CN110850660A - All-optical wavelength converter - Google Patents

Abstract

The invention discloses an all-optical wavelength converter with high energy efficiency and high performance for a 64-QAM coherent optical communication system. The invention relates to a method for forming an all-optical wavelength converter with high energy efficiency and high performance, which comprises the following steps: a tunable laser source emits a beam of continuous wave laser, which is attenuated by an attenuator and then amplified by an erbium-doped fiber amplifier to be used as pump light; the obtained pumping light passes through a first optical band-pass filter to remove amplified spontaneous emission noise of the erbium-doped fiber amplifier; the 64-QAM signal light is generated by an external cavity laser and is obtained by modulating by an in-phase quadrature Mach-Zehnder modulator. Has the advantages that: high pump power is a major challenge for all-optical wavelength converters based on aluminum-doped highly nonlinear fibers in practical applications; the high performance is the main appeal of a high-order modulation 64-QAM coherent optical communication system, and the high-energy-efficiency and high-performance method provided by the invention well solves the problems.

Description

All-optical wavelength converter

technical field

The invention relates to the field of communication, in particular to an all-optical wavelength converter with high energy efficiency and high performance for a 64-QAM coherent optical communication system.

Background technique

High-bandwidth applications such as high-definition video, live streaming, and cloud services have driven tremendous growth in global traffic over the past decade. The coherent optical communication system using the high-order 64-QAM modulation format will play a huge advantage in the future large-capacity long-distance communication. However, with the popularity of 5G and the development of the Internet of Things, IP traffic demand will further increase. Cisco's latest "Visual Networking Index" predicts that global IP traffic will triple in the next five years, and by 2022, the annual global IP traffic will reach 4.8ZB.

In addition to huge traffic demands, optical networks also face other problems such as electronic bottlenecks, wavelength blocking, modulation format opaque, high latency, and more. The all-optical wavelength converter can improve the flexibility of the optical network and relieve the constraint of conflicting wavelengths through wavelength management, and is an important network component. All-optical wavelength converters can also increase network capacity and relay distance by compensating for fiber nonlinearity in optical phase conjugate networks. At the same time, an optical network equipped with an all-optical wavelength converter does not require additional components to convert back and forth between optoelectronics.

There are many schemes for configuring all-optical wavelength conversion systems, such as semiconductor optical amplifiers based on cross-gain modulation, highly nonlinear optical fibers based on four-wave mixing, and various waveguides based on four-wave mixing. The highly nonlinear optical fiber solution based on four-wave mixing has the advantages of simple structure, fast response speed and high conversion efficiency.

The traditional technology has the following technical problems:

In order to obtain higher conversion efficiency, methods such as phase or frequency jittering of the pump, metal doping and strain control techniques have been proposed to increase the pump launch into aluminum-doped highly nonlinear fibers by increasing the stimulated Brillouin scattering threshold Pu power. However, higher pump power will result in greater energy consumption and damage to optical components. Idle light is also disturbed by high pump powers close to the threshold of stimulated Brillouin scattering.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for forming an all-optical wavelength converter with high energy efficiency and high performance for a 64-QAM coherent optical communication system.

In order to solve the above technical problems, the present invention provides a method for forming an all-optical wavelength converter with high energy efficiency and high performance for a 64-QAM coherent optical communication system, including:

A tunable laser source emits a continuous wave laser, which is attenuated by an attenuator and then amplified by an erbium-doped fiber amplifier as pump light;

The obtained pump light is removed by the first optical bandpass filter to remove the amplified spontaneous emission noise of the erbium-doped fiber amplifier;

The 64-QAM signal light is generated by an external cavity laser and then modulated by an in-phase and quadrature Mach-Zehnder modulator;

Generate two de-correlated pseudo-random binary sequence signals to drive in-phase and quadrature Mach-Zehnder modulators;

The modulated 64-QAM signal light is amplified by another erbium-doped fiber amplifier and the second optical bandpass filter is used to filter out the amplified spontaneous emission noise;

The polarizations of pump light and 64-QAM signal light are adjusted by their respective polarization controllers to obtain maximum conversion efficiency;

Then, the pump light and the 64-QAM signal light are coupled through a coupler and then passed through an isolator and then launched into the aluminum-doped high nonlinear fiber, wherein the isolator is used to block the induced Brillouin scattering. The reflected wave protects the front-end erbium-doped fiber amplifier;

The pump light and the 64-QAM signal light undergo degenerate four-wave mixing in the aluminum-doped high nonlinear fiber, and the output light wave is filtered by the third optical band-pass filter to obtain the idle light.

Beneficial effects of the present invention:

High pump power is the main challenge for all-optical wavelength converters based on aluminum-doped high nonlinear fibers in practical applications; high performance is the main requirement of high-order modulation 64-QAM coherent optical communication systems. An energy-efficient and high-performance approach addresses these issues well.

In one of the embodiments, an arbitrary waveform generator generates two 12.5 Gbaud pseudo-random binary sequence signals with a length of 2 ¹⁵ -1 to drive the in-phase and quadrature Mach-Zehnder modulators.

In one of the embodiments, the pump light and the 64-QAM signal light are coupled through a 90:10 coupler and then passed through an isolator and then launched into an aluminum-doped high nonlinear fiber.

In one embodiment, the insertion loss of the first optical bandpass filter is 1.74dB; the insertion loss of the second optical bandpass filter is 3.34dB.

In one of the embodiments, the output light wave is filtered by a third optical bandpass filter with a bandwidth of 0.4 nm and an insertion loss of 4 dB to obtain phase-conjugated 64-QAM idle light.

In one embodiment, a part of the obtained idle light is connected to a spectrum analyzer to measure the optical signal-to-noise ratio value and record the spectrum for conversion efficiency calculation; the other part is amplified by an erbium-doped fiber amplifier and then attenuated by an attenuator and then emitted Advance coherent optical receivers for detection and performance evaluation.

In one embodiment, the coherent optical receiver includes a local oscillator, a 90-degree optical mixer and four balanced optical detectors; the received optical signal is first at 90 degrees with the light generated by the local oscillator Mixed in an optical mixer, and then passed through four balance detectors for balance detection.

A computer device includes a memory, a processor, and a computer program stored on the memory and executable on the processor, the processor implementing the steps of any one of the methods when the processor executes the program.

A computer-readable storage medium having a computer program stored thereon, the program implementing the steps of any one of the methods when executed by a processor.

A processor for running a program, wherein the program executes any one of the methods when the program is running.

Description of drawings

FIG. 1 is a schematic diagram of the all-optical wavelength converter based on degenerate four-wave mixing in the all-optical wavelength converter of the present invention.

FIG. 2 is a curve of the conversion efficiency calculated by simulation with the optical power of the input signal under different pump powers in the all-optical wavelength converter of the present invention.

FIG. 3 is a curve of the nonlinear power in the idle light and the input signal power calculated by simulation under different pump powers in the all-optical wavelength converter of the present invention.

FIG. 4 is a curve of the conversion efficiency calculated by simulation with the wavelength of the signal light under different pump powers in the all-optical wavelength converter of the present invention.

FIG. 5 is a structural diagram of an all-optical wavelength converter based on the four-wave mixing effect of an aluminum-doped highly nonlinear fiber according to the present invention.

FIG. 6 is a graph of the conversion efficiency measured experimentally with the wavelength of the input signal light under different pump powers in the all-optical wavelength converter of the present invention.

FIG. 7 is the output spectrum of the aluminum-doped highly nonlinear fiber in the all-optical wavelength converter of the present invention.

FIG. 8 is a graph of the experimentally measured idle optical bit error rate versus input signal power under different pump powers in the all-optical wavelength converter of the present invention.

FIG. 9 is a graph of the experimentally measured idle optical bit error rate versus optical signal-to-noise ratio under different pump powers in the all-optical wavelength converter of the present invention.

10 is a constellation diagram of the input back-to-back 64-QAM signal and the phase-conjugated 64-QAM idle light generated under different pump and signal powers in the all-optical wavelength converter of the present invention.

11 is a graph of the bit error rate versus the optical signal-to-noise ratio of the input back-to-back signals and the idle light generated under different pump and signal powers, respectively, measured experimentally in the all-optical wavelength converter of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

In optical phase-conjugate networks, all-optical wavelength converters are usually symmetrically deployed in the midspan of discrete amplified coherent optical transmission systems, and the compensation effect of fiber nonlinearity depends on the quality of idle light. Since the constellation points of the high-order modulated 64-QAM signal are denser and the distance between the constellation points is smaller, the performance of the all-optical wavelength converter has a greater impact on it. Slightly serious noise will cause the divergence of the constellation points. A large number of decision errors are caused, which ultimately affects the signal bit error rate performance. Therefore, high-performance all-optical wavelength converters are more important for high-order modulation of 64-QAM signals. The quality of the idle light depends largely on the power of the pump and 64-QAM signal launched into the Al-doped highly nonlinear fiber. Increasing pump power to improve conversion efficiency is not the only way to improve idle light performance.

The invention establishes an all-optical wavelength conversion scheme with a higher stimulated Brillouin scattering threshold based on an aluminum-doped high nonlinear fiber, and calculates and measures the conversion efficiency theoretically and experimentally. Although lower pump power results in lower conversion efficiency, the idle light performance can be improved by optimizing the signal power launched into the aluminum-doped highly nonlinear fiber. The invention experimentally measures the bit error rate curve of idle light when the pump power is 20.7dBm, 22.7dBm, 24.7dBm, 26.7dBm and 28.7dBm, corresponding to the optimal signal power of 11.3dBm, 8.9dBm, 5.9 Five idle lights with similar bit error rate performance were obtained at dBm and 3.7dBm. Therefore, by optimizing the pump power and signal power, the all-optical wavelength converter has multiple stable optimal conditions, which can provide multiple options for the optical phase conjugate network under the premise of considering the instrument operating conditions and energy consumption.

As shown in Figure 1, an all-optical wavelength conversion scheme based on the four-wave mixing effect can be realized through a degenerate four-wave mixing process. When a strong pump light is emitted into the nonlinear medium, the interaction between the 64-QAM signal light and the pump light produces an idle light that is phase-conjugated to the signal light. The idle light carries the same information as the 64-QAM signal light, but the spectra of the two are mirror images of each other. Therefore, the phase-conjugate relationship between 64-QAM signal light and idle light can be used to eliminate accumulated dispersion and nonlinear noise in the entire link.

The main factors limiting the performance of the all-optical wavelength conversion system are as follows: 1. Since the pump power is limited by stimulated Brillouin scattering, the conversion efficiency cannot be continuously increased. 2. The resulting balance between the low optical signal-to-noise ratio of the idle light at low signal power and the non-ideal nonlinear crosstalk that occurs at high signal power. From the coupled nonlinear Schrödinger equation of the composite amplitudes of the three light waves in the degenerate four-wave mixing process, it can be seen that in addition to the effective four-wave mixing, there are also nonlinear effects such as self-phase modulation and cross-phase modulation. They cause nonlinear distortion and crosstalk in idle light. The coupling equation can be solved numerically and the conversion efficiency can be calculated, which is defined as the ratio of the converted idle light to the transmitted signal power.

The present invention firstly calculates and obtains the variation curve of the conversion efficiency with the signal power under different pump powers, as shown in FIG. 2 . In the present invention, a 150-meter long aluminum-doped high nonlinear optical fiber is used, and various parameters thereof are shown in Table 1. The stimulated Brillouin scattering threshold is calculated and considering the device loss of 3.2dB, the pump power launched into the aluminum-doped high nonlinear fiber is limited below 31.2dBm. As can be seen from Figure 2, when the signal power is lower than 20dBm, the conversion efficiency is relatively stable, because the conversion efficiency is mainly determined by the pump power at this time. With further increase in signal power, the conversion efficiency drops rapidly due to pumping losses.

Table 1 Parameters of Al-doped high nonlinear fiber

parameter Numerical value unit Effective length 135 m nonlinear coefficient 6.9 W^-1·k loss 6.2 dB/k Dispersion slope 0.024 ps/nm zero dispersion wavelength 1545 nm SBS threshold and effective length 86 W m

Then, for the generated idle light, the EGN model proposed in the application of the present invention (R. Dar, M. Feder, A. Mecozzi, and M. Shtaif, "Accumulation of nonlinear interference noise infiber-optic systems," Opt. Express. 22, 14199-14211 (2014)..R.Dar,M.Feder,A.Mecozzi,and M.Shtaif,"Properties of nonlinear noise in long,dispersion-uncompensated fiber links,"Opt.Express.21,25685- 25699 (2013).), adjust the signal power from -5dBm to 30dBm, and calculate the nonlinear power in the idle light under different pump powers, as shown in Figure 3. Obviously, when the transmit signal power is low, the nonlinear power in the idle light increases with the pump power, which is mainly caused by the enhanced four-wave mixing effect caused by the pump power. However, the generated idle optical power will increase with the transmitted signal power, so the nonlinearity induced by the self-phase modulation effect will produce distortion and degrade the performance of the all-optical wavelength conversion system. Here, the pump and signal are detuned to about 5 nm, and the cross-phase modulation effect is not taken into account. In addition, as indicated by the arrows in Fig. 3, as the pump power increases, the signal power threshold for serious self-phase modulation effect in the idle light also increases with the increase of the pump power.

Finally, the present invention sets the signal power input into the aluminum-doped high nonlinear fiber to 0 dBm, and it is calculated that when the pump power is 21.4 dBm, 25.4 dBm, 27.4 dBm, 29.4 dBm and 31.2 dBm, the conversion efficiency varies with the wavelength of the signal light. curve, as shown in Figure 4. It can be clearly seen that the conversion efficiency increases with increasing pump power, but it is not possible to continuously increase the pump power due to the limitation of the stimulated Brillouin scattering threshold. Finally, the present invention obtains a theoretically achievable maximum conversion efficiency of -1.5dB and a conversion bandwidth of 55nm.

Figure 5 is an experimental structural diagram of an all-optical wavelength converter based on an aluminum-doped highly nonlinear fiber. First, a tunable laser source emits a continuous wave laser, which is attenuated by an attenuator and then amplified by an erbium-doped fiber amplifier as a pump light. The resulting pump light is passed through an optical bandpass filter with an insertion loss of 1.74dB to remove the amplified spontaneous emission noise of the erbium-doped fiber amplifier. The 64-QAM signal light is generated by an external cavity laser and then modulated by an in-phase/quadrature Mach-Zehnder modulator. An in-phase quadrature (in-phase/quadrature) Mach-Zehnder modulator is generated by generating two 2 ¹⁵ -1 de-correlated 12.5Gbaud pseudo-random binary sequence signals through an arbitrary waveform generator. The modulated signal light is amplified by another erbium-doped fiber amplifier and another optical band-pass filter with an insertion loss of 3.34dB to filter out the amplified spontaneous emission noise. The polarizations of the pump light and 64-QAM signal light are adjusted by their respective polarization controllers to obtain the maximum conversion efficiency. Then, the pump and 64-QAM signals are coupled through a 90:10 coupler (90% pump, 10% signal), and then passed through an isolator and then launched into the aluminum-doped high nonlinear fiber. The isolator is It is used to protect the front-end erbium-doped fiber amplifier by blocking the reflected wave caused by stimulated Brillouin scattering. The pump and the 64-QAM signal have a degenerate four-wave mixing effect in the aluminum-doped high nonlinear fiber. The output light wave is filtered by an optical bandpass filter with a bandwidth of 0.4nm and an insertion loss of 4dB to obtain a phase common. 64-QAM idle light of the yoke. A part of the obtained idle light is connected to a spectrum analyzer to measure the optical signal-to-noise ratio and record the spectrum for conversion efficiency calculation. The other part is amplified by the erbium-doped fiber amplifier and then attenuated to 6.5dBm by the attenuator, and then launched into the coherent optical receiver for detection and performance evaluation.

The coherent optical receiver consists of a local oscillator, a 90-degree optical mixer and four balanced photodetectors. The received optical signal is first mixed with the light generated by the local oscillator in a 90-degree optical mixer, and then passed through four balanced detectors for balance detection. Finally, the detected signal is converted from analog to digital by a 100-GS/s digital storage oscilloscope, and then the data is digitized. The collected data is processed offline through digital signal processing algorithms, including delay and orthogonality correction, data resampling, finite impulse response filter to eliminate intersymbol interference and carrier phase recovery. Finally, the quality of idle light is evaluated by calculating the bit error rate.

In the experiment of all-optical wavelength conversion, the signal power emitted to the HNLF was first set to 0dBm, and the pump wavelength was set to 1547.316nm. The present invention measures the curve of the conversion efficiency with the wavelength of the signal light when the pump power is 29.4dBm, 27.4dBm, 25.4dBm, 23.4dBm, 21.4dBm and 19.4dBm, as shown in FIG. 6 . The experimental results are consistent with the simulation calculations. Considering the insertion loss of the device used in the experiment, the pump power launched into the Al-doped high nonlinear fiber was limited below 29.4dBm, and a maximum conversion efficiency of -6dB was obtained.

FIG. 7 is the output spectrum of the aluminum-doped highly nonlinear fiber corresponding to the six positions marked 1 to 6 in FIG. 6 . In Figure 7, "S1", "S2", "S3", "S4", "S5" and "S6" represent wavelengths at 1535.036 nm, 1540.162 nm, 1544.924 nm, 1550.116 nm, 1554.940 nm and 1560.200 nm, respectively signal of. And "I1", "I2", "I3", "I4", "I5" and "I6" represent their corresponding converted idle lights.

Although the all-optical wavelength conversion experimental system of the present invention obtains a relatively large conversion efficiency of -6dB, and the larger conversion efficiency helps to improve the optical signal-to-noise ratio of idle light. On the other hand, due to the effect of severe self-phase modulation that may occur in idle light, its performance cannot be continuously improved by continuously increasing the signal power. As discussed above, as the input signal power increases, not only the optical signal-to-noise ratio of the idle light will increase, but also the non-ideal crosstalk caused by the self-phase modulation effect in the idle light, which will Greatly reduces the quality of idle light. Therefore, the present invention measures the variation curve of the bit error rate of the idle light with the input signal power when the pump powers are 28.7dBm, 26.7dBm, 24.7dBm, 22.7dBm and 20.7dBm respectively, so as to evaluate the all-optical wavelength The performance of the conversion system is shown in Figure 7. The wavelengths of the pump and signal were set at 1547.316 nm and 1542.529 nm, respectively. The present invention also measures the optical signal-to-noise ratio value of the idle light under the above-mentioned conditions, and Fig. 8 shows the transformation curve of the measured bit error rate of the idle light with the optical signal-to-noise ratio.

It is worth noting that the degradation of idle light performance caused by the severe self-phase modulation effect shown in Fig. 3 does not occur in Fig. 8. This is because due to the limitation of experimental equipment, the signal power is not enough to make the idle light produce serious self-phase modulation effect. Therefore, the all-optical wavelength conversion system of the present invention is not affected by non-ideal nonlinear crosstalk, and its noise mainly comes from the amplified spontaneous emission noise of the erbium-doped fiber amplifier. Finally, by properly adjusting the emitted pump and signal power, idle light with high optical signal-to-noise ratio and high performance can be generated.

It can be seen from Figure 8 that under the condition of constant pump power, with the increase of signal power, the bit error rate curve of idle light is improved, but it will converge. Once the signal power exceeds the signal power threshold required for BER convergence, severe distortion as shown in Figure 3 occurs. The threshold value of signal power decreases with the increase of pump power, and when the pump power is greater than 24.7dBm (CE is greater than -15dB), the threshold value of signal power does not change much. This is why signal power optimization is ignored in most high conversion efficiency all-optical wavelength conversion schemes, since only very low signal power is required to converge the bit error performance of idle light. Moreover, it can be seen from the curve in FIG. 8 that under the condition of higher conversion efficiency, the signal power range for the convergence of the BER performance of the idle light is larger, and at this time, optimizing the signal power cannot improve the performance of the idle light.

On the other hand, the BER performance of idle light depends on its optical signal-to-noise ratio, as shown in Figure 9. Therefore, for the idle light obtained by a specific pump power, its optical signal-to-noise ratio can be improved by optimizing the signal power. In theory, the present invention can arbitrarily adjust the pump and signal power to obtain idle light with a given bit error rate or optical signal-to-noise ratio. However, the optimal signal power will be affected by the pump power due to pump losses and undesirable nonlinear distortions in the idle light.

Figure 10 is the constellation diagram of the measured back-to-back signal and the generated idle light under different pump and signal power, corresponding to the five positions in Figure 8: A (Pp=28.7dBm, Ps=3.7dBm), B ( Pp=26.7dBm, Ps=5.9dBm), C (Pp=24.7dBm, Ps=8.9dBm), D (Pp=22.7dBm, Ps=11.3dBm) and E (Pp=20.7dBm, Ps=11.3dBm). Compared with the back-to-back signal in Fig. 10(a), the idle light in Fig. 10(b)(c) and (d) has similar performance, while the idle light in Fig. 10(e) and (f) Performance has degraded a bit.

By placing a variable optical attenuator at the front end of the erbium-doped fiber amplifier close to the receiver to change the optical signal-to-noise ratio of the idle light, the bit error rate curve of the idle light is measured, as shown in Figure 11. The present invention compares the code errors of the idle light obtained under five different operating conditions in FIG. 8 with the back-to-back signals, respectively. It can be clearly seen that when the bit error rate is 10 ⁻³ , the power damage of all idle light due to the all-optical wavelength conversion system of the present invention is less than 1 dB. In addition, when the pump power and signal power are set to 22.7dBm and 11.3dBm, respectively, a low conversion efficiency of -19.1dB is obtained, and when the pump power and signal power are set to 28.7dBm and 3.7dBm, respectively, a low conversion efficiency of -7.9dB is obtained. In the two cases of high conversion efficiency, the power damage of idle light is not much different. It can be seen that in the case of low pump power, the idle light with the same high bit error rate performance as that in the case of high pump power can still be obtained. Therefore, high-performance all-optical wavelength conversion does not require increasing pump power to generate higher conversion efficiencies.

All-optical wavelength converters have important application value in wavelength routing optical networks and optical phase conjugate networks, and can effectively solve the limitation of wavelength conflict and the compensation of fiber nonlinearity. High-performance all-optical wavelength converters generally require higher pump powers to produce higher conversion efficiencies. On the one hand, the SBS threshold power of the fiber limits the pump power emitted, so complex techniques are required to increase the SBS threshold power of the fiber. On the other hand, high pump power is not energy efficient and can damage optics. In this work, the present invention explores the feasibility of utilizing lower pump power to achieve high-performance all-optical wavelength conversion. Although lower pump power produces lower conversion efficiencies, the converted idle light performance can be improved by optimizing the transmit signal power. The present invention experimentally measures the bit error rate curves of five idle lights with conversion efficiencies between -23dB and -8dB, and their power damages are all lower than 1dB. All in all, high pump power is the main challenge faced by all-optical wavelength converters based on aluminum-doped highly nonlinear fibers in practical applications, and the method with high energy efficiency and high performance proposed in the present invention solves this problem well.

All-optical wavelength converters based on aluminum-doped high nonlinear fibers have the characteristics of fast response speed and are the best choice for future large-capacity optical networks. At the same time, it does not require any additional components to convert back and forth between optoelectronics. All-optical wavelength converters play an important role in both optical networks that require wavelength routing to alleviate wavelength contention conflicts and optical phase conjugation networks to reduce fiber nonlinearity. Conversion efficiency is usually a key evaluation index for all-optical wavelength converters, and higher conversion efficiency means better transmission performance. However, since the pump power injected into Al-doped highly nonlinear fibers is usually limited by its threshold of stimulated Brillouin scattering, it is difficult to achieve higher conversion efficiency. In fact, the performance of the all-optical wavelength converter, that is, the performance of the generated idle light, depends on both the conversion efficiency and the transmitted signal power. Therefore, by optimizing the signal power launched into the Al-doped high nonlinear fiber, the idle light obtained under the condition of low conversion efficiency and high conversion efficiency can have similar performance. The experimental results of the present invention verify the above analysis and obtain similar bit error performance in all-optical wavelength converters with conversion efficiencies of -23.1dB, -19.1dB, -15.2dB, -11.4dB and -7.9dB.

The above-mentioned embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention is subject to the claims.

Claims (10)

1. A method for constructing an energy-efficient and high-performance all-optical wavelength converter for a 64-QAM coherent optical communication system, comprising:

a tunable laser source emits a beam of continuous wave laser, which is attenuated by an attenuator and amplified by an erbium-doped fiber amplifier to be used as pump light.

The obtained pumping light passes through a first optical band-pass filter to remove amplified spontaneous emission noise of the erbium-doped fiber amplifier;

the 64-QAM signal light is generated by an external cavity laser and is obtained by modulating by an in-phase orthogonal Mach-Zehnder modulator;

generating two paths of decorrelated pseudo-random binary sequence signals to drive an in-phase orthogonal Mach-Zehnder modulator;

amplifying the modulated 64-QAM signal light by using another erbium-doped optical fiber amplifier and filtering out amplified spontaneous radiation noise by using a second optical band-pass filter;

the polarization of the pump light and the polarization of the 64-QAM signal light are adjusted through respective polarization controllers to obtain the maximum conversion efficiency;

then, the pump light and the 64-QAM signal light are coupled through a coupler and then emitted into the aluminum-doped high-nonlinearity fiber through an isolator, wherein the isolator is used for blocking reflected waves caused by stimulated Brillouin scattering so as to protect an erbium-doped fiber amplifier at the front end;

the pump light and the 64-QAM signal light generate degenerate four-wave mixing effect in the aluminum-doped high-nonlinearity fiber, and the output light wave is filtered by a third optical band-pass filter to obtain phase-conjugated 64-QAM idle light.

2. The method of claim 1, wherein the two 2-way 2-wavelength converter is generated by an arbitrary waveform generator¹⁵-1 decorrelated 12.5Gbaud pseudo-random binary sequence signal to drive an in-phase-quadrature mach-zehnder modulator.

3. The method of claim 1, wherein the pump light and the 64-QAM signal light are coupled by a 90:10 coupler and then emitted into the al-doped high-nonlinearity fiber via an isolator.

4. The method of claim 1, wherein the first optical bandpass filter has an insertion loss of 1.74 dB; the insertion loss of the second optical bandpass filter is 3.34 dB.

5. The method of claim 1, wherein the output optical wave is filtered by a third optical band-pass filter with a bandwidth of 0.4nm and an insertion loss of 4dB to obtain the idle light.

6. The method of claim 1, wherein a portion of the obtained idle light is dropped into an optical spectrum analyzer, and the optical signal-to-noise ratio value is measured and the spectrum is recorded for conversion efficiency calculation; the other part is amplified by an erbium-doped fiber amplifier, attenuated by an attenuator and transmitted into a coherent optical receiver for detection and performance evaluation.

7. The method of claim 6, wherein said coherent optical receiver comprises a local oscillator, a 90-degree optical mixer and four balanced optical detectors; the received optical signal is first mixed with light generated by a local oscillator in a 90-degree optical mixer and then balanced by four balanced detectors.

8. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the steps of the method of any of claims 1 to 7 are implemented when the program is executed by the processor.

9. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 7.

10. A processor, characterized in that the processor is configured to run a program, wherein the program when running performs the method of any of claims 1 to 7.

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