CN107328404B

CN107328404B - Oversized Sagnac interference type fiber-optic gyroscope with N-multiplied effective fiber-optic length

Info

Publication number: CN107328404B
Application number: CN201710631991.7A
Authority: CN
Inventors: 胡宗福
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2017-07-28
Filing date: 2017-07-28
Publication date: 2020-07-28
Anticipated expiration: 2037-07-28
Also published as: CN107328404A

Abstract

The invention relates to an oversized Sagnac interference type fiber-optic gyroscope with the effective fiber length N multiplied, which comprises a Y-shaped branch waveguide modulator, a fiber-optic sensing coil, a fiber-optic coupler, a photoelectric detector, two fiber-optic shunts, an optical amplifier and an optical switch, wherein the fiber length N multiplied is realized by the on-off state of the optical switch and the working state of the optical amplifier. The optical switch, the optical fiber coupler and the Y-shaped branch waveguide modulator are sequentially connected in series, the photoelectric detector is connected with the optical fiber coupler, one input end of each of the two optical fiber splitters is connected with the Y-shaped branch waveguide modulator, the other input end of each of the two optical fiber splitters is connected with the optical amplifier to form a loop, and one output end of each of the two optical fiber splitters is connected with two ends of the optical fiber sensing coil. Compared with the prior art, the invention can increase the effective length of the optical fiber sensing coil by N times, can output Sagnac signals with the effective optical fiber length of 1-N times, and is beneficial to the suppression of nonreciprocal error phase shift.

Description

Oversized Sagnac interference type fiber-optic gyroscope with N-multiplied effective fiber-optic length

Technical Field

The invention relates to an interference type optical fiber gyroscope, in particular to an oversized Sagnac interference type optical fiber gyroscope with the effective optical fiber length N multiplied.

Background

The interference type fiber optic gyroscope is an inertial navigation device based on a Sagnac fiber optic sensing coil and an integrated optical device, is used for autonomously measuring the rotation motion (rotation angular velocity) of a carrier relative to an inertial space, and has a key role in sensing the accurate position and direction of the carrier by an inertial system. An optical gyroscope is an angular velocity sensor based on the Sagnac effect, which is: when the optical loop coil rotates, a phase difference is generated between two beams of light which pass through the same loop clockwise and anticlockwise. An interference type fiber optic gyroscope (IFOG) is characterized in that interference between light transmitted clockwise and anticlockwise through an optical fiber sensing coil converts a phase difference signal into an output light intensity signal, the output light intensity signal is converted into an electric signal through a photoelectric detector, and a gyroscope circuit processes and outputs the rotation angular velocity of a carrier. Therefore, the fiber-optic gyroscope has no moving parts, and the loss of the optical fiber is extremely low, so that the length can reach kilometer level, and the precision can reach 0.001o/h level. And the fiber-optic gyroscope has the advantages of impact resistance, long service life, high precision, price, size and weight, is suitable for large-scale production, expands a plurality of new purposes in industrial and military application, and becomes one of the most rapidly developed inertia devices at present.

The main technical performance indexes of the interference type fiber-optic gyroscope include scale factors, stability and symmetry of the scale factors, angle random walk and zero-offset stability. The main reasons for the stability and symmetry of the scale factor are the stability of the average center wavelength of the light source and the length of the sensing coil, and the linearity of the Y-branch waveguide modulator and the signal processing circuit. The angle random walk is a parameter related to the signal-to-noise ratio, is a measurement of the minimum detectable sensitivity of the gyroscope, and is related to the equalization design and the noise suppression and filtering technology. The zero-bias stability of the gyroscope can be regarded as the credible detection sensitivity of the gyroscope, and the zero-bias error of the gyroscope mainly comes from a polarization-maintaining optical fiber sensing coil, including polarization crosstalk, Faraday effect, and nonreciprocal phase shift caused by time-varying environment temperature and stress (vibration and sound wave). The interference type optical fiber gyroscope consists of a sensing optical gauge head and a modulation and demodulation circuit, wherein the traditional sensing optical gauge head also consists of an integrated Y-shaped branch waveguide modulator and an optical fiber sensing coil. The precision of the fiber-optic gyroscope is mainly determined by a sensing optical gauge head and is also a main error source of the gyroscope.

The accuracy of the interference type fiber-optic gyroscope is mainly determined by the maximum value of the sensitivity and the zero offset error. Sensitivity is the minimum detectable signal magnitude in a gyroscopic system, and the minimum detected signal is the sum of the Sagnac signal and the zero offset error. On the other hand, the minimum detectable phase difference corresponding to the sensitivity of the photoelectric detector is in the micro radian magnitude, and the Sagnac phase shift is in direct proportion to the length and the angular speed of the sensing optical fiber, so that the method for increasing the length of the sensing coil optical fiber is a direct and effective method for improving the sensitivity and the precision of the interference type optical fiber gyroscope. However, the increase of the length of the sensing coil optical fiber not only increases the cost, the volume, the weight and the difficulty of the winding process, but also increases nonreciprocal errors such as polarization crosstalk, Shuppe effect and vibration, and the like, which can increase the zero-offset stability of the interference type optical fiber gyroscope; moreover, the longer the sensing fiber, the greater the loss, which in turn increases the random angular wandering of the interference fiber-optic gyroscope, and ultimately does not achieve the goal of improving the gyroscope accuracy.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide the oversized Sagnac interferometer structure gyroscope with the effective optical fiber length N multiplied, the actual optical fiber sensing coil length is shorter, the multiplied Sagnac phase shift signal is generated through the effective optical fiber length N multiplication, the nonreciprocal error phase shift can be maintained at the size of the actual optical fiber coil, and the contradiction between the increase of the Sagnac phase shift and the zero offset error by the oversized sensing optical fiber coil is solved. An optical amplifier is used for compensating the annular loss, and the contradiction between increasing Sagnac phase shift and reducing angle random walk is solved.

The purpose of the invention can be realized by the following technical scheme:

The utility model provides an effective optic fibre length N multiplicates super large Sagnac interference type fiber-optic gyroscope, includes Y shape branch waveguide modulator, optic fibre sensing coil, light source, fiber coupler and photoelectric detector, still includes photoswitch, two fiber splitter and light amplifier, an input of two fiber splitter all is connected with Y shape branch waveguide modulator, and another input all is connected with light amplifier and constitutes the loop that circles, and the output of two fiber splitter is connected with the both ends of optic fibre sensing coil respectively, two fiber splitter, light amplifier and fiber sensing coil form the optical loop, photoswitch connects between light source and fiber coupler.

The optical switch and the optical amplifier are in a synchronous conversion state, when the optical switch is in an on state, the optical amplifier is in an attenuation state, and when the optical switch is in an off state, the optical amplifier is in a gain state, so that the effective optical fiber length N is multiplied.

The on-time of the optical switch is equal to the transmission time tau of the optical fiber sensing coil, the off-time is (N-1) tau, and the period is N tau.

The method for realizing the effective optical fiber length N multiplication specifically comprises the following steps:

The optical switch is in an open state, the optical amplifier is in an attenuation state, the light source outputs clockwise light and anticlockwise light through the optical fiber coupler and the Y-branch waveguide modulator, the clockwise light and the anticlockwise light respectively enter the optical fiber sensing coil through the two optical fiber shunts correspondingly and then return to the two optical fiber shunts to be divided into two paths of output, the optical switch is converted into a break state, the optical amplifier is converted into a gain state, one path of output forms 1-time loop output through the Y-branch waveguide modulator, the other path of output returns to the optical fiber sensing coil through the two optical fiber shunts after passing through the optical amplifier, and N-time loop output is formed in a circulating mode.

And the photoelectric detector sequentially detects and obtains gyro signals with the multiplication number of the effective optical fiber length from 1 to N.

The optical amplifier is an erbium-doped fiber amplifier.

Compared with the prior art, the invention has the following advantages:

(1) The invention inserts a loop circuit between the CW and CCW directions between the Y-branch waveguide modulator and the optical fiber sensing coil, so that the effective optical fiber length of the sensing coil is increased by N times, the Sagnac phase shift is increased by N times, the sensitivity of the gyroscope is increased by N times, and the actual optical fiber sensing coil with the length of several kilometers can be multiplied to the effective length of dozens to hundreds of kilometers.

(2) The effective fiber length multiplication number is sequentially output by the gyro signals from 1 to N, so that the nonreciprocal error phase shift information in different multiplication processes can be obtained, and the nonreciprocal error phase shift in the N multiplication gyro signals is compensated to the size of an actual fiber coil.

(3) The actual volume and weight of the fiber coil are several kilometers, and the ultra-large Sagnac interferometer can be realized by using a coil winding process of several kilometers.

Drawings

FIG. 1 is a schematic structural view of the present invention;

Fig. 2 is a timing chart showing two states of on and off of the optical switch and two states of attenuation and amplification of the optical amplifier, wherein (a) is a timing chart showing the state of the optical switch, (b) is a timing chart showing the state of the optical amplifier, and (c) is a timing chart showing the state of the output optical power.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

As shown in fig. 1, this embodiment provides an oversized Sagnac interferometric fiber optic gyroscope with an effective fiber length N multiplied, which includes a Y-branch waveguide modulator 4, a fiber sensing coil 8, a light source 1, a fiber coupler 3, a photodetector 9, an optical switch 2, two

fiber splitters

5 and 6, and an optical amplifier 7, wherein one input ends of the two

fiber splitters

5 and 6 are connected to the Y-branch waveguide modulator 4, the other input ends are connected to the optical amplifier 7 to form a loop, output ends of the two

fiber splitters

5 and 6 are connected to two ends of the fiber sensing coil 8, the two

fiber splitters

5 and 6, the optical amplifier 7 and the fiber sensing coil 8 form an optical loop, and the optical switch 2 is connected between the light source 1 and the fiber coupler 3.

The optical switch 2 and the optical amplifier 7 synchronously change states, when the optical switch 2 is in an on state, the optical amplifier 7 is in an attenuation state, and when the optical switch 2 is in an off state, the optical amplifier 7 is in a gain state, so that the effective optical fiber length N is multiplied. The on time of the optical switch is equal to the transmission time tau of the optical fiber sensing coil, the off time is (N-1) tau, and the period is Ntau. The photoelectric detector 9 sequentially detects and obtains gyro signals with the multiplication number of the effective optical fiber length from 1 to N. In this embodiment, the optical amplifier 7 is an erbium-doped fiber amplifier. The fiber coupler 3 is a 3dB fiber coupler.

As shown in fig. 2, a light source 1 outputs clockwise CW and counterclockwise CCW through an optical switch 2 in an on state, a fiber coupler 3 and a Y-branch waveguide modulator 4, CW light enters a fiber sensing coil 8 through a fiber splitter 5, when reaching a fiber splitter 6, the optical switch 2 is turned off from on, an optical amplifier 7 is turned on from attenuation to gain, the output of the fiber splitter 6 is divided into two paths, one path reaches a photodetector 9 through the Y-branch waveguide modulator 4 and the fiber coupler 3 to become a 1-fold gyro signal output, the other path is amplified by an optical amplifier 7 to compensate ring loss, then enters the fiber sensing coil 8 again through the fiber splitter 5, when reaching the fiber splitter 6, the optical switch 2 is kept off, the optical amplifier 7 keeps the gain state, the output of the fiber splitter 6 is divided into two paths, one path reaches the photodetector 9 through the Y-branch waveguide modulator 4 and the fiber coupler 3 to become a 2-fold gyro signal output, the other path is amplified by the optical amplifier 7 to compensate the ring loss, enters the optical fiber sensing coil 8 again through the optical fiber branching unit 5, when reaching the optical fiber branching unit 6, the optical switch 2 keeps the off state, the optical amplifier 7 keeps the gain state, the cycle is repeated, until the moment of Ntau, the optical amplifier 7 is converted into the attenuation state, two paths of output of the optical fiber branching unit 6 are obtained, one path reaches the photoelectric detector 9 through the Y-branch waveguide modulator 4 and the optical fiber coupler 3 to become the output of the N-times gyro signal, and the other path is approximately 0 after the optical amplifier 7 attenuates by about 60 dB. Meanwhile, the optical switch 2 is turned to the on state, clockwise CW and counterclockwise CCW light are input again, the cycle is repeated, and the gyro signals are output by 1, 2, … and N times according to the time slot output again.

The above examples are only for illustrating the technical idea and features of the present invention, and should not be construed as limiting the scope of the present invention. All according to the inventive idea: inserting a loop circuit between the CW direction and the CCW direction between the Y-branch waveguide modulator and the fiber sensing coil to realize equivalent transformation or modification of Sagnac phase shift multiplication is also within the scope of the present invention.

Claims

1. An oversized Sagnac interference type fiber-optic gyroscope with the effective fiber length N multiplied comprises a Y-shaped branch waveguide modulator (4), a fiber-optic sensing coil (8), a light source (1), a fiber-optic coupler (3) and a photoelectric detector (9), it is characterized by also comprising an optical switch (2), two optical fiber splitters (5 and 6) and an optical amplifier (7), one input ends of the two optical fiber shunts (5, 6) are connected with the Y-shaped branch waveguide modulator (4), the other input ends are connected with the optical amplifier (7) to form a loop circuit, the output ends of the two optical fiber shunts (5, 6) are respectively connected with two ends of the optical fiber sensing coil (8), the two optical fiber splitters (5, 6), the optical amplifier (7) and the optical fiber sensing coil (8) form an optical loop, the optical switch (2) is connected between the light source (1) and the optical fiber coupler (3);

The optical switch (2) and the optical amplifier (7) synchronously change states, when the optical switch (2) is in an on state, the optical amplifier (7) is in an attenuation state, and when the optical switch (2) is in an off state, the optical amplifier (7) is in a gain state, so that the effective optical fiber length N is multiplied;

The optical switch (2) is in an on state, the optical amplifier (7) is in an attenuation state, the light source (1) outputs clockwise light and anticlockwise light through the optical fiber coupler (3) and the Y-branch waveguide modulator (4), the clockwise light and the anticlockwise light respectively enter the optical fiber sensing coil (8) through the two optical fiber shunts (5, 6) and then return to the two optical fiber shunts (5, 6) to be divided into two paths of output, at the moment, the optical switch (2) is turned into an off state, the optical amplifier (7) is turned into a gain state, one path of output forms 1 time of loop output through the Y-branch waveguide modulator, the other path of output returns to the optical fiber sensing coil (8) through the two optical fiber shunts (5, 6) after passing through the optical amplifier (7) to form N times of loop output, the on time of the optical switch is equal to the transmission time tau of the optical fiber sensing coil, and the off time is (N-1), the period is N τ;

And the photoelectric detector (9) sequentially detects and obtains gyro signals with the effective optical fiber length multiplication number from 1 to N.

2. An oversized Sagnac interferometric fiber optic gyroscope with N-fold effective fiber length according to claim 1, characterized in that said optical amplifier (7) is an erbium doped fiber amplifier.