical fiber loop combined with the disk-type acceleration probe can be used as the sensing arm of the Mach-Zehnder fiber interferometer to measure the acceleration.

8. The polarization multiplexing based M-Z and Sagnac composite interferometer according to claim 7, characterized in that The second optical fiber loop and the third optical fiber loop are bonded to the upper and lower sides of the elastic disk of the disk-type acceleration probe.

9. The polarization multiplexing-based M-Z and Sagnac compound interferometer according to claim 7, characterized in that The interference optical signals of the Mach-Zehnder fiber interferometer are output from the e3 port and the e4 port of the second coupler, and the third detector and the fourth detector perform differential detection on the interference optical signals of the Mach-Zehnder fiber interferometer.

10. A method for measuring acceleration and angular velocity by using the polarization multiplexing based M-Z and Sagnac composite interferometer according to any one of claims 1-9, characterized in that The method includes the following steps: Step 1: The light emitted by the input light source becomes polarized light after passing through the polarizer, enters the fast axis and slow axis of the polarization-maintaining fiber through the 45-degree polarization-maintaining fiber solder joint, and the polarized light of the fast and slow axes is divided into two paths by the first coupler after passing through the circulator; Step 2: The polarized light of the fast and slow axes of the two paths are respectively divided into fast-axis light and slow-axis light after passing through the first polarization beam splitter and the second polarization beam splitter; Step 3: One path of slow-axis light passes through the first phase modulator, then passes through the first optical fiber loop, then passes through the second polarization beam splitter, and enters the first coupler. The other path of slow-axis light passes through the first optical fiber loop, then passes through the first polarization beam splitter, and enters the first coupler. The two paths of slow-axis light constitute the two sensing optical signals of the Sagnac fiber interferometer. The two sensing optical signals converge and interfere at the first coupler. The interference signal is divided into two paths by the first coupler. One path passes through the circulator and reaches the first detector, and the other path reaches the second detector. The differential interference optical signal is detected by the first detector and the second detector respectively and converted into a differential interference electrical signal. The differential interference electrical signal is transmitted to the first signal processing unit through the first electrical wire, and then transmitted to the computer through the first data transmission line for carrier phase demodulation to obtain the angular velocity signal; Step 4: One path of fast-axis light passes through the second phase modulator, then passes through the second optical fiber loop and enters the second coupler. The other path of fast-axis light passes through the third optical fiber loop and enters the second coupler. The two paths of fast-axis light constitute the two sensing optical signals of the Mach-Zehnder fiber interferometer. The two sensing optical signals converge and interfere at the second coupler. The interference signal is divided into two paths by the second coupler, and is detected by the third detector and the fourth detector respectively and converted into a differential interference electrical signal. The differential interference electrical signal is transmitted to the second signal processing unit through the second electrical wire, and then transmitted to the computer through the second data transmission line for carrier phase demodulation to obtain the acceleration signal.

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