CN102967371B - Device and method for measuring brillouin gain spectrum in non-scanning manner based on pumping-detection method - Google Patents

Abstract

A device and a method for measuring a brillouin gain spectrum in a non-scanning manner based on a pumping-detection method relate to a device and a method for measuring the brillouin gain spectrum and aim to solve the problems of low signal-to-noise ratio, long measurement time and complex device of the conventional device and method in brillouin gain spectrum measurement. In the device for measuring the brillouin gain spectrum in the non-scanning manner based on the pumping-detection method, the laser output end of an optical fiber laser is communicated with the first port of an optical fiber circulator; the second port of the optical fiber circulator is communicated with the first port of a polarization controller, and the second port of the polarization controller is communicated with one end of an optical fiber to be measured; the laser output end of an ASE (Amplified Spontaneous Emission) light source is communicated with the light input end of an optical fiber isolator; the light output end of the optical fiber isolator is communicated with the other end of the optical fiber to be measured; and the third port of the optical fiber circulator serves as the light output end of the device for measuring the brillouin gain spectrum in the non-scanning manner based on the pumping-detection method; and besides, the connection is optical fiber connection. The device and the method provided by the invention are suitable for measuring the brillouin gain spectrum.

Description

Device and method for non-scanning measurement of Brillouin gain spectrum by pump-probe method

technical field

The invention relates to a device and method for measuring Brillouin gain spectrum.

Background technique

Brillouin gain spectrum contains important information such as Brillouin frequency shift, linewidth and gain envelope, and is widely used in distributed optical fiber sensing, filtering and amplification of weak signals, and Brillouin lidar detection. At present, there are two main types of devices and methods for measuring the Brillouin gain spectrum: one is the single-ended method, that is, only the pump light is input into the nonlinear medium (such as optical fiber, water, etc.), and then the Brillouin The spectrum of scattered Stokes light is called the Brillouin gain spectrum of nonlinear media; the second is the double-ended method, that is, the pump-probe method, "-" represents that this method uses two paths of light, one for pump light and the other for To detect light, a tunable laser or microwave generator is used to control the electro-optic intensity modulator to generate Stokes frequency-shifted probe light, which interacts with the counter-propagating pump light in the Brillouin amplifier medium to achieve pumping The energy or power transfer from the light to the detection light, when the frequency of the detection light is continuously scanned near the Stokes frequency shift, the amplified detection light spectrum is obtained at the output of the amplifier, which is the Brillouin gain spectrum. The device of method 1 is relatively simple, only need to introduce a beam of pump light, but the signal-to-noise ratio of the measured Brillouin gain spectrum is poor (see Opt.Lett.2010, vol.35, 3985-3987), especially in the distribution In the application of optical fiber sensing, this method seriously restricts its detection distance; although the device of method 2 is more complicated, the signal-to-noise ratio of the measured Brillouin gain spectrum is high (see Opt.Lett.2011, vol.36, 2378-2380), which is a commonly used device and method for distributed optical fiber sensing. However, in the second method, the frequency of the probe light needs to be scanned, which results in a long measurement time of the Brillouin gain spectrum and the inability to obtain sensing information in real time, accurately and quickly, which is also the main defect that limits its application. Publication No. CN101247179A is the closest prior art to the present application.

Contents of the invention

The purpose of the present invention is to solve the problems of low signal-to-noise ratio, long measurement time and complex devices for measuring the Brillouin gain spectrum in the existing devices and methods, and provides a pump-detection method for non-scanning measurement of the Brillouin gain Spectrum devices and methods.

The pump-probe non-scanning device for measuring the Brillouin gain spectrum consists of a fiber laser, a fiber circulator, a polarization controller, an optical fiber to be tested, a fiber isolator and an ASE light source;

The laser output end of the fiber laser is connected to the first port of the fiber circulator, the second port of the fiber circulator is connected to the first port of the polarization controller, and the second port of the polarization controller is connected to one end of the fiber to be tested; ASE light source The laser output end of the fiber optic isolator is connected to the light input end of the fiber isolator, and the light output end of the fiber isolator is connected to the other end of the optical fiber to be tested. The optical output end of the Liouin gain spectrum device, the above connections are optical fiber connections.

The method for obtaining the Brillouin gain spectrum with a device for measuring the Brillouin gain spectrum in a non-scanning manner by the pump-probe method comprises the following specific steps:

Step A1, the fiber laser outputs C-band narrow-band laser;

Step A2, the C-band narrow-band laser enters one end of the optical fiber to be tested through the first port, the second port and the polarization controller of the fiber circulator in turn, and this light is used as pump light;

Step A3, the ASE light source outputs a C-band broadband laser;

Step A4, the C-band broadband laser enters the other end of the optical fiber to be tested through the fiber isolator, and this light is used as the detection light;

Step A5. In the optical fiber to be tested, the frequency components in the pump light and the probe light that meet the Brillouin frequency shift of the fiber to be tested and within the range of the Brillouin gain spectrum interact simultaneously, and Brillouin the probe light enlarge;

Step A6, the amplified probe light enters the optical fiber circulator through the polarization controller, and is output from the third port of the optical fiber circulator;

Step A7: Process the amplified detection light by means of Fabry-Perot interferometer or heterodyne detection to obtain its spectral distribution, which is the Brillouin gain spectrum of the optical fiber to be tested.

The present invention is based on the pump-detection method, and replaces the traditional tunable narrow-band laser or microwave generator and electro-optical intensity modulator with an ASE light source. It does not need to scan the frequency of the probe light, which can save scanning time and greatly shorten the measurement time. Real-time detection; Compared with the single-ended method, the present invention can more flexibly adjust the strength of the probe light, and its power is stable, and the signal-to-noise ratio is increased by more than 10dB, and the present invention does not require a scanning device, so it is better than the existing pump- The detection method has a simple device and has great application potential in long-distance distributed optical fiber sensing.

Description of drawings

1 is a schematic diagram of the composition and structure of a device for non-scanning measurement of the Brillouin gain spectrum by the pump-probe method;

Fig. 2 is the Brillouin gain spectrum measured with the device of the present invention in the eighth embodiment, curve a is the curve measured by experiment, and curve b is the Lorentz fitting curve;

Fig. 3 is a flowchart of a method for obtaining a Brillouin gain spectrum using a pump-probe non-scanning device for measuring the Brillouin gain spectrum.

Detailed ways

Specific embodiment one: this embodiment is described in conjunction with Fig. 1, the pump-detection method non-scanning measuring device of Brillouin gain spectrum described in this embodiment, it consists of fiber laser 1, fiber circulator 2, polarization controller 3 , an optical fiber to be tested 4, an optical fiber isolator 5 and an ASE light source 6;

The laser output end of the fiber laser 1 communicates with the first port 2-1 of the fiber circulator 2, the second port 2-2 of the fiber circulator 2 communicates with the first port of the polarization controller 3, and the second port of the polarization controller 3 The port is communicated with one end of the optical fiber 4 to be tested; the laser output end of the ASE light source 6 is communicated with the optical input end of the fiber isolator 5, and the optical output end of the optical fiber isolator 5 is communicated with the other end of the optical fiber 4 to be tested, and the optical fiber circulator 2 The third port 2-3 is the optical output end of the device for non-scanning measurement of the Brillouin gain spectrum by the pump-probe method, and the above-mentioned connections are optical fiber connections.

The invention adopts the ASE light source as the detection light source, not only can effectively shorten the measurement time, but also has a higher signal-to-noise ratio of the Brillouin gain spectrum, and the measurement device is simple and easy to operate.

Embodiment 2: The difference between this embodiment and the device for non-scanning measurement of the Brillouin gain spectrum by the pump-probe method in Embodiment 1 is that the laser output by the fiber laser 1 is a C-band narrow-band laser, The wavelength is 1550nm, and the linewidth range is 1KHz-10MHz.

Embodiment 3: The difference between this embodiment and the device for non-scanning Brillouin gain spectrum measurement by the pump-probe method in Embodiment 1 is that the laser output by the ASE light source 6 is a C-band broadband laser, The spectrum is flat around 1550nm, and the range of spectral flatness is 1nm-40nm.

Specific embodiment four: this embodiment is described in conjunction with Fig. 3, the method for obtaining the Brillouin gain spectrum by using the pump-probe non-scanning device for measuring the Brillouin gain spectrum described in the specific embodiment one, which includes specific Proceed as follows:

Step A1, the fiber laser 1 outputs a C-band narrow-band laser;

Step A2, the C-band narrow-band laser enters one end of the optical fiber to be tested through the first port, the second port and the polarization controller 3 of the optical fiber circulator 2 in turn, and this light is used as pump light;

Step A3, ASE light source 6 outputs C-band broadband laser;

Step A4, the C-band broadband laser enters the other end of the optical fiber to be tested through the fiber isolator 5, and this light is used as the detection light;

Step A5. In the optical fiber to be tested, the frequency components in the pump light and the probe light that meet the Brillouin frequency shift of the fiber to be tested and within the range of the Brillouin gain spectrum interact simultaneously, and Brillouin the probe light enlarge;

Step A6, the amplified probe light enters the optical fiber circulator 2 through the polarization controller 3, and is output from the third port of the optical fiber circulator 2;

Step A7: Process the amplified detection light by means of Fabry-Perot interferometer or heterodyne detection to obtain its spectral distribution, which is the Brillouin gain spectrum of the optical fiber to be tested.

Specific embodiment five: the difference between this embodiment and the method for obtaining the Brillouin gain spectrum described in specific embodiment four is that the C-band narrowband laser in the step A1 has a wavelength of 1550nm and a linewidth range of 1KHz- 10MHz laser.

Embodiment 6: The difference between this embodiment and the method for obtaining the Brillouin gain spectrum described in Embodiment 4 is that the C-band broadband laser in the step A3 has a flat spectrum near 1550nm, and the range of flat spectrum is 1nm-40nm laser.

Embodiment 7: The difference between this embodiment and the method for obtaining the Brillouin gain spectrum described in Embodiment 4 is that the power of the pump light in the step A2 is controlled to be within the excited Brillouin range of the optical fiber to be tested. below the scatter threshold.

Embodiment 8: The difference between this embodiment and the method for obtaining the Brillouin gain spectrum described in Embodiment 7 is that the method for selecting the stimulated Brillouin scattering threshold of the optical fiber to be tested is: the pump When the ratio of the backscattered light power generated by the pump light passing through the fiber under test to the pump light power is 1%, the corresponding pump light power is the stimulated Brillouin scattering threshold of the fiber under test.

Specific Embodiment Nine: This embodiment provides a specific embodiment of a method for obtaining a Brillouin gain spectrum using a pump-probe method for non-scanning measurement of the Brillouin gain spectrum. The Brillouin gain spectrum measurement device is shown in the figure 1.

Step A1, the output wavelength of the fiber laser is 1550nm, and the laser line width is 50kHz C-band narrow-band laser;

Step A2, the C-band narrow-band laser enters one end of a 1000m-long single-mode fiber through the first port, the second port and the polarization controller of the fiber circulator in turn, and this light is used as pump light;

Step A3, the ASE light source outputs a C-band broadband laser with a flat spectrum in the range of 1525nm-1565nm;

Step A4, the C-band broadband laser enters the other end of the 1000m-long single-mode optical fiber through the fiber isolator, and this light is used as the detection light;

Step A5. In the 1000m-long single-mode fiber, the frequency components in the pump light and the probe light that meet the Brillouin frequency shift of the fiber to be tested and within the range of the Brillouin gain spectrum interact simultaneously, and perform a test on the probe light Brillouin magnification;

Step A6, the amplified probe light enters the optical fiber circulator through the polarization controller, and is output from the third port of the optical fiber circulator;

Step A7: Measure the amplified detection light spectrum by means of heterodyne detection, and obtain the corresponding Brillouin gain spectrum when the detection light magnification is 2.2 times.

The fiber laser in this embodiment is selected from Koheras Adjustik System of NKT photonic company, the output power is adjustable in the range of 0-100mW, the output wavelength is 1550nm, and the laser line width is 50kHz.

The ASE light source in this embodiment is selected as an ASE light source with a maximum output power of 10 mW and an output laser with a flat spectrum range of 1525 nm-1565 nm.

Since the probe light contains all frequency components in the Brillouin gain spectrum, these frequency components are amplified simultaneously after being acted on by the pump light, so frequency scanning is not required.

Figure 2 shows the corresponding Brillouin gain spectrum when the detection light magnification is 2.2 times. It can be seen that the spectrum shape is Lorentzian, the Brillouin frequency shift is 10.87GHz, and the linewidth is 22.5MHz, which is different from the traditional The measurement results of the method are consistent; the Brillouin gain spectrum curve measured based on the invention is relatively smooth, and the signal-to-noise ratio is high.

Claims (8)

1. The pump-probe non-scanning device for measuring the Brillouin gain spectrum, which consists of a fiber laser (1), a fiber circulator (2), a polarization controller (3), an optical fiber to be tested (4), and an optical fiber isolation device (5) and ASE light source (6); It is characterized in that the laser output end of the fiber laser (1) communicates with the first port (2-1) of the fiber circulator (2), and the second port (2-2) of the fiber circulator (2) communicates with the polarization controller The first port of (3) is connected, and the second port of the polarization controller (3) is connected with an end of the fiber to be tested (4); the laser output end of the ASE light source (6) is connected with the light input end of the fiber isolator (5) connected, the light output end of the fiber isolator (5) is connected with the other end of the optical fiber (4) to be tested, and the third port (2-3) of the fiber optic circulator (2) is the non-scanning type of the pump-detection method The optical output end of the device for measuring the Brillouin gain spectrum, the above connections are optical fiber connections. 2. the device of the non-scanning Brillouin gain spectrum of the pump-detection method according to claim 1, is characterized in that, the laser light of described fiber laser (1) output is C band narrow-band laser, and wavelength is 1550nm, The line width range is 1KHz-10MHz. 3. the device of the non-scanning Brillouin gain spectrum of the pump-probe method according to claim 1, is characterized in that, the laser light of described ASE light source (6) output is C wave band broadband laser, near 1550nm spectrum Flat, the spectral flat range is 1nm-40nm. 4. adopt the method for obtaining the Brillouin gain spectrum by the device of the non-scanning measurement Brillouin gain spectrum of the pump-detection method claimed in claim 1, the concrete steps that it comprises are as follows: Step A1, the fiber laser (1) outputs a C-band narrowband laser; Step A2, the C-band narrowband laser enters one end of the optical fiber to be tested through the first port, the second port and the polarization controller (3) of the fiber circulator (2) in turn, and this light is used as pump light; Step A3, ASE light source (6) outputs C-band broadband laser; Step A4, the C-band broadband laser enters the other end of the optical fiber to be tested through the fiber isolator (5), and this light is used as the detection light; Step A5. In the optical fiber to be tested, the frequency components in the pump light and the probe light that meet the Brillouin frequency shift of the fiber to be tested and within the range of the Brillouin gain spectrum interact simultaneously, and Brillouin the probe light enlarge; Step A6, the amplified probe light enters the optical fiber circulator (2) through the polarization controller (3), and is output by the third port of the optical fiber circulator (2); Step A7: Process the amplified detection light by means of Fabry-Perot interferometer or heterodyne detection to obtain its spectral distribution, which is the Brillouin gain spectrum of the optical fiber to be tested. 5. The method for obtaining the Brillouin gain spectrum according to claim 4, characterized in that the C-band narrowband laser in the step A1 is a laser with a wavelength of 1550nm and a linewidth range of 1KHz-10MHz. 6. The method for obtaining the Brillouin gain spectrum according to claim 4, characterized in that, the C-band broadband laser in the step A3 is a laser with a flat spectrum around 1550nm, and a flat spectrum range of 1nm-40nm. 7. The method for obtaining the Brillouin gain spectrum according to claim 4, characterized in that the power of the pump light in the step A2 is controlled below the stimulated Brillouin scattering threshold of the optical fiber to be tested. 8. The method for obtaining the Brillouin gain spectrum according to claim 7, wherein the selection method of the stimulated Brillouin scattering threshold of the optical fiber to be tested is: the pump light is generated by the optical fiber to be tested When the ratio of the backscattered light power to the pump light power is 1%, the corresponding pump light power is the stimulated Brillouin scattering threshold of the optical fiber to be tested.