CN116073897B - Optical time domain reflectometer based on broadband random photoelectric oscillator and measuring method thereof - Google Patents
Optical time domain reflectometer based on broadband random photoelectric oscillator and measuring method thereof Download PDFInfo
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Abstract
The invention discloses an optical time domain reflectometer based on a broadband random photoelectric oscillator and a measuring method thereof. The optical time domain reflectometer comprises: the tunable continuous wave laser comprises a tunable continuous wave laser, an electro-optic modulator, a first optical circulator, a random interval grating, an optical amplifier, an optical coupler, a first photoelectric detector, a first electric amplifier, an electric coupler, an optical fiber to be tested, a second optical circulator, a second photoelectric detector, a second electric amplifier and an oscilloscope; when the loop gain is larger than the oscillation threshold, an oscillation signal is generated, and as the gain is further increased and due to random distributed feedback introduced by the random interval grating, a broadband random signal with large bandwidth, high randomness and low time lag is finally output; the invention solves the problem of the trade-off of the detection distance and the spatial resolution in the existing optical time domain reflection technology, obtains the ultra-high spatial resolution of the order of centimeters or even sub-centimeters without sacrificing the detection distance, and effectively solves the problem of the fault positioning interference of the optical fiber link caused by time lag characteristics.
Description
Technical Field
The invention belongs to the technical field of optical time domain reflectometers, and particularly relates to an optical time domain reflectometer based on a broadband random photoelectric oscillator and a measurement method thereof.
Background
Optical time domain reflectometry is an important method for detecting the link faults of the optical fiber network. With the rapid development of new generation information technology and fiber to the home, the requirements on the spatial resolution and the dynamic range of the optical time domain reflection technology are higher and higher. Conventional pulsed optical time domain reflectometry techniques locate fiber faults by transmitting optical pulses and analyzing the energy and time delay of the echo signals. The detection distance is limited by the energy of the light pulse, and in order to increase the detection distance and avoid nonlinearity of the light pulse during transmission, a method of increasing the pulse width is generally adopted to increase the detection distance. However, an increase in pulse width results in a decrease in spatial resolution.
The correlation optical time domain reflection technology using the pseudo random pulse sequence as the detection signal can overcome the contradiction between the detection distance and the spatial resolution of the traditional pulse optical time domain reflection technology, and the detection distance is increased under the condition of not sacrificing the spatial resolution; however, its spatial resolution is still limited by the pseudo-random modulation bandwidth bottleneck.
The chaotic light time domain reflection technology utilizes the correlation of broadband chaotic light to improve the spatial resolution, and is irrelevant to the detection distance. Because of its high spatial resolution and ultra-long detection distance, the chaotic optical time domain technology is a candidate for fault detection and distributed optical fiber sensing of an optical fiber access network.
As in the prior art, chinese patent publication No. CN101226100B discloses a chaotic optical time domain reflectometer and a measuring method thereof, in which a chaotic optical signal is also mentioned to replace a pseudo-random code modulated optical pulse in the optical time domain reflectometer by a correlation method as a detection signal; the chaotic laser signal has no obvious periodicity, has higher bandwidth than the pseudo-random code signal, and can greatly improve the resolution and the dynamic range of the optical time domain reflectometer; however, the chaotic light source in the current chaotic light time domain reflectometer mainly comprises a semiconductor laser and an external cavity feedback device, and the chaotic light source has a simple structure, but has obvious relaxation oscillation, so that the bandwidth of the generated chaotic signal is limited.
The chaotic light source of the existing chaotic light time domain reflection technology has obvious relaxation oscillation characteristics, and the energy of a chaotic signal is mainly concentrated at the relaxation oscillation characteristics, so that the low-frequency-band energy is too low. Therefore, when the detection bandwidth is smaller, the energy utilization rate of the chaotic signal is insufficient, and the detection distance of the chaotic light time domain reflection technology is severely limited.
Although the optical fiber loop technology can realize the delay self-interference of the chaotic laser, the low-frequency band energy of the chaotic signal can be improved, so that the detection distance of the chaotic optical time domain reflection technology is improved. However, the introduction of the optical fiber ring can lead to the generated chaotic signal to have obvious periodicity, so that the randomness of the chaotic signal is reduced, and the correlation curve of the chaotic signal also presents obvious time lag characteristics and can seriously influence the positioning of the fault point of the optical fiber link. Therefore, how to generate a wideband random signal with low time lag features is an urgent problem to be solved in the optical time domain reflectometry field.
One approach to solving the above problems is an optical time domain reflectometer based on a broadband random optoelectronic oscillator. The method can solve the technical problems of space resolution and detection distance tradeoff in optical fiber length measurement and fault detection and positioning interference caused by time lag phenomenon due to the characteristics of large bandwidth, high randomness and low time lag of signals generated by the broadband random photoelectric oscillator, and has strong practicability and wide application prospect. However, the optical time domain reflection technology based on the broadband random photoelectric oscillator is not reported so far, and a specific optical time domain reflectometer is left in the absence.
Therefore, an optical time domain reflectometer based on a broadband random photoelectric oscillator and a measurement method thereof are needed.
Disclosure of Invention
Aiming at the problems in the related art, the invention provides an optical time domain reflectometer based on a broadband random photoelectric oscillator and a measuring method thereof, which are used for solving the technical problems that the detection distance and the spatial resolution are balanced in the existing optical time domain reflectometry technology and the detection signal has obvious time lag phenomenon to cause positioning interference.
The technical scheme of the invention is realized as follows: the optical time domain reflectometer based on the broadband random photoelectric oscillator comprises the broadband random photoelectric oscillator, an optical fiber to be tested, a second optical circulator, a second photoelectric detector, a second electric amplifier and an oscilloscope;
the broadband random photoelectric oscillator comprises a tunable continuous wave laser, an electro-optic modulator, a first optical circulator, a random feedback device, an optical amplifier, an optical coupler, a first photoelectric detector, a first electric amplifier and an electric coupler;
in the broadband random photoelectric oscillator, the electro-optic modulator, the first optical circulator, the optical amplifier, the optical coupler, the first photoelectric detector, the first electric amplifier and the electric coupler are sequentially connected to form a closed loop.
Preferably, the random feedback device is a random interval grating;
preferably, the center wavelength of the random interval grating is 1549.943 nm, which is provided with 21 grating regions, the length of each grating region is 5 mm, and the grating region intervals are randomly distributed between 3.5 mm and 5.0 mm;
the characteristic that the grating interval of the random interval grating is random is utilized, and the intensity modulation optical signal is reflected by the random grating and then is led into random distributed feedback;
meanwhile, the optical time domain reflectometer based on the broadband random photoelectric oscillator has no fixed loop length, so that the optical time domain reflectometer based on the broadband random photoelectric oscillator can obtain random signals with low time lags and no fixed mode interval.
Preferably, the tunable continuous wave laser is a semiconductor laser, or a fiber laser.
Preferably, the wavelength of the tunable continuous wave laser is set to 1549.943 nm.
In the optical time domain reflectometer based on the broadband random photoelectric oscillator, the connection relation of each device is as follows:
the output port of the tunable continuous wave laser is connected with the optical input port of the electro-optical modulator, the optical output port of the electro-optical modulator is connected with the first port of the first optical circulator, and the second port of the first optical circulator is connected with the random feedback device; the third port of the first optical circulator is connected with the input port of the optical amplifier; the output port of the optical amplifier is connected with the input port of the optical coupler;
the first output port of the optical coupler is connected with the optical input port of the first photoelectric detector; the electric output port of the first photoelectric detector is connected with the input port of the first electric amplifier; the output port of the first electric amplifier is connected with the input port of the electric coupler; the first output port of the electric coupler is connected with the microwave input port of the electro-optic modulator; the second output port of the electric coupler is connected with the first input port of the oscilloscope;
a second output port of the optical coupler is connected with a first port of the second optical circulator; the second port of the second optical circulator is connected with the optical fiber to be tested; the third port of the second optical circulator is connected with the optical input port of the second photoelectric detector; the electric output port of the second photoelectric detector is connected with the input port of the second electric amplifier; the output port of the second electric amplifier is connected with the second input port of the oscilloscope.
In the optical time domain reflectometer based on the broadband random photoelectric oscillator, the functions and transmission relations of all devices are as follows:
the tunable continuous wave laser generates an optical carrier and transmits the optical carrier to the electro-optic modulator;
the electro-optical modulator is used for carrying out intensity modulation on the optical carrier wave to form an intensity modulated optical signal and transmitting the intensity modulated optical signal to the first optical circulator;
the first optical circulator transmits the intensity-modulated optical signal to a random feedback device and transmits a reflected optical signal of the random feedback device to an optical amplifier;
the random feedback device is used for carrying out random distributed feedback on the intensity-modulated optical signals;
the optical amplifier is used for amplifying the power of the weak reflected optical signal and transmitting the amplified optical signal to the optical coupler;
the optical coupler divides the amplified optical signal into two paths of optical signals, one path is a measuring optical signal, and the other path is a reference optical signal; the reference optical signal is transmitted to the first photoelectric detector, and the measuring optical signal is transmitted to the second optical circulator;
the first photoelectric detector is used for performing photoelectric conversion on the reference optical signal, converting the reference optical signal into an annular cavity microwave signal and transmitting the annular cavity microwave signal to the first electric amplifier;
the first electric amplifier is used for amplifying the power of the ring cavity microwave signal and transmitting the amplified ring cavity microwave signal to the electric coupler;
the electric coupler divides the amplified ring cavity microwave signal into two paths, and transmits one path of ring cavity microwave signal to a microwave input port of the electro-optical modulator, and the other path of ring cavity microwave signal is transmitted to a first input port of the oscilloscope as a reference microwave signal;
the second optical circulator transmits the measurement light signal output by the optical coupler to the optical fiber to be measured and transmits the reflected light signal of the optical fiber to be measured to the second photoelectric detector;
the second photoelectric detector is used for performing photoelectric conversion on the reflected light signal of the optical fiber to be detected, converting the reflected light signal of the optical fiber to be detected into a measurement microwave signal and transmitting the measurement microwave signal to the second electric amplifier;
the second electric amplifier is used for amplifying the power of the measurement microwave signal and transmitting the amplified measurement microwave signal to a second input port of the oscilloscope;
the oscilloscope collects and stores the measurement microwave signals and the reference microwave signals;
and performing cross-correlation calculation on the measurement microwave signals acquired and stored by the oscilloscope and the reference microwave signals to obtain a cross-correlation curve, and finally obtaining the fault point of the optical fiber link through the peak value of the cross-correlation curve.
The broadband random signal generated by the broadband random photoelectric oscillator has the characteristic of large bandwidth due to the broadband characteristic of the broadband random photoelectric oscillator; the low-time-lag frequency domain broadband random signal can be subjected to time domain compression by performing cross-correlation processing on the output reference microwave signal and the measurement microwave signal to obtain a cross-correlation curve;
the full width at half maximum of the cross correlation peak in the cross correlation curve can reach the order of centimeters or even sub-centimeters, thereby obtaining the ultra-high spatial resolution of the order of centimeters or even sub-centimeters without sacrificing the detection distance.
In addition, due to the low time lag characteristic of the broadband random signal, the problem of positioning interference existing in the optical time domain reflection technology based on the conventional ring laser chaotic signal is solved.
The method for measuring the optical time domain reflectometer based on the broadband random photoelectric oscillator is applied to the optical time domain reflectometer based on the broadband random photoelectric oscillator, and specifically comprises the following steps of:
and step 6, performing cross-correlation calculation on the two paths of signals to obtain a cross-correlation curve, and acquiring the detection distance and the spatial resolution.
Compared with the existing optical time domain reflection technology, the optical time domain reflectometer based on the broadband random photoelectric oscillator and the measuring method thereof have the following beneficial effects:
(1) The invention benefits from the random distributed feedback of the random interval grating and the broadband characteristic of the broadband random photoelectric oscillator, the output broadband random signal has no obvious periodicity, has high randomness and large signal bandwidth, solves the problem of tradeoff between detection distance and spatial resolution in the existing optical time domain reflection technology, and can obtain the ultra-high spatial resolution in the order of centimeters or even sub-centimeters without sacrificing the detection distance;
(2) The invention benefits from the low time lag characteristic of the broadband random signal, solves the problem of positioning interference caused by the time lag characteristic, and can greatly improve the measurement accuracy of the optical time domain reflection technology.
Drawings
Fig. 1 is a schematic structural diagram of an optical time domain reflectometer based on a wideband random optoelectronic oscillator of embodiment 1;
fig. 2 is a schematic diagram of the structure of a wideband random optoelectronic oscillator of embodiment 1;
fig. 3 is an output frequency domain diagram of the wideband random optoelectronic oscillator of embodiment 1;
FIG. 4 is an output time domain signal autocorrelation graph of the wideband random optoelectronic oscillator of example 1;
FIG. 5 is a graph of the detection results of the broadband stochastic photoelectric oscillator-based optical time domain reflectometer of example 1 for 25 km and 50 km fiber breakpoint positioning;
FIG. 6 is a graph of dynamic range results for a 25 km fiber length for a wideband random optoelectronic oscillator based optical time domain reflectometer of example 1;
FIG. 7 is a graph of the spatial resolution results of the broadband stochastic photoelectric oscillator-based optical time domain reflectometer of example 2 for 500m fiber break point detection;
fig. 8 is a graph of the results of dual event detection for 500m fiber break point detection using the broadband stochastic photoelectric oscillator-based optical time domain reflectometer of example 2.
Reference numerals:
1. a tunable continuous wave laser; 2. an electro-optic modulator; 3. a first optical circulator; 4. a random spacing grating; 5. an optical amplifier; 6. an optical coupler; 7. a first photodetector; 8. a first electrical amplifier; 9. an electric coupler; 10. an optical fiber to be measured; 11. a second optical circulator; 12. a second photodetector; 13. a second electrical amplifier; 14. an oscilloscope; 15. broadband random optoelectronic oscillators.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Example 1
In this embodiment, as shown in fig. 1, the optical time domain reflectometer based on a wideband random photoelectric oscillator includes a wideband random photoelectric oscillator 15, an optical fiber to be measured 10, a second optical circulator 11, a second photodetector 12, a second electric amplifier 13 and an oscilloscope 14;
specifically, as shown in fig. 2, the wideband random optoelectronic oscillator 15 includes a tunable continuous wave laser 1, an electro-optical modulator 2, a first optical circulator 3, a random feedback device, an optical amplifier 5, an optical coupler 6, a first photodetector 7, a first electrical amplifier 8, and an electrical coupler 9;
in the wideband random optoelectronic oscillator 15, the electro-optical modulator 2, the first optical circulator 3, the optical amplifier 5, the optical coupler 6, the first photodetector 7, the first electrical amplifier 8 and the electrical coupler 9 are sequentially connected to form a closed loop.
In the optical time domain reflectometer based on the broadband random photoelectric oscillator, the connection relation of each device is as follows:
the output port of the tunable continuous wave laser 1 is connected with the optical input port of the electro-optical modulator 2, the optical output port of the electro-optical modulator 2 is connected with the first port of the first optical circulator 3, and the second port of the first optical circulator 3 is connected with the random feedback device; the third port of the first optical circulator 3 is connected with the input port of the optical amplifier 5; an output port of the optical amplifier 5 is connected with an input port of the optical coupler 6;
a first output port of the optical coupler 6 is connected with an optical input port of the first photodetector 7; the electric output port of the first photoelectric detector 7 is connected with the input port of the first electric amplifier 8; the output port of the first electric amplifier 8 is connected with the input port of the electric coupler 9; the first output port of the electric coupler 9 is connected with the microwave input port of the electro-optic modulator 2; the second output port of the electric coupler 9 is connected with the first input port of the oscilloscope 14;
a second output port of the optical coupler 6 is connected with a first port of the second optical circulator 11; the second port of the second optical circulator 11 is connected with the optical fiber 10 to be tested; the third port of the second optical circulator 11 is connected with the optical input port of the second photodetector 12; the electrical output port of the second photodetector 12 is connected with the input port of the second electrical amplifier 13; the output port of the second electrical amplifier 13 is connected to a second input port of the oscilloscope 14.
In the optical time domain reflectometer based on the broadband random photoelectric oscillator, the functions and transmission relations of all devices are as follows:
the tunable continuous wave laser 1 generates an optical carrier wave and transmits the optical carrier wave to the electro-optical modulator 2;
the electro-optical modulator 2 performs intensity modulation on the optical carrier wave to form an intensity-modulated optical signal, and transmits the intensity-modulated optical signal to the first optical circulator 3;
the first optical circulator 3 transmits the intensity-modulated optical signal to a random feedback device and transmits a reflected optical signal of the random feedback device to an optical amplifier 5;
the random feedback device is used for carrying out random distributed feedback on the intensity-modulated optical signals;
the optical amplifier 5 performs power amplification on the weak reflected optical signal, and transmits the amplified optical signal to the optical coupler 6;
the optical coupler 6 divides the amplified optical signal into two paths of optical signals, one path is a measurement optical signal, and the other path is a reference optical signal; wherein the reference optical signal is transmitted to the first photodetector 7, and the measurement optical signal is transmitted to the second optical circulator 11;
the first photoelectric detector 7 performs photoelectric conversion on the reference optical signal, converts the reference optical signal into an annular cavity microwave signal, and transmits the annular cavity microwave signal to the first electric amplifier 8;
the first electric amplifier 8 is used for amplifying the power of the ring cavity microwave signal and transmitting the amplified ring cavity microwave signal to the electric coupler 9;
the electric coupler 9 divides the amplified ring cavity microwave signal into two paths, and transmits one path of ring cavity microwave signal to the microwave input port of the electro-optical modulator 2, and the other path of ring cavity microwave signal is transmitted to the first input port of the oscilloscope 14 as a reference microwave signal;
the second optical circulator 11 transmits the measurement optical signal output by the optical coupler 6 to the optical fiber 10 to be measured, and transmits the reflected optical signal of the optical fiber 10 to be measured to the second photodetector 12;
the second photodetector 12 performs photoelectric conversion on the reflected light signal of the optical fiber 10 to be measured, so that the reflected light signal of the optical fiber 10 to be measured is converted into a measurement microwave signal, and the measurement microwave signal is transmitted to the second electrical amplifier 13;
the second electric amplifier 13 is used for amplifying the power of the measurement microwave signal and transmitting the amplified measurement microwave signal to a second input port of the oscilloscope 14;
the oscilloscope 14 collects and stores measurement microwave signals and reference microwave signals;
and performing cross-correlation calculation on the measured microwave signals and the reference microwave signals acquired and stored by the oscilloscope 14 to obtain a cross-correlation curve, and finally obtaining the fault point of the optical fiber link through the peak value of the cross-correlation curve.
Specifically, the tunable continuous wave laser 1 is a semiconductor laser, or is an optical fiber laser;
in the present embodiment, the wavelength of the tunable continuous wave laser 1 used for the experiment was set to 1549.943 nm;
specifically, the random feedback device is a random interval grating 4;
in this embodiment, the center wavelength of the randomly spaced grating 4 used in the experiment is 1549.943 nm, which is provided with 21 grating regions, the length of each grating region is 5 mm, and the grating region intervals are randomly distributed between 3.5 mm and 5.0 mm;
by utilizing the characteristic that the grating intervals of the random interval grating 4 are random, the intensity modulation optical signal is reflected by the random grating and then is introduced into random distributed feedback.
In the wideband random optoelectronic oscillator 15, when the gain of the closed loop is greater than the oscillation threshold, an oscillation signal will be generated, and as the gain is further increased and due to the random distributed feedback introduced by the random interval grating 4, a wideband random signal will be output finally; the broadband random signal output has no significant periodicity, high randomness and large signal bandwidth, which benefits from the random distributed feedback of the random grating and the broadband nature of the broadband random optoelectronic oscillator 15.
As shown in the output frequency domain plot of the wideband random optoelectronic oscillator 15 of fig. 3, the wideband random optoelectronic oscillator 15 is flat and has no fixed mode spacing in the 10 GHz range (depending on the bandwidth of the wideband random optoelectronic oscillator 15), which wideband feature is beneficial for achieving higher spatial resolution.
In addition, compared with a microwave signal (low noise) obtained under the condition of open loop of the optical time domain reflectometer, the output signal power of the broadband random photoelectric oscillator 15 is obviously enhanced, which is beneficial to improving the dynamic range of the optical time domain reflectometer and obtaining a longer detection distance;
the condition that the optical time domain reflectometer is open-loop means that the electric coupler 9 is disconnected from the electro-optical modulator 2, and at this time, the electro-optical modulator 2, the first optical circulator 3, the optical amplifier 5, the optical coupler 6, the first photodetector 7, the first electric amplifier 8 and the electric coupler 9 cannot form a closed loop, and meanwhile, the electric coupler 9 cannot transmit the amplified ring cavity microwave signal to the microwave input port of the electro-optical modulator 2.
The method for measuring the optical time domain reflectometer based on the broadband random photoelectric oscillator is applied to the optical time domain reflectometer based on the broadband random photoelectric oscillator, and specifically comprises the following steps of:
and step 6, performing cross-correlation calculation on the two paths of signals to obtain a cross-correlation curve, and acquiring the detection distance and the spatial resolution.
As shown in the output time domain signal autocorrelation graph of the wideband random optoelectronic oscillator 15 in fig. 4, the signal autocorrelation function curve in fig. 4 approximates a delta function and has no side lobe, so that the generated signal has no obvious periodicity (i.e. no obvious time lag characteristic), has white noise-like characteristics, can effectively avoid the problem of positioning interference caused by the time lag characteristic, and can greatly improve the measurement accuracy of the optical time domain reflectometer.
In this embodiment 1, as shown in the detection result diagram of the optical time domain reflectometer based on the wideband random photoelectric oscillator of fig. 5 for locating the break points of the 25 km and 50 km optical fibers, fresnel reflection on the end surface of the optical fibers is used to detect the break points of the optical fibers, 25 km and 50 km optical fibers are respectively used as the optical fibers 10 to be detected, the oscilloscope 14 is used to collect and store the measured microwave signal and the reference microwave signal, and finally the cross correlation calculation is performed on the two paths of signals, so as to obtain the cross correlation curve shown in fig. 5; the peak value of the cross-correlation curve is the breakpoint position of the optical fiber, and the lengths of the optical fibers are accurately measured to be 25420.37 m and 50598.37 m respectively based on the embodiment 1 of the invention; fig. 6 is a graph of the dynamic range result of the optical time domain reflection based on the wideband random optoelectronic oscillator 15 for the optical fiber length of 25 km in the present embodiment 1, the dynamic range of 39.52 dB is still remained based on the detection distance of 25 km, and the transmission loss of the G652 single-mode optical fiber adopted in the present experiment is 0.20 dB/km, so as to calculate the limit detection distance of the embodiment 1 of the present invention to be about 123.8 km.
Example 2
The features of this embodiment, which are not explained in this embodiment, are illustrated in fig. 7 to 8, and are explained in embodiment 1, and are not described in detail here. This embodiment differs from embodiment 1 in that:
an optical time domain reflectometer based on a broadband random photoelectric oscillator and a measurement method thereof, comprising an optical time domain reflectometer based on a broadband random photoelectric oscillator 15 and a measurement method thereof in embodiment 1;
as shown in the spatial resolution and dual event detection result diagrams of the optical time domain reflectometer based on the wideband random optoelectronic oscillator 15 in fig. 7-8, the spatial resolution of the optical time domain technology of the correlation method is independent of the test length, and therefore, the embodiment performs the spatial resolution and dual event detection based on the optical fiber length of about 500 m; in this embodiment, the fresnel reflection on the end face of the optical fiber is used to detect the breakpoint of the optical fiber, the optical fiber with the length of about 500m is used as the optical fiber 10 to be detected, the oscilloscope 14 is used to collect and store the measured microwave signal and the reference microwave signal, and finally the cross-correlation calculation is performed on the two stored signals to obtain the cross-correlation curve as shown in fig. 7 and 8, the peak value of the cross-correlation curve is the breakpoint position of the optical fiber, the spatial resolution is determined to be about 10.21 mm by judging the full width at half maximum of the peak value of the cross-correlation curve, and the dual-event detection with the interval of about 9.23 mm is successfully realized.
Variations and modifications to the above would be obvious to persons skilled in the art to which the invention pertains from the foregoing description and teachings. Therefore, the invention is not limited to the specific embodiments disclosed and described above, but some modifications and changes of the invention should be also included in the scope of the claims of the invention. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present invention in any way.
Claims (10)
1. The optical time domain reflectometer based on the broadband random photoelectric oscillator is characterized by comprising the broadband random photoelectric oscillator, an optical fiber to be tested, a second optical circulator, a second photoelectric detector, a second electric amplifier and an oscilloscope;
the broadband random photoelectric oscillator comprises a tunable continuous wave laser, an electro-optic modulator, a first optical circulator, a random feedback device, an optical amplifier, an optical coupler, a first photoelectric detector, a first electric amplifier and an electric coupler;
the output port of the tunable continuous wave laser is connected with the optical input port of the electro-optical modulator, the optical output port of the electro-optical modulator is connected with the first port of the first optical circulator, and the second port of the first optical circulator is connected with the random feedback device; the third port of the first optical circulator is connected with the input port of the optical amplifier; the output port of the optical amplifier is connected with the input port of the optical coupler;
the first output port of the optical coupler is connected with the optical input port of the first photoelectric detector; the electric output port of the first photoelectric detector is connected with the input port of the first electric amplifier; the output port of the first electric amplifier is connected with the input port of the electric coupler; the first output port of the electric coupler is connected with the microwave input port of the electro-optic modulator; the second output port of the electric coupler is connected with the first input port of the oscilloscope;
a second output port of the optical coupler is connected with a first port of the second optical circulator; the second port of the second optical circulator is connected with the optical fiber to be tested; the third port of the second optical circulator is connected with the optical input port of the second photoelectric detector; the electric output port of the second photoelectric detector is connected with the input port of the second electric amplifier; the output port of the second electric amplifier is connected with the second input port of the oscilloscope;
in the broadband random photoelectric oscillator, the electro-optic modulator, the first optical circulator, the optical amplifier, the optical coupler, the first photoelectric detector, the first electric amplifier and the electric coupler are sequentially connected to form a closed loop; the wideband random optoelectronic oscillator generates a wideband random signal.
2. The broadband stochastic optoelectronic oscillator-based optical time domain reflectometer of claim 1, wherein the tunable continuous wave laser generates an optical carrier and transmits the optical carrier to an electro-optic modulator;
the electro-optical modulator is used for carrying out intensity modulation on the optical carrier wave to form an intensity modulated optical signal and transmitting the intensity modulated optical signal to the first optical circulator;
the first optical circulator transmits the intensity-modulated optical signal to a random feedback device and transmits a reflected optical signal of the random feedback device to an optical amplifier;
the random feedback device is used for carrying out random distributed feedback on the intensity-modulated optical signals;
the optical amplifier is used for amplifying the power of the weak reflected optical signal and transmitting the amplified optical signal to the optical coupler;
the optical coupler divides the amplified optical signal into two paths of optical signals, one path is a measuring optical signal, and the other path is a reference optical signal; the reference optical signal is transmitted to the first photoelectric detector, and the measuring optical signal is transmitted to the second optical circulator.
3. The optical time domain reflectometer of claim 2 based on a wideband random optoelectronic oscillator, wherein the first photodetector performs photoelectric conversion on a reference optical signal, and simultaneously converts the reference optical signal into an annular cavity microwave signal and transmits the annular cavity microwave signal to a first electrical amplifier;
the first electric amplifier is used for amplifying the power of the ring cavity microwave signal and transmitting the amplified ring cavity microwave signal to the electric coupler;
the electric coupler divides the amplified ring cavity microwave signal into two paths, and transmits one path of ring cavity microwave signal to the microwave input port of the electro-optic modulator, and the other path of ring cavity microwave signal is transmitted to the first input port of the oscilloscope as a reference microwave signal.
4. The optical time domain reflectometer based on the broadband random photoelectric oscillator according to claim 2, wherein the second optical circulator transmits the measurement optical signal output by the optical coupler to the optical fiber to be measured, and transmits the reflected optical signal of the optical fiber to be measured to the second photodetector;
the second photoelectric detector is used for performing photoelectric conversion on the reflected light signal of the optical fiber to be detected, converting the reflected light signal of the optical fiber to be detected into a measurement microwave signal and transmitting the measurement microwave signal to the second electric amplifier;
and the second electric amplifier is used for amplifying the power of the measurement microwave signal and transmitting the amplified measurement microwave signal to a second input port of the oscilloscope.
5. The broadband stochastic optoelectronic oscillator-based optical time domain reflectometer according to any one of claims 3 or 4, wherein the oscilloscope collects and stores measurement and reference microwave signals;
and performing cross-correlation calculation on the measurement microwave signals acquired and stored by the oscilloscope and the reference microwave signals to obtain a cross-correlation curve, and finally obtaining the fault point of the optical fiber link through the peak value of the cross-correlation curve.
6. The broadband stochastic optoelectronic oscillator-based optical time domain reflectometer of claim 1, wherein the stochastic feedback device is a randomly spaced grating.
7. The broadband stochastic photoelectric oscillator-based optical time domain reflectometer of claim 6, wherein the random spacing grating has a center wavelength of 1549.943 nm and is provided with 21 grating regions, each of which has a length of 5 mm, and the grating region intervals are randomly distributed between 3.5 mm and 5.0 mm.
8. The broadband stochastic optoelectronic oscillator-based optical time domain reflectometer of claim 1, wherein the tunable continuous wave laser is a semiconductor laser or a fiber laser.
9. The broadband stochastic optoelectronic oscillator-based optical time domain reflectometer of claim 1, wherein the wavelength of the tunable continuous wave laser is set to 1549.943 nm.
10. An optical time domain reflectometer measurement method based on a broadband random photoelectric oscillator, which is applied to the optical time domain reflectometer based on the broadband random photoelectric oscillator as claimed in any one of claims 1 to 9, comprises the following steps:
step 1, preparing an intensity-modulated optical signal by using a tunable continuous wave laser and an electro-optical modulator, and carrying out random distributed feedback on the intensity-modulated optical signal by using a random feedback device;
step 2, performing power amplification by using an optical amplifier, and splitting light by using an optical coupler, wherein one path is a measurement optical signal, and the other path is a reference optical signal;
step 3, transmitting a measurement light signal to the optical fiber to be measured and transmitting a reference light signal to the first photoelectric detector;
step 4, receiving a reference light signal by using a first photoelectric detector, receiving a measurement light signal reflected by an optical fiber to be detected by using a second photoelectric detector, performing photoelectric conversion respectively, obtaining an annular cavity microwave signal and a measurement microwave signal respectively, and performing power amplification by using an electric amplifier respectively; dividing the amplified ring cavity microwave signal into two paths through an electric coupler, wherein one path is injected into a microwave input port of the electro-optical modulator for modulating the optical signal, and the other path is used as a reference microwave signal for outputting;
step 5, acquiring and storing a measurement microwave signal and a reference microwave signal by using an oscilloscope;
and step 6, performing cross-correlation calculation on the two paths of signals to obtain a cross-correlation curve, and acquiring the detection distance and the spatial resolution.
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