16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF

Abstract

The present invention relates to a 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF, and belongs to the field of communication technology. The system includes two LDs, an IQ modulator, a PRBS, a DC, six EDFAs, five HNLFs, three FD-OPs, two coherent receivers, three WDMs and a wave plate; the PIA process requires an HNLF and an FD-OP to generate a new phase-locked pump; the PSA process requires an HNLF and an FD-OP to convert 16QAM / 8QAM into a co-directional component and an orthogonal component; the SPM process requires an EDFA and an HNLF to perform phase deflection on the co-directional component and the orthogonal component to obtain a signal processing method for the final required format conversion. The system of the present invention directly generates a phase-locked pump through the PIA process, avoids the use of a phase-locked loop, and has a simple system structure.

Description

Technical Field

[0001] The invention belongs to the technical field of communication and relates to a 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF. Background Art

[0002] With the continuous development of fixed networks, we have entered the era of the fifth generation of fixed networks (F5G). F5G needs to transmit data under all-optical conditions and requires ultra-large bandwidth. In F5G, when multi-domain networks are interconnected, optical signals from different domains may have different modulation formats, or different transmission scenarios may also require different modulation formats. This inevitably requires the all-optical network to have the basic ability to perform all-optical format conversion. In response to the high bandwidth requirements of F5G under all-optical conditions, quadrature amplitude modulation (QAM) has received widespread attention for its higher spectral efficiency and ability to withstand greater dispersion and nonlinear effects. Several existing technologies attempt to use the four-wave mixing (FWM) effect and self-phase modulation (SPM) of optical fiber to convert the hexadecimal quadrature amplitude modulation (16QAM) format into a quadrature phase shift keying (QPSK) format that is more suitable for long-distance communication. However, some of these conversion technologies require the use of a feedback circuit to phase-lock with the local oscillator laser in order to convert and demodulate the signal, which limits the conversion speed; some conversion technologies can only perform format conversion on 16QAM, and the conversion format is relatively simple; some use FWM and SPM in dual polarization states to perform all-optical modulation format conversion on 16QAM, but the FWM efficiency is low in dual polarization states and the conversion result is sensitive to the signal polarization angle, which can easily cause errors in the format conversion result. Summary of the invention

[0003] In view of this, the object of the present invention is to provide a 16-ary or 8-ary quadrature amplitude modulation (16QAM or 8QAM) all-optical modulation format conversion system based on PSA and HNLF, avoiding the use of a phase-locked loop and simplifying the system structure.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF mainly includes: two LDs (LD1-LD2), an IQ modulator, a PRBS, a DC, six EDFAs (EDFA1-EDFA6), five HNLFs (HNLF1-HNLF5), three FD-OPs (FD-OP1-FD-OP3), and two coherent receivers (Coherent receiver), three WDMs (WDM1~WDM3) and a wave plate; among them, HNLF1 and FD-OP1 are used to form PIA; HNLF2 / HNLF3 and FD-OP2 / FD-OP3 are used to form PSA; EDFA5 / EDFA6 and HNLF4 / HNLF5 are used to form SPM; LD denotes continuous wave laser source, PRBS denotes signal generator, DC denotes direct current voltage source, EDFA denotes erbium-doped fiber amplifier, HNLF denotes highly nonlinear fiber, FD-OP denotes optical filter, WDM denotes wavelength division multiplexer, PIA denotes phase insensitive amplification, PSA denotes phase sensitive amplification, and SPM denotes self-phase modulation.

[0006] The light source signal emitted by LD1 is divided into two paths: one path is injected into WDM1, coupled with the first signal of the light source signal emitted by LD2, and then injected into HNLF1 to excite PIA to generate a new pump phase-locked with LD1 and LD2. The new pump is filtered by FD-OP1 and amplified by EDFA4 before being injected into WDM2 and WDM3 respectively; the other path is injected into WDM2 and WDM3 respectively after passing through the IQ modulator, where the transmitter that generates 16QAM / 8QAM adopts the traditional square constellation mapping;

[0007] The second signal of the light source signal emitted by LD2 is amplified by EDFA2 and then injected into WDM2; the third signal is phase-shifted 180 degrees by the wave plate, then amplified by EDFA3 and then injected into WDM3;

[0008] The signals coupled by WDM2 or WDM3 are all stimulated by PSA at the wavelength position of LD1 through an HNLF. The stimulated PSA process is filtered by an FD-OP. The filtered optical signals are first amplified by an EDFA signal and then stimulated by the HNLF SPM process. They are then input into the coherent receiver to obtain the 16QAM / 8QAM signal after all-optical modulation format conversion. The signal constellation mapping after format conversion will show a specific rule, which is specifically related to the constellation mapping at the transmitter.

[0009] Furthermore, the PIA is used to generate a new pump that is phase-locked with LD1 and LD2, avoiding the use of a phase-locked loop.

[0010] Furthermore, the PSA is used to convert a 16QAM or 8QAM signal into an in-phase component and an orthogonal component.

[0011] Furthermore, the SPM is used to perform phase shifting on the co-directional component and the orthogonal component to obtain a signal processing method for the final required format conversion, that is, a 16QAM signal can simultaneously convert two QPSK modulation formats, or an 8QAM signal can simultaneously convert BPSK and QPSK modulation formats without losing information.

[0012] The beneficial effects of the present invention are as follows: the 16QAM / 8QAM all-optical modulation format conversion system of the present invention is applicable to the 16QAM / 8QAM all-optical modulation format conversion based on reconfigurable PSA and HNLF, applicable to the new phase-locked pump based on PIA, applicable to the method of converting 16QAM / 8QAM into co-directional components and orthogonal components based on PSA, and the signal processing method of performing phase deflection on the co-directional components and orthogonal components based on SPM to obtain the final required format conversion, that is, the 16QAM signal can be converted into two QPSK modulation formats at the same time, or the 8QAM signal can be converted into BPSK and QPSK modulation formats at the same time without losing information. The system of the present invention directly generates a phase-locked pump through the PIA process, avoids the use of a phase-locked loop, and has a simple system structure.

[0013] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0015] Figure 1 This is a structural diagram of a 16QAM / 8QAM all-optical modulation format conversion system according to an embodiment of the present invention;

[0016] Figure 2 A 16QAM constellation diagram of a fixed 16-symbol transmission sequence for 16QAM all-optical modulation format conversion for the system according to the embodiment of the present invention;

[0017] Figure 3 The system of the embodiment of the present invention performs 16QAM all-optical modulation format conversion to fix 16 symbol transmission sequences, and the PAM4 signal constellation diagram ( Figure 3 a) and waveform diagram ( Figure 3 b);

[0018] Figure 4 The system of the embodiment of the present invention performs 16QAM all-optical modulation format conversion, fixes 16 symbol transmission sequences, and generates a PAM4 signal constellation diagram of the orthogonal component (Q) during the PSA process ( Figure 4 a) and waveform diagram ( Figure 4 b);

[0019] Figure 5 For the system of the embodiment of the present invention, 16 transmission sequences are fixed for 16QAM all-optical modulation format conversion. After PSA and SPM, a QPSK2 signal constellation diagram of format conversion is generated ( Figure 5 a) and waveform diagram ( Figure 5 b);

[0020] Figure 6 The system of the embodiment of the present invention performs 16QAM all-optical modulation format conversion, fixes 16 symbol transmission sequences, passes through PSA, and then passes through SPM to generate a QPSK1 signal constellation diagram of format conversion ( Figure 6 a) and waveform diagram ( Figure 6 b);

[0021] Figure 7 The system of the embodiment of the present invention performs 16QAM all-optical modulation format conversion and randomly sends a 16QAM constellation diagram with 4 times the number of fixed symbol sequences;

[0022] Figure 8 The system of the embodiment of the present invention performs 16QAM all-optical modulation format conversion and randomly sends 4 times the number of fixed symbol sequences. After PSA, the QPSK1 signal constellation diagram of the format conversion is generated after SPM ( Figure 8 a) and waveform diagram ( Figure 8 b);

[0023] Fig. 9 The system of the embodiment of the present invention performs 16QAM all-optical modulation format conversion and randomly sends 4 times the number of fixed symbol sequences. After PSA, the QPSK2 signal constellation diagram of the format conversion is generated after SPM ( Fig. 9 a) and waveform diagram ( Fig. 9 b);

[0024] Fig.10 An 8QAM constellation diagram of a fixed 8-symbol transmission sequence for 8QAM all-optical modulation format conversion performed by the system according to the embodiment of the present invention;

[0025] Fig.11 The system of the embodiment of the present invention performs 8QAM all-optical modulation format conversion, fixes 8 symbol transmission sequences, passes through PSA, and then passes through SPM to generate a format-converted BPSK signal constellation diagram ( Fig.11 a) and waveform diagram ( Fig.11 b);

[0026] Fig.12 The system of the embodiment of the present invention performs 8QAM all-optical modulation format conversion to fix 8 symbol transmission sequences. After PSA, the resulting PAM4 signal constellation diagram ( Fig.12 a) and waveform diagram ( Fig.12 b);

[0027] Fig.13 The system of the embodiment of the present invention performs 8QAM all-optical modulation format conversion, fixes 8 symbol transmission sequences, passes through PSA, and then passes through SPM to generate a QPSK signal constellation diagram of format conversion ( Fig.13 a) and waveform diagram ( Fig.13 b);

[0028] Fig.14 The system of the embodiment of the present invention performs 8QAM all-optical modulation format conversion and randomly sends an 8QAM constellation diagram with 4 times the number of fixed symbol sequences;

[0029] Fig.15 The system of the embodiment of the present invention performs 8QAM all-optical modulation format conversion and randomly sends 4 times the number of fixed symbol sequences. After PSA, the BPSK signal constellation diagram of format conversion is generated after SPM ( Fig.15 a) and waveform diagram ( Fig.15 b);

[0030] Fig.16 The system of the embodiment of the present invention performs 8QAM all-optical modulation format conversion and randomly sends 4 times the number of fixed symbol sequences. After PSA, the QPSK signal constellation diagram of the format conversion is generated after SPM ( Fig.16 a) and waveform diagram ( Fig.16 b). DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0032] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0033] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0034] See also Figures 1 to 16 The present invention provides a 16QAM / 8QAM all-optical modulation format conversion system based on reconfigurable PSA and HNLF, such as Figure 1 As shown, the system mainly includes: 2 LDs ((LD1~LD2)), 1 IQ modulator, a PRBS, a DC, 6 EDFAs (EDFA1~EDFA6), 5 HNLFs (HNLF1~HNLF5), 3 FD-OPs (FD-OP1~FD-OP3), 2 coherent receivers, 3 WDMs (WDM1~WDM3) and 1 wave plate.

[0035] The signal processing process of this system is:

[0036] (1) LD1 is amplified by EDFA1, coupled with LD2 by WDM1, and then injected into HNLF1, which stimulates the phase-insensitive amplification (PIA) process and generates a new pump that is phase-locked with LD1 and LD2.

[0037] (2) LD2 is amplified by EDFA2.

[0038] (3) The new pump is filtered by FD-OP1 and then amplified by EDFA4.

[0039] (4) LD1 is used as the light source and is modulated by the IQ modulator to generate a 16QAM / 8QAM optical signal.

[0040] (5) The optical signals generated in (2) to (4) are coupled through WDM2 and injected into a HNLF2 to stimulate the PSA process at the wavelength position of LD1.

[0041] (6) The PSA process stimulated by (5) is filtered by FD-OP2, and the filtered optical signal is amplified by EDFA5 and then passes through HNLF4 to obtain a 16QAM / 8QAM signal after all-optical modulation format conversion.

[0042] (7) Before performing step (2), a wave plate is introduced, and then the process from (2) to (6) is performed to obtain another signal after 16QAM / 8QAM is converted into an all-optical modulation format.

[0043] like Figure 1 As shown, the IQ modulator is Figure 1 It includes all the devices of the two MZM paths, wherein the signal generator (PRBS) and the devices in the dotted box next to the PRBS work together to generate a 16QAM / 8QAM optical signal, wherein the mapping table of 16QAM / 8QAM in the PRBS uses a traditional square constellation diagram mapping, and these two devices are used to provide the system of the present invention with an input of an electrical signal and an output of an optical signal after being processed by the system.

[0044] In the present invention, all optical signals are in the same polarization state.

[0045] In order to phase-lock the signals before PSA, the present invention is as follows: Figure 1 As shown in the figure, the PIA operation is performed, assuming that the LD1 wavelength (1550nm) frequency f0 signal is used as the pump signal A1 and the power is strong enough, the phase is β1, and the LD2 wavelength frequency f0+Δf signal is used as A3 with a phase of β3. The power of the LD1 wavelength after passing through EDFA1 is much greater than the power of the LD2 wavelength signal (|A1| 2 >>|A3| 2 ), Δf is 16 times the symbol rate.

[0046] The coupling equation after A1 and A3 are injected into WDM1 and pass through the PIA dotted box HNLF1 is:

[0047]

[0048] Among them, Δk=β3+β4-2β1, γ is a nonlinear parameter, and the idler wave generated in the PIA process is obtained by calculating and solving the coupling equation to satisfy the following formula:

[0049]

[0050] Where, κ=2γ|A1| 2 +Δk,

[0051] The A4 idler wave generated by the PIA process has a frequency of f0-Δf, which copies all the information of the signal wave A3, and the phase is conjugated. The A4 idler wave has a specific relationship with the input A1 and A3, and the phase has a fixed relationship, so the input A1 and A3 and the output idler wave A4 have a phase-locking effect. Therefore, the PIA process performs phase-locking processing on all signals before the PSA process.

[0052] Figure 1 The PSA process shown in FIG. 1 requires that the various signals input into the PSA process be initially phase-locked, and the 16QAM / 8QAM optical signal with a wavelength frequency f0 is injected into WDM2 and WDM3 respectively.

[0053] Figure 1 The PIA process shown in the figure obtains a phase-locked idle wave after filtering by FD-OP1 and then is power amplified by EDFA4 and injected into WDM2 and WDM3 respectively. The wavelength frequency of LD2 is f0+Δf and is injected into WDM2 through EDFA2 power amplification without a wave plate phase shift of 180 degrees. The wavelength frequency of LD2 is f0+Δf and is injected into WDM3 through EDFA3 power amplification with a wave plate phase shift of 180 degrees.

[0054] The 16QAM / 8QAM signal wavelength frequency f0 injected into WDM2 and the phase-locked idler wavelength frequency f0-Δf generated by PIA are coupled through the EDFA4 power amplification signal and the LD2 without wave plate phase shift after EDFA2 power amplification signal and then undergo the PSA process. Assume that the 16QAM / 8QAM optical signal is A3, the phase-locked idler signal generated by PIA is A2, and the signal amplified by LD2 without phase shift is A1. A1 and A2 are used as pump waves, and the three signal powers satisfy |A1| 2 ,|A2| 2 >>|A3| 2 , the coupling equations of the HNLF after the three signals are injected into WDM2 and enter the PSA process are as follows:

[0055]

[0056] Assume that the initial phases of the two pump wave signals A1 and A2 are and The initial phase of the 16QAM / 8QAM signal wave is is the initial phase and is the phase modulation information of the 16QAM / 8QAM modulation format. By solving the above coupling equation, the final PSA process result formula can be obtained as follows:

[0057]

[0058] The three input signals injected into WDM3 undergo the PSA process in the same manner as described above for the PSA operation through WDM2.

[0059] Figure 1 Through the PSA process, the filtering wavelength of FD-OP2 and FD-OP3 in the two PSAs is f0. The signals obtained are the co-directional component and the orthogonal component. After filtering, the two PSA processes are respectively amplified by EDFA5 and EDFA6 in the SPM process, and finally injected into HNLF4 and HNLF5 to stimulate SPM.

[0060] Figure 1 The PSA process is filtered and then passes through the SPM process. Assume that the signal entering the SPM is A0. The coupling equation of the signal in the SPM through the HNLF is:

[0061]

[0062] By coupling the equation After calculation, the result equation after SPM is:

[0063]

[0064] From the above formula, it can be seen that A0 controls the change of A0 signal phase through power and nonlinear parameter γ, as well as HNLF length. Figure 1 In the SPM block diagram, it is necessary to first perform EDFA power amplification. Therefore, after SPM, the phase of the co-directional components and orthogonal components generated by the two PSAs is changed to finally obtain the 16QAM / 8QAM all-optical modulation format conversion result.

[0065] The specific implementation of the present invention is based on the simulation performed by the professional optical communication system simulation software VPITransmissionMaker. The traditional square mapping table is used in the PRBS to generate 16QAM / 8QAM electrical signals, wherein a coherent receiver is used to check the waveforms of each signal to see whether the waveforms achieve the expected effect.

[0066] for Figure 1 The traditional square mapping table of PRBS generating 16QAM / 8QAM electrical signals is shown in Table 1. The 16QAM / 8QAM column represents each sequence, and the information in the IQ columns corresponds to the amplitude of the sequence mapped to the IQ path.

[0067] Table 1 16QAM / 8QAM traditional square constellation mapping table

[0068]

[0069] By using VPITransmissionMaker simulation software Figure 1 To simulate, first simulate the transmission of 16QAM optical signal. For the 16QAM all-optical modulation format conversion process, first simulate the transmission of 16 fixed sequences. The 16QAM optical signal is generated by the signal generator (PRBS) and the devices in the dashed box next to the PRBS. The 16 fixed sequences are shown in Table 2. Then LD1 is injected into WDM1 after passing through EDFA1 and LD2 for PIA process. The devices used for PIA are as follows: Figure 1 As shown in the PIA dotted line diagram, the signal of LD1 amplified by EDFA1 is used as the pump wave, and all the signals before PSA are phase-locked through PIA. The 16QAM optical signal and the signal of LD2 amplified by EDFA2 without phase shift, and the phase-locked idler generated by PIA amplified by EDFA4 are injected into WDM2 for PSA operation. The devices used in PSA are as follows: Figure 1 As shown in the PSA dotted box diagram, the 16QAM signal, the phase-shifted signal of LD2 amplified by EDFA3, and the idler signal generated by PIA amplified by EDFA4 are injected into WDM3 for PSA operation, and the PSA process generates co-directional components and orthogonal components.

[0070] Figure 2 This is the 16QAM constellation diagram of a fixed 16-symbol transmission sequence for 16QAM all-optical modulation format conversion performed by the system in this embodiment. By observing and comparing the constellation diagram with the 16QAM mapping table, it can be seen that the constellation diagram is a traditional square constellation diagram. Figure 3 (a) is the PAM4 signal constellation diagram of the in-phase component (I) obtained after the PSA process of the fixed 16-symbol transmission sequence of the 16QAM all-optical modulation format conversion system based on PSA and HNLF. Figure 3 (b) is the PAM4 signal waveform of the in-phase component (I) obtained after the PSA process.

[0071] Figure 4 (a) is a PAM4 signal constellation diagram of the orthogonal component (Q) obtained after the PSA process of fixing the 16-symbol transmission sequence in the 16QAM all-optical modulation format conversion in the system of this embodiment, Figure 4 (b) is the PAM4 signal waveform of the orthogonal component (Q) obtained after the PSA process.

[0072] The orthogonal components and the co-directional components obtained after PSA are injected into the SPM, and finally the desired QPSK1 and QPSK2 signals are obtained.

[0073] Figure 5(a) is the 16QAM all-optical modulation format conversion performed by the system of this embodiment. After the fixed 16 transmission sequences pass through PSA and SPM, the QPSK2 signal constellation diagram of the format conversion is obtained. Figure 5 (b) is the waveform diagram of the QPSK2 signal after format conversion after passing through PSA and then SPM.

[0074] Figure 6 (a) is the 16QAM all-optical modulation format conversion performed by the system of this embodiment. After the fixed 16 symbols in the transmission sequence pass through PSA and then pass through SPM, the QPSK1 signal constellation diagram of the format conversion is obtained. Figure 6 (b) is the waveform diagram of the QPSK1 signal after format conversion after passing through PSA and then SPM.

[0075] By sampling and judging the two generated QPSK1 and QPSK2 waveforms, it can be obtained that the final sampling and judgment result has a regularity with the transmitted fixed sequence, and finally this regularity can be used to perfectly judge and demodulate a signal sequence without error. The regularity is shown in Table 2.

[0076] Table 2 Decision rules for 16QAM all-optical modulation format conversion in the 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF

[0077]

[0078] In the process of sending the fixed sequence, the 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF successfully converts the 16QAM all-optical modulation format into two QPSK signals. Then, without changing the 16QAM mapping table, the 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF randomly sends 4 times the number of fixed symbol sequences, and the generated 16QAM signal constellation diagram is as follows: Figure 7 shown.

[0079] The signal before PSA is phase-locked through PIA, and finally two successfully converted QPSK signals are obtained through SPM after PSA.

[0080] Figure 8 (a) In the 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF, a 16QAM optical signal is generated by randomly sending 4 times the number of fixed symbol sequences. After PIA and PSA, the QPSK1 signal constellation diagram of the format conversion is obtained after SPM. Figure 8 (b) is the waveform of the QPSK1 signal after format conversion through SPM.

[0081] Fig. 9 (a) In the 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF, a 16QAM optical signal is generated by randomly sending 4 times the number of fixed symbol sequences. After PIA and PSA, and then SPM, the QPSK2 signal constellation diagram after format conversion is obtained. Fig. 9 (b) is the waveform of the QPSK2 signal after format conversion through SPM.

[0082] After obtaining QPSK1 and QPSK2, the IQ paths of QPSK1 and QPSK2 are sampled and judged as 1 if the amplitude is positive, and 0 if the amplitude is negative. Finally, the two QPSK signal IQ paths and the transmitted signal are perfectly demodulated into a sequence without error through the regular table in Table 2.

[0083] By using VPITransmissionMaker simulation software Figure 1 Simulation is performed to simulate the transmission of 8QAM optical signals in modulation format. For the 8QAM all-optical format conversion process, the transmission of 8 fixed sequences is simulated first, and the 8QAM signal is generated by the signal generator (PRBS) and the device in the dotted box next to the PRBS. The 8 fixed sequences are shown in Table 3. Then the signal of LD1 after EDFA1 power amplification and LD2 are injected into WDM1, and all pre-PSA signals are phase-locked during the PIA process. The 8QAM signal and the signal of LD2 without wave plate phase shift after EDFA2 power amplification, and the signal of the phase-locked idler generated by PIA after EDFA4 power amplification are injected into WDM2 for PSA operation; the 8QAM signal and the signal of LD2 after wave plate phase shift after EDFA3 power amplification, and the signal of the phase-locked idler generated by PIA after EDFA4 power amplification are injected into WDM3 for PSA operation. After passing through WDM2 and WDM3, the in-phase component and the orthogonal component are generated by PSA. Then the signal generated by PSA is processed by SPM to finally obtain the successfully converted signal.

[0084] Fig.10 To perform 8QAM all-optical modulation format conversion for the system of this embodiment, an 8QAM mapping table as shown in Table 1 is set to be applied to the PRBS, and an 8QAM constellation diagram generated by a fixed 8-symbol transmission sequence is used.

[0085] Fig.11 (a) The system of this embodiment performs 8QAM all-optical modulation format conversion, fixes 8 symbol transmission sequences, and obtains the BPSK signal constellation diagram of the format conversion after passing through PSA and then SPM. Fig.11(b) is the waveform diagram of the BPSK signal after format conversion after passing through PSA and then SPM.

[0086] Fig.12 (a) is the PAM4 signal constellation diagram obtained after PSA when the system of this embodiment performs 8QAM all-optical modulation format conversion and fixes 8 symbol transmission sequences. Fig.12 (b) is the PAM4 signal waveform obtained after PSA.

[0087] Fig.13 (a) The system of this embodiment performs 8QAM all-optical modulation format conversion to fix 8 symbol transmission sequences, and after the PSA process, the format-converted QPSK signal constellation diagram is obtained after SPM. Fig.13 (b) is the waveform diagram of the QPSK signal after format conversion after passing through PSA and then SPM.

[0088] Table 3 Decision rules for 8QAM all-optical modulation format conversion in the 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF

[0089]

[0090]

[0091] The initial success of the format conversion can be judged by the BPSK and QPSK waveforms and constellation diagrams. Then, after sampling judgment, the error-free signal sequence can be successfully demodulated through the regularity table in Table 3.

[0092] In the above process of sending a fixed sequence, the 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF performs 8QAM all-optical modulation format conversion to fix 8 symbol transmission sequences and successfully converts BPSK and QPSK signals. Then, the 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF performs 8QAM all-optical modulation format conversion to randomly send 4 times the number of fixed symbol sequences while the 8QAM mapping table remains unchanged. The generated 8QAM optical signal constellation diagram is as follows Fig.14 shown.

[0093] The signal before PSA is phase-locked through PIA, and then the successfully converted BPSK and QPSK signals are obtained through SPM.

[0094] Fig.15 (a) The system of this embodiment performs 8QAM all-optical modulation format conversion and randomly sends 4 times the number of fixed symbol sequences. After PSA and SPM, the BPSK signal constellation diagram after format conversion is obtained. Fig.15(b) is the waveform of the BPSK signal after format conversion through SPM.

[0095] Fig.16 (a) The system of this embodiment performs 8QAM all-optical modulation format conversion by randomly sending 4 times the number of fixed symbol sequences, and obtains the QPSK signal constellation diagram of the format conversion after passing through PSA and SPM. Fig.16 (b) is the waveform of the QPSK signal after format conversion through SPM.

[0096] After obtaining BPSK and QPSK, the amplitudes of the BPSK I channel and QPSK IQ channels are judged as 1 if they are positive, and 0 if they are negative. Finally, the BPSK signal I channel and QPSK signal IQ channel determined by the final judgment are perfectly demodulated with the transmission signal through the regular table in Table 3 to obtain a sequence without code errors.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A 16QAM / 8QAM all-optical modulation format conversion system based on PSA and HNLF, characterized in that: The system includes: two LDs, namely LD1~LD2, an IQ modulator, a PRBS, a DC, six EDFAs, namely EDFA1~EDFA6, five HNLFs, namely HNLF1~HNLF5, three FD-OPs, namely FD-OP1~FD-OP3, two coherent receivers, three WDMs, namely WDM1~WDM3, and a wave plate; wherein HNLF1 and FD-OP1 are used to form PIA; HNLF2 / HNLF3 and FD-OP2 / FD-OP3 are used to form PSA; EDFA5 / EDFA6 and HNLF4 / HNLF5 are used to form SPM; LD represents a continuous wave laser source, PRBS represents a signal generator, DC represents a direct current voltage source, EDFA represents an erbium-doped fiber amplifier, HNLF represents a highly nonlinear fiber, FD-OP represents an optical filter, WDM represents a wavelength division multiplexer, PIA represents a phase-insensitive amplification, PSA represents a phase-sensitive amplification, and SPM represents a self-phase modulation; the PIA is used to generate a new pump phase-locked with LD1 and LD2; the PSA is used to convert a 16QAM or 8QAM signal into a co-directional component and an orthogonal component; the SPM is used to perform phase deflection on the co-directional component and the orthogonal component to obtain a signal with a final desired format conversion, that is, to simultaneously convert a 16QAM signal into two QPSK modulation formats, or to simultaneously convert an 8QAM signal into BPSK and QPSK modulation formats without losing information; The light source signal emitted by LD1 is divided into two paths: one path is injected into WDM1 after being amplified by EDFA1, coupled with the first path of the light source signal emitted by LD2, and then injected into HNLF1 to excite PIA to generate a new pump phase-locked with LD1 and LD2. The new pump is filtered by FD-OP1 and amplified by EDFA4 before being injected into WDM2 and WDM3 respectively; the other path is injected into WDM2 and WDM3 respectively after being generated by IQ modulator 16QAM / 8QAM; The second signal of the light source signal emitted by LD2 is amplified by EDFA2 and then injected into WDM2; the third signal is phase-shifted 180 degrees by the wave plate, then amplified by EDFA3 and then injected into WDM3; The signals coupled by WDM2 or WDM3 are all stimulated by a HNLF at the wavelength position of LD1 to undergo a PSA process. The stimulated PSA process is filtered by an FD-OP. The filtered optical signals are first amplified by an EDFA signal and then stimulated by an HNLF to undergo an SPM process. They are then input into a coherent receiver to obtain a 16QAM / 8QAM signal after all-optical modulation format conversion.

Images