CN104618013B - A kind of related optical time domain reflectometer based on all -fiber wide range chaos light source - Google Patents

Abstract

The invention discloses a correlated optical time domain reflectometer based on an all-fiber wide-spectrum chaotic light source, and relates to the fields of chaotic fiber lasers and optical time domain reflectometers. The reflectometer includes: all-fiber chaotic light source and related optical time-domain reflection system; related optical time-domain reflectometry system includes: adjustable attenuator, optical filter, coupler, circulator, photodetector, oscilloscope; all-fiber The output light of the chaotic light source is injected into the correlation type optical time domain reflection system, and first passes through the adjustable attenuator, the optical filter, and the coupler in turn, and the chaotic optical signal passing through the coupler is divided into a reference signal and a detection signal, and the reference signal is directly obtained by the The photoelectric detector is converted into an electrical signal and collected and stored by an oscilloscope; the detection signal is passed through a circulator to realize the function of a reflector, and the reflected signal is converted into an electrical signal by another photodetector and then collected and stored by the same oscilloscope. The invention has the advantages of simple system structure, high stability, high resolution sensing and long distance at the same time.

Description

A correlative optical time domain reflectometer based on an all-fiber wide-spectrum chaotic light source

technical field

The invention relates to the fields of chaotic fiber lasers and optical time domain reflectometers, in particular to a correlation type optical time domain reflectometer based on full fiber broadband chaotic lasers.

Background technique

With the development of the information society, optical fiber communication and sensor networks are becoming larger and larger, and they are playing an increasingly important role in people's lives. For optical networks and devices, optical reflectometer technology is an important means of fault diagnosis. In this context, the development of optical reflectometer technology has received more and more attention.

Optical reflectometer technology mainly includes three types: optical time domain reflectometry, low coherent frequency domain reflectometry, and coherent optical frequency domain reflectometry. These three optical reflectometer technologies are restricted in various indicators such as measurement distance, spatial resolution, detection sensitivity and accuracy. For example, low-coherence frequency-domain reflectometry has extremely high detection sensitivity and submillimeter-level spatial resolution, but its detection distance usually does not exceed several meters; while optical time-domain reflectometry is usually used for long distances or even ultra-long distances ( Tens of kilometers) applications, but the resolution is low, usually only to the meter level; optical frequency domain reflectometer technology can achieve millimeter-level sensing accuracy and reach Sensing distance of several kilometers.

It can be said that the comprehensive detection and sensing capability of optical frequency domain reflectometer technology is between the other two technologies, and it is an effective supplement to them. However, optical frequency domain reflectometry requires fine frequency-sweeping light sources and homodyne coherent detection, and its technical difficulty is greater than that of optical time domain reflectometry, and low-coherence frequency domain reflectometry is basically impossible for long-distance sensing . The prior technology CN101226100A uses LD-pumped chaotic light source to achieve 6cm sensing accuracy, but limited by its signal power and detector gain, its sensing distance is only tens of meters.

Compared with the chaotic laser pumped by the semiconductor laser, the all-fiber broadband chaotic light source of the present invention has a larger bandwidth and simpler setting, and can realize a sensing length of tens of kilometers and a centimeter-level resolution.

And the correlative optical time domain reflectometer based on the all-fiber wide-spectrum chaotic light source of the present invention utilizes the wide-band continuous chaotic optical signal produced by all-fiber devices as reference signal and detection signal respectively, and then performs cross-correlation calculation on the reflected signal and reference signal The breakpoint of the optical fiber network can be detected and located. Its positioning accuracy can reach the order of centimeters or even millimeters, and the sensing length can reach tens of kilometers.

Contents of the invention

The purpose of the present invention is to provide a correlation type optical time domain reflectometer with simple system structure, high stability, high resolution sensing and long distance, aiming at the problems existing in the optical reflectometer technology in the background technology.

The technical solution of the present invention is a correlated optical time-domain reflectometer based on an all-fiber wide-spectrum chaotic light source, which includes: an all-fiber chaotic light source and a correlated optical time-domain reflection system; Including: an adjustable attenuator, an optical filter, a coupler, a circulator, a photodetector, and an oscilloscope; the outgoing light of the all-fiber chaotic light source is injected into a related optical time domain reflection system, and first passes through the adjustable attenuator, Optical filter, coupler, the chaotic optical signal passing through the coupler is divided into reference signal and detection signal, the reference signal is directly converted into an electrical signal by the photodetector and collected and stored by the oscilloscope; the detection signal realizes the reflectometer function through the circulator, The reflected signal is converted into an electrical signal by another photodetector and collected and stored by the same oscilloscope.

The all-fiber chaotic light source includes: a Raman pump light source, an optical isolator, and a zero-dispersion-shifted optical fiber. The pump light emitted by the Raman pump light source passes through the optical isolator and the zero-dispersion-shifted optical fiber in sequence.

The length of the zero-dispersion-shifted optical fiber is 10-20 km.

The Raman pumping light source in the all-fiber chaotic light source is a 1455nm Raman pumping light source.

In summary, owing to adopting above-mentioned technical scheme, the beneficial effect of the present invention is:

1. The present invention adopts an all-fiber broadband chaotic light source, and uses a Raman fiber laser to pump a zero-dispersion shifted optical fiber to realize an ultra-broadband chaotic light source output. Compared with a traditional semiconductor laser pumped chaotic light source, its structure is simpler. Larger output bandwidth can achieve higher precision spatial resolution;

2. Because the input signal is a continuous signal rather than a pulse signal, the spatial resolution of the correlated optical time domain reflectometer based on the full-fiber broadband chaotic light source is not determined by the pulse width of the signal, so the full-fiber wide-spectrum chaotic light source based on The correlative optical time domain reflectometer can realize long-distance positioning sensing while ensuring high spatial resolution;

3. Compared with the prior art, the present invention does not need a high-performance pulse light source or an expensive electrical domain random signal generator, so the cost is lower and the practicability is better.

Description of drawings

The invention will be illustrated by way of example with reference to the accompanying drawings, in which:

Fig. 1 is the structural representation of the correlative optical time domain reflectometer based on the all-fiber broadband chaotic light source of the present invention;

Fig. 2 is the spectrogram of the broadband all-fiber chaotic light source in the embodiment of the present invention;

Fig. 3 is the time-domain diagram of the broadband all-fiber chaotic light source in the embodiment of the present invention;

Fig. 4 is the reflection point positioning result of the 25km test optical fiber in the embodiment of the present invention, the spatial resolution reaches 5.2cm, and the signal-to-noise ratio is 18dB.

In Figure 1: 1. 1455nm Raman pump light source; 2. Optical isolator; 3. Zero dispersion shifted fiber; 4. Adjustable optical attenuator; 5. Optical filter; 6. Coupler; 7. Photodetector; 8. Circulator; 9. Photodetector (same as 7); 10. Test fiber (G.652); 11. Real-time oscilloscope.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, it is a schematic structural diagram of a correlated optical time domain reflectometer based on an all-fiber wide-spectrum chaotic light source according to the present invention. The system includes a 1455nm Raman pump light source 1, an optical isolator 2, and a zero-dispersion-shifted optical fiber 3,1. . 652)10 and real-time oscilloscope11. The length of the zero-dispersion-shifted optical fiber 3 is 16 km, and its length determines the pump power required by the ultra-broadband chaotic light source. In the present invention, the length of the zero-dispersion-shifted optical fiber 3 should be between 10-20 km. The center wavelength of the optical filter 5 is 1550.2nm, and the 3dB bandwidth is 0.26nm.

The circulator 8 has port one, port two and port three, the port one is connected to the coupler, the port two is connected to the test fiber, and the port three is connected to the photodetector.

Fig. 2 is the spectrogram of the all-fiber chaotic light source of the present invention, and Fig. 3 is the time-domain diagram of the broadband all-fiber chaotic light source in the embodiment of the present invention; Fig. 4 is that the detection technology of the present invention is applied to 25km optical fiber Example results of breakpoint location detection. The non-zero dispersion-shifted fiber used in the experiment has a total length of 15km, the zero-dispersion-shifted wavelength is 1440nm, the dispersion slope is 0.045ps/nm ² /km, and the 1455nm pump works in the normal dispersion region. As the pump power increases gradually, the bandwidth of the chaotic light source also increases gradually. When the pump power reaches 1.48W, the bandwidth of the chaotic light source reaches a maximum of 141nm (10dB bandwidth). Continue to increase the pump power, due to stimulated Raman scattering, the power gradually shifts to the second-order and third-order Stokes light, and gathers around 1550nm to 1650nm.

Fig. 3 is a fixed-point test result diagram of the application of the correlative optical time domain reflectometer technology based on the all-fiber wide-spectrum chaotic light source according to the present invention to a 25km test fiber. The Raman pump light source is 1.48W so that the chaotic light source has the maximum bandwidth output. The splitting ratio of the coupler is 1:99, 1% end output is used as reference light, and 99% end output is used as probe light. By adjusting the adjustable attenuator, the two signals after splitting by the coupler have more appropriate optical power. In this experiment, the output power of the 1% end is -17dBm, and the output power of the 99% end is 0.8dBm. The Fresnel reflection is used to simulate the break point at the end, and the reflectivity is considered to be 4%, and the output optical power of the three ports of the circulator is -25dBm. In addition, the two photodetectors used are 1GHz detectors with the same bandwidth, the oscilloscope used has a bandwidth of 25GHz, and the sampling rate is set to 25Gs/s. Finally, after calculating the cross-correlation function of the two signals, the cross-correlation curve shown in Figure 3 is obtained. The peak of the cross-correlation curve is the position of the reflection point of the fiber. The technology of the present invention accurately measures the length of the fiber to 24768.94 meters, and the spatial resolution is determined to be 5.2 cm by judging the full width at half maximum of the peak curve.

Claims (3)

1. a kind of related optical time domain reflectometer based on all -fiber wide range chaos light source, the reflectometer includes：All -fiber chaos light Source and relationship type optical time domain reflection system；The relationship type optical time domain reflection system includes：Adjustable attenuator, optical filter, coupling Clutch, circulator, photodetector, oscillograph；The emergent light of all -fiber chaos light source injects relationship type optical time domain reflection System, passes sequentially through adjustable attenuator, optical filter, coupler first, is divided into reference by the chaos optical signal of coupler Signal and detectable signal, reference signal are directly converted to electric signal by photodetector and are gathered and stored by oscillograph；Detection letter Number reflectometer function is realized by circulator, reflected signal is converted to after electric signal by same oscillograph by another photodetector Gather and store；The all -fiber chaos light source includes：Raman pump light source, optoisolator, zero dispersion shift fiber, Raman pump The pump light that Pu light source is sent passes sequentially through optoisolator, zero dispersion shift fiber.

2. a kind of related optical time domain reflectometer based on all -fiber wide range chaos light source as claimed in claim 1, its feature exists In the zero dispersion shift fiber length be 10~20km.

3. a kind of related optical time domain reflectometer based on all -fiber wide range chaos light source as claimed in claim 1, its feature exists Raman pump light source is 1455nm raman pump light sources in all -fiber chaos light source.