CN110850660A - All-optical wavelength converter - Google Patents
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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
Technical Field
The invention relates to the field of communication, in particular to an efficient and high-performance all-optical wavelength converter for a 64-QAM coherent optical communication system.
Background
High bandwidth applications such as high definition video, online live broadcast, and cloud services have pushed a tremendous increase in global traffic over the past decade. Coherent optical communication systems using high-order 64-QAM modulation formats will offer great advantages for future large capacity long distance communications. However, with the popularization of 5G and the development of the internet of things, the IP traffic demand will further increase. Cisco's latest "visual network index" forecasts that global IP traffic will increase 3-fold in the next 5 years, and by 2022, global annual IP traffic will reach 4.8 ZB.
In addition to the huge traffic demands, optical networks face other problems such as electronic bottlenecks, wavelength blocking, modulation format opaqueness, high delay, etc. All-optical wavelength converters can improve the flexibility of optical networks and alleviate the constraints of conflicting wavelengths through wavelength management, and are an important network component. The all-optical wavelength converter can also increase network capacity and relay distance by compensating for fiber nonlinearities in the optical phase conjugate network. At the same time, optical networks configured with all-optical wavelength converters do not require additional components for optical-to-electrical conversion back and forth.
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 scheme of the highly nonlinear optical fiber based on four-wave mixing has the advantages of simple structure, high response speed and high conversion efficiency, and has the advantage of competitiveness.
The traditional technology has the following technical problems:
in order to obtain higher conversion efficiency, methods such as phase or frequency dithering of the pump, metal doping, and strain control techniques have been proposed to increase the pump power launched into aluminum-doped highly nonlinear fibers by raising the stimulated brillouin scattering threshold. However, higher pump powers will result in greater energy consumption and damage to the optical components. The idle light is also disturbed by the high pump power near the stimulated brillouin scattering threshold.
Disclosure of Invention
The invention aims to provide a method for constructing an efficient and high-performance all-optical wavelength converter for a 64-QAM coherent optical communication system.
In order to solve the above technical problem, the present invention provides 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 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 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 idle light.
The invention has the beneficial effects 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 method with high energy efficiency and high performance provided by the invention well solves the problems.
In one embodiment, two paths with length of 2 are generated by an arbitrary waveform generator15-1 decorrelated 12.5Gbaud pseudorandom binary sequence signalTo drive an in-phase and quadrature mach-zehnder modulator.
In one embodiment, the pump light and the 64-QAM signal light are coupled by a 90:10 coupler and then emitted into the aluminum-doped high-nonlinearity fiber through an isolator.
In one embodiment, the insertion loss of the first optical bandpass filter is 1.74 dB; the insertion loss of the second optical bandpass filter is 3.34 dB.
In one embodiment, the output light wave is filtered by a third optical band-pass filter with a bandwidth of 0.4nm and an insertion loss of 4dB to obtain phase-conjugated 64-QAM idle light.
In one embodiment, a portion of the obtained idle light is coupled into an optical spectrum analyzer, 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.
In one embodiment, the coherent optical receiver comprises a local oscillator, a 90-degree optical mixer, and four balanced photodetectors; 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.
A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps of any of the methods when executing the program.
A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of any of the methods.
A processor for running a program, wherein the program when running performs any of the methods.
Drawings
Fig. 1 is a schematic diagram of an all-optical wavelength converter based on degenerate four-wave mixing in an all-optical wavelength converter of the present invention.
Fig. 2 is a graph of conversion efficiency as a function of optical power of an input signal, calculated by simulation, for different pump powers in the all-optical wavelength converter of the present invention.
Fig. 3 is a curve of nonlinear power in idle light with input signal power, calculated by simulation, at different pump powers in the all-optical wavelength converter of the present invention.
Fig. 4 is a plot of conversion efficiency as a function of signal wavelength for different pump powers in an all-optical wavelength converter of the present invention.
Fig. 5 is a structural diagram of the all-optical wavelength converter based on the aluminum-doped high-nonlinearity optical fiber four-wave mixing effect according to the present invention.
Fig. 6 is a graph of conversion efficiency as a function of input signal light wavelength experimentally measured for different pump powers in an all-optical wavelength converter of the present invention.
Fig. 7 is the output spectrum of an aluminum-doped highly nonlinear fiber in an all-optical wavelength converter of the present invention.
Fig. 8 is a plot of experimentally measured idle optical bit error rate versus input signal power for different pump powers in an all-optical wavelength converter of the present invention.
Fig. 9 is a graph of idle ber with osnr measured experimentally for different pump powers in the all-optical wavelength converter of the present invention.
Fig. 10 is a constellation diagram of input back-to-back 64-QAM signals and phase conjugate 64-QAM idle light generated at different pump and signal powers in an all-optical wavelength converter of the present invention.
Fig. 11 is a graph of bit error rate with osnr of an input back-to-back signal and idle light generated under different pump and signal powers, respectively, measured experimentally in an all-optical wavelength converter of the present invention.
Detailed Description
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.
In optical phase conjugate networks, all-optical wavelength converters are typically deployed symmetrically at the midspan of a discrete amplified coherent optical transmission system, and the compensation effect of fiber nonlinearities depends on the quality of the idle light. Because the constellation points of the high-order modulation 64-QAM signal are denser and the distance between the constellation points is smaller, the performance of the all-optical wavelength converter has larger influence on the constellation points, and slightly serious noise can cause the divergence of the constellation points, thereby causing a large number of judgment errors and finally influencing the signal error rate performance. Therefore, a high-performance all-optical wavelength converter is more important for high-order modulation of 64-QAM signals. The quality of the idle light is largely dependent on the pump launched into the aluminum-doped highly nonlinear fiber and the 64-QAM signal power. Increasing the pump power to increase the conversion efficiency is not the only way to improve idle light performance.
The invention establishes an all-optical wavelength conversion scheme which has a higher stimulated Brillouin scattering threshold value and is based on the aluminum-doped high-nonlinearity optical fiber, and calculates and measures the conversion efficiency theoretically and experimentally. While lower pump power results in lower conversion efficiency, the performance of the idler light can be improved by optimizing the signal power launched into the aluminum-doped highly nonlinear fiber. The invention experimentally measures the error rate curves of idle light under the conditions that the pump powers are respectively 20.7dBm, 22.7dBm, 24.7dBm, 26.7dBm and 28.7dBm, and obtains five idle lights with similar error rate performances under the conditions that the optimal signal powers are 11.3dBm, 8.9dBm, 5.9dBm and 3.7 dBm. Therefore, by optimizing the pump power and the signal power, the all-optical wavelength converter has a plurality of stable optimal conditions, and can provide a plurality of choices for the optical phase conjugate network under the premise of considering the operating conditions and the energy consumption of instruments.
As shown in fig. 1, an all-optical wavelength conversion scheme based on the four-wave mixing effect can be realized by a degenerate four-wave mixing process. When a strong pump light is emitted into the nonlinear medium, the interaction of the 64-QAM signal light and the pump light generates an idle light conjugated with the phase of 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. The phase conjugate relationship between the 64-QAM signal light and the idle light can be used to eliminate the accumulated dispersion and nonlinear noise in the entire link.
The main factors limiting the performance of all-optical wavelength conversion systems are as follows: 1. since the pump power is limited by the stimulated brillouin scattering, the conversion efficiency cannot be continuously increased. 2. The resulting idle light has a balance between the low optical signal-to-noise ratio at low signal power and the non-ideal non-linear crosstalk that occurs at high signal power. From the coupled nonlinear schrodinger equation of the composite amplitude of three optical waves in the degenerate four-wave mixing process, it can be seen that in addition to the effective four-wave mixing, nonlinear effects such as self-phase modulation and cross-phase modulation occur, which cause nonlinear distortion and crosstalk in the idle light. The coupling equation can be solved numerically and the conversion efficiency, defined as the ratio of converted idle light to emitted signal power, can be calculated.
The present invention first calculates the curve of the conversion efficiency with the change of the signal power under different pump powers, as shown in fig. 2. The present invention uses a 150 meter length of aluminum-doped highly nonlinear fiber, with the parameters shown in table 1. The stimulated Brillouin scattering threshold is calculated and the device loss of 3.2dB is considered, and the pumping power launched into the aluminum-doped high-nonlinearity fiber is limited to be below 31.2 dBm. As can be seen from fig. 2, the conversion efficiency is relatively stable when the signal power is lower than 20dBm, because the conversion efficiency is mainly determined by the pump power. With further increase in signal power, the conversion efficiency drops rapidly due to pump losses.
TABLE 1 parameters of aluminum-doped highly nonlinear optical fibers
| Parameter(s) | Numerical value | Unit of |
| Effective length | 135 | m |
| Coefficient of non-linearity | 6.9 | W-1·k |
| Loss of power | 6.2 | dB/k |
| Slope of dispersion | 0.024 | ps/nm |
| |
1545 | nm |
| SBS threshold effective length | 86 | W·m |
Then, for the generated idle light, the EGN model proposed in the present application (r.dar, m.feder, a.mecozzi, and m.shtaif, "Accumulation of nonlinear interaction noise in fiber-optical systems," opt.express.22,14199-14211 (2014.). r.dar, m.feder, a.mecozzi, and m.shtaif, "Properties of nonlinear fiber in long, dispersion-uncompensated fiber links," opt.express.21,25685-25699 (2013)), which adjusts the signal power from-5 dBm to 30dBm, respectively, calculates the nonlinear power in the idle light at different pump powers, as shown in fig. 3. It is clear that when the transmitted signal power is low, the nonlinear power in the idle light increases with increasing pump power, which is mainly caused by the enhanced four-wave mixing effect caused by the pump power. However, the idle optical power generated will increase with increasing transmit signal power, and thus the non-linearity induced by the self-phase modulation effect will produce distortion and reduce the performance of the all-optical wavelength conversion system. Here the pump and signal are detuned to about 5nm, and cross-phase modulation effects are not taken into account. In addition, as shown by the arrows in fig. 3, as the pump power increases, the signal power threshold of the idle light, which causes a severe self-phase modulation effect, also increases as the pump power increases.
Finally, the invention sets the signal power input into the aluminum-doped high-nonlinearity fiber to 0dBm, and calculates the curve of the conversion efficiency with the wavelength of the signal light under the conditions that the pump power is 21.4dBm,25.4dBm,27.4dBm,29.4dBm and 31.2dBm, as shown in FIG. 4. It is clearly seen that the conversion efficiency increases with increasing pump power, but it is not possible to continue to increase the pump power due to the limitations of the stimulated brillouin scattering threshold. Finally, the invention obtains the maximum conversion efficiency which can be theoretically reached and is-1.5 dB, and the conversion bandwidth is 55 nm.
Fig. 5 is an experimental block diagram of an all-optical wavelength converter based on an aluminum-doped highly nonlinear fiber. Firstly, 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 resulting pump light removes the amplified spontaneous emission noise of the erbium-doped fiber amplifier via an optical bandpass filter with an insertion loss of 1.74 dB. The 64-QAM signal light is generated by an external cavity laser and is modulated by an in-phase/quadrature Mach-Zehnder modulator. Two paths 2 are generated by an arbitrary waveform generator15-1 decorrelated 12.5Gbaud pseudo-random binary sequence signal to drive an in-phase/quadrature Mach-Zehnder modulator. The modulated signal light is amplified by another erbium-doped fiber amplifier and filtered by another optical band-pass filter with insertion loss of 3.34dB to obtain amplified spontaneous emission noise. The polarization of the pump light and the 64-QAM signal light are adjusted by respective polarization controllers to obtain maximum conversion efficiency. Then, the pump and 64-QAM signals are coupled through a 90:10 coupler (90% is pump and 10% is signal), and then are transmitted into the aluminum-doped high-nonlinearity fiber through an isolator, wherein the isolator is used for blocking stimulated BrillouinThe induced reflected waves are scattered to protect the erbium doped fiber amplifier at the front end. The pump and 64-QAM signals generate degenerate four-wave mixing effect in the aluminum-doped high-nonlinearity fiber, and the output light waves are filtered by an optical band-pass filter with the bandwidth of 0.4nm and the insertion loss of 4dB to obtain phase-conjugated 64-QAM idle light. A portion of the obtained idle light is taken into a spectrum analyzer, 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 to 6.5dBm by an attenuator and then transmitted into a 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 light generated by a local oscillator in a 90-degree optical mixer and then balanced by four balanced detectors. Finally, the detected signals are subjected to analog-to-digital conversion through a 100-GS/s digital storage oscilloscope, and then the data are subjected to digital processing. The acquired data is processed off line through a digital signal processing algorithm, and the processing comprises delay and orthogonality correction, data resampling, intersymbol interference elimination of a finite impulse response filter, carrier phase recovery and the like. And finally, evaluating the quality of the idle light by calculating the bit error rate.
In the experiments for all-optical wavelength conversion, the signal power transmitted to HNLF was first set to 0dBm, and the pump wavelength was set to 1547.316 nm. The experiment of the present invention measured the curves of the conversion efficiency with the wavelength of the signal light under the conditions of the pump powers of 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 calculation. The pump power launched into the aluminum-doped highly nonlinear fiber was limited to below 29.4dBm, giving a maximum conversion efficiency of-6 dB, taking into account the insertion loss of the devices used in the experiments.
Fig. 7 is the output spectrum of the aluminum-doped highly nonlinear fiber for 6 positions labeled 1 to 6 in fig. 6. In fig. 7, "S1", "S2", "S3", "S4", "S5" and "S6" represent signals at wavelengths of 1535.036nm, 1540.162nm, 1544.924nm, 1550.116nm, 1554.940nm and 1560.200nm, respectively. And "I1", "I2", "I3", "I4", "I5", and "I6" represent their corresponding converted idle light.
Although the all-optical wavelength conversion experimental system obtains relatively high conversion efficiency of-6 dB, the higher conversion efficiency is beneficial to improving 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 the idle light, the performance cannot be continuously improved by increasing the signal power. As discussed above, not only the osnr of the idle light increases with the increase of the input signal power, but also the non-ideal crosstalk caused by the self-phase modulation effect in the idle light, which greatly reduces the quality of the idle light. Therefore, the present invention measures the variation curve of the error rate of idle light with the input signal power under the condition that the pump power is respectively 28.7dBm, 26.7dBm, 24.7dBm, 22.7dBm and 20.7dBm, so as to evaluate the performance of the all-optical wavelength conversion system, as shown in fig. 7. The wavelengths of the pump and signal are set at 1547.316nm and 1542.529nm, respectively. The invention also measures the optical signal-to-noise ratio of the idle light under the above conditions, and fig. 8 shows the conversion curve of the measured error rate of the idle light with the optical signal-to-noise ratio.
It is noted 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, limited by experimental equipment, the signal power is not sufficient to meet the requirements for the idle light to produce a severe self-phase modulation effect. Therefore, the all-optical wavelength conversion system of the present invention is not affected by non-ideal nonlinear crosstalk, and the noise thereof 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 of high performance in terms of optical signal-to-noise ratio can be generated.
As can be seen from fig. 8, under the condition of a certain pump power, the bit error rate curve of the idle light is improved but converged with the increase of the signal power. Once the signal power exceeds the signal power threshold required for bit error rate convergence, severe distortion occurs as shown in fig. 3. The threshold of the signal power decreases with increasing pump power, while it does not change much when the pump power is greater than 24.7dBm (CE greater than-15 dB). This is why signal power optimization is neglected in most high conversion efficiency all-optical wavelength conversion schemes, since only low signal power is needed to converge the error performance of the idle light. Moreover, as can be seen from the curve of fig. 8, under the condition of higher conversion efficiency, the signal power range for converging the idle light bit error rate performance is larger, and at this time, optimizing the signal power cannot achieve the performance improvement of the idle light.
On the other hand, the BER performance of the idle light depends on its optical signal-to-noise ratio, as shown in fig. 9. Therefore, the optical signal-to-noise ratio of the idle light obtained for a specific pump power can be improved by optimizing the signal power. In theory, the present invention can adjust the pump and signal power arbitrarily to obtain idle light with a given bit error rate or optical signal-to-noise ratio. However, the optimum signal power will be affected by the pump power due to pump losses and undesirable nonlinear distortions in the idler light.
Fig. 10 is a constellation diagram of measured back-to-back signals and generated idle light at different pump and signal powers, corresponding to 5 positions in fig. 8, respectively: 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 ═ 11.3 dBm). The idle light in fig. 10(b) (c) and (d) has similar performance compared to the back-to-back signal in fig. 10(a), while the idle light performance in fig. 10(e) and (f) is slightly degraded.
The ber curve of the idle light was measured by placing a variable optical attenuator in front of the erbium doped fiber amplifier near the receiver to change the osnr of the idle light, as shown in fig. 11. The invention compares the idle light obtained under five different operating conditions in fig. 8 with the back-to-back signals respectively. It is evident that at a bit error rate of 10-3In this case, all idle light is less than 1dB of power penalty due to the all-optical wavelength conversion system of the present invention. In addition, the pump power and the signal power were set to 22.7dBm and 11.3dBm, respectivelyWhen a-19.1 dB low conversion efficiency is obtained and the pump power and the signal power are respectively set to be 28.7dBm and 3.7dBm, the power damage difference of idle light is not large under two conditions of obtaining a-7.9 dB high conversion efficiency. Therefore, idle light with the same high bit error rate performance as that under the condition of high pump power can still be obtained under the condition of low pump power. Thus, high performance all-optical wavelength conversion does not require increased pump power to produce higher conversion efficiency.
The all-optical wavelength converter has important application value in a wavelength routing optical network and an optical phase conjugate network, and can effectively solve the problems of wavelength conflict limitation and optical fiber nonlinearity compensation. High performance all-optical wavelength converters typically require higher pump power to produce higher conversion efficiency. On the one hand, the stimulated brillouin scattering threshold of the optical fiber limits the emitted pump power, so that a complicated technique needs to be adopted to increase the SBS threshold power of the optical fiber. On the other hand, high pump powers are not efficient and energy efficient and can also damage optical components. In this work, the present invention discusses the feasibility of using lower pump power to achieve high performance all-optical wavelength conversion. Although lower pump powers result in lower conversion efficiencies, the converted idle optical performance can be improved by optimizing the transmit signal power. The invention tests and measures the error rate curves of five idle lights with the conversion efficiency between-23 dB and-8 dB, and the power damage of the five idle lights is lower than 1 dB. In summary, the high pump power is a major challenge in practical applications of all-optical wavelength converters based on aluminum-doped high-nonlinearity optical fibers, and the problem is well solved by the energy-efficient and high-performance method provided by the invention.
The all-optical wavelength converter based on the aluminum-doped high-nonlinearity optical fiber has the characteristic of high response speed, and is the best choice for a future high-capacity optical network. At the same time, it does not require any additional components to perform the conversion back and forth between the photovoltaics. All-optical wavelength converters play an important role in both optical networks requiring wavelength routing to mitigate wavelength contention conflicts and networks used to reduce optical phase conjugation of fiber nonlinearities. Conversion efficiency is often a key evaluation indicator for all-optical wavelength converters, with higher conversion efficiency meaning better transmission performance. However, since the pump power injected into an aluminum-doped highly nonlinear fiber is generally limited by its stimulated brillouin scattering threshold, it is difficult to achieve higher conversion efficiency. In practice, the performance of an all-optical wavelength converter, i.e. the performance of the generated idle light, depends on both the conversion efficiency and the emitted signal power. Therefore, the idle light obtained under the conditions of low conversion efficiency and high conversion efficiency has similar performance by optimizing the power of the signal emitted into the aluminum-doped high-nonlinearity fiber. The experimental results of the present invention verified the above analysis and obtained similar error performance in all-optical wavelength converters with conversion efficiencies of-23.1 dB, -19.1dB, -15.2dB, -11.4dB and-7.9 dB.
The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the 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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