Optical fiber signal polarization state detection and high-gain amplification method based on stimulated Brillouin scattering effect

Abstract

The invention relates to an optical fiber signal polarization state detection and high-gain amplification method based on a stimulated Brillouin scattering effect. The method comprises the following steps: firstly, establishing a fitting polynomial mapped by stimulated Brillouin scattering gain and each parameter in a signal light Stokes vector under three specific pumping polarization forms ([100] T, [010] T and [001] T); then measuring the gains of the signal light in the three specific pumping polarization states again during detection, and substituting the gains into the fitting polynomial to obtain a polarization state vector of the signal light; and finally, adjusting the polarization state of the pump light according to the reconstructed Stokes vector of the signal light to obtain high-gain output. According to the invention, the operation is simple, the high-precision signal light polarization state vector can be obtained, and the amplification gain is effectively improved.

Description

Technical Field

[0001] The invention relates to the fields of optical fiber signal polarization state detection technology and power amplification technology, and in particular to an optical fiber signal polarization state detection and high-gain amplification method using stimulated Brillouin scattering (SBS) effect. Background Art

[0002] SBS is one of the most important nonlinear effects in optical fiber, and its application in fields such as optical amplification has attracted widespread attention. The gain of an amplifier based on SBS is affected by the relative polarization state of the pump light and the signal light. When the pump light and the signal light have the same polarization state, the gain is maximum; when the pump light and the signal light polarization state are in an orthogonal state, the gain is minimum. In order to obtain high gain efficiency of the fiber Brillouin amplifier, it is first necessary to adjust the polarization state of the pump light according to the polarization state of the signal light. Therefore, it is of great significance to achieve fast and accurate detection of the polarization state of the signal light.

[0003] At present, there are three main methods for realizing polarization detection: modulation type, spectroscopic type and interference type. The modulation type detection system modulates the light intensity by rotating the optical elements (such as polarizers, wave plates, etc.) in the optical path or introducing a modulator (such as an electro-optical modulator, etc.) in the optical path, and measures the modulated light intensity to obtain the Stokes parameter. The spectroscopic detection method can be further divided into two methods: amplitude division and wavefront division. The amplitude division method uses a partial reflector or other spectroscopic device to divide the light to be measured into multiple optical paths of different polarization analyzers, and uses multiple photodetectors to measure the power of each path at the same time, thereby obtaining the Stokes parameter of the light wave at a certain moment; the wavefront division method usually uses multiple apertures of the same size to divide the wavefront of the light wave into multiple paths according to the power, and then associates and modulates each optical signal, and then simultaneously detects the light intensity of each path and calculates the Stokes parameter. The interference detection system constructs an interference optical path, converges the multi-path modulated light beams with polarization information on the detection surface to make them interfere, and obtains the polarization state of the light wave by analyzing the interference image. This method is suitable for polarization detection of single wavelength or narrow linewidth light waves. The above methods can all realize the measurement of the polarization state of optical signals, but all require additional complex optical paths and analysis systems, which greatly increases the cost of the amplifier.

[0004] The purpose of the present invention is to solve the problem of detecting the polarization state of signal light of an optical fiber Brillouin amplifier and thereby achieve the purpose of improving the amplifier gain, and propose an optical fiber signal polarization state detection and high-gain amplification method based on SBS. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The present invention provides a method for detecting the polarization state of optical fiber signals and amplifying them with high gain based on SBS, the purpose of which is to achieve the purpose of detecting the polarization state of signal light and outputting them with high gain.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention proposes a method for detecting the polarization state of an optical fiber signal and amplifying the optical fiber signal based on SBS, using polarization-maintaining optical fiber as a gain medium, and further comprising:

[0009] Step 1: Establish SBS gain and signal light Stokes vector The fitting polynomials of the parameter mapping in are: Set the pump light polarization state to Adjust the value of the first parameter s1 in the signal light Stokes vector (from -1 to 1) and record the corresponding SBS gain G1, establish the mapping polynomial s1 = f1 (G1) between the SBS gain and s1; then set the pump light polarization state to Adjust the value of the second parameter s2 in the signal light Stokes vector (from -1 to 1) and record the corresponding SBS gain G2, establish the mapping polynomial s2 = f2 (G2) between the SBS gain and s2; finally, set the pump light polarization state to Adjust the value of the third parameter s3 in the signal light Stokes vector (from -1 to 1) and record the corresponding SBS gain G3, and establish a mapping polynomial s3=f3(G3) between the SBS gain and s3;

[0010] Step 2: Reconstruct the Stokes vector of any signal light according to the fitting polynomial and SBS gain: Set the polarization state of the pump light to Test the SBS gain and substitute the first parameter s1 of the signal light Stokes vector into the fitting polynomial f1(G1); set the pump light polarization state to Test the SBS gain and substitute the second parameter s2 of the signal light Stokes vector into the fitting polynomial f2(G2); set the polarization state of the pump light to Test the SBS gain and substitute it into the fitting polynomial f3(G3) to calculate the third parameter s3 of the signal light Stokes vector;

[0011] Step 3: Adjust the polarization state of the pump light according to the reconstructed Stokes vector of the signal light to achieve high gain amplification.

[0012] As a preferred example, the fitting polynomial can be a third-order polynomial, a fourth-order polynomial, a fifth-order polynomial or a sixth-order polynomial.

[0013] (III) Beneficial effects

[0014] The present invention discloses a method for detecting the polarization state of optical fiber signals and amplifying them with high gain based on SBS. First, in the preparation stage, three specific pump light polarization states are constructed [1 0 0] T , [0 1 0] Tand [0 0 1] T The SBS gain is mapped to the fitting polynomials of the three parameters s1, s2 and s3 in the signal light Stokes vector respectively; then in the test phase, the polarization state of the pump light is set to [1 0 0] T , [0 1 0] T and [0 0 1] T , the three SBS gains obtained at this time are substituted into the fitting polynomial to reconstruct the signal light Stokes vector; finally, the polarization state of the pump light is adjusted to achieve high gain amplification. This method uses SBS to achieve optical fiber signal polarization state measurement and high gain amplification. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0016] Figure 1 This is a schematic diagram of the optical path structure of the optical fiber signal polarization state detection and high gain amplification method based on SBS;

[0017] Figure 2 It is a specific implementation flow chart of the optical fiber signal polarization state detection and high gain amplification method based on SBS;

[0018] Figure 3 It is the measured data and the third-order fitting curve diagram of the corresponding relationship between the SBS gain and each component of the signal light Stokes vector;

[0019] Figure 4 It is the maximum deviation angle between the test polarization state and the original polarization state among the 100 test data sets;

[0020] Figure 5 This is a comparison chart of the final output gain of 100 groups of signal light and the target gain. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The purpose of the present invention is to provide a method for detecting the polarization state of an optical fiber signal and amplifying the optical fiber signal with high gain based on SBS, so as to realize the polarization state measurement and high gain amplification of the optical fiber signal.

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0024] Figure 1 The schematic diagram of the optical path structure of a method for polarization state detection and high gain amplification of optical fiber signals based on SBS provided by the present invention. The optical signal is input from the left side of the gain fiber, amplified by the stimulated Brillouin scattering effect, and then output through the circulator. The polarization state of the pump light is controlled by the polarization controller before it is input into the optical fiber from the right side through the circulator. The polarization state of the pump light is set to [1 0 0] in sequence. T , [0 1 0] T and [0 0 1] T After three specific states, the gains corresponding to the output fiber signals are and The polarization state of the signal light can be calculated from the three gain values.

[0025] like Figure 2 A specific implementation flow chart of a method for detecting polarization state of optical fiber signal and amplifying high gain based on SBS provided by the present invention includes:

[0026] Step 1: Establish the stimulated Brillouin scattering (SBS) gain and the signal light Stokes vector The fitting polynomials of the parameter mapping in are: Set the pump light polarization state to Adjust the value of the first parameter s1 in the signal light Stokes vector (from -1 to 1) and record the corresponding SBS gain G1, establish the mapping polynomial s1=f1(G1) between the SBS gain and s1; set the pump light polarization state to Adjust the value of the second parameter s2 in the signal light Stokes vector (from -1 to 1) and record the corresponding SBS gain G2, establish the mapping polynomial s2 = f2 (G2) between the SBS gain and s2; set the pump light polarization state to Adjust the value of the third parameter s3 in the signal light Stokes vector (from -1 to 1) and record the corresponding SBS gain G3, and establish the mapping polynomial s3 = f3 (G3) between the SBS gain and s3. When the polarization state of the pump light is set to [1 0 0] T , [0 1 0] T and [0 0 1] T When , the corresponding relationship between the SBS gain and the three components s1, s2 and s3 in the signal light Stokes vector is as follows: Figure 3As shown in the square box, it can be seen that the SBS gain has a monotonically increasing relationship with s1, s2 and s3. Figure 3 The solid line in the middle is obtained by fitting the box points in the figure using a third-order polynomial. The expression of the third-order polynomial is:

[0027]

[0028] In formula 1, A3 = 9.36 × 10 -5 , A2=0.30×10 -2 , A1=0.68×10 -1 , A0=-0.97.

[0029] Step 2: Reconstruct the Stokes vector of the signal light based on the fitting polynomial and the SBS gain: Set the polarization state of the pump light to Test the SBS gain and substitute the first parameter of the signal light Stokes vector into the fitting polynomial f1(G1); set the pump light polarization state to Test the SBS gain and substitute it into the fitting polynomial f2(G2) to calculate the second parameter of the signal light Stokes vector; set the polarization state of the pump light to The SBS gain is tested and substituted into the fitting polynomial f3(G3) to calculate the third parameter of the signal light Stokes vector. 100 groups of signal light input fibers with different polarization states are randomly selected, and the signal light polarization state is reconstructed by the test method based on stimulated Brillouin scattering effect. Figure 4 The figure shows the group with the largest deviation between the test polarization state and the original polarization state among the 100 groups of reconstructed signal lights, where the original polarization state vector is [-0.1710 0.9698 -0.1737] T , and the polarization state vector obtained by the test is [-0.2494 0.9350 -0.2522] T , the deviation angle is 6.669°.

[0030] Step 3: Adjust the polarization state of the pump light according to the reconstructed Stokes vector of the signal light to achieve high gain amplification. Figure 5 The solid line in the middle is the output gain of 100 groups of signal light, and the dotted line represents the target gain (29.8177 dB) that can be achieved when the polarization states of the pump light and the signal light are exactly the same. By comparison, it can be found that the difference between the actual gain and the target gain is only 0.0519 dB, indicating that the method of the present invention can achieve high-gain amplification based on stimulated Brillouin scattering effect.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting polarization state of optical fiber signal and high gain amplification based on stimulated Brillouin scattering effect, characterized in that: Using polarization-maintaining fiber as the gain medium, also includes: Step 1: Establish the stimulated Brillouin scattering (SBS) gain and the signal light Stokes vector Fitting polynomials for the parameter mappings in : 1.1 Set the polarization state of the pump light to Adjust the value of the first parameter s1 in the signal light Stokes vector (from -1 to 1) and record the corresponding SBS gain G1, and establish a mapping polynomial s1=f1(G1) between the SBS gain and s1; 1.2 Set the polarization state of the pump light to Adjust the value of the second parameter s2 in the signal light Stokes vector (from -1 to 1) and record the corresponding SBS gain G2, and establish a mapping polynomial s2 = f2 (G2) between the SBS gain and s2; 1.3 Set the polarization state of the pump light to Adjust the value of the third parameter s3 in the signal light Stokes vector (from -1 to 1) and record the corresponding SBS gain G3, and establish a mapping polynomial s3=f3(G3) between the SBS gain and s3; Step 2: Reconstruct the Stokes vector of any signal light according to the fitting polynomial and SBS gain: 2.1 Set the polarization state of the pump light to Test the SBS gain G1 and substitute it into the fitting polynomial f1(G1) to calculate the first parameter s1 of the signal light Stokes vector; 2.2 Set the polarization state of the pump light to Test the SBS gain G2 and substitute it into the fitting polynomial f2(G2) to calculate the second parameter s2 of the signal light Stokes vector; 2.3 Set the polarization state of the pump light to Test the SBS gain G3 and substitute it into the fitting polynomial f3(G3) to calculate the third parameter s3 of the signal light Stokes vector; Step 3: Adjust the polarization state of the pump light according to the reconstructed Stokes vector of the signal light to achieve high gain amplification.

2. The method for detecting polarization state of optical fiber signal and amplifying high gain based on stimulated Brillouin scattering effect according to claim 1, characterized in that: The polynomial may be a third-order polynomial, a fourth-order polynomial, a fifth-order polynomial or a sixth-order polynomial.

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