CN111030755A - Analog domain carrier recovery method based on photoelectric cooperation - Google Patents
Analog domain carrier recovery method based on photoelectric cooperation Download PDFInfo
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Abstract
The invention provides a carrier recovery method in an analog domain based on photoelectric cooperation, which is characterized in that I, Q electric signals obtained through coherent reception are used for driving a modulator, signal peak values and bias voltages are set according to an output curve of the modulator, the average intensities of output optical signals after different amplitude distributions are modulated are inconsistent, the average intensity of the output optical signals of the modulator is detected by a low-speed PD (potential difference detector), the amplitude distribution of signals I, Q components can be determined, an adjustable optical delay line is inserted into a local oscillation optical link, and the adjustable optical delay line is output and fed back and controlled by the low-speed PD, so that the carrier recovery in the analog domain can be realized. The invention has the beneficial effects that: the analog domain carrier recovery method based on photoelectric cooperation is provided, the complexity is reduced well, the implementation is easy, and the implementation cost and the power consumption are reduced.
Description
Technical Field
The invention relates to a carrier recovery method in an analog domain, in particular to a carrier recovery method in the analog domain based on photoelectric cooperation.
Background
In recent years, with the development of new internet services such as cloud services, broadband videos, file sharing and the like and the large-scale popularization of wireless terminals, the medium-short distance (10-100km) optical information traffic covering data center networks, access networks and metropolitan area networks has increased explosively. Therefore, it is urgently needed to propose a new medium-short distance optical fiber communication scheme to meet the future traffic demand and keep the implementation cost and the system complexity as low as possible. In the method, coherent light receiving can realize linear receiving of optical signals through phase diversity, polarization diversity receiving and balanced detection, so that demodulation of light field four-dimensional signals is realized, and the system spectrum efficiency is greatly improved. In addition, by increasing the LO optical power, the receiver sensitivity can be improved, and the receiver sensitivity approaches to the quantum limit. However, limited by the complexity of coherent optical receivers and the corresponding high power consumption of DSPs, conventional coherent optical reception schemes have very limited applications in medium and short range optical interconnects. Relevant researchers look at simplifying coherent optical receivers, through reasonable optical link design, and by combining with a proper optical control device and analog electric domain calculation, the complexity of a coherent optical receiving corresponding algorithm can be reduced, even completely eliminated, and the coherent optical communication of DSP-free is realized. This reduces the implementation cost while still maintaining the advantages of the conventional coherent optical reception scheme, making it possible to apply the coherent optical reception scheme to medium-short distance optical interconnects. Among these, how to eliminate the carrier phase noise in an analog manner is one of the difficulties.
The current scheme for realizing carrier recovery in the analog domain is mainly based on an optical phase-locked loop or an electric phase-locked loop. The carrier recovery scheme based on the optical phase-locked loop adjusts the local oscillator laser through the generated frequency correction signal, and therefore, the local oscillator laser is required to have broadband frequency modulation response. On the other hand, the loop of the optical phase-locked loop contains a local oscillator laser, a 90-degree mixer, a photodetector, and electronics for carrier recovery, and thus, the loop delay is a major challenge of the optical phase-locked loop. The carrier recovery scheme based on the electric phase-locked loop eliminates the requirements of the optical phase-locked loop on local oscillation light and loop delay, but still needs a complex analog circuit to realize carrier recovery. Therefore, how to provide a carrier recovery scheme with lower complexity is a technical problem to be urgently solved by those skilled in the art.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an analog domain carrier recovery method based on photoelectric cooperation.
The invention provides a carrier recovery method in an analog domain based on photoelectric cooperation, which is characterized in that I, Q electric signals obtained through coherent reception are used for driving a modulator, signal peak values and bias voltages are set according to an output curve of the modulator, the average intensities of output optical signals after different amplitude distributions are modulated are inconsistent, the average intensity of the output optical signals of the modulator is detected by a low-speed PD (potential difference detector), the amplitude distribution of signals I, Q components can be determined, an adjustable optical delay line is inserted into a local oscillation optical link, and the adjustable optical delay line is output and fed back and controlled by the low-speed PD, so that the carrier recovery in the analog domain can be realized.
As a further improvement of the invention, the method comprises the following steps:
s1, dividing a light beam emitted by a laser light source into two beams by a coupler, wherein one beam is used as a signal modulation carrier, and the other beam is used as local oscillation light;
s2, modulating the signal modulation carrier by the IQ modulator, and loading the signal to form signal light;
s3, transmitting the modulated signal light and the local oscillator light to a receiving end along two paths of optical fibers respectively, generating spontaneous radiation noise through a noise source with adjustable power, and optically coupling the spontaneous radiation noise and the modulated signal light to set an optical signal-to-noise ratio;
s4, inserting an adjustable light delay line in front of the receiver by the local oscillator light, and applying control voltage to adjust the phase of the local oscillator light, wherein the adjustable light delay line is controlled by the field programmable gate array;
s5, detecting the signal light and the local oscillator light by a balance detector after passing through the frequency mixer respectively, and outputting two paths of light currents of the I component and the Q component;
s6, respectively dividing parts of the two paths of optical currents for feedback compensation of phase deviation, and using the rest parts for signal receiving, and directly sampling and judging after phase compensation is completed;
s7, amplifying the photoelectric current for feedback compensation of phase shift to a set peak value by an electric amplifier after passing through a low-pass filter, and modulating an input carrier as a driving signal of a modulator, wherein the signal is modulated into external modulation or internal modulation;
s8, detecting the optical signal modulated by the modulator by using the low-speed PD, and inputting the electric signal obtained by low-speed PD detection to the field programmable gate array;
s9, the field programmable gate array receives and processes an input electric signal in a test period Ts, and a control voltage corresponding to the minimum electric signal is found through a climbing method;
and S10, applying the control voltage to the adjustable light delay line to realize carrier phase compensation.
As a further improvement of the present invention, the operating wavelength of the laser source is 1310nm, i.e. the 0-dispersion wavelength of the optical fiber.
As a further improvement of the present invention, in step S4, a series of test voltages are pre-stored in the FPGA, the test voltages introduce phase shifts in the range of-50 to 50 and are uniformly distributed, and the test voltages are applied in a test period TsAnd the light-adjustable delay lines are sequentially applied to the light-adjustable delay lines.
As a further improvement of the present invention, in step S7, the signal modulation is externally modulated by a mach-zehnder modulator or internally modulated by a direct modulation laser.
The invention also provides a photoelectric cooperation based analog domain carrier recovery method, which comprises the following steps:
1) the light beam emitted by the laser light source is divided into two beams by the coupler, wherein one beam is used as a signal modulation carrier, the other beam is used as local oscillation light, and the working wavelength of the laser light source is 1310nm, namely the 0-dispersion wavelength of the optical fiber;
2) generating a 28GS/s QPSK level signal by an arbitrary waveform generator, and then inputting the signal to an IQ modulator to modulate a signal carrier;
3) the modulated signal light and the local oscillator light are transmitted to a receiving end along two paths of optical fibers respectively, spontaneous radiation noise is generated through a noise source with adjustable power, the spontaneous radiation noise and the modulated optical signal are optically coupled, and the optical signal-to-noise ratio is set to be 20 dB;
4) the local oscillator light path is inserted with an adjustable light delay line in front of the receiver, the phase of the local oscillator light can be adjusted by applying control voltage, the adjustable light delay line is controlled by a field programmable gate array, 21 test voltages are prestored in the field programmable gate array, the test voltages can be introduced to have phase deviation within the range of-50 degrees and are uniformly distributed, and the test voltages are sequentially applied to the adjustable light delay line within a test period Ts;
5) the signal light and the local oscillator light are detected by a balance detector after passing through the frequency mixer, and photocurrents of the I component and the Q component are output;
6) a small part of the two paths of optical current is used for feedback compensation of phase deviation, the rest part of the two paths of optical current is used for signal receiving, and sampling and judgment can be directly carried out after phase compensation is finished;
7) photoelectric current for feedback compensation of phase deviation is amplified to a set peak value by an electric amplifier after passing through a low-pass filter, and is used as a driving signal of a Mach-Zehnder modulator to modulate an input carrier wave, the bias voltage of the Mach-Zehnder modulator is set to be 0, and the input carrier wave is provided by a laser at a receiving end;
8) detecting an optical signal modulated by the Mach-Zehnder modulator by using the low-speed PD, and inputting the electrical signal obtained by low-speed PD detection to the field programmable gate array;
9) receiving and processing an input electric signal in a test period Ts by the field programmable gate array, and finding out a control voltage corresponding to the minimum electric signal by a climbing method;
10) and applying the control voltage to the adjustable light delay line to realize carrier phase compensation.
The invention also provides a photoelectric cooperation based analog domain carrier recovery method, which comprises the following steps:
1) the light beam emitted by the laser light source is divided into two beams by the coupler, wherein one beam is used as a signal modulation carrier, the other beam is used as local oscillation light, and the working wavelength of the laser light source is 1310nm, namely the 0-dispersion wavelength of the optical fiber;
2) generating a 28GS/s QPSK level signal by an arbitrary waveform generator, and then inputting the signal to an IQ modulator to modulate a signal carrier;
3) the modulated signal light and the local oscillator light are transmitted to a receiving end along two paths of optical fibers respectively, spontaneous radiation noise is generated through a noise source with adjustable power, the spontaneous radiation noise and the modulated optical signal are optically coupled, and the optical signal-to-noise ratio is set to be 20 dB;
4) the local oscillator light path is inserted with an adjustable light delay line in front of the receiver, the phase of the local oscillator light can be adjusted by applying control voltage, the adjustable light delay line is controlled by a field programmable gate array, 21 test voltages are prestored in the field programmable gate array, the test voltages can be introduced to have phase deviation within the range of-50 degrees and are uniformly distributed, and the test voltages are sequentially applied to the adjustable light delay line within a test period Ts;
5) the signal light and the local oscillator light are detected by a balance detector after passing through the frequency mixer, and photocurrents of the I component and the Q component are output;
6) a small part of the two paths of optical current is used for feedback compensation of phase deviation, the rest part of the two paths of optical current is used for signal receiving, and sampling and judgment can be directly carried out after phase compensation is finished;
7) the photoelectric current for feedback compensation of phase deviation is amplified to a set peak value by an electric amplifier after passing through a low-pass filter, and is used as a driving signal for directly modulating the laser;
8) detecting an optical signal modulated by the direct modulation laser by using the low-speed PD, and inputting an electric signal obtained by low-speed PD detection to the field programmable gate array;
9) receiving and processing an input electric signal in a test period Ts by the field programmable gate array, and finding out a control voltage corresponding to the minimum electric signal by a climbing method;
10) and applying the control voltage to the adjustable light delay line to realize carrier phase compensation.
The invention has the beneficial effects that: the analog domain carrier recovery method based on photoelectric cooperation is provided, the complexity is reduced well, the implementation is easy, and the implementation cost and the power consumption are reduced.
Drawings
Fig. 1 is a small constellation diagram with different polarization rotation angles and an I-component amplitude distribution diagram thereof of an analog domain carrier recovery method based on photoelectric cooperation.
FIG. 2 is a MZM transmission curve diagram of an analog domain carrier recovery method based on photoelectric coordination.
FIG. 3 is a PD output photocurrent curve diagram under different phase shifts of an analog domain carrier recovery method based on photoelectric cooperation.
Fig. 4 is a flow chart of an embodiment of an analog domain carrier recovery method based on photoelectric cooperation according to the present invention.
FIG. 5 is a graph of low-speed PD output power under different phase offset values of simulation scanning of an analog domain carrier recovery method based on photoelectric cooperation.
Fig. 6 is a flow chart of an embodiment of an analog domain carrier recovery method based on photoelectric cooperation according to the present invention.
FIG. 7 is a graph of low-speed PD output power under different phase offset values of simulation scanning of an analog domain carrier recovery method based on photoelectric cooperation.
Detailed Description
The invention is further described with reference to the following description and embodiments in conjunction with the accompanying drawings.
As shown in fig. 1 to 7, an analog domain carrier recovery method based on photoelectric cooperation is mainly applicable to a system using full-duplex fiber communication inside a data center or between data centers. In this case, the laser at the transmitting end is divided into two beams by the coupler, one of the two beams serves as a signal modulation carrier, and the other beam serves as local oscillation light and is transmitted along two paths of optical fibers respectively. Although the transmission scheme has certain local oscillator optical power cost, the requirement of a receiving end on a local oscillator laser can be eliminated, and because a signal carrier and the local oscillator light source are in the same laser, frequency deviation does not exist, a frequency estimation module is not needed, and the implementation cost and the power consumption can be further reduced. In addition, the communication distance between the data centers is short, and full-duplex communication is easy to realize. By adopting the scheme, the frequency locking of the local oscillator light and the signal light can be realized, but as the local oscillator light and the signal light are transmitted by different optical fibers, the phase deviation can exist inevitably, and the phase deviation can slowly drift along with the change of the external environment. The invention provides a method for eliminating the phase noise based on photoelectric cooperation, under the condition, a digital signal processing module can be completely avoided, and the coherent optical communication of DSP-free is realized.
The basic principle can be described as follows: the phase shift is expressed in the constellation point by rotating the signal constellation point by a certain angle, and in the case where there is no frequency deviation between the local oscillator light and the signal light, it can be considered that the phase shift of each symbol point is the same for a considerably long duration. As shown in fig. 1(a), (b), and (c) which show the constellation diagrams under the condition of phase offsets of 0 °, 20 °, and 45 °, respectively, the amplitude distribution of the signal I, Q component under different rotation angles is statistically analyzed, and as shown in fig. 1(d), (e), and (f) which show the amplitude distribution frequency diagrams of the I component under the phase offsets of 0 °, 20 °, and 45 °, respectively, it can be found that the amplitude distribution frequencies of the I component under different phase rotation angles have great differences. The frequency of the amplitude distribution of the I component near 0 is increased along with the increase of the phase rotation angle, the frequency is minimum at 0 DEG and maximum at 45 DEG, namely, the signal phase rotation angle and the amplitude distribution of the I component have a one-to-one correspondence relationship; further, the larger the signal phase rotation angle, the larger the amplitude distribution range of the I component (the Q component amplitude distribution characteristic coincides with the I component). Therefore, the amplitude distribution of the I component or the Q component of the signal can be counted in a certain way to determine the phase rotation angle.
Based on the principle, I, Q electric signals obtained through coherent reception can be used for driving the modulator, and the peak value of the signal and the bias voltage can be reasonably set according to the output curve of the modulator. The average intensity of the output optical signals of different amplitude distributions after modulation is inconsistent, and the average intensity of the output optical signals of the modulator is detected by the low-speed PD, so that the amplitude distribution of the components of the signal I, Q can be determined. For example, using an MZM modulator whose transmission curve is as shown in fig. 2, the bias voltage is set to zero, and the peak-to-peak value of the signal is set near the half-wave voltage, in this case, the smaller the probability that the amplitude of the I, Q component is distributed near zero, the smaller the output power of the low-speed PD is. By simulating and scanning the photocurrent output of the low-speed PD at different phase rotation angles, the result shown in fig. 3 is that the photocurrent output by the low-speed PD is minimal when the phase deflection is 0 °. Therefore, a tunable optical delay line (VODL) can be inserted into the local oscillator optical link, and the VODL is output and feedback controlled by the low-speed PD, so that carrier recovery in an analog domain can be realized.
The specific process is as follows:
1. the light beam emitted by the laser source is divided into two beams by the coupler, wherein one beam is used as a signal modulation carrier, the other beam is used as local oscillation light, and the working wavelength of the laser source is 1310nm, namely the 0-dispersion wavelength of the optical fiber.
2. The signal carrier is modulated by an IQ modulator (IQM), loading the signal.
3. The modulated signal light and the local oscillator light are transmitted to a receiving end along two paths of optical fibers respectively, spontaneous emission noise (ASE) is generated through a noise source with adjustable power, and the ASE and the modulated optical signal are optically coupled to set an optical signal to noise ratio (OSNR).
4. The local oscillator optical path has a tunable optical delay line (VODL) in front of the receiver, and the phase of the local oscillator light can be adjusted by applying a control voltage. The adjustable light delay line is controlled by a Field Programmable Gate Array (FPGA), a series of test voltages are prestored in the FPGA, and the test voltages can be introduced to have phase deviation within the range of-50 degrees and are uniformly distributed. These test voltages are applied in a test period TsApplied sequentially to the VODL.
5. The signal light and the local oscillator light are detected by a balance detector (BPD) after passing through the frequency mixer, and photocurrents of I components and Q components are output.
6. A small part of the two paths of light currents is used for feedback compensation of phase deviation, the rest part of the two paths of light currents is used for signal receiving, and sampling and judgment can be directly carried out after phase compensation is finished.
7. The photoelectric current for feedback compensation of the phase shift is passed through a Low Pass Filter (LPF) and amplified to a set peak-to-peak value by an electric amplifier, and the input carrier is modulated as a driving signal of a modulator, and the signal modulation may be external modulation (mach-zehnder modulator (MZM)) or internal modulation (for example, using a Direct Modulation Laser (DML) or a Vertical Cavity Surface Emitting Laser (VCSEL)).
8. And detecting the modulated optical signal by using the low-speed PD, and inputting an electric signal obtained by low-speed PD detection to the FPGA.
9. FPGA receives and processes a test period TsAnd (4) internally inputting the electric signals, and finding out the control voltage corresponding to the minimum electric signal by a climbing method.
10. The carrier phase compensation can be realized by applying the control voltage to the VODL.
The analog domain carrier recovery method based on photoelectric cooperation can realize analog domain carrier recovery and further can realize coherent reception of DSP-free.
Example one
Fig. 4 is a block diagram of a flowchart provided in embodiment 1 of the present invention, which is specifically as follows:
the light beam emitted by the laser source is divided into two beams by the coupler, wherein one beam is used as a signal modulation carrier, and the other beam is used as local oscillation light which is respectively transmitted along two paths of optical fibers. An arbitrary waveform generator generates a 28GS/s QPSK level signal, and then inputs the signal to an IQ modulator to modulate a signal carrier. Next, white gaussian noise is generated by a variable power noise source and coupled with the modulated optical signal by an optical coupler. After the mixed light is detected by a balance detector, a small part of the output light current is divided for feedback compensation of phase deviation. The photocurrent is amplified to a set peak-to-peak value by an electrical amplifier after passing through a low-pass filter, and is used as an MZM drive signal to modulate an input carrier, and the MZM bias voltage is set to 0. And an optical signal output by the MZM is input to the FPGA after being detected by the PD, and an adjustable optical delay line is feedback-controlled, so that carrier phase recovery is realized.
The specific process is as follows:
1. the light beam emitted by the laser source is divided into two beams by the coupler, wherein one beam is used as a signal modulation carrier, the other beam is used as local oscillation light, and the working wavelength of the laser source is 1310nm, namely the 0-dispersion wavelength of the optical fiber.
2. An arbitrary waveform generator generates a 28GS/s QPSK level signal, and then inputs the signal to an IQ modulator to modulate a signal carrier.
3. The modulated signal light and the local oscillator light are transmitted to a receiving end along two paths of optical fibers respectively, spontaneous emission noise (ASE) is generated through a noise source with adjustable power, the ASE and the modulated optical signal are optically coupled, and the OSNR is set to be 20 dB.
4. The local oscillator optical path has an adjustable optical delay line in front of the receiver, and the phase of the local oscillator light can be adjusted by applying control voltage. The adjustable light delay line is controlled by a Field Programmable Gate Array (FPGA), 21 test voltages are prestored in the FPGA, and the test voltages can be introduced to have phase deviation within the range of-50 degrees and are uniformly distributed. These test voltages are sequentially applied to the VODL within one test period Ts.
5. The signal light and the local oscillator light are detected by the balance detector after passing through the frequency mixer, and the photocurrent of the I component and the Q component is output.
6. A small part of the two paths of light currents is used for feedback compensation of phase deviation, the rest part of the two paths of light currents is used for signal receiving, and sampling and judgment can be directly carried out after phase compensation is finished.
7. The photoelectric current for feedback compensation phase offset is amplified to a set peak value by an electric amplifier after passing through a Low Pass Filter (LPF), and is used as a driving signal of the MZM modulator to modulate an input carrier wave, and the MZM bias voltage is set to be 0. The input carrier is provided by a laser at the receiving end.
8. And detecting the modulated optical signal by using the low-speed PD, and inputting an electric signal obtained by low-speed PD detection to the FPGA.
9. And the FPGA receives and processes the input electric signal in a test period Ts, and finds out the control voltage corresponding to the minimum electric signal by a climbing method.
10. The carrier phase compensation can be realized by applying the control voltage to the VODL.
The embodiment shown in fig. 5 scans the output power curve of the low-speed PD under different phase offset values by VIP simulation. As can be seen from the figure, the output power is minimal when the phase offset is zero. Therefore, the FPGA can generate a test voltage, the FPGA determines a control voltage corresponding to the PD minimum output power according to the current output by the low-speed PD through a climbing method, and the control voltage controls the VODL, so that the carrier phase compensation can be realized.
Example two
Embodiment one uses the transmission curve characteristic of MZM to count the frequency characteristic of I, Q component distribution around 0, thereby determining the phase offset of signal. Another obvious feature of the amplitude distribution frequency of I, Q components at different phase rotation angles is that the larger the signal phase rotation angle, the larger the amplitude distribution range of I, Q components. This characteristic can be detected using a Directly Modulated Laser (DML). Fig. 7 (a) shows a transmission curve of a DML having a cutoff voltage of 28mV, by setting the gain of the amplifier so that the average amplitude of the amplified signal is near the cutoff voltage when the phase shift is 0. At this time, as long as there is a phase shift in the signal, the average optical power output by the DML modulation will increase. Thus, the amplitude distribution of the I, Q components can be reflected by the average output optical power of the DML, further reflecting the signal dependent magnitude. Embodiment flow for carrier phase recovery using DML is shown in fig. 6, and the process is basically the same as the embodiment except that the MZM is replaced with DML.
The specific process is as follows:
1. the light beam emitted by the laser source is divided into two beams by the coupler, wherein one beam is used as a signal modulation carrier, the other beam is used as local oscillation light, and the working wavelength of the laser source is 1310nm, namely the 0-dispersion wavelength of the optical fiber.
2. An arbitrary waveform generator generates a 28GS/s QPSK level signal, and then inputs the signal to an IQ modulator to modulate a signal carrier.
3. The modulated signal light and the local oscillator light are transmitted to a receiving end along two paths of optical fibers respectively, spontaneous emission noise (ASE) is generated through a noise source with adjustable power, the ASE and the modulated optical signal are optically coupled, and the OSNR is set to be 20 dB.
4. The local oscillator optical path has an adjustable optical delay line in front of the receiver, and the phase of the local oscillator light can be adjusted by applying control voltage. The adjustable light delay line is controlled by a Field Programmable Gate Array (FPGA), 21 test voltages are prestored in the FPGA, and the test voltages can be introduced to have phase deviation within the range of-50 degrees and are uniformly distributed. These test voltages are sequentially applied to the VODL within one test period Ts.
5. The signal light and the local oscillator light are detected by the balance detector after passing through the frequency mixer, and the photocurrent of the I component and the Q component is output.
6. A small part of the two paths of light currents is used for feedback compensation of phase deviation, the rest part of the two paths of light currents is used for signal receiving, and sampling and judgment can be directly carried out after phase compensation is finished.
7. The photoelectric current for feedback compensation of phase shift is amplified to a set peak-to-peak value by an electric amplifier after passing through a Low Pass Filter (LPF) as a driving signal of the DML.
8. And detecting the modulated optical signal by using the low-speed PD, and inputting an electric signal obtained by low-speed PD detection to the FPGA.
9. And the FPGA receives and processes the input electric signal in a test period Ts, and finds out the control voltage corresponding to the minimum electric signal by a climbing method.
10. The carrier phase compensation can be realized by applying the control voltage to the VODL.
Fig. 7 shows (a) DML transmission curves and (b) low-speed PD output power curves for different phase offset values in the simulation scan of the second embodiment. As can be seen from the figure, the output power is minimal when the phase offset is zero. Therefore, by adopting a method similar to the embodiment, the FPGA generates the test voltage, the FPGA determines the control voltage corresponding to the minimum output power of the low-speed PD by the current output by the low-speed PD through a climbing method, and the VODL is controlled by the control voltage, so that the carrier phase compensation can be realized.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (7)
1. A carrier recovery method in an analog domain based on photoelectric cooperation is characterized in that: i, Q electric signals obtained through coherent reception are used for driving a modulator, signal peak values and bias voltages are set according to an output curve of the modulator, the average intensities of output optical signals after different amplitude distributions are modulated are inconsistent, the average intensity of the output optical signals of the modulator is detected by a low-speed PD, the amplitude distribution of signals I, Q components can be determined, an adjustable optical delay line is inserted into a local oscillation optical link, the adjustable optical delay line is output and fed back and controlled by the low-speed PD, and carrier recovery in an analog domain can be achieved.
2. The method for recovering the carrier wave in the analog domain based on the photoelectric coordination as claimed in claim 1, characterized by comprising the following steps:
s1, dividing a light beam emitted by a laser light source into two beams by a coupler, wherein one beam is used as a signal modulation carrier, and the other beam is used as local oscillation light;
s2, modulating the signal modulation carrier by the IQ modulator, and loading the signal to form signal light;
s3, transmitting the modulated signal light and the local oscillator light to a receiving end along two paths of optical fibers respectively, generating spontaneous radiation noise through a noise source with adjustable power, and optically coupling the spontaneous radiation noise and the modulated signal light to set an optical signal-to-noise ratio;
s4, inserting an adjustable light delay line in front of the receiver by the local oscillator light, and applying control voltage to adjust the phase of the local oscillator light, wherein the adjustable light delay line is controlled by the field programmable gate array;
s5, detecting the signal light and the local oscillator light by a balance detector after passing through the frequency mixer respectively, and outputting two paths of light currents of the I component and the Q component;
s6, respectively dividing parts of the two paths of optical currents for feedback compensation of phase deviation, and using the rest parts for signal receiving, and directly sampling and judging after phase compensation is completed;
s7, amplifying the photoelectric current for feedback compensation of phase shift to a set peak value by an electric amplifier after passing through a low-pass filter, and modulating an input carrier as a driving signal of a modulator, wherein the signal is modulated into external modulation or internal modulation;
s8, detecting the optical signal modulated by the modulator by using the low-speed PD, and inputting the electric signal obtained by low-speed PD detection to the field programmable gate array;
s9, the field programmable gate array receives and processes an input electric signal in a test period Ts, and a control voltage corresponding to the minimum electric signal is found through a climbing method;
and S10, applying the control voltage to the adjustable light delay line to realize carrier phase compensation.
3. The analog domain carrier recovery method based on photoelectric cooperation according to claim 2, wherein: the operating wavelength of the laser source is 1310nm, which is the 0-dispersion wavelength of the optical fiber.
4. The analog domain carrier recovery method based on photoelectric cooperation according to claim 2, wherein: in step S4, a series of test voltages are pre-stored in the fpga, the test voltages introduce phase offsets in the range of-50 ° -50 ° and are uniformly distributed, and the test voltages are applied for a test period TsAnd the light-adjustable delay lines are sequentially applied to the light-adjustable delay lines.
5. The analog domain carrier recovery method based on photoelectric cooperation according to claim 2, wherein: in step S7, the signal modulation is externally modulated by a mach-zehnder modulator or internally modulated by a direct modulation laser.
6. An analog domain carrier recovery method based on photoelectric cooperation is characterized by comprising the following steps:
1) the light beam emitted by the laser light source is divided into two beams by the coupler, wherein one beam is used as a signal modulation carrier, the other beam is used as local oscillation light, and the working wavelength of the laser light source is 1310nm, namely the 0-dispersion wavelength of the optical fiber;
2) generating a 28GS/s QPSK level signal by an arbitrary waveform generator, and then inputting the signal to an IQ modulator to modulate a signal carrier;
3) the modulated signal light and the local oscillator light are transmitted to a receiving end along two paths of optical fibers respectively, spontaneous radiation noise is generated through a noise source with adjustable power, the spontaneous radiation noise and the modulated optical signal are optically coupled, and the optical signal-to-noise ratio is set to be 20 dB;
4) the local oscillator light path is inserted with an adjustable light delay line in front of the receiver, the phase of the local oscillator light can be adjusted by applying control voltage, the adjustable light delay line is controlled by a field programmable gate array, 21 test voltages are prestored in the field programmable gate array, the test voltages can be introduced to have phase deviation within the range of-50 degrees and are uniformly distributed, and the test voltages are sequentially applied to the adjustable light delay line within a test period Ts;
5) the signal light and the local oscillator light are detected by a balance detector after passing through the frequency mixer, and photocurrents of the I component and the Q component are output;
6) a small part of the two paths of optical current is used for feedback compensation of phase deviation, the rest part of the two paths of optical current is used for signal receiving, and sampling and judgment can be directly carried out after phase compensation is finished;
7) photoelectric current for feedback compensation of phase deviation is amplified to a set peak value by an electric amplifier after passing through a low-pass filter, and is used as a driving signal of a Mach-Zehnder modulator to modulate an input carrier wave, the bias voltage of the Mach-Zehnder modulator is set to be 0, and the input carrier wave is provided by a laser at a receiving end;
8) detecting an optical signal modulated by the Mach-Zehnder modulator by using the low-speed PD, and inputting the electrical signal obtained by low-speed PD detection to the field programmable gate array;
9) receiving and processing an input electric signal in a test period Ts by the field programmable gate array, and finding out a control voltage corresponding to the minimum electric signal by a climbing method;
10) and applying the control voltage to the adjustable light delay line to realize carrier phase compensation.
7. An analog domain carrier recovery method based on photoelectric cooperation is characterized by comprising the following steps:
1) the light beam emitted by the laser light source is divided into two beams by the coupler, wherein one beam is used as a signal modulation carrier, the other beam is used as local oscillation light, and the working wavelength of the laser light source is 1310nm, namely the 0-dispersion wavelength of the optical fiber;
2) generating a 28GS/s QPSK level signal by an arbitrary waveform generator, and then inputting the signal to an IQ modulator to modulate a signal carrier;
3) the modulated signal light and the local oscillator light are transmitted to a receiving end along two paths of optical fibers respectively, spontaneous radiation noise is generated through a noise source with adjustable power, the spontaneous radiation noise and the modulated optical signal are optically coupled, and the optical signal-to-noise ratio is set to be 20 dB;
4) the local oscillator light path is inserted with an adjustable light delay line in front of the receiver, the phase of the local oscillator light can be adjusted by applying control voltage, the adjustable light delay line is controlled by a field programmable gate array, 21 test voltages are prestored in the field programmable gate array, the test voltages can be introduced to have phase deviation within the range of-50 degrees and are uniformly distributed, and the test voltages are sequentially applied to the adjustable light delay line within a test period Ts;
5) the signal light and the local oscillator light are detected by a balance detector after passing through the frequency mixer, and photocurrents of the I component and the Q component are output;
6) a small part of the two paths of optical current is used for feedback compensation of phase deviation, the rest part of the two paths of optical current is used for signal receiving, and sampling and judgment can be directly carried out after phase compensation is finished;
7) the photoelectric current for feedback compensation of phase deviation is amplified to a set peak value by an electric amplifier after passing through a low-pass filter, and is used as a driving signal for directly modulating the laser;
8) detecting an optical signal modulated by the direct modulation laser by using the low-speed PD, and inputting an electric signal obtained by low-speed PD detection to the field programmable gate array;
9) receiving and processing an input electric signal in a test period Ts by the field programmable gate array, and finding out a control voltage corresponding to the minimum electric signal by a climbing method;
10) and applying the control voltage to the adjustable light delay line to realize carrier phase compensation.
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