CN102305985B - All-optical regeneration method and device for high-speed DQPSK modulated signal - Google Patents

Abstract

An all-optical regeneration method and device for a high-speed DQPSK modulated signal. The method includes demodulation of DQPSK signal, regeneration of OOK signal and recovery of DQPSK signal. The degraded DQPSK optical signal on the transmission link enters the demodulation unit of the DQPSK signal, and the DQPSK signal is demodulated into an OOK signal, and the phase noise is converted into an intensity noise at the same time, and then the amplitude of the optical signal is regenerated by the OOK signal regenerator, and finally Then, the OOK signal is converted into a DQPSK signal through a polarization controller and a polarizer, thereby realizing all-optical regeneration of DQPSK. The method and device of the present invention can realize all-optical regeneration of DQPSK signals, which is not only expected to solve a difficult problem in all-optical regeneration of DQPSK signals, but also provides a possible solution to similar problems in high-speed optical signal processing.

Description

All-optical regeneration method and device for high-speed DQPSK modulated signal

technical field

The invention relates to the technical field of high-speed and large-capacity all-optical network communication, in particular to an all-optical regeneration method and device of a high-speed new modulation format.

Background technique

In recent years, wavelength division multiplexing technology, forward error correction coding, Raman distributed amplifiers, and new transmission optical fibers have greatly improved the capacity and distance of optical fiber communication systems. The modulation format of the optical fiber communication system mainly adopts the traditional On-Off-Keying (OOK), and a series of new modulation formats are gradually getting attention in the optical fiber communication system. The new modulation format improves the signal for color chromatic dispersion, optical filtering, and nonlinear tolerance. These modulation formats include CRZ (Chirped Return to Zero), AMI (Alternate Mark Inversion), CSRZ (Carrier Suppressed Return to Zero) and PSK (Phase Shift Keying). At present, the highest transmission capacity of a single fiber reported has reached 25.6Tb/s. For such a high transmission rate, it is difficult to realize the OOK modulation signal using the traditional RZ or NRZ code type, and only the multi-ary modulation format of the phase-amplitude mixed modulation with higher spectral efficiency can be used. For this reason, modulation formats such as DQPSK have been widely studied in current high-speed optical transmission schemes, and are recognized as ideal choices for next-generation broadband optical fiber communication systems.

At the same time, although the phase modulation format has a higher tolerance to the nonlinear effect in transmission than the traditional OOK modulation format, the linear phase noise introduced by the optical amplifier in high-speed transmission and the nonlinear effect caused by the line Nonlinear phase noise will still cause serious deterioration in the quality of phase modulation signals such as differential phase shift keying (DPSK) and quadrature relative phase shift keying (DQPSK). In order to ensure the transmission quality of signals in future high-speed and large-capacity optical networks, DPSK and DQPSK signals must be regenerated. Therefore, it is an inevitable requirement to adapt to the development of future high-speed optical transmission technology to develop an all-optical regeneration technology that can realize phase modulation signals.

At present, there have been considerable reports in the world on the research on the regeneration technology of phase modulation signals, but most of them are mainly focused on the regeneration of DPSK signals. Several common schemes are: 1. Reamplification and reshaping of RZ-DPSK signals are realized by using cross-phase modulation or fiber parametric amplification effect in highly nonlinear optical fiber; 2. Realization by using semiconductor optical amplifier (SOA) combined with Sagnac ring DPSK regeneration amplification; 3. Convert the phase noise of DPSK to intensity noise through the polarization interference structure, and at the same time retain the phase information in the OOK data pulse, use SOA to reshape the intensity signal, and finally use the low-noise EDFA to The regenerated DPSK signal is re-amplified.

However, there are few relevant reports on the research on the regeneration technology of DQPSK signal. The German research group K. Cvecek proposed to use the nonlinear magnifying loop mirror (NALM) to perform amplitude regeneration experiments on DQPSK signals, but this scheme can only regenerate the amplitude noise caused by ASE, and has no ability to degrade the phase noise in the DQPSK signal. to regenerate. In the regeneration scheme proposed by the Japanese research group Masayuki Matsumoto through simulation, the DQPSK signal is first converted into an OOK signal through delay interference, and then the OOK signal is reshaped and amplitude-regenerated by a 2R regenerator. The regenerated OOK signal is subsequently The all-optical phase modulator interacts with the extracted clock pulse, and finally obtains the regenerated DQPSK signal.

In China, the research results of all-optical regeneration technology are mostly reflected in the regeneration of OOK signals. In contrast, the research on phase modulation signals is carried out late in many universities and research institutions, and most of them are based on theoretical simulation research. host. For the research on DQPSK signals, most of the work focuses on signal modulation, transmission, and demodulation.

The important thing is that the current international phase modulation format represented by DPSK and DQPSK has received a lot of attention in the research of high-speed optical transmission technology, and has become an inevitable research trend. However, most of the research on its regeneration technology is still limited to the research on DPSK, and no effective solution has been proposed for the regeneration of DQPSK.

Contents of the invention

The purpose of the present invention is to realize the all-optical regeneration of DQPSK modulation signals, to solve the problems of complex system, high cost, poor stability and the like in current DQPSK signal regeneration methods, and to provide a novel high-speed all-optical regeneration method and device for DQPSK modulation signals.

The present invention at first provides a kind of all-optical regeneration device of high-speed DQPSK modulated signal, and this device comprises:

The first polarization controller: used to convert the deteriorated DQPSK signal light input on the transmission link to 45° linear polarization;

Differential group delay line: for the DQPSK signal converted by the first polarization controller to realize that the signals on the two polarization states of the x axis and the y axis have a delay of one symbol period;

The first optical coupler: used to divide the optical signal after differential group delay into two paths, the first path is used as the real part of the DQPSK signal, and the second path is used as the imaginary part of the DQPSK signal;

The first path includes: a second polarization controller, a second optical coupler, and a first polarization beam splitter. The real part of the first path DQPSK signal passes through the second polarization controller to generate a + 45° phase difference, after passing through the second optical coupler, the two orthogonal ellipsometric lights enter the first polarization beam splitter, and then the ellipsometric lights become two orthogonal and complementary linear polarized lights, and finally the two complementary OOK data After the streams go through the same path in the ring, polarization interference occurs at the output of the first polarization beam splitter, and at this time, a part of the phase noise in DQPSK is converted into amplitude noise and exists in the two complementary OOK data streams;

The second path includes: a third polarization controller, a third optical coupler, and a second polarization beam splitter. The imaginary part of the second path DQPSK signal also passes through the third polarization controller to generate a polarization state between the two main axes. -45° phase difference, after passing through the third optical coupler, the two orthogonal ellipsoidal lights enter the second polarizing beam splitter, and then the ellipsometric lights become two orthogonal and complementary linear polarized lights, and finally two complementary OOK After the data streams go through the same distance in the ring, polarization interference will occur at the output of the second polarization beam splitter, and at this time, a part of the phase noise in DQPSK is converted into amplitude noise and exists in the two complementary OOK data streams;

Mach-Zehnder structure regenerator: used to complete the light intensity regeneration of the above two channels of data, adjust the delay of the two channels of signals at the same time, and finally interfere the two channels of optical signals into one signal;

Optical bandpass filter: used to filter out the noise introduced by optical amplification during the regeneration process of the Mach-Zehnder structure regenerator;

Fourth polarization controller:

Polarizer: Turn two or two orthogonal signals into a polarization state to regenerate DQPSK signals;

Erbium-doped fiber amplifier:

The Mach-Zehnder structure regenerator is a semiconductor optical amplifier with a Mach-Zehnder structure and regeneration function.

The present invention simultaneously provides a kind of all-optical regeneration method that adopts above-mentioned device to realize high-speed DQPSK modulated signal, and this method realizes by following steps:

1. The polarization state of the deteriorated DQPSK signal is changed to a 45° linear polarization state by the first polarization controller (PC1);

2. Send the DQPSK signal deflected in the previous step into the differential group delay line (DGD), so that the signals on the two polarization states of the x-axis and the y-axis have a delay of one symbol period;

Thirdly, the output of the differential group delay line is divided into the same two channels through the first optocoupler (OC1): the first channel above represents the real part I channel, while the second channel below represents the imaginary part Q channel ;

4. In the first real part I channel, a +45° phase difference is generated between the polarization states of the two main axes through the second polarization controller, and then the two are orthogonal after passing through the second optical coupler (OC2). The ellipsometric light enters the first polarization beam splitter (PBS1), and then the ellipsometric light becomes two orthogonal and complementary linear polarized lights. After the last two complementary OOK data streams go through the same distance in the ring, they pass through the first polarization beam splitter. The output of the beamer produces polarization interference, at this time a part of the phase noise in DQPSK is converted into amplitude noise and exists in the two complementary OOK data streams;

5. Similarly, in the second imaginary part Q channel, a -45° phase difference is generated between the polarization states of the two main axes through the third polarization controller, and then the last two through the third optical coupler (OC3) The orthogonal ellipsometric light enters the second polarization beam splitter (PBS2), and then the ellipsometric light becomes two orthogonal and complementary linearly polarized lights. After the two complementary OOK data streams go through the same path in the ring, they pass through the second The output of the polarization beam splitter produces polarization interference, at this time a part of the phase noise in DQPSK is converted into amplitude noise and exists in two complementary OOK data streams;

6. The signals of the first real part I channel and the second imaginary part Q channel are processed in step 4 and step 5 respectively and then enter the Mach-Zehnder structure regenerator, and use the regenerator to complete the amplitude regeneration of the two signals respectively Function; at the output of the Mach-Zehnder structure regenerator, the relative phase relationship between the first and second signals is adjusted by adjusting the current of the two arms, and finally the regenerated signals of the two routes are in the Mach-Zehnder structure regenerator. The output terminal interferes and becomes a signal;

7th, use optical bandpass filter to filter out the noise introduced by amplification in OOK signal regeneration;

8. Use the fourth polarization controller to change the orthogonal signals of the polarization state to 45° respectively corresponding to one polarization axis, and finally change the two orthogonal signals into one polarization state through the polarizer to regenerate the DQPSK signal;

Ninth, the regenerated DQPSK signal is amplified for subsequent application.

Advantages and beneficial effects of the present invention:

1. The scheme is simple, economical and practical. Except for the Mach-Zehnder structure regenerator and the erbium-doped fiber amplifier (EDFA), the rest are passive devices with a simple structure. 2. All-optical regeneration in the true sense, which does not involve light-electricity-light conversion. 3. It solves the problem that the DQPSK signal cannot be fully optical at present.

Description of drawings

Fig. 1 is the overall structural representation of DQPSK signal all-optical regeneration among the present invention;

Fig. 2 is a working block diagram of DQPSK signal conversion in the present invention.

In the figure, 1 is the first polarization controller, 2 is the second polarization controller, 3 is the third polarization controller, 4 is the first optical coupler, 5 is the second optical coupler, 6 is the third optical coupler , 7 is a first polarization beam splitter, 8 is a second polarization beam splitter, 9 is an optical bandpass filter, 10 is a fourth polarization controller, 11 is a polarizer, and 12 is an erbium-doped fiber amplifier.

The process of all-optical regeneration of the DQPSK signal will now be described in detail with reference to the accompanying drawings.

Detailed ways

Embodiment 1, the all-optical regeneration device of high-speed DQPSK modulated signal

As shown in Figure 1, the device includes:

The first polarization controller 1: used to convert the deteriorated DQPSK signal light input on the transmission link to 45° linear polarization;

Differential group delay line: for the DQPSK signal converted by the first polarization controller to realize that the signals on the two polarization states of the x axis and the y axis have a delay of one symbol period;

The first optical coupler 4: used to divide the optical signal after differential group delay into two paths, the first path is used as the real part of the DQPSK signal, and the second path is used as the imaginary part of the DQPSK signal;

The first path includes: a second polarization controller 2, a second optical coupler 5, and a first polarization beam splitter 7. The real part of the first path DQPSK signal passes through the second polarization controller to make the polarization states of the two main axes between A +45° phase difference is generated, and after passing through the second optical coupler, two orthogonal ellipsoidal lights enter the first polarizing beam splitter, and then the ellipsoidal lights become orthogonal and complementary two linearly polarized lights, and finally two complementary After the OOK data stream in the ring passes through the same distance, polarization interference is generated at the output end of the first polarization beam splitter. At this time, a part of the phase noise in DQPSK is converted into amplitude noise and exists in two complementary OOK data streams;

The second path includes: a third polarization controller 3, a third optical coupler 6 and a second polarization beam splitter 8, and the imaginary part of the second path DQPSK signal is also passed through the third polarization controller to make the polarization state of the two main axes A -45° phase difference is generated between them, and then the two orthogonal ellipsoidal lights enter the second polarizing beam splitter after passing through the third optical coupler, and then the ellipsometric lights become two orthogonal and complementary linear polarized lights, and the last two After the complementary OOK data streams go through the same distance in the ring, polarization interference will occur at the output of the second polarization beam splitter. At this time, part of the phase noise in DQPSK is converted into amplitude noise and exists in the two complementary OOK data streams middle;

Mach-Zehnder structure regenerator: used to complete the light intensity regeneration of the above two channels of data, adjust the delay of the two channels of signals at the same time, and finally interfere the two channels of optical signals into one signal;

Optical bandpass filter 9: used to filter out the noise introduced by optical amplification during the regeneration process of the Mach-Zehnder structure regenerator;

The fourth polarization controller 10: change the polarization state orthogonal signals corresponding to one polarization axis to 45°;

Polarizer 11: convert two or two orthogonal signals into a polarization state to regenerate DQPSK signals;

Erbium-doped fiber amplifier 12: amplifies the regenerated DQPSK signal for subsequent application;

The Mach-Zehnder structure regenerator is a semiconductor optical amplifier with a Mach-Zehnder structure and regeneration function.

Embodiment 2, the all-optical regeneration method of high-speed DQPSK modulation signal

The all-optical regeneration method of high-speed DQPSK modulation signal among the present invention comprises, the demodulation of DQPSK signal, OOK signal regeneration, the generation of DQPSK signal after regeneration. Specific steps are as follows:

The deteriorated DQPSK signal that comes from the transmission line first enters the DQPSK signal demodulation part of the regeneration device shown in Figure 1, and the polarization state of the deteriorated DQPSK signal is changed to 45 ° of linear polarization state by the first polarization controller 1 (PC1);

Then the DQPSK signal passes through the differential group delay line (DGD), so that the signals on the two polarization states of the x-axis and the y-axis have a delay of one symbol period;

Then, the output of the differential group delay line DGD is divided into the same two channels through the first optocoupler 4 (OC1): the first channel above represents the I channel, and the second channel below represents the Q channel. In the I channel Through the second polarization controller 2 (PC2), a +45° phase difference is generated between the polarization states of the two main axes, and then through the second optical coupler 5 (OC2), the two orthogonal ellipsometric lights enter the first polarization Beam splitter 7 (PBS1), after which the ellipsometric light becomes two orthogonal and complementary linearly polarized lights, after the last two complementary OOK data streams go through the same distance in the ring, they will be transmitted at the output of the first polarizing beam splitter Polarization interference occurs, at this time a part of the phase noise in DQPSK is transformed into amplitude noise and exists in two complementary OOK data streams. In the Q channel, a -45° phase difference is generated between the polarization states of the two main axes through the third polarization controller 3 (PC3), and then two orthogonal ellipsoids are passed through the third optical coupler 6 (OC3). After entering the second polarizing beam splitter 8 (PBS2), the ellipsometric light becomes two orthogonal and complementary linear polarized lights, and finally the two complementary OOK data streams go through the same path in the ring, and then pass through the second polarizing beam splitter Polarization interference will occur at the output of the DQPSK, at this time, a part of the phase noise in DQPSK is converted into amplitude noise and exists in two complementary OOK data streams. Two complementary OOK signals are obtained here, and the phase noise of the DQPSK signal is converted into amplitude noise in the process, as shown in Figure 2.

The above-mentioned I-channel and Q-channel signals enter the Mach-Zehnder structure regenerator, and the regenerator is used to complete the amplitude regeneration function of the two signals respectively.

In the Mach-Zehnder structure regenerator, the relative phase relationship of the upper and lower signals can be adjusted by adjusting the currents of the two arms. Finally, the regenerated signals of the two channels interfere at the output of the Mach-Zehnder structure regenerator and become one In this process, the amplitude noise is eliminated to regenerate the OOK signal, and at the same time, two complementary signals are synthesized into one.

Next, the noise introduced by the amplifier in the preceding regeneration process is filtered out by an optical bandpass filter 9 .

Finally, the regenerated signal is changed into the same mode as the original DQPSK signal through the fourth polarization controller 10 and the polarizer 11, and optically amplified through the erbium-doped fiber amplifier 12 for later application.

Claims (3)

1. the full optical reproducing apparatus of high speed four phase RPSK relative phase shift keying modulation signals is characterized in that this device comprises:

The first Polarization Controller: the deterioration four phase RPSK relative phase shift keying flashlights that are used for inputting on the transmission link are realized the conversion of 45 ° of line polarisations;

Differential group delay line: be used for four phase RPSK relative phase shift keying signals after the conversion of the first Polarization Controller are realized that signal on x axle and two polarization states of y axle has the time-delay of a symbol period;

The first photo-coupler: be used for the light signal behind the differential group delay is divided into two-way, the first via is as the real part of four phase RPSK relative phase shift keying signals, the second tunnel imaginary part as four phase RPSK relative phase shift keying signals;

The first via comprises: the second Polarization Controller, the second photo-coupler and the first polarization beam apparatus, the real part of the first via four phase RPSK relative phase shift keying signals makes by the second Polarization Controller and produces one+45 ° phase differential between the polarization state of two main shafts, ellipse polarisation by second latter two quadrature of photo-coupler enters the first polarization beam apparatus again, ellipse polarisation becomes quadrature and two complementary line polarisations afterwards, latter two complementary on-off keying data stream is passed through after the identical distance in ring, output terminal at the first polarization beam apparatus produces polarization interference, and a part of phase noise in the four phase RPSK relative phase shift keyings is transformed into amplitude noise and is present in the on-off keying data stream of two complementations at this moment;

The second the tunnel comprises: the 3rd Polarization Controller, the 3rd photo-coupler and the second polarization beam apparatus, the imaginary part of the second tunnel four phase RPSK relative phase shift keying signal makes by the 3rd Polarization Controller equally and produces-45 ° of phase differential between the polarization state of two main shafts, ellipse polarisation by the 3rd latter two quadrature of photo-coupler enters the second polarization beam apparatus again, ellipse polarisation becomes quadrature and two complementary line polarisations afterwards, latter two complementary on-off keying data stream is passed through after the identical distance in ring, output terminal at the second polarization beam apparatus can produce polarization interference, and a part of phase noise in the four phase RPSK relative phase shift keyings is transformed into amplitude noise and is present in the on-off keying data stream of two complementations at this moment;

Mach moral structure regenerator once: be used for finishing the light intensity regeneration to above-mentioned two paths of data, adjust simultaneously the time-delay of two paths of signals, and two ways of optical signals is interfered and become one road signal the most at last;

Optical band pass filter: be used for the noise that the once moral structure regenerator regenerative process light amplification of filtering Mach is introduced;

The 4th Polarization Controller: corresponding polarization axle change is at 45 ° respectively the signal of polarization state quadrature;

The polarizer: the signal of pairwise orthogonal is become a polarization state to regenerate four phase RPSK relative phase shift keying signals;

Erbium-Doped Fiber Amplifier (EDFA): be used for the amplification to four phase RPSK relative phase shift keying signals after regenerating.

2. device according to claim 1, it is characterized in that described Mach once moral structure regenerator be to have once moral structure and have the semiconductor optical amplifier of regeneration function of Mach.

3. one kind is adopted the described device of claim 1 to realize the at a high speed full optical regeneration method of four phase RPSK relative phase shift keying modulation signals, it is characterized in that, the method realizes as follows:

The polarization state of the four phase RPSK relative phase shift keying signals that 1st, will worsen by the first Polarization Controller (PC1) becomes linear polarization at 45 °;

2nd, four phase RPSK relative phase shift keying signals after turning the upper step are partially sent into differential group delay line (DGD), make signal on two polarization states of x axle and y axle that the time-delay of a symbol period be arranged;

3rd, and then by the first photo-coupler (OC1) output of differential group delay line is divided into identical two-way: the first via is expressed as real part I passage wherein, and following the second the tunnel represent imaginary part Q passage;

The 4th, in first via real part I passage, make by the second Polarization Controller and produce one+45 ° phase differential between the polarization state of two main shafts, ellipse polarisation by latter two quadrature of the second photo-coupler (OC2) enters the first polarization beam apparatus (PBS1) again, ellipse polarisation becomes quadrature and two complementary line polarisations afterwards, latter two complementary on-off keying data stream is passed through after the identical distance in ring, output terminal at the first polarization beam apparatus produces polarization interference, and a part of phase noise in the four phase RPSK relative phase shift keyings is transformed into amplitude noise and is present in the on-off keying data stream of two complementations at this moment;

The 5th, equally, in the second tunnel imaginary part Q passage, make by the 3rd Polarization Controller and produce-45 ° of phase differential between the polarization state of two main shafts, ellipse polarisation by latter two quadrature of the 3rd photo-coupler (OC3) enters the second polarization beam apparatus (PBS2) again, ellipse polarisation becomes quadrature and two complementary line polarisations afterwards, latter two complementary on-off keying data stream is passed through after the identical distance in ring, output terminal at the second polarization beam apparatus produces polarization interference, and a part of phase noise in the four phase RPSK relative phase shift keyings is transformed into amplitude noise and is present in the on-off keying data stream of two complementations at this moment;

6th, above-mentioned first via real part I passage and the second tunnel imaginary part Q channel signal enter once moral structure regenerator of Mach respectively after the 4th step, the 5th step process, and utilize regenerator respectively two paths of signals to be finished the amplitude regeneration function; Once in the moral structure regenerator, realize adjusting the relative phase relation of the first via, the second road signal at Mach by the electric current of regulating two arms, the signal after the final two-way regeneration Mach once the output terminal of moral structure regenerator interfere and become one road signal;

7th, with amplifying the noise of introducing in the signal regeneration of optical band pass filter filtering on-off keying;

8th, corresponding polarization axle change is at 45 ° respectively the signal of polarization state quadrature to use the 4th Polarization Controller, by the polarizer signal of pairwise orthogonal is become a polarization state to regenerate four phase RPSK relative phase shift keying signals at last;

9th, four phase RPSK relative phase shift keying signals after the regeneration are amplified so that subsequent applications.

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