CN110940991A - Large-distance and micro-relative-distance measuring instrument based on OEO (optical emission output) rapid switching - Google Patents
Large-distance and micro-relative-distance measuring instrument based on OEO (optical emission output) rapid switching Download PDFInfo
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Abstract
The invention discloses a large-distance and micro-relative-distance measuring instrument based on OEO (optical output and input) quick switching, which comprises an instrument internal delay switching module, a loop switching module and a frequency metering and distance conversion module, wherein the instrument internal delay switching module and the loop switching module are connected into a double-cavity switching photoelectric oscillator structure through cables and optical fibers, and the instrument internal delay switching module is connected with the frequency metering and distance conversion module. The invention applies the accumulation amplification principle to the measuring scheme of tiny relative distance change in a large distance range by utilizing OEO, can measure tiny relative distance in a large distance (km magnitude) range, and has measuring precision reaching mum magnitude; the distance measuring system is simple and easy to operate, can be widely applied to the fields of industrial measurement and control, precision instrument manufacturing and the like, and has good application prospect in the military field due to strong anti-interference capability and good concealment.
Description
Technical Field
The invention relates to the field of optical carrier microwave distance measurement, in particular to a large-distance and micro-relative-distance measuring instrument based on OEO (optical-electrical-optical-output) rapid switching.
Background
The development of the measurement technology is the premise and the basis of all scientific and technical development, the length is taken as one of 7 basic physical quantities, the length and the angle measurement form the basis of all geometric quantity measurement, and the development determines the capability of human beings to know the world and transform the world and is also a mark for measuring the technical level of measurement in one country. In recent years, with the development of science and technology, scientific research and production construction have brought more and more urgent demands on large-distance and micro-relative distance measurement, such as: the production, assembly and operation monitoring of large-scale equipment and components, the requirements of the fields of space exploration, navigation and the like in China and the like.
The traditional laser ranging principle is divided into 3 types: the method comprises a pulse time-of-flight method, a phase method and an interference method, wherein the pulse time-of-flight method ranging is the earliest application of laser in the ranging field, and a large testing range is realized by utilizing the characteristics of extremely short duration and large instantaneous power of laser pulse, but the testing precision and resolution are very low, so that the development and application of the laser are limited; the phase method laser ranging is to measure the distance of a measured target by using distance information contained in the phase difference between emitted modulated light and received light reflected by the measured target, wherein the measuring precision is influenced by the modulation frequency and the phase discrimination precision, a fuzzy distance exists, and a multi-frequency modulation method is needed to expand the measuring range; interferometric ranging is a classical precision ranging method, which is also a phase method ranging in principle, but it does not measure the phase difference of laser modulation signals, but measures the phase interference of light waves themselves. Recently, the high-speed development of the femtosecond mode-locked laser provides more selection schemes for high-precision long-distance absolute distance measurement, and the measurement precision and the measurement range of the interferometric measurement technology can be improved by utilizing the unique advantages of the frequency comb in terms of line width and absolute frequency position, however, the method greatly depends on the stability of pulse repetition rate and the detection precision of pulse envelope phase.
At present, the method for measuring large distance and high precision relative length mainly converts the distance measurement into the time measurement (flight time method) or the phase measurement (phase measurement method and interferometry), obtains more accurate measurement results by continuously improving the measurement resolution, has higher requirement on the measurement resolution, has higher technical difficulty and has higher sensitivity to other interference factors. The measurement precision of the method for measuring the relative distance of a large distance (km magnitude) is difficult to reach the mum magnitude. In fact, there is an effective measurement method, which can obtain a very high precision measurement result by amplifying the physical quantity to be measured and then measuring the physical quantity, i.e. by using a relatively low resolution measurement method, i.e. by using an accumulation amplification principle, such as a classical pendulum cycle test, and by using a multi-cycle swing time test, even if a common stopwatch is used, an extremely high precision measurement result can still be obtained.
For the measurement of large distance and micro relative distance, the following ideas can be adopted: the measured distance forms a resonant cavity, and after resonance is formed, the cavity length (namely the measured length) determines the fundamental frequency f of the resonant cavitybAt this time, the detection accuracy of the fundamental frequency is the length measurement accuracy. Considering that the fundamental frequency is the inverse of the round-trip time of the signal in the cavity, this means that the fundamental frequency measurement is practically as difficult as the time-of-flight method, e.g. 1 μm accuracy at (fundamental frequency 300kHz) and 0.0006Hz for frequency detection. But when the cavity oscillates at higher harmonics, the actual resonant frequency fN＝N×fbThe change in fundamental frequency is amplified by a factor of N, again to an accuracy of 1 μm over a length of 500m, when the resonant frequency oscillates at 30GHz (N-10)5) The measurement accuracy of the frequency is only 60 Hz. To achieve the above assumption, there are two requirements for the resonant cavity:
(1) the measured distance forms a portion of the cavity length;
(2) oscillating at high enough harmonics to ensure sufficient amplification factor;
optoelectronic oscillators (OEOs) are a new type of oscillator developed in recent years that requires a long resonant cavity to provide high stored energy; generally, the oscillation is carried out at a frequency of tens of GHz to dozens of GHz, the output spectrum purity is very high and can reach the mHz magnitude, and the two requirements are completely met.
Generally, people adopt OEO to measure absolute distance with wide range and high precision, and in order to obtain the length of the distance to be measured, namely, accurately obtain fNAnd fbThe value of (a), the system is required to stabilize single-mode oscillation; since the OEO system uses long length optical fiber (usually in km level) for energy storage, the cavity length is easily changed by the influence of ambient temperature and stressIn order to ensure the accuracy of the measurement precision, the cavity length of the reference loop is usually controlled by adopting a method of controlling a piezoelectric ceramic optical fiber stretcher by using a phase-locked loop, the theoretical control precision of the cavity length needs to reach the order of mum, a plurality of piezoelectric ceramic optical fiber stretchers with different stretching amounts and precisions and a complex control algorithm are needed, and the complexity of the system is increased. In addition, in order to ensure single-mode oscillation starting of the whole system, a system structure adopting a polarization double-ring or a wavelength double-ring is generally required to simulate a side mode, so that the cost and the complexity of the whole system are greatly increased.
However, a measurement method based on an OEO large-distance high-precision relative length is not proposed so far, and an effective solution is not proposed at present aiming at the problems in the prior art.
Disclosure of Invention
The invention aims to provide a large-distance and micro-relative-distance measuring instrument based on OEO (optical electronic optical output) quick switching, which aims to solve the problems in the prior art, and can detect the micro-relative-distance change of a large distance (km magnitude) by applying an accumulation amplification principle to a high-precision relative-distance length measuring scheme by utilizing OEO, wherein the detection precision can reach the mum magnitude.
In order to achieve the purpose, the invention provides the following scheme:
a large-distance and micro-relative-distance measuring instrument based on OEO (optical output) quick switching comprises an instrument internal delay switching module, a loop switching module and a frequency metering and distance conversion module, wherein the instrument internal delay switching module and the loop switching module are connected through a cable and an optical fiber to form a double-cavity switching photoelectric oscillator structure, and the frequency metering and distance conversion module is connected with the instrument internal delay switching module.
Preferably, the internal delay switching module of the instrument includes: laser instrument, polarization controller, electro-optic modulator, three-port circulator, light amplifier, photoelectric detector, band-pass filter, microwave amplifier, the electric coupler that sets gradually, the electric coupler includes the first output port of electric coupler, electric coupler second output port, the first output port of electric coupler is connected with the radio frequency input port of electro-optic modulator, electric coupler second output port is connected with frequency measurement and distance conversion module, loop switching module includes photoswitch, photoswitch is connected with test reflector and at least one first collimater respectively, first collimater corresponds with first measurement reflector.
Preferably, the three-port circulator includes a first circulator port, a second circulator port, and a third circulator port, the optical switch includes an optical switch input port, a test optical switch output port, and a first measurement optical switch output port corresponding to the first collimator, where the first circulator port is connected to the output end of the electro-optical modulator, the third circulator port is connected to the input end of the optical amplifier, the second circulator port is connected to the optical switch optical input port through the wide-range analog fiber, the test optical switch output port is connected to the test mirror, and the first measurement optical switch output port is connected to the first collimator.
Preferably, the laser is a semiconductor laser or a light laser.
Preferably, the electro-optical modulator is a lithium niobate intensity modulator, a lithium niobate phase modulator, or an electro-absorption modulator of a semiconductor structure.
Preferably, the optical amplifier is an erbium-doped optical fiber amplifier, an ytterbium-doped optical fiber amplifier, a thulium-doped optical fiber amplifier or a semiconductor optical amplifier.
Preferably, the test mirror and the first measurement mirror are devices or structures having light intensity reflection and certain transmission characteristics.
Preferably, the test reflector and the first measurement reflector are coated reflectors, reflectors formed by a three-port circulator and an electric coupler, reflectors built by Sagnac rings, or Faraday polarizers.
The invention discloses the following technical effects:
1. the invention applies the accumulation amplification principle to the measurement of micro relative distance change in a large distance range by utilizing the OEO, utilizes the characteristics of long OEO resonant cavity, high spectral purity and high resonant frequency, and is to be measuredMeasured change is amplified by 105～106The measurement accuracy can reach the micron order by utilizing the OEO to measure the tiny relative distance in a large-distance (km order) range;
2. although the resonance can effectively improve the testing precision, the measured distance and the instrument form a resonant cavity together, and when the measured distance and the instrument drift, the resonant frequency is changed. Therefore, the drift of the instrument and the change of the measured distance cannot be distinguished by a single resonant cavity, and the influence of the drift of the measuring instrument on the measuring precision is further aggravated by considering the long energy storage optical fiber structure of the OEO; the invention adopts a structure of switching the OEO at an ultra-high speed, the time delay inside the range finder forms an OEO as a test OEO, the time delay inside the range finder and different distances to be tested form other measurement OEOs, the test OEO and the measurement OEO are switched and started to vibrate, when the switching frequency reaches the kHz magnitude, the time delay inside the range finder can be regarded as unchanged within millisecond time, the influence of environmental change on the stability of the time delay inside the range finder is eliminated, and the measurement precision is ensured;
3. the distance measuring system is simple and easy to operate, based on the advantages, the distance measuring system is widely applied to the fields of industrial measurement and control, precision instrument manufacturing and the like, has strong anti-interference capability and good concealment, and has excellent application prospect in the military field.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a schematic structural diagram according to a first embodiment of the present invention;
FIG. 2 is a schematic structural diagram according to a second embodiment of the present invention;
wherein: 1 is an internal delay switching module of the instrument; 2 is a loop switching module; 3 is a frequency measurement and distance conversion module; 4 is a laser; 5 is a polarization controller; 6 is an electro-optic modulator; 7 is a three-port circulator; 7a is a first circulator port; 7b is a second circulator port; 7c is a third circulator port; 8 is an optical amplifier; 9 is a photoelectric detector; 10 is a band-pass filter; 11 is a microwave filter; 12 is an electric coupler; 12a is an electrical coupler first output port; 12b is an electrical coupler second output port; 13 is a wide range analog fiber; 14 is an optical switch; 14a is an optical switch input port; 14b0 is the output port of the test optical switch; 14b1 is the first measuring optical switch output port; 14bn is the output port of the (n + 1) optical switch; 151 is a first collimator; 15n is an nth collimator; 160 is a test mirror; 161 is a first measuring mirror; 16n is the nth measurement mirror.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 1 and 2, the invention discloses a large-distance and micro-relative-distance measuring instrument based on OEO fast switching, which comprises an instrument internal delay switching module 1, a loop switching module 2 and a frequency metering and distance conversion module 3, wherein the instrument internal delay switching module 1 and the loop switching module 2 are connected through a cable and an optical fiber to form a double-cavity switching photoelectric oscillator structure, the frequency metering and distance conversion module 3 is connected with the instrument internal delay switching module 1, and the frequency metering and distance conversion module 3 is used for recording system output frequency and further calculating measurement distance information according to the system output frequency.
Further optimize the scheme, the module 1 is switched in the inside time delay of instrument includes: the laser 4, the polarization controller 5, the electro-optical modulator 6, the three-port circulator 7, the optical amplifier 8, the photoelectric detector 9, the band-pass filter 10, the microwave amplifier 11 and the electric coupler 12 are arranged in sequence; the electric coupler 12 includes a first output port 121 of the electric coupler, and a second output port 122 of the electric coupler, the first output port 121 of the electric coupler is connected to the rf input port of the electro-optical modulator, the second output port 122 of the electric coupler is connected to the frequency measurement and distance conversion module 3, the loop switching module 2 includes an optical switch 14, the optical switch 14 is connected to the test mirror 160 and at least one first collimator 151, respectively, and the first collimator 151 corresponds to the first measurement mirror 161.
In a further optimized solution, the three-port circulator 7 includes a first circulator port 71, a second circulator port 72, and a third circulator port 73, the optical switch 14 includes an optical switch input port 14a, a test optical switch output port 14b0, and a first measurement optical switch output port 14b1 corresponding to the first collimator 151, wherein the first circulator port 71 is connected to the output of the electro-optical modulator 6, the third circulator port 73 is connected to the input of the optical amplifier 8, the second circulator port 72 is connected to the optical switch input port 14a through a wide-range analog fiber 13, the test optical switch output port 14b0 is connected to the test mirror 160, and the first measurement optical switch output port 14b1 is connected to the first collimator 151.
In a further optimized scheme, the laser 4 is a semiconductor laser or a light laser.
In a further optimized scheme, the electro-optical modulator 6 is a lithium niobate intensity modulator, a lithium niobate phase modulator or an electro-absorption modulator with a semiconductor structure.
In a further optimized solution, the loop switching module 2 includes: the optical fiber measuring device comprises a1 xn optical switch 14, a first collimator 14b1 …, an nth collimator 14bn, a testing reflector 160, a first measuring reflector 161 …, an nth measuring reflector 16n, wherein the testing reflector 160 and the first measuring reflector 161 are devices or structures with square reflection and certain projection characteristics, and can be reflectors formed by a three-port circulator 7 and a Faraday 12, or reflectors of a Sagnac ring structure formed by a non-3 dB optical fiber coupler, or optical fiber reflectors with coated optical fiber end faces with certain transmission action, or optical rotation third mirrors; the optical amplifier 8 is a device having an amplification effect on an optical signal, and may be an erbium-doped optical fiber amplifier, an ytterbium-doped optical fiber amplifier, a thulium-doped optical fiber amplifier, or a semiconductor optical amplifier; the internal delay switching module 1 and the loop switching module 2 of the instrument are connected into a multi-cavity switching photoelectric feedback structure through optical fibers and cables, and the length of a resonant cavity is rapidly switched between the inherent length of the instrument and the sum of the inherent length of the instrument and the distances to be measured along with the rapid switching of the optical switch from 1 to n.
The resonant frequency of an OEO is determined by two factors: 1) an oscillation mode determined by loop delay; 2) selecting a mode device; the distance to be measured is used as a part of an OEO oscillation loop, and the distance to be measured can be deduced by measuring the resonant frequency.
The interval of the oscillation starting mode of the OEO oscillation loop, i.e. the fundamental frequency fbThe delay of the optical signal is determined by the loop, namely: f. ofb1/tau, where tau is the delay, which can be divided into two parts, a fixed delay tau consisting of a circuit and a fixed fibre0And a delay τ determined by the distance L to be measuredL＝nLAnd c, wherein n is the refractive index and c is the speed of light in vacuum. Thus, it is possible to obtain:
due to f in the oscillatorbThe integral multiple frequency can satisfy the oscillation condition of OEO, the actual resonant frequency f of OEONThe filter is obtained by mode selection of a band-pass filter, and meets the following requirements: f. ofN＝NfbWherein N is a natural number, and the actual resonant frequency fNAt a fundamental frequency fbN times, for example: an accuracy of 1 μm is to be achieved over a length of 500m (fundamental frequency 300kHz), for the fundamental frequency fbThe frequency detection precision of the frequency detection circuit is 0.0006 Hz; under the condition of 30GHz, the N value is 105The magnitude of the fundamental frequency variation caused by the distance of the relation is amplifiedN times (a 1 μm change would result in a 60Hz change in resonant frequency), it can be seen that: under the same observation condition and test precision, directly measuring fbIs far less than the value of measurement fNAnd N and fbThe obtained precision is high, and the measurement error is greatly reduced, so that the distance L to be measured can be obtained by the following formula:
it follows that the accuracy of the measurement of the distance L to be measured depends in fact on two factors: f. ofNAnd the correctness of the value of N, wherein fNThe theoretical accuracy (assuming that the test accuracy is high enough) of the present invention depends on the spectral purity of the oscillator output frequency, and the present invention can obtain high quality microwave source output with spectral purity of mHz using an OEO structure. By
It can be seen that the distance sum f to be measuredNThe correlation of L can be accurately measured as long as the correctness of N is ensured.
The value of N can be measured by rough measurement fbThe method of (1) yields:
wherein
The symbol represents a rounding operation, fb*Representing the fundamental frequency, fbA coarse measurement of. By measuring fNAnd fb*To find the corresponding N value and then to find fbAnd (3) accurate value, obtaining ring length information and realizing high-precision measurement of distance.
Example one
As shown in fig. 1, the large-distance and micro-relative-distance measuring instrument based on OEO fast switching includes an instrument internal delay switching module 1, a loop switching module 2, and a frequency measurement and distance conversion module 3, wherein the instrument internal delay switching module 1 includes: the laser 4, the polarization controller 5, the electro-optical modulator 6, the three-port circulator 7, the optical amplifier 8, the photoelectric detector 9, the band-pass filter 10, the microwave amplifier 11 and the electric coupler 12 are arranged in sequence; the electric coupler 12 is connected with a radio frequency input port of the electro-optical modulator 6 through a first output port 121 of the electric coupler, is connected with the frequency metering and distance conversion module 3 through a second output port 122 of the electric coupler, the frequency metering and distance conversion module 3 is connected and used for recording the output frequency of the system, the measured distance information is further calculated according to the output frequency of the system, and the three-port circulator 7 is respectively connected with the wide-range analog optical fiber 13 and the optical amplifier 8. The loop switching module 2 includes an optical switch 14, a first collimator 161, a testing mirror 160, and a first measuring mirror 161, the second circulator port 72 is connected to the optical switch input port 14a through a wide range analog optical fiber 13, the testing optical switch output port 14b0 is connected to the testing mirror 160, the first measuring optical switch output port 14b1 is connected to the first collimator 151, and the first collimator 151 is aligned with the first measuring mirror 161 through a distance to be measured a1, where the optical switch 14 is a1 × 2 optical switch; the optical switch input port 14a is a1 × 2 optical switch input port; the test optical switch output port 14b0 is a1 × 2 test optical switch output port; the first measurement optical switch output port 14b1 is a1 × 2 first measurement optical switch output port; the laser 4 is a fiber laser; the electro-optical modulator 6 is a lithium niobate intensity modulator; the optical amplifier 8 is a semiconductor optical amplifier; the optical switch 14 is a1 × 2 acousto-optic switch; the test mirror 160 … n th measurement mirror 16n is a faraday rotator mirror;
when in specific use: an optical signal emitted by the laser 4 enters the electro-optical modulator 6 through the polarization controller 5, and the modulated optical signal enters the three-port circulator 7 through the first circulator port 71 and then is output from the second circulator port 72 to enter the optical switch 14; when the optical switch 14 is turned on at its test optical switch output port 14b0, the optical signal is directly injected onto the test mirror 160 directly connected to the test optical switch output port 14b0, and then reflected back to the test optical switch output port 14b0, passes through the optical switch 14, enters the three-port circulator 7 through the second circulator port 72, and then is output through the third circulator port 73 and enters the optical amplifier 8;
when the optical switch 14 turns on its first measurement optical switch output port 14b1, the optical signal passes through the distance to be measured a1, is injected onto the first measurement mirror 161 and then reflected back to the first measurement optical switch output port 14b1, after passing through the optical switch 14, entering the three-port circulator 7 through the second circulator port 72, then entering the optical amplifier 8 after being output from the third circulator port 73, the optical signal amplified by the optical amplifier 8 is injected into the photodetector 9, the optical signal is converted into a microwave signal after passing through the photodetector 9, and after passing through the band-pass filter 10 and the microwave amplifier 11, the microwave signal is divided into two parts by the electric coupler, namely a first output port 121 of the electric coupler and a second output port 122 of the electric coupler, wherein the first output port 121 of the electric coupler is used as a modulation signal of the modulator to drive the electro-optical modulator 6 to form a closed feedback loop, and the second output port 122 of the electric coupler is used as an output signal to connect with a frequency metering and distance conversion module; when the optical switch 14 is turned on at its test optical switch output port 14b0, the feedback loop forms an OEO, defined as the test OEO, when the output signal is fN0For calculating the cavity length L of the test OEO0(ii) a When the optical switch 14 is turned on at its first measurement optical switch output port 14b1, the feedback loop forms an OEO, defined as the measurement OEO, when the output signal is fN1For calculating the cavity length L of the first measurement OEO1Wherein the length of the distance to be measured is L1-L0。
Example two
As shown in fig. 2, the large-distance and micro-relative-distance measuring instrument based on OEO fast switching includes an internal delay switching module 1, a loop switching module 2, and a frequency measurement and distance conversion module 3, wherein the internal delay switching module 2 includes: the laser 4, the polarization controller 5, the electro-optical modulator 6, the three-port circulator 7, the optical amplifier 8, the photoelectric detector 9, the band-pass filter 10, the microwave amplifier 11 and the electric coupler 12 are arranged in sequence; the electric coupler 12 is connected with the radio frequency input port of the electro-optical modulator 6 through a first output port 121 of the electric coupler, and is connected with the frequency measurement and distance conversion module 3 through a second output port 122 of the electric coupler, the three-port circulator 7 is connected with the wide range analog optical fiber 13 and the optical amplifier 8, respectively, the loop switching module 2 includes an optical switch 14, a first collimator 151, … … n-th collimator 15n, a testing mirror 160, a first measuring mirror 161, … … n-th measuring mirror 16n, a third circulator port 73 is connected with an optical switch input port 14a, a testing optical switch output port 14b0 is connected with the testing mirror 160, a first measuring optical switch output port 14b1 is connected with the first collimator connection 151, an n-th optical switch output port 14bn of … … … is connected with the n-th collimator 15n, the first collimator 151 is aligned with the first measuring mirror 160 through a first distance to be measured a1, wherein the optical switch 14 is a1 xn optical switch; the optical switch input port 14a is a1 xn optical switch input port; the test optical switch output port 14b0 is a1 xn test optical switch output port; the first measurement optical switch output port 14b1 is a1 xn first measurement optical switch output port; the laser 4 is a Bragg feedback type semiconductor laser; the electro-optical modulator 6 is a lithium niobate intensity modulator; the optical amplifier 8 is an erbium-doped fiber amplifier; the optical switch 14 is a1 xn magneto-optical switch; the test mirror 160 … n th measurement mirror 16n is a faraday rotator mirror;
when in specific use: an optical signal emitted by the laser 4 enters the electro-optical modulator 6 through the polarization controller 5, and the modulated optical signal enters the three-port circulator 7 through the first circulator port 71 and then is output from the second circulator port 72 to enter the optical switch 14; when the optical switch 14 is turned on at its test optical switch output port 14b0, the optical signal is directly injected onto the test mirror 160 directly connected to the test optical switch output port 14b0, and then reflected back to the test optical switch output port 14b0, passes through the optical switch 14, enters the three-port circulator 7 through the second circulator port 72, and then is output through the third circulator port 73 and enters the optical amplifier 8;
when the optical switch 14 is turned on at its first measurement optical switch output port 14b0, the optical signal passes through the distance to be measured a1, is injected onto the first measurement mirror 161 and then reflected back to the first measurement optical switch output port 14b1, passes through the optical switch 14, enters the three-port circulator through the second circulator port 72, and then passes through the third circulatorThe output of the port enters an optical amplifier; when the optical switch is switched on at the output port of the (n + 1) th optical switch, the optical signal passes through the nth section of space to be measured for the distance AnThen, the optical signal is injected into the nth measuring reflector and then reflected back to the (n + 1) th optical switch output port, enters the three-port circulator 7 through the second circulator port 72 after passing through the optical switch 14, enters the optical amplifier 8 after being output through the third circulator port 73, and is injected into the photodetector 9 after being amplified by the optical amplifier 8; the optical signal is converted into a microwave signal through the photoelectric detector 9, then the microwave signal passes through the band-pass filter 10 and the microwave amplifier 11 and is divided into two parts by the electric coupler, namely, a first output port 121 of the electric coupler and a second output port 122 of the electric coupler, the first output port 121 of the electric coupler is used as a modulation signal of the modulator to drive the electro-optical modulator 6 to form a closed feedback loop, and the second output port 122 of the electric coupler is used as an output signal to be connected with the frequency metering and distance converting module 3; when the optical switch 14 is turned on at its test optical switch output port 14b0, the feedback loop forms an OEO, defined as the test OEO, when the output signal is fN1For calculating the cavity length L of the test OEO1(ii) a When the optical switch is connected with the output port of the optical switch, the feedback loop forms an OEO which is defined as a first measurement OEO, and the output signal is fN2For calculating the cavity length L of the first measurement OEO2Wherein the length of the distance to be measured in the first space is L2-L1(ii) a When the optical switch is connected with the output port of the (n + 1) th optical switch, the feedback loop forms an OEO defined as the n-th measurement OEO, and the output signal is fNnFor calculating the cavity length L of the n-th measured OEOnWherein the length of the distance to be measured in the nth section of space is Ln-L1。
In summary, by means of the above technical scheme of the present invention, the characteristics of long OEO resonant cavity, high spectral purity and high resonant frequency are utilized, and the measured change is amplified by 105～106The method is multiplied, so that the common measuring instrument can measure the relative distance in a large range (km magnitude) and can achieve high measuring precision (mum); adopts a structure of switching the OEO at a super high speed and is composed of a time delay structure in a distance measuring instrumentThe method has the advantages that one OEO is formed and used as a test OEO, the time delay inside the distance measuring instrument and different distances to be measured form other measurement OEOs, the switching start oscillation of the test OEO and the measurement OEO can be realized, when the switching frequency reaches the kHz magnitude, the time delay inside the distance measuring instrument can be regarded as unchanged within ms, therefore, the influence of environmental change on the stability of the time delay inside the distance measuring instrument can be eliminated, and the measurement accuracy is guaranteed.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solution of the present invention is defined by the claims.
Claims (8)
1. A large-distance and micro-relative-distance measuring instrument based on OEO fast switching is characterized in that: the device comprises an instrument internal delay switching module (1), a loop switching module (2) and a frequency metering and distance conversion module (3), wherein the instrument internal delay switching module (1) and the loop switching module (2) are connected into a double-cavity switching photoelectric oscillator structure through cables and optical fibers, and the frequency metering and distance conversion module (3) is connected with the instrument internal delay switching module (1).
2. The OEO fast switching large distance, micro relative distance measuring instrument according to claim 1, wherein the instrument internal delay switching module (1) comprises a laser (4), a polarization controller (5), an electro-optical modulator (6), a three-port circulator (7), an optical amplifier (8), a photodetector (9), a band-pass filter (10), a microwave amplifier (11), and an electric coupler (12) arranged in sequence, the electric coupler (12) comprises a first output port (121) of the electric coupler and a second output port (122) of the electric coupler, the first output port (121) of the electric coupler is connected with a radio frequency input port of the electro-optical modulator (6), the second output port (122) of the electric coupler is connected with a frequency metering and distance conversion module (3), and the loop switching module comprises an optical switch (14), the optical switch (14) is connected to a test mirror (160) and to at least one first collimator (151), respectively, the first collimator (151) corresponding to a first measuring mirror (161).
3. The OEO fast switching large distance, micro relative distance measurement instrument according to claim 2, characterized in that the three-port circulator (7) comprises a first circulator port (71), a second circulator port (72), a third circulator port (73), the optical switch (14) comprises an optical switch input port (14a), a test optical switch output port (14b0) and a first measurement optical switch output port (14b1) corresponding to the first collimator (151), wherein the first circulator port (71) is connected with the output of the electro-optical modulator (6), the third circulator port (73) is connected with the input of the optical amplifier (8), the second circulator port (72) is connected with the optical switch optical input port (14a) through a large range analog fiber (13), and the test optical switch output port (14b0) is connected with the test mirror (160), the first measuring optical switch output port (14b1) is connected with a first collimator (151).
4. The OEO fast switching based large distance, micro relative distance measuring instrument according to claim 2, wherein: the laser (4) is a semiconductor laser or a light laser.
5. The OEO fast switching based large distance, micro relative distance measuring instrument according to claim 2, wherein: the electro-optical modulator (6) is a lithium niobate intensity modulator, a lithium niobate phase modulator or an electro-absorption modulator with a semiconductor structure.
6. The OEO fast switching based large distance, micro relative distance measuring instrument according to claim 2, wherein: the optical amplifier (8) is an erbium-doped optical fiber amplifier, an ytterbium-doped optical fiber amplifier, a thulium-doped optical fiber amplifier or a semiconductor optical amplifier.
7. The OEO fast switching based large distance, micro relative distance measuring instrument according to claim 2, wherein: the test mirror (160) and the first measurement mirror (161) are devices or structures having light intensity reflection and certain transmission characteristics.
8. The OEO fast switching based large distance, micro relative distance measuring instrument of claim 7, wherein: the test reflector (160) and the first measurement reflector (161) are coated reflectors, reflectors formed by a three-port circulator and an electric coupler together, reflectors built by a Sagnac ring, or Faraday polariscope.
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| CN111060896A (en) * | 2019-12-06 | 2020-04-24 | 天津大学 | Large-range and high-precision absolute distance measuring instrument based on OEO (optical output interface) quick switching |
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