A compact three-axis fiber optic gyroscope based on time division multiplexing

Abstract

The present invention discloses a compact three-axis fiber optic gyroscope based on time division multiplexing. The beam transmitting and receiving unit of the gyroscope transmits a light beam and receives a light beam containing three-axis angular velocity, outputs a voltage signal containing three-axis angular velocity to a sampling and demodulation circuit, and demodulates the three-axis angular velocity information. The optical signals transmitted by the three optical fiber sensing rings of different lengths in the three-axis angular velocity sensing unit are all modulated by the same multifunctional integrated optical circuit. The transit times of the three optical fiber sensing rings are different, so the three optical signals are modulated at different time periods of the modulation cycle, thereby achieving the separation of the three optical signals carrying the three-axis angular velocity in the time domain. The present invention separates the three-axis angular velocity signals in the time domain by adjusting the length ratio and modulation frequency of the three optical fiber sensing rings, thereby achieving three-axis angular velocity sensing. The present invention also multiplexes the light source, detector and multifunctional integrated optical circuit, further reducing the cost and volume of the gyroscope and promoting its application in the fields of micro- and telecommunication satellites.

Description

Technical Field

[0001] The present invention relates to a compact three-axis fiber optic gyroscope, and relates to the technical field of fiber optic gyroscopes, in particular to a compact three-axis fiber optic gyroscope based on time division multiplexing. Background Art

[0002] The fiber optic gyroscope is an angular velocity sensor based on the Sagnac effect. It is a key component for attitude measurement and inertial navigation. It has the advantages of high theoretical accuracy, full solid-state, and long service life. It is widely used in inertial measurement fields such as aviation, aerospace, and navigation.

[0003] In practical applications, it is often necessary to measure angular velocity information along three axes. A simple implementation involves combining three single-axis fiber optic gyroscopes, but the size, power consumption, and cost of the combined system often make it difficult to meet system requirements. To reduce system size and cost, device multiplexing has become a key technology. The adoption of time-division multiplexing technology allows gyros to further reuse detectors based on traditional multiplexed light sources, improving the multiplexing ratio. However, current multiplexing solutions do not reuse multifunctional integrated optical circuits, which account for a significant portion of the fiber optic gyroscope's cost. To further improve the multiplexing ratio and reduce the cost and size of a three-axis gyroscope, a three-axis gyroscope solution is needed that simultaneously multiplexes the light source, detector, and multifunctional integrated optical circuit. Summary of the Invention

[0004] To address the problems in the background art, the present invention provides a compact three-axis fiber optic gyroscope based on time division multiplexing. This invention enables simultaneous multiplexing of light sources, detectors, and multifunctional integrated optical circuits, further reducing the cost and size of the three-axis gyroscope. By adjusting the modulation frequency and the length ratio of the three fiber sensing loops, the angular velocity information of the three axes is separated in the time domain, achieving three-axis angular velocity sensing.

[0005] The technical solution adopted in the present invention is:

[0006] 1. A compact three-axis fiber optic gyroscope based on time division multiplexing, comprising:

[0007] The light beam transmitting and receiving unit is used to transmit a light beam and receive a returned light beam containing three-axis angular velocity information, and output a voltage signal containing the three-axis angular velocity information to an external sampling and demodulation circuit, and finally demodulate the three-axis angular velocity information.

[0008] The multifunctional integrated optical circuit is used to split the light beam emitted by the light beam transmitting and receiving unit and combine the returned light beams, and phase modulate the light beam after an external sampling and demodulation circuit applies a square wave modulation voltage to the multifunctional integrated optical circuit.

[0009] The three-axis angular velocity sensing unit is used to receive the split light beam transmitted by the multifunctional integrated optical circuit and return the light beam containing the three-axis angular velocity information to the light beam transmitting and receiving unit after combining the light beam through the multifunctional integrated optical circuit. The three-axis angular velocity sensing unit contains three optical fiber sensing rings of different lengths for realizing time domain separation of the three-axis angular velocity information.

[0010] The optical signals transmitted by the three optical fiber sensing loops of different lengths in the three-axis angular velocity sensing unit are all modulated by the same multifunctional integrated optical circuit. The transit times of the three optical fiber sensing loops are different, so the three optical signals are modulated at different times of the modulation cycle, thereby achieving the separation of the three optical signals carrying the three-axis angular velocity in the time domain.

[0011] The light beam transmitting and receiving unit includes a light source, a photodetector and an optical circulator. The output end of the light source is connected to the first end of the optical circulator, the second end of the optical circulator is connected to the beam combining end of the multifunctional integrated optical circuit, the third end of the optical circulator is connected to the photodetector, and the two sides of the beam splitting end of the multifunctional integrated optical circuit are respectively connected to the three-axis angular velocity sensing unit.

[0012] The three-axis angular velocity sensing unit includes a first 1×3 polarization-maintaining coupler, a second 1×3 polarization-maintaining coupler, a first optical fiber sensing ring, a second optical fiber sensing ring, and a third optical fiber sensing ring. The two sides of the beam splitting end of the multifunctional integrated optical circuit are respectively connected to the beam combining end of the first 1×3 polarization-maintaining coupler and the second 1×3 polarization-maintaining coupler. The first sides of the beam splitting ends of the first 1×3 polarization-maintaining coupler and the second 1×3 polarization-maintaining coupler are respectively connected to the first optical fiber sensing ring. The second sides of the beam splitting ends of the first 1×3 polarization-maintaining coupler and the second 1×3 polarization-maintaining coupler are respectively connected to the second optical fiber sensing ring. The third sides of the beam splitting ends of the first 1×3 polarization-maintaining coupler and the second 1×3 polarization-maintaining coupler are respectively connected to the third optical fiber sensing ring.

[0013] The first optical fiber sensing ring, the second optical fiber sensing ring and the third optical fiber sensing ring share the same light beam transmitting and receiving unit and the multifunctional integrated optical circuit. The optical fiber length ratio of the first optical fiber sensing ring, the second optical fiber sensing ring and the third optical fiber sensing ring is 5:3:1.

[0014] Three fiber optic sensing rings measure the angular velocity information of three axes and are received by the same photodetector. By adjusting the lengths of the three fiber optic sensing rings, the angular velocity signals of the three axes are modulated at different times, realizing the separation of the angular velocity signals in the time domain.

[0015] The square wave modulation voltage applied to the multifunctional integrated optical circuit has a modulation frequency equal to the eigenfrequency of the second fiber optic sensing loop. At this modulation frequency, the signal light of the first fiber optic sensing loop is modulated only during the second third of the modulation half-cycle, the signal light of the second fiber optic sensing loop is modulated throughout the entire modulation half-cycle, and the signal light of the third fiber optic sensing loop is modulated only during the first third of the modulation half-cycle.

[0016] 2. A modulation method for a compact three-axis fiber optic gyroscope, comprising:

[0017] The light beam emitted by the light source of the light beam transmitting and receiving unit passes through an optical circulator and then passes through a multifunctional integrated optical circuit for phase modulation and is split into an upper light beam and a lower light beam. The upper light beam is split by a first 1×3 polarization-maintaining coupler and enters the first optical fiber sensing ring, the second optical fiber sensing ring, and the third optical fiber sensing ring respectively for forward propagation, and then is combined by a second 1×3 polarization-maintaining coupler, and finally returns to the multifunctional integrated optical circuit for phase modulation; the lower light beam is split by a second 1×3 polarization-maintaining coupler and enters the first optical fiber sensing ring, the second optical fiber sensing ring, and the third optical fiber sensing ring respectively for reverse propagation, and then is combined by the first 1×3 polarization-maintaining coupler, and finally returns to the multifunctional integrated optical circuit for phase modulation; the multifunctional integrated optical circuit combines the signals input by the first 1×3 polarization-maintaining coupler and the second 1×3 polarization-maintaining coupler, and then passes through the optical circulator to be received by a photodetector and finally transmitted to an external sampling circuit for sampling.

[0018] The length difference between the first fiber optic sensing ring and the second fiber optic sensing ring, as well as the length difference between the second fiber optic sensing ring and the third fiber optic sensing ring, are both greater than the decoherence length of the light source. That is, the light beam passing through the first fiber optic sensing ring, the light beam passing through the second fiber optic sensing ring, and the light beam passing through the third fiber optic sensing ring are mutually incoherent lights. The light intensity ultimately obtained by the photodetector is the superposition of the light intensities of the three pairs of signal lights transmitted by the first fiber optic sensing ring, the second fiber optic sensing ring, and the third fiber optic sensing ring after interference.

[0019] Since the three optical fiber sensor rings have different lengths, the corresponding signal lights are modulated by the multifunctional integrated optical circuit at different times. In the sampling sequence obtained by the external sampling circuit, the sampling points at different times contain the angular velocity information of the three optical fiber sensor rings. The total number of all sampling points in the first half of the modulation cycle is recorded as N, the average voltage value of the first N / 3 sampling points is recorded as V1, the average voltage value of the middle N / 3 sampling points is recorded as V2, and the average voltage value of the last N / 3 sampling points is recorded as V3; the total number of all sampling points in the second half of the modulation cycle is recorded as N, the average voltage value of the first N / 3 sampling points is recorded as V1', the average voltage value of the middle N / 3 sampling points is recorded as V2', and the average voltage value of the last N / 3 sampling points is recorded as V3'; then, the difference V between the average voltage values ​​of the middle N / 3 sampling points in the first half of the modulation cycle and the second half of the modulation cycle is used to calculate the average voltage of the three optical fiber sensor rings. 22 Demodulate the angular velocity information of the second fiber optic sensing ring, V 22 = V2-V2'; using the difference in the average voltage value of the first N / 3 sampling points in the first half cycle of the modulation and the second half cycle of the modulation V 11 And the difference between the average voltage values ​​of the middle N / 3 sampling points V 22 The difference between the two V 12 Demodulate the angular velocity information of the third fiber optic sensor ring, V 12 =V 11 -V 22 , V 11 = V1-V1′; using the difference in the average voltage value of the last N / 3 sampling points in the first half cycle of the modulation and the second half cycle of the modulation V 33 And the difference between the average voltage values ​​of the middle N / 3 sampling points V 22 The difference between the two V 32 Demodulate the angular velocity information of the first fiber optic sensing ring, V 32 =V 33 -V 22 , V 33 = V3 - V3′; Finally, the three-axis angular velocity information is obtained based on the angular velocity information of the three fiber optic sensing rings. The sampling points in different parts of the modulation period contain the angular velocity information of different fiber optic sensing rings, so each part should be demodulated separately.

[0020] The present invention adds two couplers and two fiber optic sensing rings behind the multifunctional integrated optical circuit in a single-axis gyroscope. By adjusting the length ratio of the three fiber optic sensing rings and modulating the frequency, time division multiplexing is achieved. The light source, detector and multifunctional integrated optical circuit are also multiplexed, further reducing the cost and size of the three-axis gyroscope.

[0021] The beneficial effects of the present invention are:

[0022] The present invention adds two couplers and two fiber optic sensing rings to the multifunctional integrated optical circuit in a single-axis gyroscope to form a three-axis fiber optic gyroscope. The present invention provides a novel time-division multiplexing method. By rationally designing the lengths and modulation frequencies of the three fiber optic sensing rings, the three-axis angular velocities are separated in the time domain, allowing the three fiber optic sensing rings to be modulated at different time intervals. This achieves time-division multiplexing and facilitates subsequent signal extraction. The angular velocity information of the different fiber optic sensing rings can be extracted from the interference light intensity at different time intervals within the modulation cycle, thus realizing three-axis angular velocity sensing. The present invention multiplexes the light beam transmitting and receiving unit and the multifunctional integrated optical circuit, reducing the size and cost of the three-axis integrated gyroscope and promoting its application in fields such as microsatellites and telecommunications satellites. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the optical path structure of the compact three-axis fiber optic gyroscope of the present invention;

[0024] Figure 2 Schematic diagram of the modulation voltage waveform and the modulation phase difference of the light propagating in each optical fiber sensing ring of the present invention;

[0025] Figure 3 Schematic diagram of the modulation voltage waveform and the voltage of the photodetector in one modulation cycle of the present invention;

[0026] In the figure: 1. light source, 2. photodetector, 3. optical circulator, 4. multifunctional integrated optical circuit, 5. first 1×3 polarization-maintaining coupler, 6. second 1×3 polarization-maintaining coupler, 7. first fiber optic sensing ring, 8. second fiber optic sensing ring, 9. third fiber optic sensing ring. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1As shown, the compact three-axis fiber optic gyroscope based on time division multiplexing of the present invention includes a light beam transmitting and receiving unit, a multifunctional integrated optical circuit 4 and a three-axis angular velocity sensing unit. The light beam transmitting and receiving unit transmits a light beam and receives a returned light beam containing three-axis angular velocity information, and then outputs a voltage signal containing the three-axis angular velocity information to an external sampling and demodulation circuit, and finally demodulates the three-axis angular velocity information; the multifunctional integrated optical circuit 4 splits the light beam emitted by the light beam transmitting and receiving unit and combines the returned light beam, and the external sampling and demodulation circuit applies a modulation voltage to the multifunctional integrated optical circuit 4 to phase modulate the light beam; the three-axis angular velocity sensing unit is used to receive the split light beam transmitted by the multifunctional integrated optical circuit and return the light beam containing the three-axis angular velocity information to the light beam transmitting and receiving unit after combining the light beam through the multifunctional integrated optical circuit. The three-axis angular velocity sensing unit includes three optical fiber sensing rings 7, 8, and 9 of different lengths for realizing time domain separation of the three-axis angular velocity information.

[0029] The optical signals transmitted by the three optical fiber sensing loops 7, 8, and 9 of different lengths in the triaxial angular velocity sensing unit are all modulated by the same multifunctional integrated optical circuit 4. The transit times of the three optical fiber sensing loops 7, 8, and 9 differ, so the three optical signals are modulated at different times during the modulation cycle, thereby achieving temporal separation of the three optical signals carrying the triaxial angular velocity. The first, second, and third optical fiber sensing loops 7, 8, and 9 share the same optical beam transmitting and receiving unit and multifunctional integrated optical circuit 4. The fiber length ratio of the first, second, and third optical fiber sensing loops 7, 8, and 9 is 5:3:1. The three optical fiber sensing loops 7, 8, and 9 measure angular velocity information along the three axes and are received by the same photodetector 8. By adjusting the lengths of the three optical fiber sensing loops 7, 8, and 9, the angular velocity signals along the three axes are modulated at different times, achieving temporal separation of the angular velocity signals.

[0030] The first, second, and third fiber optic sensing loops 7, 8, and 9 measure angular velocity information along three axes, respectively. The fiber length ratio of these loops is set to 5:3:1, corresponding to a fiber transit time of 5:3:1. A square wave modulation voltage is applied to the multifunctional integrated optical circuit 4, with the modulation frequency equal to the intrinsic frequency of the second fiber optic sensing loop 8. At this modulation frequency, the signal light from the first fiber optic sensing loop 7 is modulated only during the second third of the modulation half-cycle, the signal light from the second fiber optic sensing loop 8 is modulated throughout the entire modulation half-cycle, and the signal light from the third fiber optic sensing loop 9 is modulated only during the first third of the modulation half-cycle. At this point, optical signals along different axes pass through the multifunctional integrated optical circuit 4 at different times, meaning they are modulated at different times, thus achieving time division multiplexing.

[0031] The light beam transmitting and receiving unit includes a light source 1, a photodetector 2 and an optical circulator 3. The output end of the light source 1 is connected to the first end of the optical circulator 3, the second end of the optical circulator 3 is connected to the beam combining end of the multifunctional integrated optical circuit 4, the third end of the optical circulator 3 is connected to the photodetector 2, and the two sides of the beam splitting end of the multifunctional integrated optical circuit 4 are respectively connected to the three-axis angular velocity sensing unit.

[0032] The three-axis angular velocity sensing unit includes a first 1×3 polarization-maintaining coupler 5, a second 1×3 polarization-maintaining coupler 6, a first optical fiber sensing ring 7, a second optical fiber sensing ring 8 and a third optical fiber sensing ring 9. The two sides of the beam splitting end of the multifunctional integrated optical circuit 4 are respectively connected to the beam combining end of the first 1×3 polarization-maintaining coupler 5 and the second 1×3 polarization-maintaining coupler 6. The first sides of the beam splitting ends of the first 1×3 polarization-maintaining coupler 5 and the second 1×3 polarization-maintaining coupler 6 are respectively connected to the first optical fiber sensing ring 7. The second sides of the beam splitting ends of the first 1×3 polarization-maintaining coupler 5 and the second 1×3 polarization-maintaining coupler 6 are respectively connected to the second optical fiber sensing ring 8. The third sides of the beam splitting ends of the first 1×3 polarization-maintaining coupler 5 and the second 1×3 polarization-maintaining coupler 6 are respectively connected to the third optical fiber sensing ring 9.

[0033] The modulation method of the compact three-axis fiber optic gyroscope of the present invention is specifically as follows:

[0034] The light beam emitted by the light source 1 of the light beam transmitting and receiving unit passes through the optical circulator 3 and then passes through the multifunctional integrated optical circuit 4 for phase modulation and is split into an upper beam and a lower beam. The upper beam is split by the first 1×3 polarization-maintaining coupler 5 and then enters the first optical fiber sensing ring 7, the second optical fiber sensing ring 8, and the third optical fiber sensing ring 9 respectively for forward propagation. It is then combined by the second 1×3 polarization-maintaining coupler 6 and finally returns to the multifunctional integrated optical circuit 4 for phase modulation. The lower beam is split by the second 1×3 polarization-maintaining coupler 6 and then enters the first optical fiber sensing ring 7, the second optical fiber sensing ring 8, and the third optical fiber sensing ring 9 respectively for reverse propagation. It is then combined by the first 1×3 polarization-maintaining coupler 5 and finally returns to the multifunctional integrated optical circuit 4 for phase modulation. The multifunctional integrated optical circuit 4 combines the signals input by the first 1×3 polarization-maintaining coupler 5 and the second 1×3 polarization-maintaining coupler 6, and then passes through the optical circulator 3 to be received by the photodetector 2 and finally transmitted to an external sampling circuit for sampling.

[0035] The length difference between the first fiber optic sensing ring 7 and the second fiber optic sensing ring 8, as well as the length difference between the second fiber optic sensing ring 7 and the third fiber optic sensing ring 9, are both greater than the decoherence length of the light source 1. That is, the light beam passing through the first fiber optic sensing ring 7, the light beam passing through the second fiber optic sensing ring 8, and the light beam passing through the third fiber optic sensing ring 9 are mutually incoherent lights. The light intensity finally obtained by the photodetector 2 is the superposition of the light intensities after interference of the three pairs of signal lights transmitted by the first fiber optic sensing ring 7, the second fiber optic sensing ring 8, and the third fiber optic sensing ring 9.

[0036] Since the three optical fiber sensor rings 7, 8, and 9 have different lengths, the corresponding signal lights are modulated by the multifunctional integrated optical circuit 4 at different times. In the sampling sequence obtained by the external sampling circuit, the sampling points at different times contain the angular velocity information of the three optical fiber sensor rings 7, 8, and 9. The total number of sampling points in the first half of the modulation cycle is recorded as N, the average voltage value of the first N / 3 sampling points is recorded as V1, the average voltage value of the middle N / 3 sampling points is recorded as V2, and the average voltage value of the last N / 3 sampling points is recorded as V3; the total number of sampling points in the second half of the modulation cycle is recorded as N, the average voltage value of the first N / 3 sampling points is recorded as V1′, the average voltage value of the middle N / 3 sampling points is recorded as V2′, and the average voltage value of the last N / 3 sampling points is recorded as V3′; then, the difference V between the average voltage values ​​of the middle N / 3 sampling points in the first half of the modulation cycle and the second half of the modulation cycle is used to calculate the average voltage of the three optical fiber sensor rings 7, 8, and 9. 22 Demodulate the angular velocity information of the second optical fiber sensing ring 8, V 22 = V2-V2'; using the difference in the average voltage value of the first N / 3 sampling points in the first half cycle of the modulation and the second half cycle of the modulation V 11 And the difference between the average voltage values ​​of the middle N / 3 sampling points V 22 The difference between the two V 12 Demodulate the angular velocity information of the third optical fiber sensor ring 9, V 12 =V 11 -V 22 , V 11 = V1-V1′; using the difference in the average voltage value of the last N / 3 sampling points in the first half cycle of the modulation and the second half cycle of the modulation V 33 And the difference between the average voltage values ​​of the middle N / 3 sampling points V 22 The difference between the two V 32 Demodulate the angular velocity information of the first optical fiber sensor ring 7, V 32 =V 33 -V 22 , V 33 = V3 - V3′; finally, the three-axis angular velocity information is obtained based on the angular velocity information of the three fiber optic sensing rings 7, 8, and 9. The sampling points in different parts of the modulation period contain the angular velocity information of different fiber optic sensing rings 7, 8, and 9, so each part should be demodulated separately.

[0037] like Figure 2 As shown, under the modulation frequency of the multifunctional integrated optical circuit 4, the angular velocity signals of the three axes are modulated at different times, achieving separation of the angular velocity signals in the time domain. The signal light of the first optical fiber sensing ring 7 is modulated only in the last 1 / 3 of the modulation half cycle, the signal light of the second optical fiber sensing ring 8 is modulated throughout the modulation half cycle, and the signal light of the third optical fiber sensing ring 9 is modulated only in the first 1 / 3 of the modulation half cycle. Figure 2 middle, is the modulated square wave at time t, To modulate the depth, the three fiber optic sensor rings (7, 8, 9) are subjected to and Phase modulation.

[0038] Apply constant angular velocities in the x, y, and z directions to the first optical fiber sensing ring 7, the second optical fiber sensing ring 8, and the third optical fiber sensing ring 9, respectively. Figure 3 As shown, it is the waveform of the photodetector 2 in one modulation cycle. The light intensity at different times represents the angular velocity information of different axes. The light intensity detected by the photodetector 2 is as follows:

[0039]

[0040] in, Represents different periods of time T i The light intensity detected by photodetector 2, I i (i=1,2,3) represents the DC light intensity of the i-th fiber optic sensing ring; L i (i=1,2,3) represents the length of the i-th optical fiber sensing loop; D i (i=1,2,3) represents the diameter of the i-th fiber optic sensing ring, Ω i (i=x, y, z) represents the angular velocity detected by the i-th fiber optic sensing ring, Φ b is the modulation phase, λ is the average wavelength of the light source 1, and c is the speed of light in vacuum.

[0041] At different time periods, the signal light carrying different axial angular velocities is modulated, and the corresponding light intensity is also different. The light intensity of the corresponding time period is subtracted, as follows:

[0042]

[0043] The final angular velocity of the three axes is as follows:

[0044]

[0045] In terms of signal demodulation, the sampling points in different parts of the modulation period contain angular velocity information of different axes, so each part should be demodulated separately. The demodulation algorithm is as follows:

[0046] The total number of sampling points in the first half of the modulation cycle is recorded as N, the average value of the first N / 3 sampling points is recorded as V1, the average value of the middle N / 3 sampling points is recorded as V2, and the average value of the last N / 3 sampling points is recorded as V3; similarly, the total number of sampling points in the second half of the modulation cycle is also N, among which the average value of the first N / 3 sampling points is recorded as V1′, the average value of the middle N / 3 sampling points is recorded as V2′, and the average value of the last N / 3 sampling points is recorded as V3′. Then the angular velocity of the y-axis is Ω y =(V2-V2′) / SI y , the angular velocity of the x-axis Ω x =[(V3-V3′)-(V2-V2′)] / SI x , the angular velocity of the z-axis Ω z =[(V1-V1′)-(V2-V2′)] / SI z , among which, SI x 、SI y and SI z Represents the scale factors corresponding to the x-, y-, and z-axis angular velocity signals, respectively.

[0047] Therefore, the present invention proposes a novel time-division multiplexing method in a fiber optic gyroscope, which can simultaneously multiplex the light source 1, the photodetector 2 and the multifunctional integrated optical circuit 4. By adjusting the length ratio and the modulation frequency of the three fiber optic sensing rings 7, 8, and 9, the three-axis signals are separated in the time domain, further reducing the cost and volume of the three-axis gyroscope.

[0048] The above-described embodiment is merely a technical concept and preferred solution of the present invention and does not limit the scope of protection of this invention. Any equivalent transformation or modification by a person skilled in the relevant art based on the present invention, which utilizes a single multifunctional integrated optical circuit 4 and three optical fiber sensing rings 7, 8, and 9 with specific length ratios to achieve time-division multiplexing and reduce the cost and volume of a three-axis gyroscope, should be within the scope of protection of this invention.

Claims

1. A modulation method for a compact three-axis fiber optic gyroscope based on time division multiplexing, wherein the compact three-axis fiber optic gyroscope comprises a light beam transmitting and receiving unit, a multifunctional integrated optical circuit (4) and a three-axis angular velocity sensing unit, wherein the light beam transmitting and receiving unit is used to transmit a light beam and receive a returned light beam containing three-axis angular velocity information, and output a voltage signal containing the three-axis angular velocity information to an external sampling and demodulation circuit, and finally demodulate the three-axis angular velocity information; A multifunctional integrated optical circuit (4) is used to split the light beam emitted by the light beam transmitting and receiving unit and to combine the returned light beam, and to perform phase modulation on the light beam after applying a modulation voltage to the multifunctional integrated optical circuit (4) in an external sampling and demodulation circuit; a three-axis angular velocity sensing unit is used to receive the split light beam transmitted by the multifunctional integrated optical circuit (4) and to combine the light beam containing the three-axis angular velocity information through the multifunctional integrated optical circuit (4) and return it to the light beam transmitting and receiving unit, and the three-axis angular velocity sensing unit includes three optical fiber sensing rings (7, 8, 9) of different lengths for realizing time domain separation of the three-axis angular velocity information; the three-axis angular velocity sensing unit includes a first 1×3 polarization maintaining coupler (5), a second 1×3 polarization maintaining coupler (6), and a second polarization maintaining coupler (7). The multifunctional integrated optical circuit (4) is a multifunctional integrated optical circuit comprising a first optical fiber sensing ring (6), a first optical fiber sensing ring (7), a second optical fiber sensing ring (8) and a third optical fiber sensing ring (9), the two sides of the beam splitting end of the multifunctional integrated optical circuit (4) are respectively connected to the beam combining end of the first 1×3 polarization maintaining coupler (5) and the second 1×3 polarization maintaining coupler (6), the first sides of the beam splitting ends of the first 1×3 polarization maintaining coupler (5) and the second 1×3 polarization maintaining coupler (6) are respectively connected to the first optical fiber sensing ring (7), the second sides of the beam splitting ends of the first 1×3 polarization maintaining coupler (5) and the second 1×3 polarization maintaining coupler (6) are respectively connected to the second optical fiber sensing ring (8), the third sides of the beam splitting ends of the first 1×3 polarization maintaining coupler (5) and the second 1×3 polarization maintaining coupler (6) are respectively connected to the third optical fiber sensing ring (9), and the first sides of the beam splitting ends of the first 1×3 polarization maintaining coupler (5) and the second 1×3 polarization maintaining coupler (6) are respectively connected to the third optical fiber sensing ring (9). ) connection; the first optical fiber sensing ring (7), the second optical fiber sensing ring (8) and the third optical fiber sensing ring (9) share the same light beam transmitting and receiving unit and the multifunctional integrated optical circuit (4), characterized in that: the light beam emitted by the light source (1) of the light beam transmitting and receiving unit passes through the optical circulator (3) and then passes through the multifunctional integrated optical circuit (4) for phase modulation and is split into an upper light beam and a lower light beam, the upper light beam is split by the first 1×3 polarization-maintaining coupler (5) and then enters the first optical fiber sensing ring (7), the second optical fiber sensing ring (8) and the third optical fiber sensing ring (9) for forward propagation, and then is combined by the second 1×3 polarization-maintaining coupler (6), and finally returns to the multifunctional integrated optical circuit (4) for phase modulation. The lower optical beam is split by the second 1×3 polarization-maintaining coupler (6) and then enters the first optical fiber sensing ring (7), the second optical fiber sensing ring (8) and the third optical fiber sensing ring (9) for reverse propagation, and then is combined by the first 1×3 polarization-maintaining coupler (5) and finally returns to the multifunctional integrated optical circuit (4) for phase modulation; the multifunctional integrated optical circuit (4) combines the signals input by the first 1×3 polarization-maintaining coupler (5) and the second 1×3 polarization-maintaining coupler (6) and then passes through the circulator (3) and is received by the photodetector (2), and finally transmitted to the external sampling circuit for sampling; the optical fiber length ratio of the first optical fiber sensing ring (7), the second optical fiber sensing ring (8) and the third optical fiber sensing ring (9) is 5:3:1;The modulation voltage applied to the multifunctional integrated optical circuit (4) has a modulation frequency equal to the eigenfrequency of the second optical fiber sensing ring (8); at the modulation frequency, the signal light of the first optical fiber sensing ring (7) is modulated only in the last 1 / 3 of the modulation half cycle, the signal light of the second optical fiber sensing ring (8) is modulated throughout the entire modulation half cycle, and the signal light of the third optical fiber sensing ring (9) is modulated only in the first 1 / 3 of the modulation half cycle; The three optical fiber sensor rings (7, 8, 9) have different lengths, and the corresponding signal lights are modulated by the multifunctional integrated optical circuit (4) at different times. In the sampling sequence obtained by the external sampling circuit, the sampling points at different times contain the angular velocity information of the three optical fiber sensor rings (7, 8, 9). The total number of all sampling points in the first half cycle of modulation is recorded as N, the average voltage value of the first N / 3 sampling points is recorded as V1, the average voltage value of the middle N / 3 sampling points is recorded as V2, and the average voltage value of the last N / 3 sampling points is recorded as V3; the total number of all sampling points in the second half cycle of modulation is recorded as N, the average voltage value of the first N / 3 sampling points is recorded as V1′, the average voltage value of the middle N / 3 sampling points is recorded as V2′, and the average voltage value of the last N / 3 sampling points is recorded as V3′; then the difference V between the average voltage values ​​of the middle N / 3 sampling points in the first half cycle of modulation and the second half cycle of modulation is used to calculate the average voltage of the three optical fiber sensor rings (7, 8, 9). 22 Demodulate the angular velocity information of the second optical fiber sensing ring (8), V 22 =V2-V2′; using the difference in the average voltage value of the first N / 3 sampling points in the first half cycle of the modulation and the second half cycle of the modulation V 11 And the difference between the average voltage values ​​of the middle N / 3 sampling points V 22 The difference between the two V 12 Demodulate the angular velocity information of the third optical fiber sensing ring (9), V 12 =V 11 -V 22 , V 11 =V1-V1′; using the difference in the average voltage value of the last N / 3 sampling points in the first half cycle of modulation and the second half cycle of modulation V 33 And the difference between the average voltage values ​​of the middle N / 3 sampling points V 22 The difference between the two V 32 Demodulate the angular velocity information of the first optical fiber sensing ring (7), V 32 =V 33 -V 22 , V 33 =V3-V3′; finally, the three-axis angular velocity information is obtained according to the angular velocity information of the three optical fiber sensing rings (7, 8, 9).

2. The modulation method of the compact three-axis fiber optic gyroscope according to claim 1, characterized in that: The length difference between the first optical fiber sensing ring (7) and the second optical fiber sensing ring (8), as well as the length difference between the second optical fiber sensing ring (7) and the third optical fiber sensing ring (9), are both greater than the decoherence length of the light source (1), that is, the light beam passing through the first optical fiber sensing ring (7), the light beam passing through the second optical fiber sensing ring (8), and the light beam passing through the third optical fiber sensing ring (9) are mutually incoherent lights, and the light intensity finally obtained by the photoelectric detector (2) is the superposition of the light intensities of the three pairs of signal lights transmitted from the first optical fiber sensing ring (7), the second optical fiber sensing ring (8), and the third optical fiber sensing ring (9) after interference.

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