CN1213552C - Return-to-zero code super long distance transmission method and equipment - Google Patents
Return-to-zero code super long distance transmission method and equipment Download PDFInfo
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- CN1213552C CN1213552C CNB021250774A CN02125077A CN1213552C CN 1213552 C CN1213552 C CN 1213552C CN B021250774 A CNB021250774 A CN B021250774A CN 02125077 A CN02125077 A CN 02125077A CN 1213552 C CN1213552 C CN 1213552C
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Abstract
The present invention discloses a return-to-zero code super long distance transmission method and a device. A laser is directly modulated by using clock signals synchronous with data signals so as to generate RZ optical pulse signals; the output RZ optical pulse signals are accompanied with frequency changed along with time, namely chatter; a chatter symbol is opposite to a chatter symbol caused by non-linear self phase modulation (SPM) in the process of transmitting the RZ optical pulse signals in optical fiber. Compared with the existing RZ code transmission plan, an RZ pulse generating modulator and a corresponding special driver are saved, a chatter symbol in the RZ signals output by the laser after modulation is opposite to a chatter symbol caused by an SPM effect in the process of transmitting the RZ optical pulse signals in the optical fiber, and both can cancel exactly with each other. Thereby, a transmission distance can be long.
Description
Technical field:
The present invention relates to a kind of NRZ (NZ) light signal super long distance transmission method and device.
Background technology:
The signal transmission pattern of using in optical transmission system is generally two kinds of NRZ (nonreturn to zero code) and RZ, and the width of NRZ sign indicating number " 1 " pulse equals 1 bit period of transmission signals, and the width of " 1 " pulse of RZ sign indicating number is less than half of transmission signals 1 bit period.Because the transmission technology cost of nrz encoding is lower, the optical transmission system of most of commercializations is SDH/SONET (Optical synchronization digital transmission network) or DWDM (dense wave division multipurpose) systems that utilize the NRZ sign indicating number.
Yet, the transmission range of NRZ sign indicating number optical transmission system is restricted, usually be difficult to the correct regeneration (comprising opto-electronic conversion, clock recovery and shaping) that needs electricity that receives owing to OSNR (Optical Signal To Noise Ratio) worsens behind the transmission 500-600km, the construction cost of system is increased.Reduce the image intensifer spacing or improve each channel signal power and can extend transmission distance, the reducing of image intensifer spacing can be improved the launched power of amplifier thereby improved OSNR, but can increase the construction cost and the maintenance cost of system; The raising of every channel signal power can increase OSNR equally, but the nonlinear effect that raising power causes distorts transmitted waveform, has limited the application of this technology in dwdm system.
A kind of technology that realizes the extra long distance transmission is to utilize RAMAN (Raman) amplifier to replace EDFA (Erbium-Doped Fiber Amplifier), the RAMAN amplifier has utilized the RAMAN effect in the optical fiber, when obtaining the wide amplification of wide range, the noise figure of amplifier is also little than EDFA, and the RAMAN amplifier can also utilize Transmission Fibers (carrying the optical fiber of transmission signals) to realize distributed amplification, reduced the requirement to launched power, nonlinear effect also is inhibited.Be the topological structure of general extra long distance transmission as shown in Figure 1, the light signal of ITU-T provision wavelengths and power is satisfied in continuous-wave laser output, through modulator signal to be transmitted is modulated on the light signal, above-mentioned laser and modulator can integrate, modulator generally is electric absorption (EA) or Mach-Zender type lithium acid niobium modulator, also can directly be modulated at signal to be transmitted on the laser.The light signal that carries information is input to Transmission Fibers after amplifying, through after the transmission of common 80-120km, image intensifer amplifies the light signal after decaying, dispersion compensation device is carried out dispersion compensation, recover because the waveform broadening that chromatic dispersion causes, recover its original waveform, recover its original power through amplifying again, import Transmission Fibers again, image intensifer, dispersion compensation device, image intensifer etc., this process continues until the receiving terminal of arriving signal, receiver is finished the conversion of light signal to the signal of telecommunication, obtains transmission information through oversampling clock and data extract again, finishes the extra long distance transmission of information.In order to realize the extra long distance transmission, amplifier among Fig. 1 can be the combination of RAMAN amplifier or RAMAN amplifier and EDFA amplifier, there is following shortcoming in this technology: 1, cost height, because the RAMAN amplifier utilizes the nonlinear effect in the optical fiber, conversion efficiency is low, realize the amplification of light signal, and pump power is bigger, generally reach more than the 1W, powerful pumping brings the raising of cost.2, poor stability, described in 1, powerful pumping causes potential safety hazard.3, system maintenance difficulty, same because big pump power has proposed requirements at the higher level to system maintenance, can damage end face etc. as fiber end face is unclean.
The another kind of technology that realizes that extra long distance transmits is the optical soliton transmission, the about 30ps of soliton pulse width, because the comprehensive function of nonlinear effect and dispersion compensation technology, through tens thousand of kilometers transmission, pulse shape remains unchanged in optical fiber.If realize orphan's transmission, laser and modulator among Fig. 1 need particular design, thereby cost increases, and in order to realize that the orphan transmits, image intensifer must be less at interval, keeps needed luminous power, the accumulation of the noise of optical amplifier of many cascades can cause orphan's time jitter (GORDON-HAUS effect, the GH effect), reduce the filter of the necessary extra particular design of GH effect, so the complexity of system and cost increase.Therefore through 20 years of researches, it is practical that the orphan system does not still reach.
The RZ coding techniques also is the effective means that realizes the extra long distance transmission, under the situation of same average power, the pulse power of RZ sign indicating number has improved 3dB, thereby has improved the receiving sensitivity of receiver, and the spacing between the RZ pulse is bigger, can suppress the influence of PMD (polarization mode dispersion).Laser part among Fig. 1 is replaced by the RZ pulse generator just can realize the transmission of RZ sign indicating number, as shown in Figure 2.The light signal process and the clock signal modulators modulate of the wavelength and the power of ITU-T requirement satisfied in laser output, output and the synchronous RZ pulse of data-signal, through the data modulator modulation, data to be transmitted is modulated on the light signal, realize the transmission of RZ code optical signal.This implementation has following shortcoming: 1, with the situation of NRZ sign indicating number same average power under, the power of RZ pulse is higher, easily causes nonlinear effect, and waveform is distorted, and influences signal quality.2, realize that cost is higher.
Summary of the invention:
The purpose of this invention is to provide a kind of return-to-zero code super long distance transmission method and device, cost is low, and transmission range is long.
For achieving the above object, the present invention proposes a kind of return-to-zero code super long distance transmission method and device
Described return-to-zero code super long distance transmission method comprises the steps:
(1), use and the direct modulated laser of data-signal clock signal synchronous, be used for producing RZ (being NRZ) light pulse signal, and make the RZ light pulse signal of output have time dependent frequency, just warble; In the process that symbol that this is warbled and RZ light pulse signal transmit in optical fiber because of the non-linear opposite in sign of warbling that produces from phase modulated (SPM) effect;
(2), by modulator the RZ light pulse signal that produces in the step (1) is modulated, information to be passed is modulated on the RZ light pulse signal with data-signal;
(3), the RZ light pulse signal that produces in the step (2) is transmitted in optical fiber, and receive with receiver, realize the transmission of signal at the other end of optical fiber.
Described return-to-zero code super long distance transmitting device comprises laser, data signal modulation device, Transmission Fibers and receiver, it is characterized in that: also comprise the direct modulating device of laser, be used to and the direct modulated laser of data-signal clock signal synchronous, to produce the RZ light pulse signal; And make the RZ light pulse signal of output have time dependent frequency, just warble; The opposite in sign of warbling that produces because of non-linear self phase modulation in the process that symbol that this is warbled and RZ light pulse signal transmit in optical fiber; Described data signal modulation device is used for the RZ light pulse signal that laser produces being modulated by modulator with data-signal, and information to be passed is modulated on the RZ light pulse signal; Described Transmission Fibers is used for the above-mentioned RZ light pulse signal after the modulation of data signal modulation device of transmission; Receiver is arranged at the other end of optical fiber.
Owing to adopted above scheme, directly laser is modulated, compare with existing RZ sign indicating number transmission plan, save the RZ pulse and produced modulator and corresponding special purpose driver; And the opposite in sign of warbling that produces because of non-linear SPM effect in the process that symbol of warbling in the RZ signal of modulation back laser output and RZ light pulse signal transmit in optical fiber, the two just in time can be cancelled out each other, thereby makes that transmission range can be longer.
Description of drawings:
Fig. 1 is the general topology structural representation of existing extra long distance transmission.
Fig. 2 is the generation schematic diagram of prior art RZ coded signal.
Fig. 3 is the structural representation of RZ sign indicating number optical transmission system of the present invention.
Fig. 4 has the RZ pulse schematic diagram of warbling.
Embodiment:
Also the present invention is described in further detail in conjunction with the accompanying drawings below by specific embodiment.
As shown in Figure 3, this extra long distance transmitting device comprises the direct modulating device of laser, laser, data signal modulation device, Transmission Fibers and receiver, in fact the described direct modulating device of laser that is used for is exactly that a clock signal adds a universal amplifier, it utilizes and the direct modulated laser of data-signal clock signal synchronous, to produce the RZ light pulse signal; And make the RZ light pulse signal of output have time dependent frequency, just warble; The opposite in sign of warbling that produces because of non-linear SPM effect in the process that symbol that this is warbled and RZ light pulse signal transmit in optical fiber; The data signal modulation device is used for the RZ light pulse signal that laser produces being modulated by modulator with data-signal, and information to be passed is modulated on the RZ light pulse signal; Transmission Fibers is used for the above-mentioned RZ light pulse signal after the modulation of data signal modulation device of transmission; Receiver is arranged at the other end of optical fiber.Compare as seen with existing transmitting device, an important feature of the present invention is its special RZ sign indicating number generating technique---directly laser is modulated, and utilized this special RZ sign indicating number to realize the extra long distance transmission.Image intensifer in the transmission line only needs ripe now EDFA amplifier, and the system configuration also transmission system with the NRZ sign indicating number is identical, and receiver is identical with the NRZ receiver.Therefore the implementation of system is simpler than other extra long distance implementations, and cost is low.
Described Transmission Fibers can be general single mode fiber (SMF), zero dispersion shift fiber (DSF) or non-zero dispersion displacement optical fiber (NZDSF).
Also image intensifer and dispersion compensation device can be set in the transmission line, be respectively applied in transmission course the RZ light pulse signal is amplified and dispersion compensation.
For the opposite in sign of warbling that the symbol that guarantees to warble and non-linear SPM effect are produced, described laser need adopt directly modulated lasers or DFB (distributed feed-back) laser.
Its transmission method is: use and the direct drive laser of data-signal clock signal synchronous; The RZ pulse of output is modulated at information to be passed on the light signal through data modulator; Transmit in optical fiber with the RZ pulse that produces, and receive with receiver, realize the transmission of signal at the other end of optical fiber.
Among the present invention, the RZ pulse of exporting from data modulator is different from general RZ pulse, has time dependent frequency (just warbling), as shown in Figure 4.Solid line among Fig. 4 is represented the RZ pulse signal, chain-dotted line is the chirp signal of RZ pulse, the light color dotted line then is because non-linear from phase modulated (SPM) effect warbling through 400km transmission back accumulation, launched power has only 0dBm (1mw), this warbling can cause the distortion of transmitted waveform, influences transmission quality.But in the solution of the present invention, the SPM effect produces warble the opposite in sign of warbling with RZ code book body therefore thisly has the RZ sign indicating number of warbling and has the ability of offsetting the nonlinear effect effect, plays the nonlinear effect that suppresses.
Another characteristics of the present invention are not only to realize the extra long distance transmission on general single mode fiber, and can realize the extra long distance transmission on the optical fiber of other types such as non-zero dispersion displacement optical fiber, zero dispersion shift fiber.
This transmitting device also can be realized equidirectional DWDM transmission system on same optical fiber, these need are selected the different wave length laser (a plurality of different wavelength of laser devices or the laser that can launch the multi-wavelength) that satisfies the ITU-T standard for use, modulate in a manner described, transmit and get final product.
Compare with RZ sign indicating number transmission plan of the prior art, the present invention has following advantage:
1, realizes that cost is low, more common RZ sign indicating number transmission system, the less device of this patent, and device technology maturation.Prior art as shown in Figure 2 needs many pulses to produce modulator and corresponding special purpose driver.
2, different RAMAN amplifiers have reduced a series of problems that the RAMAN amplifier brings.
3, be applicable to different types of optical fiber.
4, identical with a large amount of commercial NRZ code system structures, can directly upgrade to this type systematic.Though (also can directly upgrade with prior art shown in Figure 2, when upgrading cost height, transmission range little.)
The solution of the present invention realizes 4000km without electronic relay extra long distance transmission without the RAMAN amplifier through software simulation and system experimentation on general single mode fiber, realize the transmission of 1280km without electronic relay extra long distance on zero dispersive optical fiber.
Claims (10)
1, a kind of return-to-zero code super long distance transmission method is characterized in that comprising the steps:
(1), use and the direct modulated laser of data-signal clock signal synchronous, be used for producing the NRZ light pulse signal, and make the NRZ light pulse signal of output have time dependent frequency, just warble; The opposite in sign of warbling that produces because of non-linear self phase modulation in the process that symbol that this is warbled and NRZ light pulse signal transmit in optical fiber;
(2), by modulator the NRZ light pulse signal that produces in the step (1) is modulated, information to be passed is modulated on the NRZ light pulse signal with data-signal;
(3), the NRZ light pulse signal that produces in the step (2) is transmitted in optical fiber, and receive with receiver, realize the transmission of signal at the other end of optical fiber.
2, return-to-zero code super long distance transmission method as claimed in claim 1 is characterized in that: the optical fiber in the step (3) can be general single mode fiber SMF, zero dispersion shift fiber DSF or non-zero dispersion displacement optical fiber NZDSF.
3, return-to-zero code super long distance transmission method as claimed in claim 1 or 2 is characterized in that: step (3) therein, the NRZ light pulse signal in the transmission course, also amplifies, carries out dispersion compensation with dispersion compensation device with image intensifer in optical fiber.
4, return-to-zero code super long distance transmission method as claimed in claim 1 or 2 is characterized in that: described laser is directly modulated lasers or distributed feedback laser.
5, return-to-zero code super long distance transmission method as claimed in claim 1 or 2, it is characterized in that: utilize a plurality of different wave length lasers or the laser that can launch the multi-wavelength, after being modulated at information to be passed on a plurality of NRZ light pulse signals through step (1), (2), in step (3) a plurality of NRZ light pulse signals through same Optical Fiber Transmission, realize dense wave division multipurpose.
6, a kind of return-to-zero code super long distance transmitting device comprises laser, data signal modulation device, Transmission Fibers and receiver, it is characterized in that:
Also comprise the direct modulating device of laser, use and the direct modulated laser of data-signal clock signal synchronous, to produce the NRZ light pulse signal; And make the NRZ light pulse signal of output have time dependent frequency, just warble; The opposite in sign of warbling that produces because of non-linear self phase modulation in the process that symbol that this is warbled and NRZ light pulse signal transmit in optical fiber;
Described data signal modulation device is used for the NRZ light pulse signal that laser produces being modulated by modulator with data-signal, and information to be passed is modulated on the NRZ light pulse signal;
Described Transmission Fibers is used for the above-mentioned NRZ light pulse signal after the modulation of data signal modulation device of transmission;
Receiver is arranged at the other end of optical fiber.
7, return-to-zero code super long distance transmitting device as claimed in claim 6 is characterized in that: described Transmission Fibers can be general single mode fiber SMF, zero dispersion shift fiber DSF or non-zero dispersion displacement optical fiber NZDSF.
8, as claim 6 or 7 described return-to-zero code super long distance transmitting devices, it is characterized in that: also comprise image intensifer and dispersion compensation device, be respectively applied in transmission course the NRZ light pulse signal is amplified and dispersion compensation.
9, as claim 6 or 7 described return-to-zero code super long distance transmitting devices, it is characterized in that: described laser is directly modulated lasers or distributed feedback laser.
10, as claim 6 or 7 described return-to-zero code super long distance transmitting devices, it is characterized in that: described laser comprises a plurality of different wave length lasers or the laser that can launch the multi-wavelength.
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| Application Number | Priority Date | Filing Date | Title |
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| CNB021250774A CN1213552C (en) | 2002-07-10 | 2002-07-10 | Return-to-zero code super long distance transmission method and equipment |
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| CNB021250774A CN1213552C (en) | 2002-07-10 | 2002-07-10 | Return-to-zero code super long distance transmission method and equipment |
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| CN1467929A CN1467929A (en) | 2004-01-14 |
| CN1213552C true CN1213552C (en) | 2005-08-03 |
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| CN112180356B (en) * | 2020-08-27 | 2024-05-28 | 中国人民解放军空军工程大学 | Dual-chirp linear frequency modulation signal generation method and device |
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