CN102255683B - Clock recovery method for high-speed optical time-division multiplexing system - Google Patents
Clock recovery method for high-speed optical time-division multiplexing system Download PDFInfo
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- CN102255683B CN102255683B CN201110191185.5A CN201110191185A CN102255683B CN 102255683 B CN102255683 B CN 102255683B CN 201110191185 A CN201110191185 A CN 201110191185A CN 102255683 B CN102255683 B CN 102255683B
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Abstract
The invention provides a clock recovery method for a high-speed optical time-division multiplexing system. In the method, a base frequency clock is put into a high-speed optical time-division multiplexing data tape in an additional phase modulation manner, so that co-transmission of high-speed optical time-division multiplexing data and the base frequency clock is realized; and base frequency clock recovery of the optical time-division multiplexing system can be realized by only separating the base frequency clock out at a receiving end. According to the method, the defect of the need of the optical phase-locked loop structure for the recovery of a clock from optical time-division multiplexing data streams in the prior art is overcome, and a foundation is laid for the research of a high-speed optical signal processing unit orienting to a next generation all-optical communication network. The method has the characteristics of novel scheme, simple structure and high compatibility, and has extensive application prospects in the aspects of optical fiber communication system, all-optical switch networking, and the like.
Description
Technical field
The present invention relates to a kind of clock recovery method for optical time division multiplexing system, especially design a kind of method that data and clock based on additive phase modulation passes altogether scheme, realizes optical time division multiplexing system clock recovery.
Background technology
Optical Time Division Multiplexing (OTDM) technology is utilized ultrashort pulse and NRZ (RZ), and the mode interleaving by pulse is 2
nb bps of data channel of (N is positive integer) base speed is mapped to a fundamental frequency and goes in the clock cycle, in time domain 2
nthe light signal of roadbed speed is multiplexed into B * 2
nthe high-speed optical pulse data flow of bps speed.Otdm signal, after Optical Fiber Transmission, recovers each roadbed speed data signal by optical demultiplexer.Compare with wavelength division multiplexing (WDM) system, OTDM is used single light source, has avoided each road power stack of wdm system and the four wave mixing that produces is crosstalked and the problem such as Raman scattering, and the management of In-line amplifier is simplified; Although WDM has become the preferred option that improves traffic rate, but utilize OTDM can improve WDM single channel speed, reduce WDM number of communication channels, thereby just can realize vast capacity communication in existing erbium-doped fiber amplifier (EDFA) amplifies bandwidth, transfer management is simpler and more direct.OTDM technology is by the direct processing to signal in light territory, to reach, improves the object that amount of information that each radio frequency channel carries increases transmission capacity, itself is suitable as the Optic network technology scheme that adopts full light exchange and full optical routing to select.
Clock recovery refers to from high-speed light OTDM pulse data stream extracts fundamental frequency clock, fundamental frequency clock is the driving signal of demodulation multiplexer in OTDM system, Route Selection, channel selection, signal regeneration etc., so clock recovery is the requisite key technology of OTDM system.In actual OTDM system, in clock recovery, maximum obstacle is that the radio-frequency component comprising in the OTDM pulse data stream after multiplexing is B * 2
nhertz and high order harmonic component, do not comprise the B hertz frequency composition of fundamental frequency clock, cannot directly extract.At present, overwhelming majority clock recovery method is realized based on electric light or full Optical phase-locked loop, phase-locked loop is the closed loop automatic control system that can follow the tracks of input signal phase place, and a phase-locked loop is comprised of electric light/full light phase discriminator, loop filter, three elementary cells of voltage controlled oscillator.In realization, by voltage controlled oscillator, produce a local clock approaching with fundamental frequency clock frequency, this local clock is input to light phase discriminator and carries out phase bit comparison with OTDM data flow.Low pass filter, for high fdrequency component and other interference components of filtering light phase discriminator output signal, guarantees the overall performance of phase-locked loop, and increases the stability of loop.The error signal of low frequency feeds back to voltage controlled oscillator closed loop and adjusts local clock, thereby obtains fundamental frequency clock output stable, that synchronize with OTDM stream of pulses.Because phase-locked loop is the system of " having memory ", its output needs the regular hour could respond the variation of input, although the shake of this method recovered clock is little, quality is high, is difficult to obtain locking fast, is difficult to obtain Phase synchronization fast.In addition, along with the raising of multiplex rate, the electric light of two-forty (> 160Gbit/s)/full light phase discriminator is difficult to realize, and has restricted the application of the method in superelevation speed OTDM system.
Summary of the invention
For the deficiency existing in above-mentioned phase-locked loop clock restoration methods, the present invention proposes a kind of high speed OTDM system quick clock restoration methods that is applicable to, the method is in the mode of additive phase modulation, fundamental frequency clock is placed in OTDM data band, realize high speed OTDM data and fundamental frequency clock passes altogether, at receiving terminal, only fundamental frequency clock need be separated, can realize the clock recovery of optical time division multiplexing system fundamental frequency.
The present invention proposes a kind of clock recovery method of high-speed optical time-division multiplexing system, its feature comprises following steps:
Step 1 clock recovery system forms
As shown in Figure 2, clock recovery system is inserted unit and Clock Extraction cell formation by clock, clock is inserted unit and is positioned at OTDM transmitting terminal, it is comprised of Polarization Controller and phase-modulator, the OTDM data-signal of inserting clock arrives optical receiving end after Transmission Fibers transmission, data-signal is divided into two by optical power distributor afterwards, one supported signal of optical power distributor is directly exported, another supported signal of optical power distributor enters Clock Extraction unit, and Clock Extraction unit is by being with logical optical filter and photodetector to form;
Step 2 clock is inserted
At light transmitting terminal, speed is B * 2
nbps OTDM data incide in phase-modulator through Polarization Controller, the fundamental frequency clock signal of the electricity of phase-modulator mouthful incoming frequency B hertz, adjust the amplitude of clock signal, the 1 rank sideband that phase-modulation is produced is maximum, and the output signal of phase-modulator is the OTDM data-signal of having inserted fundamental frequency clock.
Step 3 Clock Extraction
Speed is B * 2
nbps OTDM data-signal through arriving optical receiving end after Optical Fiber Transmission, data-signal incides optical power distributor and is divided into two, one supported signal of optical power distributor is directly exported, another supported signal of optical power distributor enters Clock Extraction unit, in Clock Extraction unit, a fundamental frequency clock sideband that first leaches the centered carrier of otdm signal and close on through the logical optical filter of a band, or B * 2 of otdm signal
nhertz spectral line and the fundamental frequency clock sideband closing on thereof, the output light of the logical optical filter of band enters photodetector and carries out opto-electronic conversion, and the signal of telecommunication of photodetector output is the fundamental frequency clock that the frequency recovering is B hertz.
Essence the method for the present invention utilizes phase modulation method that sinusoidal fundamental frequency clock signal is placed in OTDM high-speed data waiting for transmission at transmitting terminal, and at receiving terminal, only needs from this fundamental frequency clock signal of extracting data, just can recover fundamental frequency clock simply.
Advantage of the present invention or positive effect:
The fundamental frequency clock recovery method that the present invention proposes is without utilizing phase-locked loop to realize clock recovery, due at OTDM transmitting terminal, OTDM stream of pulses is driven and is produced by fundamental frequency clock, therefore the fundamental frequency clock being loaded in OTDM data is constantly to keep synchronizeing with OTDM stream of pulses, and both have experienced identical transmission path, therefore the clock recovering at OTDM receiving terminal keeps synchronizeing with OTDM data flow always, therefore not only to meet quick clock synchronous for the method, and have advantages of system stability, simple in structure.
Accompanying drawing explanation
Fig. 1 be OTDM principle schematic (B=10G hertz, N=4).
Fig. 2 is fundamental diagram of the present invention.
Fig. 3 is OTDM data-signal spectrum and the eye pattern of inserting before clock.
Fig. 4 is OTDM data-signal spectrum and the eye pattern of inserting after clock.
Fig. 5 is that in Clock Extraction unit, band leads to the recovered clock waveform after optical filter output signal spectrum and photodetection.
Embodiment
Technical scheme for a better understanding of the present invention, is further described execution mode below in conjunction with accompanying drawing.
Shown in Optical Time Division Multiplexing basic principle as shown in Figure 1, the frequency of the fundamental frequency clock in the present embodiment is 10G hertz, it is 1550.70nm that high repetition clock produces wavelength, pulsewidth is 1.4ps, repetition is the repetition light pulse of 10G hertz, after 16 tunnels shunt, after the data that each road loading is 10G bps, the data of 16 road 10G bps are synthetic through time delay, the final high-speed data-flow output that forms 160G bps, Figure 3 shows that the eye pattern of the data-signal of 160G bps, the upper right corner subgraph of Fig. 4 is the data-signal spectrogram of 160G bps.
Step 1 clock recovery system forms
As shown in Figure 2, the high-speed data of 160G bps incides clock inserts unit, the fundamental frequency clock of 10G hertz is inserted in high-speed data, the output that clock is inserted unit be the data-signal of having inserted clock, this signal arrives Optical Clock extraction unit after long-distance optical fiber transmission, in Clock Extraction unit, first data-signal is divided into two through optical power distributor, one supported signal of optical power distributor is directly exported from the optical port of Clock Extraction unit, another supported signal of optical power distributor is after signal is processed, 10G hertz fundamental frequency clock in data is extracted and exports from the electric port of Clock Extraction unit.
Step 2 clock is inserted
As shown in Figure 2, in clock is inserted unit, the high-speed data of 160G bps is input to phase-modulator after Polarization Controller, the fundamental frequency clock signal of the electricity of phase-modulator mouthful input 10G hertz, Fig. 4 is for having inserted 160G bps of data-signal spectrum of fundamental frequency clock, and the upper right corner subgraph of Fig. 4 is the eye pattern of inserting 160G bps of data-signal after fundamental frequency clock.Owing to being phase-modulation, the eye pattern of inserting clock front and back data-signal is identical, but both can find out from spectrum in difference, cardiac wave is long therein to insert the data-signal of clock, on the spectral line of 160G hertz integral multiple, all produced clock modulation sideband,, shown that thus fundamental frequency clock has been placed in data band.
Step 3 Clock Extraction
As shown in Figure 2, in Clock Extraction unit, inserted the 10G hertz clock sideband that the data-signal of 160G bps of clock first leaches the centre wavelength of otdm signal and closes on through an optical band pass filter, or the 160G hertz spectral line of otdm signal and the 10G hertz clock sideband closing on thereof, shown in Fig. 5, the spectrum of optical band pass filter output signal, in this example, we have leached data-signal centre wavelength 1550.70nm and near 10G hertz clock upper sideband thereof, this signal is after photodetector opto-electronic conversion, the signal of telecommunication of photodetector output is the fundamental frequency clock that the frequency recovering is 10G hertz, the clock signal waveform recovering is as shown in the subgraph in Fig. 5 upper right corner.
The otdm signal clock recovery scheme that the present invention proposes is in light territory, data-signal have been carried out to preliminary treatment after optical sender He before optical receiver, realizing fundamental frequency clock and high-speed data passes altogether, reach and simplify the object that OTDM receiver clock recovers, this technical scheme itself does not change principle, structure and the design of light transmitting and optical receiver, compatible with existing optical fiber telecommunications system.This scheme has following advantage: 1, scheme is novel, clock recovery technical scheme is fully excavated the spectral characteristic of otdm signal, in the prerequisite underlying that does not affect OTDM data performance, enter clock signal, do not take the wavelength resource of other optical communication, improved the spectrum efficiency of otdm signal; 2, advanced technology, completely different from traditional electric light phase-locked loop and all-optical clock recovery, this scheme fundamental frequency clock passes altogether in data band, and both experience identical link asymmetry, and this has guaranteed that receiving terminal is to the quick obtaining of clock and stable synchronous; 3, simple in structure, this scheme has overcome tradition required Optical phase-locked loop structure of recovered clock from OTDM data flow from principle, and system configuration is simplified greatly; In addition, what particularly point out is that the clock recovery mechanism that we propose embeds base speed clock in high-speed data, it is not only applicable to ultrahigh speed OTDM data stream transmitting and the demodulation of continuous operation mode, also OTDM packet data package transmission that can compatible burst mode with process, this lays the first stone for exploring the generation All-Optical Communication Network high speed light signal processing unit that faces down.
Claims (1)
1. a clock recovery method for high-speed optical time-division multiplexing system, its feature comprises following steps:
Step 1 clock recovery system forms
Speed is B * 2
nbps high-speed light time multiplexing date signal by 2
nroadbed speed is that the light pulse data of B bps obtain after time division multiplexing, and wherein N is more than or equal to 3; Clock recovery system inserts unit by clock and Clock Extraction unit forms, clock is inserted unit and is positioned at optical time division multiplexing system transmitting terminal, it consists of Polarization Controller and phase-modulator, the Optical Time Division Multiplexing data-signal of inserting clock arrives optical receiving end after Transmission Fibers transmission, data-signal is divided into two by optical power distributor afterwards, one road light signal is directly exported, and another road light signal enters Clock Extraction unit, and Clock Extraction unit consists of optical band pass filter and photodetector;
Step 2 clock is inserted
At light transmitting terminal, speed is B * 2
nbps high-speed light time multiplexing date incide in phase-modulator through Polarization Controller, the fundamental frequency clock signal of the electricity of phase-modulator mouthful incoming frequency B hertz, adjust the amplitude of clock signal, the 1 rank sideband that phase-modulation is produced is maximum, and the output signal of phase-modulator is the Optical Time Division Multiplexing data of having inserted fundamental frequency clock;
Step 3 Clock Extraction
Speed is B * 2
nbps Optical Time Division Multiplexing data through arriving optical receiving end after Optical Fiber Transmission, data-signal incides optical power distributor and is divided into two, one supported signal of optical power distributor is directly exported, another supported signal of optical power distributor enters Clock Extraction unit, in Clock Extraction unit, a fundamental frequency clock sideband that first leaches the centered carrier of optical time division multiplex signal and close on through an optical band pass filter, or B * 2 of optical time division multiplex signal
nhertz spectral line and the fundamental frequency clock sideband closing on thereof, the output light of optical band pass filter enters photodetector and carries out opto-electronic conversion, and the signal of telecommunication of photodetector output is the fundamental frequency clock that the frequency recovering is B hertz.
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| CN104734778B (en) * | 2013-12-20 | 2018-01-30 | 中国移动通信集团公司 | The sending, receiving method and device of a kind of data-signal and monitoring signals |
| US9596074B2 (en) * | 2015-05-01 | 2017-03-14 | Tektronix, Inc. | Clock recovery for data signals |
| CN105391508B (en) * | 2015-10-15 | 2018-01-05 | 盛科网络（苏州）有限公司 | The time-multiplexed framework of QSGMII PCS sending direction state machines, its control method and system |
| WO2018045088A1 (en) * | 2016-08-30 | 2018-03-08 | Finisar Corporation | Bi-directional transceiver with time synchronization |
| CN106527576A (en) * | 2016-12-01 | 2017-03-22 | 郑州云海信息技术有限公司 | Clock separation designing method and system for PCIE device |
| US10038549B1 (en) * | 2018-03-14 | 2018-07-31 | Shanghai Zhaoxin Semiconductor Co., Ltd. | Clock and data recovery circuit |
| CN114070545A (en) * | 2020-08-10 | 2022-02-18 | 深圳星火源电子有限公司 | Clock synchronization system and clock synchronization method |
| CN114285487B (en) * | 2021-11-15 | 2023-10-03 | 北京理工大学 | Sampling method for directly eliminating time jitter of signal in optical fiber link |
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| CN1752834A (en) * | 2004-09-01 | 2006-03-29 | 富士通株式会社 | Photoswitch and the light wave shape monitoring device that utilizes photoswitch |
| CN101674174A (en) * | 2008-09-12 | 2010-03-17 | 华为技术有限公司 | Method and equipment for increasing clock stability |
| CN101803254A (en) * | 2007-09-21 | 2010-08-11 | 爱立信电话股份有限公司 | Reverse timestamp method and network node for clock recovery |
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|---|---|---|---|---|
| CN1752834A (en) * | 2004-09-01 | 2006-03-29 | 富士通株式会社 | Photoswitch and the light wave shape monitoring device that utilizes photoswitch |
| CN101803254A (en) * | 2007-09-21 | 2010-08-11 | 爱立信电话股份有限公司 | Reverse timestamp method and network node for clock recovery |
| CN101674174A (en) * | 2008-09-12 | 2010-03-17 | 华为技术有限公司 | Method and equipment for increasing clock stability |
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