CN103278150A - Optical carrier microwave gyroscopic method for detecting angular velocity - Google Patents

Abstract

The invention discloses a light-borne microwave gyro method for detecting angular velocity. The invention realizes a bidirectional photoelectric oscillator, which uses phase-locked frequency doubling technology to generate forward and reverse bidirectional high-stability microwaves in an optical fiber ring, and is used for measuring the rotational angular velocity. Its core lies in the use of frequency locking technology to lock the microwave oscillation frequency in one direction to a high-stability standard time reference source, stabilize the relative cavity length of the photoelectric oscillator in the other direction, and eliminate the temperature drift and optical parasitic of the optical fiber ring cavity Noise, which greatly improves the signal-to-noise ratio of the two-way oscillating beat frequency signal caused by the Sagnac effect. The light-borne microwave gyroscope method for detecting angular velocity of the present invention has the characteristics of high measurement precision, easy realization and the like.

Description

A Light-borne Microwave Gyro Method for Detecting Angular Velocity

technical field

The invention belongs to the technical field of high-precision gyroscopes, and in particular relates to an optical-borne microwave gyroscope method for detecting angular velocity.

Background technique

In the field of inertial navigation, gyroscopes are usually used to detect the rotational angular velocity of the carrier. Gyroscopes are widely used in the guidance and control of space vehicles, aircraft, missiles, submarines, ships, etc., and play an important role in precision measurement in military, industrial, and scientific fields. There are three main types of common high-precision gyroscopes: mechanical gyroscopes, laser gyroscopes, and fiber optic gyroscopes. Both laser gyroscopes and fiber optic gyroscopes are optical gyroscopes. Although they are not as stable as mechanical gyroscopes, they have the characteristics of compact structure and high sensitivity. They currently occupy most of the market share of high-precision gyroscopes.

The principle of optical gyro detection of angular velocity is based on the Sagnac effect. In the closed optical path, the two beams of light transmitted clockwise (CW) and counterclockwise (CCW) from the same light source have different optical path differences due to rotation, resulting in phase difference or frequency difference. The method of detecting the angular velocity of the interferometric fiber optic gyroscope is to determine the rotational angular velocity of the closed optical path by detecting the phase difference of two beams of light transmitted in the clockwise (CW) and counterclockwise (CCW) directions. Due to the low utilization rate of optical power, temperature error, parasitic noise and other limitations of the traditional interferometric fiber optic gyroscope method for detecting angular velocity, it is difficult to further improve its accuracy. The method of resonant optical gyroscope to detect angular velocity is to determine the rotational angular velocity by detecting the resonant frequency difference between two beams of light in clockwise direction (CW) and counterclockwise direction (CCW). Traditional resonant optical gyroscopes are mainly laser gyroscopes and resonant fiber optic gyroscopes. The laser gyroscope is the earliest and most mature optical gyroscope, and it is also the optical gyroscope with the highest precision at present. However, the disadvantage of this method of detecting angular velocity is that there is a latch-up effect, the system maintenance cost is high, and the production is difficult. The method of resonant fiber optic gyroscope to detect angular velocity has the advantages of short fiber length and easy miniaturization, but it has high requirements on the light source and requires a strong coherent light source with narrow bandwidth. The current resonant fiber optic gyroscope has low measurement accuracy. Difficult to be practical.

Contents of the invention

The object of the present invention is to overcome the shortcomings of the existing optical gyroscope method for detecting angular velocity, and provide an optical-borne microwave gyroscope method for detecting angular velocity.

The method for detecting the rotational angular velocity of the present invention comprises the following steps: a method for detecting the angular velocity of an optically-borne microwave gyroscope, characterized in that the method is implemented on an optically-borne microwave gyroscope for detecting angular velocity, and the optically-borne microwave gyroscope for detecting angular velocity includes the first A laser, an optical beam splitter, a first electro-optical modulator, a first optical coupler, a frequency regulator, an optical fiber ring cavity, a second optical coupler, a first photodetector, a first electric filter, and a first microwave power Divider, first electrical amplifier, second electro-optic modulator, second photodetector, second electrical filter, second microwave power divider, second electrical amplifier, difference frequency detection circuit, frequency divider, standard time source , phase detector, low-pass filter and other parts; the method comprises the following steps:

Step 1: The light output by the first laser passes through the optical beam splitter and is divided into two beams. One beam of light is sent to the first electro-optic modulator along the clockwise direction (CW), and the modulated light is sent to the first optical coupler The light output from the first optical coupler enters the optical fiber ring cavity after passing through the frequency regulator, and the light emitted from the ring cavity is sent to the first photodetector through the second optical coupler to convert the optical signal into an electrical signal. Afterwards, it is sent to the first electric filter, and the filtered microwave electrical signal is sent to the first microwave power splitter. The first microwave power splitter has two outputs, and the first output is connected to the first electro-optical modulator through the electric amplifier. A positive feedback oscillating loop is formed, and the second output is used as a clockwise resonant microwave output, denoted by RF#1.

Step 2. Another beam of light split by the optical beam splitter is sent to the second electro-optic modulator along the counterclockwise direction (CCW), and then enters the optical fiber ring cavity through the second optical coupler, and the light emitted from the ring cavity passes through the frequency The regulator and the first optical coupler are sent to the second photodetector, the optical signal is converted into an electrical signal, and then sent to the second electric filter, and the filtered microwave electrical signal is sent to the second microwave power divider, and the second The microwave power divider has three outputs, the first output is connected to the second electro-optical modulator through the second electric amplifier to form another positive feedback oscillation loop, and the second output is used as a clockwise resonant microwave output, using RF#2 It means that the third output is sent to the phase detector together with the standard time source after being divided by the frequency divider. Frequency locked loop.

。 Step 3. The difference frequency detection circuit detects the frequency difference between the clockwise resonant microwave output RF#1 obtained in step 1 and the counterclockwise resonant microwave output RF#2 obtained in step 2, that is, the beat frequency, which is recorded as

.

Step 4. Through the following formula, the rotational angular velocity can be obtained

；

;

Wherein, S is the area surrounded by the ring optical path, λ is the wavelength corresponding to the microwave oscillation center frequency, and L is the circumference of the ring cavity.

The beneficial effects of the present invention are: the present invention combines the photoelectric oscillator technology and the traditional resonant optical gyro technology to construct an optical-borne microwave gyro method based on the principle of Sagnac effect (Sagnac effect) to detect angular velocity. In this method, highly stable microwave oscillations are obtained by optoelectronic oscillations in long fiber rings instead of traditional light wave oscillations, and are used for the measurement of rotational angular velocity. The great advantage of this method is that the frequency stability of the microwave oscillation signal is extremely high, which can reach 10 ^-13 , and the oscillation frequency in one direction can be locked to a standard time reference source with higher stability, such as an atomic clock, thereby stabilizing the other The relative cavity length of the photoelectric oscillator in one direction eliminates the temperature drift and optical parasitic noise of the fiber ring cavity. At the same time, the accuracy of the difference frequency detection of microwave signals can be much higher than that of optical difference frequency detection. The former can detect the frequency difference through multiple methods such as amplification and frequency multiplication to improve the signal-to-noise ratio, while the latter is detected by photodetectors, so Limited by the size of the optical power, it is difficult to improve the signal-to-noise ratio. The angular velocity detection method provided by the invention has the characteristics of high measurement accuracy, easy implementation, etc., and can meet the requirements of high-precision gyroscope applications.

Description of drawings

Fig. 1 is a kind of system composition block diagram of the light-borne microwave gyro method of applying the present invention to detect angular velocity;

Fig. 2 is another kind of system composition block diagram of the light-borne microwave gyroscope method of applying the present invention to detect angular velocity;

In the figure, a first laser 1, an optical beam splitter 2, a first electro-optical modulator 3, a first optical coupler 4, a frequency regulator 5, a fiber ring cavity 6, a second optical coupler 7, and a first photodetector 8. The first electric filter 9, the first microwave power divider 10, the first electric amplifier 11, the second electro-optic modulator 12, the second photodetector 13, the second electric filter 14, and the second microwave power divider 15. A second electrical amplifier 16, a difference frequency detection circuit 17, a frequency divider 18, a standard time source 19, a phase detector 20, a low-pass filter 21, and a second laser 22. The part of the solid line represents the connection of the optical path, which is the optical path; the part of the dotted line represents the connection of the circuit, which is the electric path.

Detailed ways

The measurement principle of the present invention is briefly described as follows:

In the present invention, lasers, electro-optical modulators, optical couplers, optical fiber ring cavities, photoelectric detectors, electric filters, electric amplifiers, etc. are used to form two bidirectional positive feedback loops, and stable and clean spectrum are obtained by modulation and filter frequency selection. Bi-directional RF/microwave signal for sensing rotational angular velocity. At the same time, the phase-locked loop technology is adopted to control the resonance frequency through feedback adjustment, and the radio frequency/microwave signal of the loop oscillation in one direction is locked to the high-precision standard time reference source.

The invention is based on the photoelectric oscillation technology and belongs to the two-way photoelectric oscillation method. The interval of the start-up mode of the oscillation loop of the photoelectric oscillator, that is, the fundamental frequency f _b , is determined by the delay of the loop to the optical signal, that is, f _b =1/ τ , where τ is the amount of delay, determined by τ = nl/C , where n is the refractive index of the fiber, l is the loop length, and C is the speed of light. Therefore, when the optical length changes, the interval of the oscillation mode changes, and the frequency of the output resonant microwave changes. When the gyroscope rotates at an angular velocity Ω _r , the light propagating clockwise (CW) and counterclockwise (CCW) causes an optical path difference due to the Sagnac effect:

Among them, L _{cw and} L _ccw are the optical path in the clockwise and counterclockwise directions, S is the area surrounded by the circular optical path, C is the speed of light, and Ω _r is the rotational angular velocity.

The frequency difference of the resonant microwave output by the clockwise and counterclockwise bidirectional photoelectric oscillation caused by the Sagnac effect is:

Where λ is the wavelength corresponding to the center frequency of microwave oscillation, and L is the circumference of the ring cavity.

Therefore, the measurement of the rotational angular velocity can be realized by detecting the beat frequency of the radio frequency/microwave signal output by the positive and negative oscillations.

A specific implementation will be described below in conjunction with accompanying drawing 1 . The optical-borne microwave gyroscope method for detecting angular velocity of the present invention is realized on the optical-borne microwave gyroscope for detecting angular velocity. The optical-borne microwave gyroscope for detecting angular velocity includes a first laser 1, an optical beam splitter 2, a first electro-optic modulator 3, An optical coupler 4, a frequency regulator 5, an optical fiber ring cavity 6, a second optical coupler 7, a first photodetector 8, a first electrical filter 9, a first microwave power divider 10, and a first electrical amplifier 11 , second electro-optic modulator 12, second photodetector 13, second electric filter 14, second microwave power divider 15, second electric amplifier 16, difference frequency detection circuit 17, frequency divider 18, standard time source 19. Phase detector 20, low-pass filter 21 and other parts.

The method includes the following steps:

1. The light output by the first laser 1 passes through the optical beam splitter 2 and is divided into two beams of light. One beam of light is sent to the first electro-optic modulator 3 along the clockwise direction (CW), and the modulated light is sent to the first electro-optic modulator 3. Optical coupler 4, the light output from the first optical coupler 4 enters the fiber ring cavity 6 after passing through the frequency regulator 5, and the light emitted from the ring cavity is sent to the first photodetector 8 through the second optical coupler 7, The optical signal is converted into an electrical signal, and then sent to the first electric filter 9, and the filtered microwave electrical signal is sent to the first microwave power divider 10, the first microwave power divider 10 has two outputs, the first output It is connected to the first electro-optic modulator 3 through the electric amplifier 11 to form a positive feedback oscillating loop, and the second output is a clockwise resonant microwave output, represented by RF#1.

2. Another beam of light split by the optical beam splitter 2 is sent to the second electro-optic modulator 12 along the counterclockwise direction (CCW), and then enters the optical fiber ring cavity 6 through the second optical coupler 7, and the light emitted from the ring cavity Then it is sent to the second photodetector 13 through the frequency regulator 5 and the first optical coupler 4, the optical signal is converted into an electrical signal, and then sent to the second electric filter 14, and the filtered microwave electric signal is sent to the second Microwave power divider 15, the second microwave power divider 15 has three outputs, the first output is connected to the second electro-optic modulator 12 through the second electrical amplifier 16, forming another positive feedback oscillation loop, and the second output is used as Clockwise resonant microwave output, represented by RF#2, the third output is sent to the phase detector 20 together with the standard time source 19 after being divided by the frequency divider 18, and the phase detector output is connected to the The frequency regulator 5 is used to adjust the resonant frequency, thereby forming a one-way frequency-locked loop.

3. The beat frequency detection circuit 17 detects the frequency difference between the clockwise resonant microwave output RF#1 obtained in step 1 and the counterclockwise resonant microwave output RF#2 obtained in step 2, that is, the beat frequency, which is denoted as .

4. The rotational angular velocity can be obtained by the following formula

；

;

Wherein, S is the area surrounded by the ring optical path, λ is the wavelength corresponding to the microwave oscillation center frequency, and L is the circumference of the ring cavity.

Accompanying drawing 2 is the system of the second application of the light-borne microwave gyro method of detecting angular velocity of the present invention. The difference from the first embodiment is that the light input in the clockwise and counterclockwise directions is provided by two independent lasers, and the remaining parts are connected Relationships and work processes are the same.

Those skilled in the art can easily make various changes and modifications according to the written description, drawings and claims provided by the present invention without departing from the idea and scope of the present invention defined by the claims. All modifications and equivalent changes made to the above-mentioned embodiments according to the technical idea and essence of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims (1)

1. An optical microwave gyroscope method for detecting angular velocity is characterized in that the method is realized on an optical microwave gyroscope for detecting angular velocity, the optical microwave gyroscope for detecting the angular velocity comprises a first laser (1), an optical beam splitter (2), a first electro-optic modulator (3), a first optical coupler (4), a frequency regulator (5), an optical fiber annular cavity (6), a second optical coupler (7), a first photoelectric detector (8), a first electric filter (9), a first microwave power divider (10), a first electric amplifier (11), a second electro-optic modulator (12), a second photoelectric detector (13), a second electric filter (14), a second microwave power divider (15), a second electric amplifier (16), a difference frequency detection circuit (17), a frequency divider (18), a standard time source (19), a phase discriminator (20), a low-pass filter (21) and the like; the method comprises the following steps:

step 1: light output by a first laser 1 passes through a light beam splitter (2) and is divided into two beams, one beam of light is sent into a first electro-optic modulator (3) along the clockwise direction (CW), the modulated light is sent into a first optical coupler (4), the light output by the first optical coupler (4) enters an optical fiber annular cavity (6) after passing through a frequency regulator (5), the light emitted from the annular cavity is sent into a first photoelectric detector (8) after passing through a second optical coupler (7), an optical signal is converted into an electric signal and then sent into a first electric filter (9), the filtered microwave electric signal is sent into a first microwave power divider (10), the first microwave power divider (10) has two paths of output, the first path of output is connected to the first electro-optic modulator (3) through an electric amplifier (11) to form a positive feedback oscillation loop, and the second path of output is used as clockwise resonance microwave output, denoted by RF # 1;

step 2, the other beam of light split by the optical beam splitter (2) is sent to a second electro-optical modulator (12) along a counterclockwise direction (CCW), then enters an optical fiber ring cavity (6) through a second optical coupler (7), the light emitted from the ring cavity is sent to a second photoelectric detector (13) through a frequency regulator (5) and a first optical coupler (4), an optical signal is converted into an electric signal and then sent to a second electric filter (14), the filtered microwave electric signal is sent to a second microwave power divider (15), the second microwave power divider (15) has three outputs, the first output is connected to the second electro-optical modulator (12) through a second electric amplifier (16) to form another positive feedback oscillation loop, the second output is used as a clockwise resonance microwave output and is represented by RF #2, the third output is sent to a phase discriminator (20) together with a standard time source (19) after being subjected to frequency division by a frequency divider (18), the phase detection output is connected to a frequency regulator (5) after passing through a low-pass filter (21) and is used for regulating the resonant frequency, so that a one-way frequency locking loop is formed;

step 3, a difference frequency detection circuit (17) detects the frequency difference, namely beat frequency, between the clockwise resonance microwave output RF #1 obtained in step 1 and the counterclockwise resonance microwave output RF #2 obtained in step 2, and the frequency difference is recorded as

；

Step 4, obtaining the rotation angular velocity through the following formula

；

Wherein,Sis the area enclosed by the annular light path,λis the wavelength corresponding to the central frequency of the microwave oscillation,Lthe annular cavity has a perimeter.

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