DISTRIBUTED PULSED LIGHT AMPLIFIER BASED ON OPTICAL FIBER PARAMETER AMPLIFICATION, AND AMPLIFICATION AND PERFORMANCE CHARACTERIZATION METHOD

Abstract

The present invention discloses a distributed pulsed light amplifier based on optical fiber parameter amplification, comprising a pump pulsed light source, a sensing pulsed light source, a synchronization device, a two-in-one optical coupler, an optical circulator, a parameter amplification optical fiber, a first optical filter, a photoelectric detector and a signal acquisition device. According to the distributed pulsed light amplifier, high-power pulsed light is used as pump light to generate an optical fiber parameter amplification effect near a zero-dispersion wavelength of an optical fiber, thereby amplifying a power of another sensing pulsed light. Meanwhile, due to the fact that effective optical fiber parameter amplification cannot be achieved through low-power light leakage outside a duration interval of the pump pulsed light, leaked light from the sensing pulsed light cannot be amplified, and the effect of amplifying a pulse extinction ratio can be achieved at the same time.

Claims

1. A distributed pulsed light amplifier based on optical fiber parameter amplification, comprising a pump pulsed light source (1), a sensing pulsed light source (2), a synchronization device (3), a two-in-one optical coupler (4), an optical circulator (5), a parameter amplification optical fiber (6), a first optical filter (7), a photoelectric detector (8) and a signal acquisition device (9), wherein outputs of the pump pulsed light source (1) and the sensing pulsed light source (2) are combined through the two-in-one optical coupler (4) and then enter a first communication terminal of the optical circulator (5), and are output by a second communication terminal of the optical circulator (5) and then enter the parameter amplification optical fiber (6); the synchronization device (3) is used to ensure that pump pulsed light output by the pump pulsed light source (1) and sensing pulsed light output by the sensing pulsed light source (2) are synchronized in pulse time; the signal acquisition device (9) is used for acquiring a pulse synchronization trigger signal for the synchronization device (3); a Rayleigh scattering effect in the parameter amplification optical fiber (6) causes the pump pulsed light and the sensing pulsed light to generate scattered light in a direction opposite to a pulse transmission direction; the scattered light in the direction opposite to the pulse transmission direction is input by the second communication terminal of the optical circulator (5) and then output by a third communication terminal of the optical circulator (5), and only retains a sensing pulse scattered light signal after passing through the first optical filter (7); the photoelectric detector (8) is used for performing photoelectric conversion on the sensing pulse scattered light signal; the signal acquisition device (9) is used to acquire an electric signal for the sensing pulse scattered light according to the pulse synchronization trigger signal, and obtain a signal power and a signal-to-noise ratio that vary with the length of the parameter amplification optical fiber (6) according to the electric signal for the sensing pulse scattered light; and by adjusting a pump pulse power and a wavelength of the pump pulsed light source (1) and a sensing pulse power and a wavelength of the sensing pulsed light source (2), the signal power and the signal-to-noise ratio that vary with the length of the parameter amplification optical fiber (6) can both reach corresponding preset values of the signal power and the signal-to-noise ratio.

2. The distributed pulsed light amplifier based on optical fiber parameter amplification according to claim 1, wherein the signal acquisition device (9) is used to calculate the signal power that varies with the length of the parameter amplification optical fiber (6) according to a time-domain change of the electric signal for the sensing pulse scattered light and in combination with a light velocity in the parameter amplification optical fiber (6), and then calculate the signal-to-noise ratio that varies with the length of the parameter amplification optical fiber (6) in combination with a system background noise.

3. The distributed pulsed light amplifier based on optical fiber parameter amplification according to claim 1, wherein the pump pulsed light source (1) comprises a first laser (1.1), a first light intensity modulator (1.2), a first electrical pulse source (1.3), a first electrical amplifier (1.4), an optical amplifier (1.5), a second optical filter (1.6) and a polarization controller (1.7), wherein a laser signal output terminal of the first laser (1.1) is connected to an optical signal input terminal of the first light intensity modulator (1.2); an electrical pulse signal output terminal of the first electrical pulse source (1.3) is connected to an electrical signal input terminal of the first light intensity modulator (1.2) through the first electrical amplifier (1.4); the first light intensity modulator (1.2) is used to perform light intensity modulation on a laser signal by using an electrical pulse signal, and convert a laser signal of continuous waves into a pulsed light signal; a pulse width is determined by the electrical pulse signal applied to the first light intensity modulator (1.2); and the pulsed light signal passes through the optical amplifier (1.5), the second optical filter (1.6) and the polarization controller (1.7) in sequence to form a pump pulsed light signal.

4. The distributed pulsed light amplifier based on optical fiber parameter amplification according to claim 3, wherein the first electrical pulse source (1.3) is used to receive a synchronization control signal sent by the synchronization device (3).

5. The distributed pulsed light amplifier based on optical fiber parameter amplification according to claim 1, wherein the sensing pulsed light source (2) comprises a second laser (2.1), a second light intensity modulator (2.2), a second electrical pulse source (2.3) and a second electrical amplifier (2.4), wherein a laser signal output terminal of the second laser (2.1) is connected to an optical signal input terminal of the second light intensity modulator (2.2); an electrical pulse signal output terminal of the second electrical pulse source (2.3) is connected to an electrical signal input terminal of the second light intensity modulator (2.2) through the second electrical amplifier (2.4); and the second light intensity modulator (2.2) is used to perform light intensity modulation on a laser signal by using an electrical pulse signal.

6. The distributed pulsed light amplifier based on optical fiber parameter amplification according to claim 3, wherein the sensing pulsed light source (2) comprises a second laser (2.1), a second light intensity modulator (2.2), a second electrical pulse source (2.3) and a second electrical amplifier (2.4), wherein a laser signal output terminal of the second laser (2.1) is connected to an optical signal input terminal of the second light intensity modulator (2.2); an electrical pulse signal output terminal of the second electrical pulse source (2.3) is connected to an electrical signal input terminal of the second light intensity modulator (2.2) through the second electrical amplifier (2.4); and the second light intensity modulator (2.2) is used to perform light intensity modulation on a laser signal by using an electrical pulse signal.

7. The distributed pulsed light amplifier based on optical fiber parameter amplification according to claim 5, wherein the second electrical pulse source (2.3) is used to receive a synchronization control signal sent by the synchronization device (3).

8. A pulsed light amplification method based on the amplifier according to claim 1, comprising the following steps: 1, emitting pump pulsed light with a center wavelength of λ.sub.P by a pump pulsed light source (1); 2, emitting sensing pulsed light with a center wavelength of λ.sub.S by a sensing pulsed light source (2), wherein the pump pulsed light has a pulse width greater than the sensing pulsed light, the polarization of the pump pulsed light is identical with that of the sensing pulsed light, and the center length λ.sub.S is tuned within an amplifier gain spectrum range, i.e., within a range from λ.sub.S,start to λ.sub.S,stop; 3, combining the amplified pump pulsed light and sensing pulsed light by a two-in-one optical coupler (4), and ensuring that the pump pulsed light and the sensing pulsed light are synchronized in pulse time by a synchronization device (3); and 4, inputting the time-synchronized pump pulsed light and sensing pulsed light by a first communication terminal of an optical circulator (5), and outputting the same by a second communication terminal of the optical circulator (5) and then entering a parameter amplification optical fiber (6), wherein a distributed optical fiber parameter process occurs in the optical fiber transmission process, the pump pulsed light is consumed and the sensing pulsed light is amplified, and meanwhile, idler-frequency pulsed light having a center wavelength of 1/λI=2/λ.sub.P−1/λ.sub.S is generated to realize the amplification of the sensing pulsed light.

9. An amplifier performance characterization method using the pulsed light amplification method according to claim 7, comprising the following steps: 101, causing pump pulsed light and sensing pulsed light to generate scattered light in a direction opposite to a pulse transmission direction by using a Rayleigh scattering effect in a parameter amplifier optical fiber (6); inputting the scattered light in the direction opposite to the pulse transmission direction by a second communication terminal of an optical circulator (5) and then outputting the same by a third communication terminal of the optical circulator (5); filtering the scattered light in the direction opposite to the pulse transmission direction by a first optical filter (7) to remove a scattered signal derived from the pump pulsed light and the idler-frequency pulsed light, thereby obtaining a scattered light signal derived from the sensing pulsed light; converting the scattered light signal into an electric signal by a photoelectric detector (8), and acquiring the electric signal by a signal acquisition device (9); 102, turning off a pump pulsed light source (1); obtaining variations of a power and a signal-to-noise ratio of the scattered signal for the sensing pulsed light with the length of an parameter amplification optical fiber (6) by inversion calculation at a wavelength of) λ.sub.S,start, according to a time-domain electrical signal acquired by the signal acquisition device (9), denoted as P.sub.off,RS(λ.sub.S,start, z) and SNR.sub.off,RS (λ.sub.S,start, z), respectively, wherein z represents the length of the parameter amplification optical fiber (6); 103, gradually tuning the center wavelength of the sensing pulsed light by taking the wavelength λ.sub.S,step as an interval; repeating the step 102, till the length reaches λ.sub.S,stop; obtaining variations of the power and the signal-to-noise ratio of the scattered signal for the sensing pulsed light with the length of the parameter amplification optical fiber (6) and the center wavelength of the sensing pulsed light when the pumping pulsed light source (1) turned off, denoted as P.sub.off,Rs (λ.sub.S, z) and SNR.sub.off,Rs (λ.sub.S, z); 104, turning on a pump pulsed light source (1); obtaining variations of the power and the signal-to-noise ratio of the scattered signal for the sensing pulsed light with the length of the parameter amplification optical fiber (6) by inversion calculation at a wavelength of λ.sub.S,start under the conditions of the current center wavelength and power of the pump pulsed light source, according to a time-domain electrical signal acquired by the signal acquisition device (9), denoted as P.sub.on,RS(λ.sub.S,start, z) and SNR.sub.on,RS (λ.sub.S,start, z) respectively; 105, gradually tuning the center wavelength of the sensing pulsed light by taking the wavelength λ.sub.S,step as an interval; repeating the step 104, till the length reaches λ.sub.S,stop; obtaining variations of the power and the signal-to-noise ratio of the scattered signal for the sensing pulsed light with the length of the parameter amplification optical fiber (6) and the center wavelength of the sensing pulsed light under the conditions of the current center wavelength and power of the pump pulsed light source, denoted as P.sub.on,RS(λ.sub.S,z) and SNR.sub.on,RS (λ.sub.S, z); 106, calculating variations of a gain spectrum and a noise index spectrum with the length of the parameter amplifier fiber (6), that is, a spatially resolved gain spectrum and a noise index spectrum: G (λ.sub.S, z)=P.sub.on,RS(λ.sub.S, z)−P.sub.off,RS(λ.sub.S,z), NF(λ.sub.S,z)=SNR.sub.on,RS(λ.sub.S,z)−SNR.sub.off,RS(λ.sub.SZ); and 107, adjusting center wavelength and power settings of the pump pulsed light according to the requirements for the gain spectrum and the noise index spectrum, and repeating the steps 104 to 106 until the gain spectrum and the noise spectrum meet design requirements.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. 1 is a schematic structural diagram of the present invention;

[0012] FIG. 2 is a schematic structural diagram of a pump pulsed light source in the present invention; and

[0013] FIG. 3 is a schematic structural diagram of a sensing pulsed light source in the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0015] A distributed pulsed light amplifier based on optical fiber parameter amplification as designed by the present invention, as shown in FIG. 1, includes a pump pulsed light source 1, a sensing pulsed light source 2, a synchronization device 3, a two-in-one optical coupler 4, an optical circulator 5, a parameter amplification optical fiber 6, a first optical filter 7, a photoelectric detector 8 and a signal acquisition device 9, wherein outputs of the pump pulsed light source 1 and the sensing pulsed light source 2 are combined through the two-in-one optical coupler 4 and then enter a first communication terminal (Port a) of the optical circulator 5, and are output by a second communication terminal (Port b) of the optical circulator 5 and then enter the parameter amplification optical fiber 6; the synchronization device 3 is used to ensure that pump pulsed light output by the pump pulsed light source 1 and sensing pulsed light output by the sensing pulsed light source 2 are synchronized in pulse time (aligned centrally in pulse time (that is, repetition frequencies of a pumping pulse and a sensing pulse are identical, and there is always overlap in time), wherein the designed pumping pulse is longer than the sensing pulse in consideration of chromatic dispersion in the optical fiber transmission, so as to ensure there is no deviation in two time after long-distance transmission); the signal acquisition device 9 is used for acquiring a pulse synchronization trigger signal for the synchronization device 3; a Rayleigh scattering effect in the parameter amplification optical fiber 6 causes the pump pulsed light and the sensing pulsed light to generate scattered light in a direction opposite to a pulse transmission direction; the scattered light in the direction opposite to the pulse transmission direction is input through the second communication terminal of the optical circulator 5 and then output by a third communication terminal (Port c) of the optical circulator 5, and only retains a sensing pulse scattered light signal after passing through the first optical filter 7 (a bandpass optical filter); the photoelectric detector 8 is used for performing photoelectric conversion on the sensing pulse scattered light signal; the signal acquisition device 9 is used to acquire an electric signal for a sensing pulse scattered light according to the pulse synchronization trigger signal (determining a time interval for signal acquisition according to a time corresponding to pulses, and triggering the acquisition synchronously), and obtain a signal power and a signal-to-noise ratio that vary with the length of the parameter amplification optical fiber 6 according to the electric signal for the sensing pulse scattered light; and by adjusting a pump pulse power and a wavelength of the pump pulsed light source 1 and a sensing pulse power and a wavelength of the sensing pulsed light source 2, the signal power and the signal-to-noise ratio that vary with the length of the parameter amplification optical fiber 6 can both reach corresponding preset values of the signal power and the signal-to-noise ratio.

[0016] In the above technical solution, the signal acquisition device 9 is used to calculate the signal power that varies with the length of the parameter amplification optical fiber 6 according to a time-domain variation of the electric signal for the sensing pulse scattered light and in combination with a light velocity in the parameter amplification optical fiber 6, and then calculate the signal-to-noise ratio that varies with the length of the parameter amplification optical fiber 6 in combination with a system (i.e., the amplifier in the present invention) background noise.

[0017] In the above technical solution, as shown in FIG. 2, the pump pulsed light source 1 includes a first laser 1.1, a first light intensity modulator 1.2, a first electrical pulse source 1.3, a first electrical amplifier 1.4, an optical amplifier 1.5, a second optical filter 1.6 and a polarization controller 1.7, wherein a laser signal output terminal of the first laser 1.1 is connected to an optical signal input terminal of the first light intensity modulator 1.2; an electrical pulse signal output terminal of the first electrical pulse source 1.3 is connected to an electrical signal input terminal of the first light intensity modulator 1.2 through the first electrical amplifier 1.4; the first light intensity modulator 1.2 is used to perform light intensity modulation on a laser signal by using an electrical pulse signal, and convert a laser signal of continuous waves into a pulsed light signal; a pulse width is determined by the electrical pulse signal applied to the first light intensity modulator 1.2; and the pulsed light signal passes through the optical amplifier 1.5, the second optical filter 1.6 and the polarization controller 1.7 in sequence to form a pump pulsed light signal.

[0018] In the above technical solution, the first electrical pulse source 1.3 is used to receive a synchronization control signal sent by the synchronization device 3.

[0019] In the above technical solution, as shown in FIG. 3, the sensing pulsed light source 2 includes a second laser 2.1, a second light intensity modulator 2.2, a second electrical pulse source 2.3 and a second electrical amplifier 2.4, wherein a laser signal output terminal of the second laser 2.1 is connected to an optical signal input terminal of the second light intensity modulator 2.2; an electrical pulse signal output terminal of the second electrical pulse source 2.3 is connected to an electrical signal input terminal of the second light intensity modulator 2.2 through the second electrical amplifier 2.4; and the second light intensity modulator 2.2 is used to perform light intensity modulation on a laser signal by using an electrical pulse signal to form a sensing pulsed light signal.

[0020] In the above technical solution, the second electrical pulse source 2.3 is used to receive a synchronization control signal sent by the synchronization device 3.

[0021] In the parameter amplification optical fiber 6, the pump pulsed light transmits energy to the sensing pulsed light through the optical fiber parameter amplification process, so as to realize distributed light amplification of the sensing pulsed light. To ensure the effectiveness of optical fiber parameter amplification, a zero-dispersion wavelength of the optical fiber should be close to and slightly smaller than the center wavelength of the pump pulsed light (usually 1 to 5 nm smaller than the pump wavelength). In order to achieve a large effective amplification distance, the transmission loss of the optical fiber subjected to parameter amplification should be as small as possible, which is preferably not higher than the transmission loss of the existing communication optical fiber.

[0022] At the same time as the parameter amplification process occurs, the Rayleigh scattering effect in the parameter amplification optical fiber 6 causes the pump pulsed light and the sensing pulsed light to generate back-transmitted scattered light, wherein a sensing pulse back-scattered light signal is a distributed optical fiber sensing signal subjected to distributed light amplification.

[0023] The first optical filter 7 is used to obtain the distributed optical fiber sensing signal subjected to distributed light amplification, which has a center wavelength of λ.sub.S, and a passband range that should ensure that a sensing pulsed light scattering signal is retained, and a pump pulsed light scattering signal is completely filtered out.

[0024] The principle of using optical fiber parameter amplification to realize distributed light amplification of a sensing signal, and the specific process of characterization of distributed light amplification performance are as follows.

[0025] When the pump pulsed light and the sensing pulsed light in the above system enter a high nonlinear optical fiber at the same time, and the pump pulsed light and the sensing pulsed light are synchronized in time, the optical fiber parameter amplification occurs, the energy of the pump pulsed light is transferred to the sensing pulsed light to amplify the sensing pulsed light, and at the same time, idler-frequency pulse light having a wavelength of λ.sub.I is generated, with a center wavelength is λ.sub.I=2λ.sub.P−λ.sub.S. Under the premise that the power of the sensing pulsed light is relatively low, and thus a high-order four-wave mixing product can be ignored, the variations in power and relative phase difference of the pump pulsed light, the sensing pulsed light and the idler-frequency pulsed light as a function of the optical fiber length Z are given by the following set of coupled wave equations:

[00001]$\begin{array}{cc}\frac{d{P}_P}{dz}=-4{\gamma \left(P_P^2{P}_S{P}_I\right)}^{\frac{1}{2}}\sin \theta & \left(1\right)\\ \frac{d{P}_S}{dz}=2{\gamma \left(P_P^2{P}_S{P}_I\right)}^{1/2}\sin \theta & \left(2\right)\\ \frac{d{P}_I}{dz}=2{\gamma \left(P_P^2{P}_S{P}_I\right)}^{1/2}\sin \theta & \left(3\right)\\ \frac{d\theta }{dz}=\Delta \beta +\gamma \left(2P_P-P_S-P_I\right)+\gamma \left[{\left(P_P^2{P}_I/P_S\right)}^{1/2}+{\left(P_P^2{P}_I/P_S\right)}^{1/2}-4{\left(P_S{P}_I\right)}^{1/2}\right]\cos \theta & \left(4\right)\end{array}$

[0026] in which P.sub.p, P.sub.S and P.sub.I are the powers of the pump pulsed light, the sensing pulsed light and the idler-frequency pulsed light; y is a non-linear coefficient of the optical fiber; θ is a relative phase difference; z represents the length of the parameter amplification optical fiber and is given by:

θ(z)=Δβz+2ϕ.sub.P(z)−ϕ.sub.S(z)−ϕ.sub.I(z)  (5)

[0027] in which, Δβ a chromatic-dispersion-induced linear phase mismatch, which is given by:

[00002]$\begin{array}{cc}\Delta \beta =\left\{{\beta }_3\left({\omega }_P-{\omega }_0\right)+\frac{{\beta }_4}{2}\left[{\left({\omega }_P-{\omega }_0\right)}^2+\frac{1}{6}{\left({\omega }_P-{\omega }_S\right)}^2\right]\right\}{\left({\omega }_P-{\omega }_S\right)}^2& \left(6\right)\end{array}$

[0028] in which, β.sub.3 and β.sub.4 are third-order and fourth-order derivatives of a propagation constant β(ω) at a zero-dispersion circular frequency ω.sub.0, respectively. Since the effect of higher-order chromatic dispersion can be ignored, only the effects of β.sub.3 and β.sub.4 on the linear phase mismatch are considered here. ϕ.sub.P (Z), ϕ.sub.S(Z) and ϕ.sub.I(Z) are phases of the pump pulsed light, the sensing pulsed light and the idler-frequency pulsed light respectively, which are given by their respective initial phases together with the nonlinear phase shift produced by the transmission process; θ(z) represents the variation in relative phase difference (the relative phase relationship among the pump light, the sensing light and the idler-frequency light) with a transmission distance of light in the parameter amplification optical fiber; and ω.sub.P and ω.sub.S are circular frequencies of the pump pulsed light and the sensing pulsed light respectively.

[0029] When the amplifier works under a condition of phase matching, i.e., θ(z)≈π/2, the third term on the right side of the equal sign in Equation (4) can be ignored. At this time, then:

[00003]$\begin{array}{cc}\frac{d\theta }{dz}\approx \Delta \beta +\gamma \left(2P_P-P_S-P_I\right)& \left(7\right)\end{array}$

[0030] wherein the second term is a phase adaptation term caused by the nonlinear phase shift in the transmission process. In a shorter optical fiber, the optical fiber parameter amplifier works in a pumped non-depleted mode (P.sub.p »P.sub.S), then Equation (6) can be simplified as:

[00004]$\begin{array}{cc}\frac{d\theta }{dz}\approx \Delta \beta +2\gamma P_P=\kappa & \left(8\right)\end{array}$

[0031] wherein κ is a phase mismatch parameter, and the variations of the powers of the sensing pulsed light and the idler-frequency pulsed light with the length of the optical fiber are given by Equations (9) and (10):

[00005]$\begin{array}{cc}{P}_S\left(z\right)=P_S\left(0\right)\left\{1+{\left[\frac{\gamma P_P}{g}\sinh \left(gL\right)\right]}^2\right\}& \left(9\right)\\ P_I\left(z\right)={P_S\left(0\right)\left[\frac{\gamma P_P}{g}\sinh \left(gL\right)\right]}^2& \left(10\right)\end{array}$

[0032] in which, P.sub.S(z) represents the variation of the power of the sensing pulsed light with the length of the optical fiber; P.sub.s(0) represents the power of the input sensing pulsed light; P.sub.I(z) represents the variation of the power of the idler-frequency pulsed light with the length of the optical fiber; sinh is a hyperbolic sine function; and a parameter gain coefficient g is given by:

[00006]$\begin{array}{cc}{g}^2=\left[{\left(\gamma P_P\right)}^2-{\left(\kappa /2\right)}^2\right]=-\Delta \beta \left(\frac{\Delta \beta }{4}+\gamma P_P\right)& \left(11\right)\end{array}$

[0033] in which, L is an effective length of the optical fiber subjected to the parameter amplification. In the case of considering that the optical fiber has no transmission loss, L=z. In the case that the optical fiber has transmission loss, then:

[00007]$\begin{array}{cc}L=\frac{1-\exp \left(-\alpha z\right)}{\alpha }& \left(12\right)\end{array}$

[0034] in which α is a linear attenuation coefficient of the optical fiber.

[0035] When the non-depletion assumption of the pump pulsed light is set up, the power of the sensing pulsed light can be calculated according to Formula (10) and the input optical power P.sub.S(0) of the sensing pulsed light. When the non-depletion assumption of the pump pulsed light cannot be set up due to the transmission loss and the transfer of the power to the sensing pulsed light and the idler-frequency pulsed light, the power of the sensing pulsed light needs to be calculated by solving Equations sets (1) to (4). These calculation methods can provide a basis for adjusting the center wavelength and power of the pump light in the following steps.

[0036] A pulsed light amplification method based on the amplifier includes the following steps: [0037] 1, emitting pump pulsed light with a center wavelength of λ.sub.P by a pump pulsed light source 1; [0038] 2, emitting sensing pulsed light with a center wavelength of λ.sub.S by a sensing pulsed light source 2, wherein the pump pulsed light has a pulse width greater than the sensing pulsed light, the polarization of the pump pulsed light is identical with that of the sensing pulsed light, and the center length λ.sub.S is tuned within an amplifier gain spectrum range, i.e., within a range from λ.sub.S,start to λ.sub.S,stop, wherein the wavelength is set first as λ.sub.S,start; [0039] 3, combining the amplified pump pulsed light and sensing pulsed light by a two-in-one optical coupler 4, and ensuring that the pump pulsed light and the sensing pulsed light are synchronized in pulse time by a synchronization device 3; and [0040] 4, inputting the time-synchronized pump pulsed light and sensing pulsed light by a first communication terminal of an optical circulator 5, and outputting the same by a second communication terminal of the optical circulator 5 and then entering a parameter amplification optical fiber 6, wherein a distributed optical fiber parameter process occurs in the optical fiber transmission process, the pump pulsed light is consumed and the sensing pulsed light is amplified, and meanwhile, idler-frequency pulsed light having a center wavelength of 1/λ.sub.I=2/λ.sub.P−1/λ.sub.S is generated to realize the amplification of the sensing pulsed light.

[0041] An amplifier performance characterization method using the above-mentioned pulsed light amplification method includes the following steps: [0042] 101, causing pump pulsed light and sensing pulsed light to generate scattered light in a direction opposite to a pulse transmission direction by using a Rayleigh scattering effect in a parameter amplification optical fiber 6; inputting the scattered light in the direction opposite to the pulse transmission direction through a second communication terminal of an optical circulator 5 and then outputting the same by a third communication terminal of the optical circulator 5; filtering the scattered light in the direction opposite to the pulse transmission direction by a first optical filter 7 to remove a scattered signal derived from the pump pulsed light and the idler-frequency pulsed light, thereby obtaining a scattered light signal derived from the sensing pulsed light; converting the scattered light signal into an electric signal by a photoelectric detector 8, and acquiring the electric signal by a signal acquisition device 9; [0043] 102, turning off a pump pulsed light source 1; obtaining variations of a power and a signal-to-noise ration of the scattered signal for the sensing pulsed light with the length of an parameter amplification optical fiber 6 by inversion calculation at a wavelength of λ.sub.S,start according to a time-domain electrical signal acquired by the signal acquisition device 9, denoted as P.sub.off,RS(λ.sub.S,start,Z) and SNR.sub.off,RS (λ.sub.S,start, z) respectively, wherein z represents the length of the parameter amplification optical fiber 6; [0044] 103, gradually tuning the center wavelength of the sensing pulsed light by taking the wavelength λ.sub.S,step as an interval (the setting of the wavelength interval is related to the actual fineness of the gain spectrum measurement, which may usually be set at 0.1 nm); repeating the step 102, till the length reaches λ.sub.S,stop; obtaining variations of the power and the signal-to-noise ratio of the scattered signal for the sensing pulsed light with the length of the parameter amplification optical fiber 6 and the center wavelength of the sensing pulsed light when the pumping pulsed light source 1 turned off, denoted as P.sub.off,RS (λ.sub.S, z) and SNR.sub.off,RS(λ.sub.S, z); [0045] 104, turning on the pump pulsed light source 1; obtaining variations of the power and the signal-to-noise ratio of the scattered signal for the sensing pulsed light with the length of the parameter amplification optical fiber 6 by inversion calculation at a wavelength of λ.sub.S,start under the conditions of the current center wavelength and power of the pump pulsed light source, according to a time-domain electrical signal acquired by the signal acquisition device 9, denoted as P.sub.on,RS(λ.sub.S,start,z) and SNR.sub.on,RS(λ.sub.S,start,z), respectively; [0046] 105, gradually tuning the center wavelength of the sensing pulsed light by taking the wavelength λ.sub.S,step as an interval; repeating the step 104, till the length reaches λ.sub.S,stop; obtaining variations of the power and the signal-to-noise ratio of the scattered signal of the sensing pulsed light with the length of the parameter amplification optical fiber 6 and the center wavelength of the sensing pulsed light under the conditions of the center wavelength and power of the current pump pulsed light source, denoted as P.sub.on,RS(λ.sub.S,z) and SNR.sub.on,RS(λ.sub.S, z); [0047] 106, calculating variations of a gain spectrum and a noise index spectrum with the length of the parameter amplifier fiber 6, that is, a spatially resolved gain spectrum and a noise index spectrum: G(λ.sub.S, z)=P.sub.on,RS (λ.sub.S,z)−P.sub.off,RS (λ.sub.S,Z), NF(λ.sub.S,z)=SNR.sub.on,RS (λ.sub.S, z)−SNR.sub.off,RS(λ.sub.S, z); and [0048] 107, adjusting center wavelength and power settings of the pump pulsed light according to the requirements for the gain spectrum and the noise index spectrum, and repeating the steps 104 to 106 until the gain spectrum and the noise spectrum meet design requirements.

[0049] The content that has not been described in detail in this specification belongs to the prior art known to those skilled in the art.