CN116045956B - Optical fiber gyroscope and optical polarization state sensing rotation-based method thereof - Google Patents
Optical fiber gyroscope and optical polarization state sensing rotation-based method thereof Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/58—Turn-sensitive devices without moving masses
- G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
- G01C19/72—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/58—Turn-sensitive devices without moving masses
- G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
- G01C19/72—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams with counter-rotating light beams in a passive ring, e.g. fibre laser gyrometers
- G01C19/721—Details
Abstract
The invention relates to the technical field of fiber-optic gyroscopes, in particular to a fiber-optic gyroscope and a method for sensing rotation based on light polarization state, which comprises the following steps:
the linearly polarized light is decomposed into two orthogonal polarized components, the two orthogonal polarized components are transmitted in the polarization-preserving hollow photonic crystal fiber ring for one circle, and the two orthogonal polarized components are recombined and combined at the output port of the polarization beam splitter to form polarized light to be detected and projected to the polarization state detection module; the polarization state detection module detects the light intensity of polarized light to be detected, the polarization state and the polarization state change angle are calculated through the modulation and demodulation circuit board to represent the rotation rate of the fiber-optic gyroscope, meanwhile, the modulation and demodulation circuit board controls the light wavelength output by the wavelength tunable laser to sweep back and forth at a constant speed within a preset wavelength range to form polarization state modulation, and the trend item drift error related to the integral polarization state change angle in the gyroscope is eliminated. The method provided by the invention has the advantages of miniaturization, high precision and high performance.
Description
Technical Field
The invention relates to the technical field of fiber-optic gyroscopes, in particular to a fiber-optic gyroscope and a method for sensing rotation based on light polarization state.
Background
The fiber-optic gyroscope is based on the Sagnac interference principle, and adopts an optical fiber to wind into a ring to form a closed light path, so that the phase difference between two light beams transmitted in opposite directions in the closed light path represents the rotation angular velocity. The fiber optic gyroscope has the characteristics of full solid state, high sensitivity, long service life, quick start, wide dynamic range, low cost and the like, is widely applied to inertial autonomous navigation systems in the fields of sea, land, air, sky and the like, and becomes one of mainstream inertial instruments. At present, in the face of new demands of application of unmanned carrier autonomous navigation, intelligent ammunition guidance and other fields to miniaturization and high precision of inertial elements, one of the main directions of the next-stage development of the fiber-optic gyroscope is how to realize high performance and high precision under a small geometric scale. As can be seen from the angular velocity sensing mechanism of the optical gyroscope, the precision level of the interference type optical fiber gyroscope is in direct proportion to the Sagnac area, and under the condition that the Sagnac area is ensured to be certain, namely under the premise of meeting the precision requirement, compared with the conventional optical fiber ring size, the optical fiber with the small geometric dimension is required to be wound for forming the same Sagnac area by longer optical fibers.
At present, the conventional optical fiber for the fiber-optic gyroscope takes a germanium-silicon material as a fiber core and a boron-silicon material as a cladding, total internal reflection occurs on the interface of the cladding to realize light guiding of the fiber core, and the boron material is inserted into the cladding at two sides of the fiber core to endow the optical fiber with stress birefringence so as to realize polarization maintaining. Because the boron material stress areas are arranged on the two sides of the fiber core, the uniformity of the materials on the periphery of the fiber core of the traditional polarization maintaining fiber is poor, so that the polarization maintaining capacity of the traditional polarization maintaining fiber is sensitive to external stress disturbance, and meanwhile, the risk of breakage among heterogeneous materials under long-time microbending is high, and the reliability is poor. The winding optical fiber can generate bending stress in the optical fiber, the bending stress is coupled with the stress applied by the boron material, the polarization maintaining performance and the reliability of the optical fiber are affected, and the shorter the bending radius and the longer the winding optical fiber are, the more serious the short-term polarization maintaining performance and the long-term reliability are degraded. In summary, there are mechanical limitations in the application of conventional polarization maintaining fibers to miniaturized high-precision fiber optic gyroscopes.
The hollow photonic crystal fiber utilizes the cladding microstructure with the periodic lattice point structural characteristics to form a photonic band gap effect, so that light waves are bound in an air fiber core for transmission, air is used as a transmission medium, the light waves are not sensitive to the influences of heat, magnetism, irradiation and the like in the environment, ideal high-stability light transmission can be realized, and the environmental adaptability of the fiber-optic gyroscope is improved. The hollow photonic crystal fiber has excellent bending resistance due to the periodic lattice point structural characteristics, and the polarization-preserving hollow photonic crystal fiber is extremely in line with the miniaturized development requirement of the fiber-optic gyroscope because the high polarization-preserving effect and other excellent optical performances can be obtained through the differential design of the glass wall thickness of the cross section of the hollow photonic crystal fiber in the horizontal and vertical directions. However, in order to meet the precision requirement, the optical fiber ring needs to wind a long optical fiber, so that the transmission loss is too large, and the transmission loss is difficult to improve in order of magnitude in a short time, and the requirement of high precision can not be realized by supporting the interference type optical fiber gyro.
Disclosure of Invention
The invention aims to solve the technical problems of providing an optical fiber gyroscope and a method for sensing and rotating based on light polarization states, adopting a polarization-preserving hollow-core photonic crystal fiber to manufacture a polarization-preserving hollow-core photonic crystal fiber ring, constructing a miniaturized light path, fully utilizing the advantage of good bending performance of the polarization-preserving hollow-core photonic crystal fiber, improving the environmental adaptability of the optical fiber gyroscope, reducing the use length of the hollow-core photonic crystal fiber under the condition of ensuring the miniaturization and precision requirements of the hollow-core photonic crystal fiber gyroscope based on the rotation rate measurement technology of the polarization measurement optical fiber gyroscope, avoiding the engineering application problem of overlarge transmission loss of the hollow-core photonic crystal fiber, and creatively providing a wavelength modulation method which can eliminate the long-term drift error of the gyroscope and ensure the characteristics of miniaturization, high precision and high performance of the optical fiber gyroscope.
The invention is realized by the following technical scheme:
a method of optical fiber gyro based on optical polarization state sensing rotation, comprising the steps of:
step one: light output by the wavelength tunable laser is generated by a polarizer
Linearly polarized light, +.>
The linearly polarized light is decomposed into vertical polarized component light and horizontal polarized component light at the input port of the polarization beam splitter, the vertical polarized component light is transmitted by the polarization beam splitter and then transmitted in a slow axis of a tail fiber at one end of the polarization-preserving hollow photonic crystal fiber ring, the horizontal polarized component light is reflected by the polarization beam splitter and then transmitted in a fast axis of the tail fiber at the other end of the polarization-preserving hollow photonic crystal fiber ring, and the vertical polarized component light and the horizontal polarized component light are respectively returned to the polarization beam splitter;
step two: the vertical polarized component light and the horizontal polarized component light are recombined and combined at the output port of the polarization beam splitter to form polarized light to be detected and projected to the polarization state detection module;
step three: the polarization state detection module detects the light intensity of polarized light to be detected, converts a light intensity signal into a voltage signal and sends the voltage signal to the modulation and demodulation circuit board, the modulation and demodulation circuit board calculates the polarization state and the polarization state change angle of the polarized light to be detected to represent the rotation rate of the hollow photonic crystal fiber gyroscope, and meanwhile, the modulation and demodulation circuit board controls the wavelength tunable laser, so that the wavelength of light output by the wavelength tunable laser is scanned repeatedly at a constant speed within a preset wavelength range to form polarization state modulation, and trend item drift errors related to the polarization state change angle are eliminated.
In the third step, when the wavelength of the light output by the wavelength tunable laser is scanned back and forth at a constant speed within a preset wavelength range to modulate the polarization state, the lengths of the first scanning half period and the second scanning half period are equal to the transition time of the optical fiber loop
The modulation polarization state change angle is larger than the polarization state change angle of the polarized light to be measured.
Further, when the polarization state detection module detects the light intensity of the polarized light to be detected, the polarized light to be detected is equally divided into four paths of light signals and then projected to four paths of detection channels, and the light waves projected by the first detection channel in the horizontal direction are detected as light intensity signals through the first photoelectric detector
And light intensity signal +.>
Converted into voltage signals and sent to a modulation and demodulation circuit board, and a second detection channel projects light waves in the vertical direction, and the light intensity signals are detected as +.>
And light intensity signal +.>
Converted into voltage signals to be sent to a modulation and demodulation circuit board, and the third detection channel projects a signal which is +|with the horizontal direction>
The light wave with the included angle is detected by a third photoelectric detector to be light intensity signal of +>
And light intensity signal +.>
Converted into voltage signals to be sent to a modulation and demodulation circuit board, and the projection of a fourth detection channel is +|horizontal direction>
The light wave with the included angle is detected by a fourth photoelectric detector to be light intensity signal of +.>
And light intensity signal +.>
Converted into a voltage signal and sent to a modem circuit board, and the modem circuit board calculates Stokes parameters according to formulas (1) to (4)>
、/>
、/>
、/>
Then, the polarization state and the polarization state change angle of the input light are obtained according to Stokes parameters:
wherein, the liquid crystal display device comprises a liquid crystal display device,
for inputting the light intensity +.>
Light wave is in bang Gao (ball)>
Coordinates corresponding to the axes of the coordinates>
Light wave is in bang Gao (ball)>
Coordinates corresponding to the axes of the coordinates>
Light wave is in bang Gao (ball)>
The coordinates correspond to the coordinates axially. />
Further, the first detection channel projects light waves in the horizontal direction through the first polaroid with the light transmission axis in the horizontal direction, the second detection channel projects light waves in the vertical direction through the second polaroid with the light transmission axis in the vertical direction, and the third detection channel passes through the light transmission axis and forms a angle with the horizontal direction
The third polarizer with an angle of projection +.>
The fourth detection channel is a quarter wave plate with a birefringent axis in the horizontal direction and a light transmission axis in the same direction as the horizontal direction>
The fourth polarizer projection of the angle is +.>
Light waves with included angles.
Preferably, the horizontal polarized component light is coupled to one end of the polarization-maintaining hollow-core photonic crystal fiber ring through the optical fiber collimation sealing joint for transmission in the fast axis of the polarization-maintaining hollow-core photonic crystal fiber ring, and the vertical polarized component light is coupled to the other end of the polarization-maintaining hollow-core photonic crystal fiber ring through the optical fiber collimation sealing joint for transmission in the slow axis of the polarization-maintaining hollow-core photonic crystal fiber ring.
The optical fiber gyroscope is used for executing the optical polarization state sensing rotation-based method of any one of the optical fiber gyroscope, and comprises a wavelength tunable laser, a polarizer, a polarization beam splitter, a polarization-preserving hollow-core photonic crystal fiber ring, a polarization state detection module and a modulation and demodulation circuit board, wherein the output end of the wavelength tunable laser is coupled with the input end of the polarizer, the output end of the polarizer is coupled with the input end of the polarization beam splitter, the two output ends of the polarization beam splitter are respectively coupled with the two tail fibers of the polarization-preserving hollow-core photonic crystal fiber ring, the detection end of the polarization beam splitter is coupled with the input end of the polarization state detection module, the output end of the polarization state detection module is connected with the input end of the modulation and demodulation circuit board, and the control end of the modulation and demodulation circuit board is connected with the input end of the wavelength tunable laser.
Further, the polarization state detection module comprises four detection channels, the first detection channel is sequentially provided with a first polaroid and a first photoelectric detector, the light passing axis of the first polaroid is in the horizontal direction, the second detection channel is sequentially provided with a second polaroid and a second photoelectric detector, the light passing axis of the second polaroid is in the vertical direction, the third detection channel is sequentially provided with a third polaroid and a third photoelectric detector, and the light passing axis of the third polaroid forms a light passing axis with the horizontal direction
The included angle, the fourth detection channel is sequentially provided with a quarter wave plate, a fourth polaroid and a fourth photoelectric detector, the double refraction axis of the quarter wave plate is in the horizontal direction, and the light transmission axis of the fourth polaroid forms a part of the horizontal direction>
And an included angle.
Preferably, two output ends of the polarization beam splitter are respectively coupled and connected with two tail fibers of the polarization-preserving hollow-core photonic crystal fiber ring through fiber collimation sealing joints.
The invention has the beneficial effects that:
the invention adopts the polarization-maintaining hollow-core photonic crystal fiber to manufacture the polarization-maintaining hollow-core photonic crystal fiber loop, constructs a miniaturized light path, fully utilizes the advantage of good bending performance of the polarization-maintaining hollow-core photonic crystal fiber, improves the environmental adaptability of the fiber-optic gyroscope, reduces the use length of the hollow-core photonic crystal fiber under the condition of ensuring the miniaturization and precision requirements of the hollow-core photonic crystal fiber-optic gyroscope based on the rotation rate measurement technology of the polarization measurement fiber-optic gyroscope, avoids the engineering application problem of overlarge transmission loss of the hollow-core photonic crystal fiber-optic gyroscope, creatively proposes a wavelength modulation method, can eliminate the long-term drift error of the gyroscope, and ensures the characteristics of miniaturization, high precision and high performance of the fiber-optic gyroscope.
Drawings
FIG. 1 is a schematic diagram of the hollow photonic crystal fiber gyro according to the present invention.
FIG. 2 is a schematic diagram of the rotation of the present invention resulting in a change in polarization state moving on the bungjia sphere circle.
FIG. 3 is a graph showing the change of the modulation polarization state change angle with time according to the present invention.
Fig. 4 is a schematic structural diagram of a polarization detection module according to the present invention.
In the figure: 1. the optical fiber comprises a wavelength tunable laser, a polarizer, a polarization beam splitter, an optical fiber collimation sealing joint, a polarization-preserving hollow photon crystal optical fiber ring, a polarization state detection module, a modulation and demodulation circuit board, a first polarizer, a first photodetector, a second polarizer, a second photodetector, a third polarizer, a third photodetector, a fourth polarizer and a quarter wave plate.
Detailed Description
A method of optical fiber gyro based on optical polarization state sensing rotation, comprising the steps of:
step one: light output by the wavelength tunable laser is generated by a polarizer
Linearly polarized light, +.>
The linearly polarized light is decomposed into vertical polarized component light and horizontal polarized component light at the input port of the polarization beam splitter, the vertical polarized component light is transmitted by the polarization beam splitter and then transmitted in a slow axis of a tail fiber at one end of the polarization-preserving hollow photonic crystal fiber ring, the horizontal polarized component light is reflected by the polarization beam splitter and then transmitted in a fast axis of the tail fiber at the other end of the polarization-preserving hollow photonic crystal fiber ring, and the vertical polarized component light and the horizontal polarized component light are respectively returned to the polarization beam splitter;
step two: the vertical polarized component light and the horizontal polarized component light are recombined and combined at the output port of the polarization beam splitter to form polarized light to be detected and projected to the polarization state detection module;
step three: the polarization state detection module detects the light intensity of polarized light to be detected, converts a light intensity signal into a voltage signal and sends the voltage signal to the modulation and demodulation circuit board, the modulation and demodulation circuit board calculates the polarization state and the polarization state change angle of the polarized light to be detected to represent the rotation rate of the hollow photonic crystal fiber gyroscope, and meanwhile, the modulation and demodulation circuit board controls the wavelength tunable laser, so that the wavelength of light output by the wavelength tunable laser is scanned repeatedly at a constant speed within a preset wavelength range to form polarization state modulation, and trend item drift errors related to the polarization state change angle are eliminated.
In the third step, when the wavelength of the light output by the wavelength tunable laser is scanned back and forth at a constant speed within a preset wavelength range to modulate the polarization state, the lengths of the first scanning half period and the second scanning half period are equal to the transition time of the optical fiber loop
The modulation polarization state change angle is larger than the polarization state change angle of the polarized light to be measured.
The hollow photonic crystal fiber ring is manufactured based on the periodic lattice point structural characteristics of the hollow photonic crystal fiber cladding and has the advantage of good bending resistance, is applied to the optical path of the hollow photonic crystal fiber gyro, greatly reduces the minimum winding radius of the optical fiber, meets the miniaturization development requirement of the fiber gyro, and is the prior art, and the specific structure is not repeated. Meanwhile, the requirements on the length of the optical fiber are reduced by measuring the polarization state of the light in a shorter closed light path, the engineering application problem of overlarge transmission loss of the hollow photonic crystal optical fiber is avoided, the long-term drift error of the gyroscope is eliminated by a wavelength modulation method, the stability of long-term measurement of the rotation rate is improved, and the requirement on high precision of the optical fiber gyroscope in long voyage is met.
The principle is as follows:
will be
Linearly polarized light is split into two orthogonal polarized components with equal intensity, namely a horizontal polarized component and a vertical polarized component, and the two orthogonal polarized components are transmitted in a closed optical path, so that the two light beams are orthogonal to each other, are recombined and do not interfere, and only are combined to form polarized light. When there is rotation in the sensitive axis direction, the resulting differential group delay (Differential Group Delay, DGD) will generate a phase difference between the two orthogonal polarization components, refocus to form polarized light, the polarization state of which changes with it, the phase difference is the rotation polarization state change angle->
Rotation polarization state variation angle->
In direct proportion to the rotation rate, so that the polarization state variation of the refocused light with respect to the initial polarization state of the incident light beam, i.e., the rotation polarization state variation angle is in direct proportion to the rotation rate in the direction of the sensitive axis, as shown in formula (5): />
In the method, in the process of the invention,
differential group delay for rotation; />
Is the center wavelength of the light source; />
Is the area of a closed light path; />
For the speed of light->
Is the rotation rate.
The research surface has the phenomenon that the angular rate output slowly changes along with time, namely drift exists, and the drift characteristic and the rotation polarization state change angle exist in the method for realizing rotation rate acquisition through polarization state measurement under long-time work
Is sign-dependent and accumulates over time, and cannot support long-endurance high-precision navigation applications.
The schematic diagram of the polarization state change moving on the bungzhi big circle caused by rotation is shown in fig. 2, the electric field expression before the light beam enters the input port of the polarization beam splitter is shown in formula (6), after the two orthogonal polarization components are transmitted through the optical loop and recombined at the output port of the polarization beam splitter, the electric field expression is changed into formula (7) due to the polarization state change:
wherein:
for the component of polarized light in the transmission axis, +.>
For the component of polarized light in the reflection axis, +.>
For electric field amplitude +.>
Inputting a light field vector for a polarizing beam splitter, +.>
Outputting a light field vector for the polarizing beam splitter, +.>
Representing the angle of change of the rotated polarization state +.>
Cosine and complex number rotation polarization state change angle +.>
Sum of sinusoids;
because the hollow photonic crystal fiber is a polarization maintaining fiber, the hollow photonic crystal fiber has two main axes of light transmission, namely a slow axis and a fast axis, and the refractive index difference between the fast axis and the slow axis is the double refractive index
After two orthogonal polarization components are transmitted in opposite directions in the fast and slow axes of the polarization-preserving hollow photonic crystal fiber ring for one circle, the generated phase difference is the polarization state change angle +.>
As shown in formula (8):
wherein:
for the length of the optical fiber->
Is wavelength;
as can be seen from the step (8), the modulation of the light polarization state at the output port of the polarization beam splitter can be realized by modulating the wavelength, and the birefringence of the polarization-preserving hollow photonic crystal fiber is maintained
A fixed polarization state change angle bias can be generated for the gyro system, and the modulation and rotation rate measurement effect is not affected.
If the modulation and demodulation circuit board controls the wavelength tunable laser to enable the output light wavelength to be within the preset wavelength range [ ]
To->
，
) The interior is swept back and forth at a constant speed, and the wavelength of the first half period is swept back, namely from +.>
To->
Scanning is performed, the wavelength of the second half period is swept forward, i.e. from +.>
To->
Scanning, wherein the values of the polarization state change angles of the first half period and the second half period in the scanning process are equal, and the values are expressed as +.>
The sign is opposite and the polarization state variation angle forms positive and negative symmetrical modulation.
During modulation, the duration of the front half period and the rear half period are equal to the transition time of the optical fiber loop
Is the integer of (2)The change of the modulation polarization state change angle with time is shown in figure 3, and the modulation polarization state change angle is a positive and negative symmetrical sawtooth waveform with amplitude of +.>
. Integral polarization state change angle in gyroscope>
As shown in formula (9)>
By rotating the polarization state change angle->
Modulated polarization state change angle->
And a trend term drift +.>
The composition is formed.
By choosing a suitable angle of change of the modulated polarisation state, i.e
And the lengths of the front half period and the rear half period are equal to the transition time of the optical fiber loop +.>
Can drift the trend term +.>
The sign of the modulation is always the same as the change angle of the polarization state
The sign of (2) is kept consistent, i.e. the polarization state change angle is modulated +.>
Is positive, the trend term drift is generated +.>
The sign of (2) is also positive, modulating the polarization state change angle +.>
Is negative, the trend term drift is generated +.>
The sign of the first half period is also negative, the trend term drift error with positive sign is exactly offset with the trend term drift error with negative sign generated in the second half period, the modulation polarization state change angle with positive sign in the first half period is exactly offset with the modulation polarization state change angle with negative sign in the second half period, and the rotation polarization state change angle is->
Doubling the retention so that the overall polarization change angle in the gyro +.>
Angle of change with respect to rotated polarization state only>
Relatively stable, help promoting top long-term output stability.
Further, when the polarization state detection module detects the light intensity of the polarized light to be detected, the polarized light to be detected is equally divided into four paths of light signals and then projected to four paths of detection channels, and the light waves projected by the first detection channel in the horizontal direction are detected as light intensity signals through the first photoelectric detector
And light intensity signal +.>
Converted into voltage signals and sent to a modulation and demodulation circuit board, and a second detection channel projects light waves in the vertical direction, and the light intensity signals are detected as +.>
And light intensity signal +.>
Converted into voltage signals to be sent to a modulation and demodulation circuit board, and the third detection channel projects a signal which is +|with the horizontal direction>
The light wave with the included angle is detected by a third photoelectric detector to be light intensity signal of +>
And light intensity signal +.>
Converted into voltage signals to be sent to a modulation and demodulation circuit board, and the projection of a fourth detection channel is +|horizontal direction>
The light wave with the included angle is detected by a fourth photoelectric detector to be light intensity signal of +.>
And light intensity signal +.>
Converted into a voltage signal and sent to a modem circuit board, and the modem circuit board calculates Stokes parameters according to formulas (1) to (4)>
、/>
、/>
、/>
Then, the polarization state and the polarization state change angle of the input light are obtained according to Stokes parameters:
in the formula (1)
I.e. the input light intensity, corresponding to the origin of coordinates, < >>
Light wave is in bang Gao (ball)>
Coordinates corresponding to the axes of the coordinates>
Light wave is in bang Gao (ball)>
Coordinates corresponding to the axes of the coordinates>
Light wave is in bang Gao (ball)>
The coordinates correspond to the coordinates axially.
Further, the first detection channel projects light waves in the horizontal direction through the first polaroid with the light transmission axis in the horizontal direction, the second detection channel projects light waves in the vertical direction through the second polaroid with the light transmission axis in the vertical direction, and the third detection channel passes through the light transmission axis and forms a angle with the horizontal direction
The third polarizer with an angle of projection +.>
The fourth detection channel is a quarter wave plate with a birefringent axis in the horizontal direction and a light transmission axis in the same direction as the horizontal direction>
The fourth polarizer projection of the angle is +.>
Light waves with included angles. Through the arrangement, the polarized light to be detected can be evenly distributed to the four detection channels, the directions of the light waves passing through each detection channel are different, the coordinate points corresponding to the light waves on the Pongche balls are obtained, and the modulation and demodulation circuit board can calculate the polarization state and the polarization state change angle of the input light according to the detection result. />
Preferably, the horizontal polarized component light is coupled to one end of the polarization-maintaining hollow-core photonic crystal fiber ring through the optical fiber collimation sealing joint for transmission in the fast axis of the polarization-maintaining hollow-core photonic crystal fiber ring, and the vertical polarized component light is coupled to the other end of the polarization-maintaining hollow-core photonic crystal fiber ring through the optical fiber collimation sealing joint for transmission in the slow axis of the polarization-maintaining hollow-core photonic crystal fiber ring. The optical fiber collimation sealing joint has a good sealing effect, can prevent light leakage, ensures the accuracy of detection results, and is of the prior art and is not described herein.
The optical fiber gyro comprises a wavelength tunable laser 1, a polarizer 2, a polarization beam splitter 3, a polarization-preserving hollow-core photonic crystal fiber ring 5, a polarization detection module 6 and a modulation and demodulation circuit board 7, wherein the output end of the wavelength tunable laser is coupled with the input end of the polarizer, the output end of the polarizer is coupled with the input end of the polarization beam splitter, the two output ends of the polarization beam splitter are respectively coupled with two tail fibers of the polarization-preserving hollow-core photonic crystal fiber ring, the detection end of the polarization beam splitter is coupled with the input end of the polarization detection module, the output end of the polarization detection module is connected with the input end of the modulation and demodulation circuit board, and the control end of the modulation and demodulation circuit board is connected with the input end of the wavelength tunable laser.
Further, the schematic structure of the polarization state detection module is shown in fig. 4, and the polarization state detection module comprises four detection channels, wherein the first detection channel is sequentially provided with a first polaroid 8 and a first photoelectric detector 9, the light passing axis of the first polaroid is in a horizontal direction, the second detection channel is sequentially provided with a second polaroid 10 and a second photoelectric detector 11, the light passing axis of the second polaroid is in a vertical direction, the third detection channel is sequentially provided with a third polaroid 12 and a third photoelectric detector 13, and the light passing axis of the third polaroid is in a horizontal direction
The included angle, the fourth detection channel is sequentially provided with a quarter wave plate 16, a fourth polaroid 15 and a fourth photoelectric detector 14, the double refraction axis of the quarter wave plate is in the horizontal direction, and the light transmission axis of the fourth polaroid forms a +_part with the horizontal direction>
And an included angle.
The light passing axis of the first polaroid is in the horizontal direction, so that the first detection channel only allows light in the horizontal direction to pass through, the light passing axis of the second polaroid is in the vertical direction, so that the second detection channel only allows light in the vertical direction to pass through, and the light passing axis of the third polaroid is formed with the horizontal direction
An angle is formed so that the third detection channel is only allowed to be +.>
The light of the included angle passes through, the fourth detection channel is provided with a quarter wave plate and a fourth polaroid, allow only +_ to the horizontal direction>
The light of the included angle passes through, so that the directions of the light waves passing through each detection channel are different, the coordinate points corresponding to the light waves on the Pongche balls are obtained, and the modulation and demodulation circuit board can calculate the polarization state and the polarization state change angle of the input light according to the detection result.
Optimally, the two output ends of the polarization beam splitter are respectively coupled and connected with the two tail fibers of the polarization-maintaining hollow photonic crystal fiber ring through the fiber collimation sealing joint 4, and the fiber collimation sealing joint has a good sealing effect, can prevent light leakage and ensures the accuracy of detection results.
In summary, the optical fiber gyroscope and the optical polarization state sensing rotation-based method thereof provided by the invention construct a miniaturized light path, fully utilize the advantage of good bending performance of the polarization-preserving hollow-core photonic crystal fiber, simultaneously promote the environmental adaptability of the optical fiber gyroscope, reduce the use length of the hollow-core photonic crystal fiber based on the rotation rate measurement technology of the polarization measurement optical fiber gyroscope, avoid the engineering application problem of overlarge transmission loss of the hollow-core photonic crystal fiber, and eliminate the long-term drift error of the gyroscope by adopting a wavelength modulation method, thereby ensuring the characteristics of miniaturization, high precision and high performance of the optical fiber gyroscope.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. The method for sensing and rotating the optical fiber gyroscope based on the light polarization state is characterized by comprising the following steps of: the method comprises the following steps:
step one: light output by the wavelength tunable laser is generated by a polarizer
Linearly polarized light, +.>
The linearly polarized light is decomposed into vertical polarized component light and horizontal polarized component light at the input port of the polarization beam splitter, the vertical polarized component light is transmitted by the polarization beam splitter and then transmitted in a slow axis of a tail fiber at one end of the polarization-preserving hollow photonic crystal fiber ring, the horizontal polarized component light is reflected by the polarization beam splitter and then transmitted in a fast axis of the tail fiber at the other end of the polarization-preserving hollow photonic crystal fiber ring, and the vertical polarized component light and the horizontal polarized component light are respectively returned to the polarization beam splitter;
step two: the vertical polarized component light and the horizontal polarized component light are recombined and combined at the output port of the polarization beam splitter to form polarized light to be detected and projected to the polarization state detection module;
step three: the polarization state detection module detects the light intensity of polarized light to be detected, converts a light intensity signal into a voltage signal and sends the voltage signal to the modulation and demodulation circuit board, the modulation and demodulation circuit board calculates the polarization state and the polarization state change angle of the polarized light to be detected to represent the rotation rate of the hollow photonic crystal fiber gyroscope, and meanwhile, the modulation and demodulation circuit board controls the wavelength tunable laser, so that the wavelength of light output by the wavelength tunable laser is scanned repeatedly at a constant speed within a preset wavelength range to form polarization state modulation, and the drift error of trend items related to the integral polarization state change angle in the gyroscope is eliminated.
2. The method for sensing rotation of a fiber optic gyroscope according to claim 1, wherein the method comprises the steps of: in the third step, when the wavelength of the light output by the wavelength tunable laser is scanned back and forth at a constant speed within a preset wavelength range to modulate the polarization state, the duration of the first scanning half period and the second scanning half period is equal to the transition time of the optical fiber loop
The modulation polarization state change angle is larger than the polarization state change angle of the polarized light to be measured.
3. The method for sensing rotation of a fiber optic gyroscope according to claim 2, wherein the method comprises the steps of: the polarization state detection module detects to-be-detected lightWhen the light intensity of polarized light is measured, the polarized light to be measured is averagely divided into four paths of light signals and projected to four paths of detection channels, and the light wave projected by the first detection channel in the horizontal direction is detected by a first photoelectric detector to be the light intensity signal
And light intensity signal +.>
Converted into voltage signals and sent to a modulation and demodulation circuit board, and a second detection channel projects light waves in the vertical direction, and the light intensity signals are detected as +.>
And light intensity signal +.>
Converted into voltage signals to be sent to a modulation and demodulation circuit board, and the third detection channel projects a signal which is +|with the horizontal direction>
The light wave of the included angle is detected as a light intensity signal by a third photoelectric detector
And light intensity signal +.>
Converted into voltage signals to be sent to a modulation and demodulation circuit board, and the projection of a fourth detection channel is +|horizontal direction>
The light wave with the included angle is detected by a fourth photoelectric detector to be light intensity signal of +.>
And light intensity signal +.>
Converted into voltage signals and sent to a modulation and demodulation circuit board, and the modulation and demodulation circuit board calculates Stokes parameters according to (1) to (4)
、/>
、/>
、/>
Then, the polarization state and the polarization state change angle of the input light are obtained according to Stokes parameters:
wherein:
for inputting the light intensity +.>
Light wave is in bang Gao (ball)>
Coordinates corresponding to the axes of the coordinates>
Ball for light wave at bang
Coordinates corresponding to the axes of the coordinates>
Light wave is in bang Gao (ball)>
The coordinates correspond to the coordinates axially.
4. A method of optical fiber gyro rotation based on light polarization sensing according to claim 3, characterized in that: the first detection channel projects light waves in the horizontal direction through a first polaroid with a horizontal light transmission axis, the second detection channel projects light waves in the vertical direction through a second polaroid with a vertical light transmission axis, and the third detection channel projects light waves in the vertical direction through the light transmission axis
The third polarizer with an angle of projection +.>
The fourth detection channel is a quarter wave plate with a birefringent axis in the horizontal direction and a light transmission axis in the same direction as the horizontal direction>
The fourth polarizer projection of the angle is +.>
Light waves with included angles.
5. The method for sensing rotation of a fiber optic gyroscope according to claim 1, wherein the method comprises the steps of: the horizontal polarized component light is coupled to one end tail fiber of the polarization-maintaining hollow-core photonic crystal fiber ring through the optical fiber collimation sealing joint and is transmitted in the fast axis of the polarization-maintaining hollow-core photonic crystal fiber ring, and the vertical polarized component light is coupled to the other end tail fiber of the polarization-maintaining hollow-core photonic crystal fiber ring through the optical fiber collimation sealing joint and is transmitted in the slow axis of the polarization-maintaining hollow-core photonic crystal fiber ring.
6. A fiber optic gyroscope for performing a method of optical polarization state based sensing rotation of a fiber optic gyroscope according to any of claims 1 to 5, wherein: the device comprises a wavelength tunable laser, a polarizer, a polarization beam splitter, a polarization-preserving hollow-core photonic crystal fiber ring, a polarization state detection module and a modulation and demodulation circuit board, wherein the output end of the wavelength tunable laser is coupled with the input end of the polarizer, the output end of the polarizer is coupled with the input end of the polarization beam splitter, the two output ends of the polarization beam splitter are respectively coupled with two tail fibers of the polarization-preserving hollow-core photonic crystal fiber ring, the detection end of the polarization beam splitter is coupled with the input end of the polarization state detection module, the output end of the polarization state detection module is connected with the input end of the modulation and demodulation circuit board, and the control end of the modulation and demodulation circuit board is connected with the input end of the wavelength tunable laser.
7. The fiber optic gyroscope of claim 6, wherein: the polarization state detection module comprises four detection channels, wherein the first detection channel is sequentially provided with a first polaroid and a first photoelectric detector, the light passing axis of the first polaroid is in the horizontal direction, the second detection channel is sequentially provided with a second polaroid and a second photoelectric detector, the light passing axis of the second polaroid is in the vertical direction, the third detection channel is sequentially provided with a third polaroid and a third photoelectric detector, and the light passing axis of the third polaroid forms a light passing axis with the horizontal direction
The included angle, the fourth detection channel is sequentially provided with a quarter wave plate, a fourth polaroid and a fourth photoelectric detector, the double refraction axis of the quarter wave plate is in the horizontal direction, and the pass-through axis of the fourth polaroid is in the horizontal directionTo get->
And an included angle.
8. The fiber optic gyroscope of claim 6, wherein: the two output ends of the polarization beam splitter are respectively coupled and connected with two tail fibers of the polarization-preserving hollow-core photonic crystal fiber ring through fiber collimation sealing joints.
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