CN106788741A - A kind of Front haul Transmission systems based on Dispersion Flattened Fiber - Google Patents

Abstract

The present invention proposes a kind of Front haul Transmission systems based on Dispersion Flattened Fiber, and system transfer rate is 56Gbps, modulation format is 4QAM；In the case of linear transfer, the system high speed rate, the transmission characteristic of 4QAM signals are better than the transmission characteristic in NZDSF and SSMF systems；Transmission system link is more long more obvious；The best performance of the system transfers two-forty 4QAM signals, is the optimal alternative of Front haul long spans transmission, for the transmission of mobile communication Front haul long spans provides new approaches and experiment is ensured under special applications scene.

Description

A kind of Front-haul Transmission systems based on Dispersion Flattened Fiber

Technical field

The present invention relates to a kind of optical fiber telecommunications system, and in particular to a kind of Front-haul based on Dispersion Flattened Fiber is passed Defeated system, can be applied to the fields such as fiber optic communication, optical Information Processing.

Background technology

With being continuously increased for data communication and multimedia service demand, mobile communication is developed rapidly and constantly meets people Communication requirement；However, existing mobile communications network typically uses front end delivery interface CPRI (Common Public Radio Interface) or OBSAI (Open Base Station Architecture Initiative), in data speed Rate, bandwidth, time delay aspect exist significant limitation [1 Ericsson AB, Huawei Technologies Co. Ltd, NEC Corporation, Alcatel Lucent, et al. Common Public Radio Interface (CPRI); Interface Specification, (2013)； 2 OBSAI Reference Point 3 Specification, Version 4.2 [R], OBSAI, (2010) ]；For such case, the unit such as China Mobile Communications Research Institute is proposed Forward pass interface NGFI (Next Generation Front-haul Interface) [3 China mobile of future generation research institute, et al. White Paper of Next Generation Front-haul Interface, v1.0 (2015)] with meet the 5th third-generation mobile communication (5G) development demand；NGFI refers to of future generation wireless Forward pass interface in network master between Base-Band Processing function and far end radio frequency processing function, there is provided five kinds of interface division sides Case, can both use analogue transmission, can use digital transmission technology to reduce to system parameter requirement again, can flexibly accept or reject, and be The further research of mobile communication Front-haul networks provides important references.In NGFI wireless cloud center (RCC, Radio cloud center) single spanning distance of centrostigma and far end radio frequency system (RRS, radio remote system) transmits Distance is generally limited to 20km, it is contemplated that China is vast in territory, coastline is long, island are numerous, wasteland desert and the high mountain length and breadth of land etc. The swift and violent growth of the complexity and modern communicationses demand of geographical environment, realizes that Front-haul long span Optical Fiber Transmissions become day It is beneficial urgent.

Dispersion Flattened Fiber (DFF, dispersion flattened fiber) dispersion very little in telecommunication wavelength ranges And dispersion flattene, can both eliminate the monochrome signal distortion that dispersion causes, and the dispersion distortion of wide range signal can be avoided again； In the case that joint nonlinear effect produces super continuous spectrums, DFF ensure that the spectral region broader spectrum distribution of super continuous spectrums More flat [4 XU Y Z, YE H, LI H T, et al. Design of optimum supercontinuum spectrum generation in a dispersion decreasing fiber. Optoelectron. Lett. 2015, 11 (3): 217-221].Document [5 Li Xin, Zheng Hongjun, Yu Huishan, et al. Sub- picosecond chirped pulse propagation in concave-dispersion -flattened fibers. Optoelectronics letters, 2012, 8(1): 048-051；6 Zheng Hongjun, Liu Shanliang, Wu Chongqing, et al. Experimental study on pulse propagation characteristics at normal dispersion region in dispersion flatted fibers, Optics & laser technology, 2012, 44(4):763-766] pulse propagation characteristics in experimental study DFF；Document [7 Hongjun Zheng, Xin Li, Shanliang Liu, et al. Generation and transmission of a High- bit-rate optical millimeter wave with an unrepeated long single-span using Equalization amplification. Optics Communications, 356 (2015), 599-606] experiment Demonstrate 10Gbps, 40GHz optical millimeter wave balanced superperformance for amplifying transmission of the long span in nearly Dispersion Flattened Fiber.Can See, DFF is a kind of good transmission medium, there is important application in fiber optic communication, can be used as under special applications scene The alternative of Front-haul long span optical fiber transmission mediums；There is presently no carrying out Front-haul in Dispersion Flattened Fiber The Experimental report of long span transmission.

Under the overall situation that network direct broadcasting, virtual reality, 4K videos are gradually popularized, user to performance index requirements increasingly It is high；The quadrature amplitude modulation that spectrum efficiency is high, noise resisting ability is strong（QAM, quadrature amplitude modulation）Receive extensive concern [8 Matt Mazurczyk, the Spectral Shaping in Long of industry Haul Optical Coherent Systems With High Spectral Efficiency. Journal of Lightwave Technology Vol. 32, Issue 16, pp. 2915-2924 (2014)；9 Hongxiang Wang, Gen Li, and Yuefeng Ji. Phase and amplitude regeneration of a rectangular 8-QAM in a phase-sensitive amplifier with low-order harmonics. Applied Optics, Vol. 56, Issue 3, pp. 506-509 (2017)].Qam mode is with carrier signal Amplitude and phase represent different digital bits codings, multi-system is combined with quadrature carrier technology, further carry High spectrum utilization, while strengthening interference free performance ensure that the bit error rate, it is complicated in addition with high power spectrum density and low calculating The advantages of spending；QAM receives much attention as important modulation format, and its transmission experiment is limited to greatly standard single-mode fiber（SSMF）With In pulse controlled standard single-mode fiber loop instrument, single spanning distance is smaller；Sound light modulation is cut spectrum, multiple light and is put in simultaneous transmission Greatly, the complex process link such as filtering, signal shaping, dispersed light compensation, dispersion electronic compensating and denoising [10 Xiaobo Meng, Weiqin Zhou, et al. Long-haul 112 Gbit/s coherent polarization multiplexing QPSK transmission experiment on G.652 fiber with the improved DSP unit [J]. OPTIK, 2013; 124 (18): 3665；11 Tingting Zhang, Dan Wang, et al. 396.5Gb/s, 7.93b/s/Hz Hybrid 16-32QAM Transmission over 480km SSMF. OSA Technical Digest (Optical Society of America, 2014), paper SM3E.3；12 Cheng Zhang, Zhennan Zheng, et al. 2.166Tb/s, 7.88b/s/Hz, PDM-64-QAM Nyquist-WDM Transmission over 155km SSMF using Monolithic Optical Frequency Comb Generator. OSA Technical Digest (Optical Society of America, 2015), paper SpM3E.4].At present, there is not yet QAM signals Transmission experiment report in Dispersion Flattened Fiber；Meanwhile, industry communication requirement urgently expects to have biography more more preferable than SSMF characteristic Defeated system is transmitted with realizing the longer single spanning distance of QAM signals.

The content of the invention

In state natural sciences fund (numbering 61671227,61431009 and 61501213）, Shandong Province's natural science Fund（ZR2011FM015）, under " Mount Taishan scholar " construction project specific project expenditure supports, the present invention proposes a kind of flat based on dispersion The Front-haul Transmission systems of smooth optical fiber, system transfer rate is 56Gbps, modulation format is 4QAM；Within the system at a high speed The transmission characteristic of rate 4QAM signals is substantially better than in non-zero dispersion displacement optical fiber（NZDSF）Transmission with SSMF chain-circuit systems is special Property；The system is the optimal alternative of Front-haul long spans transmission, is mobile communication Front- under special applications scene The transmission of haul long spans provides new approaches and experiment is ensured.

The technical solution adopted for the present invention to solve the technical problems is：

For mobile communication Front-haul long spans transmission active demand under special applications scene, the present invention proposes a kind of base In the Front-haul Transmission systems of Dispersion Flattened Fiber, system transfer rate is 56Gbps, modulation format is 4QAM；The system The technical scheme taken：The system includes that QAM signals transmitting terminal, fiber transmission link and QAM receive the function mould of test side 3 Block；Wherein, QAM signals transmitting terminal includes bit mode generator SHF12104A, digital analog converter SHF612A, electric amplifier SHF806, I/Q modulator, laser EXFO IQS-636 and digital analog converter SHF612A, electric amplifier SHF806 and I/Q The direct current biasing DC Bias of modulator；Fiber transmission link includes 50：50 shunts, DSA8300 oscillographs, adjustable light amplification Device EDFA, DFF transmission link；QAM receives test side includes local oscillator laser, light orthogonal mixer, the pole of balance reception photoelectricity two Pipe, analog-digital converter, data pre-processor, carrier recovery processor, wave filter, balanced device；In QAM signal transmitting terminals, bit Mode generator SHF12104A produces two-way 28Gbps two-forty binary digit pseudo noise code signals, the signal to respectively enter Two digital analog converter SHF612A, postpone and the treatment of level sublevel, obtain I roads, Q roads electric signal；I roads, Q roads electric signal Respectively I/Q modulators are amplified into through two electric amplifier SHF806；The wavelength that laser EXFO IQS-636 send 1550.31nm, the continuous laser of power 15dBm enter I/Q modulators；In I/Q modulators, I roads, Q roads telecommunications after amplification Number continuous laser is modulated respectively, obtain 56Gbps, 4QAM modulated optical signal（Signal essence is identical with QPSK）；Wherein digital-to-analogue Converter SHF612A, electric amplifier SHF806, I/Q modulator are required for adjustment direct current biasing to proper states, in particular for Carefully, three direct current biasings of I/Q modulators are adjusted repeatedly；Next, 4QAM modulated optical signals enter fiber transmission link； 4QAM modulated optical signals are through 50:50 shunts, wherein signal connects DSA8300 oscillographs, observation 4QAM modulation light letters all the way Number eye pattern；Three direct current biasings for adjusting I/Q modulators can obtain good 4QAM eye patterns；Another road 4QAM modulated optical signals are entered Optical power is adjustable, and image intensifer EDFA carries out light amplification, it is ensured that the suitable luminous power needed for linear transfer, is then passed by DFF Transmission link single spanning distance is transmitted；Enter QAM afterwards and receive test side；Test side is received in QAM, after being transmitted through DFF transmission links The signal that 4QAM signals and local oscillator laser are produced enters light orthogonal mixer jointly, then through balance reception photodiode phase Stem grafting is received, and then carries out the conversion opposite with transmitting terminal through analog-digital converter, then through data pre-processor, carrier auxiliary treatment Device, wave filter and balanced device recover information source binary data, analysis 4QAM signal constellation (in digital modulation)s figure, Error Vector Magnitude（EVM）、Q- Factor, eye pattern, the bit error rate（BER）Situation of change；Analysis 4QAM modulated optical signals can be measured with spectroanalysis instrument linearly to pass Spectrum situation before and after defeated.

Beneficial effects of the present invention are as follows：

1. in the case of linear transfer, in the Front-haul Transmission systems based on Dispersion Flattened Fiber proposed by the invention High speed rate, the transmission characteristic of 4QAM signals are better than in non-zero dispersion displacement optical fiber（NZDSF）With the transmission characteristic of SSMF systems；

2. transmission system link is more long more obvious；

3. system proposed by the invention is the optimal alternative of Front-haul long spans transmission, is special applications scene Lower mobile communication Front-haul long spans transmission provides new approaches and experiment is ensured.

Brief description of the drawings

Fig. 1 is a kind of Front-haul Transmission system installation drawings based on Dispersion Flattened Fiber of the present invention；The system is divided into 3 Individual functional module：1 is QAM signal transmitting terminals, and 2 is fiber transmission link, and 3 is that QAM receives test side；Wherein, QAM signals transmitting End includes bit mode generator SHF12104A（1）, digital analog converter SHF612A（2）（3）, electric amplifier SHF806（4） （5）, I/Q modulators（6）, laser EXFO IQS-636（7）And digital analog converter SHF612A, electric amplifier SHF806 and The direct current biasing DC Bias of I/Q modulators（8）（9）（10）（11）（12）（13）（14）；Optical transmission chain includes 50：50 branches Device（15）, DSA8300 oscillographs（16）, adjustable image intensifer EDFA（17）, DFF transmission links（18）；QAM receives test side bag Include local oscillator laser（19）, light orthogonal mixer（20）, balance reception photodiode（21）（22）（23）（24）, analog-to-digital conversion Device（25）（26）（27）（28）, data pre-processor（29）, carrier recovery processor（30）, wave filter（31）, balanced device（32）；

Fig. 2 is two-forty 4QAM signal constellation (in digital modulation) figures in varied situations；Fig. 2 (a) be it is back-to-back in the case of 4QAM constellations Figure, Fig. 2 (b)-(d) is respectively then 4QAM planispheres resulting after being transmitted through DFF, NZDSF and SSMF of 25km；

Fig. 3 is changes of the EVM after 4QAM signals are transmitted through linear with input optical power, with circular, foursquare in Fig. 3 Solid line corresponds to 50km DFF and 50km NZDSF situations respectively；

Fig. 4 is changes of the Q-Factor after 4QAM signals are transmitted through linear with input optical power, and band is circular, square in figure The solid line of shape corresponds to 50km DFF and 50km NZDSF situations respectively.

Specific embodiment

Technical scheme, but protection domain not limited to this are described in detail with reference to embodiment and accompanying drawing.

The Fig. 1 of embodiment 1 is the Front-haul Transmission system installation drawings based on Dispersion Flattened Fiber, and the system is divided into 3 Individual functional module：1 is QAM signal transmitting terminals, and 2 is fiber transmission link, and 3 is that QAM receives test side；Wherein, QAM signals transmitting End includes bit mode generator SHF12104A（1）, digital analog converter SHF612A（2）（3）, electric amplifier SHF806（4） （5）, I/Q modulators（6）, laser EXFO IQS-636（7）Digital analog converter SHF612A, electric amplifier SHF806 and I/Q are adjusted The direct current biasing DC Bias of device processed（8）（9）（10）（11）（12）（13）（14）；Optical transmission chain includes 50：50 shunts （15）, DSA8300 oscillographs（16）, adjustable image intensifer EDFA（17）, DFF transmission links（18）；QAM receives test side to be included Local oscillator laser（19）, light orthogonal mixer（20）, balance reception photodiode（21）（22）（23）（24）, analog-digital converter （25）（26）（27）（28）, data pre-processor（29）, carrier recovery processor（30）, wave filter（31）, balanced device（32）. QAM signal transmitting terminals, bit mode generator SHF12104A（1）Produce two-way 28Gbps two-forty binary digit pseudorandoms Code signal, the signal respectively enters two digital analog converter SHF612A（2）（3）, postpone and the treatment of level sublevel, obtain I roads, Q roads electric signal；Wherein in the control software of digital analog converter, the corresponding interface of setting signal is D3, and level number is 2, is shaken Width is 200mV；In bit mode generator control software, CH4 and CH6 pseudo noise code data signals are gated；I roads, Q roads electric signal Through electric amplifier SHF806（4）（5）I/Q modulators are respectively enterd after amplification（6）；Laser EXFO IQS-636（7）Send Wavelength 1550.31nm, the continuous laser of power 15dBm enter I/Q modulators（6）；In I/Q modulators（6）In, the I after amplification Road, Q roads electric signal modulate continuous laser respectively, obtain 56Gbps, 4QAM modulated optical signal（Signal essence and QPSK phases Together）；Wherein digital analog converter SHF612A（2）（3）, electric amplifier SHF806（4）（5）, I/Q modulators（6）It is required for adjustment straight Stream biasing（8）（9）（10）（11）（12）（13）（14）To proper states, in particular for carefully, adjust I/Q modulators repeatedly （6）Three direct current biasings（12）（13）（14）；Next, 4QAM modulated optical signals enter fiber transmission link；4QAM is modulated Optical signal is through 50:50 shunts（15）Branch, wherein signal connects DSA8300 oscillographs all the way（16）, observation 4QAM modulation light letters Number eye pattern；Regulation I/Q modulators（6）Three direct current biasings（12）（13）（14）Can obtain good 4QAM eye patterns；Another road 4QAM modulated optical signals enter optical power tunable optical amplifier EDFA（17）Carry out light amplification, it is ensured that suitable needed for linear transfer Luminous power, then by DFF transmission links（18）Single spanning distance is transmitted；Enter QAM afterwards and receive test side；Received in QAM and detected End, through DFF transmission links（18）4QAM signals and local oscillator laser after transmission（19）It is orthogonal that the signal of generation enters light jointly Blender（20）, then through balance reception photodiode（21）（22）（23）（24）Coherent reception, then through analog-digital converter （25）（26）（27）（28）The conversion opposite with transmitting terminal is carried out, then through data pre-processor（29）, carrier recovery processor （30）, wave filter（31）And balanced device（32）Recover information source binary data, analysis 4QAM planispheres, Error Vector Magnitude （EVM）, Q-Factor, eye pattern, the bit error rate（BER）Situation of change.

Fig. 2 is two-forty 4QAM signal constellation (in digital modulation) figures in varied situations；Fig. 2 (a) be it is back-to-back in the case of 4QAM Planisphere, Fig. 2 (b)-(d) is respectively then 4QAM planispheres resulting after being transmitted through DFF, NZDSF and SSMF of 25km.Flat Under luminous power is the identical input condition of -0.95dBm, signal has carried out linear transfer (this situation through DFF, NZDSF and SSMF For 56Gbps, 4QAM modulated optical signal produced in I/Q modulators are directly entered DFF transmission link linear transfers, without light Power adjustable image intensifer EDFA carries out light amplification).It is available from Fig. 2, linear transfer 25km apart from when, 4QAM signals warp Many in critical intensive after obtaining the point of planisphere than being transmitted through SSMF after DFF and NZDSF transmission, i.e., transmission performance is well very It is many；Planisphere characteristic after QAM signals obtain planisphere than being transmitted through NZDSF after being transmitted through DFF is good；Back-to-back situation Under 4QAM signals Error Vector Magnitude（EVM, error vector magnitude）It is 7.22%, signal is through three species The power output that measures is respectively -8.95dB, -7.36dB and -7.16dB after the transmission of type linear, EVM is respectively 9.75%, 10.89% and 60.62%.The value of EVM is bigger, and the data point in corresponding planisphere is more discrete, and systematic function is poorer；Conversely, EVM is smaller, and planisphere characteristic is better.Result shows, in the case of linear transfer, input optical power is identical, power output is close, The fibre-optical dispersion of DFF, NZDSF and SSMF increases successively, and influence of the fibre-optical dispersion to two-forty 4QAM signals is occupied an leading position； Two-forty 4QAM signals are substantially better than in NZDSF and SSMF system transfers situations in the planisphere characteristic of DFF system transfers.Cause Planisphere characteristic after 4QAM signals are transmitted through SSMF is very poor, does not further relate to 4QAM signals in discussion below and is transmitted in SSMF Situation.

Fig. 3 is changes of the EVM after 4QAM signals are transmitted through linear with input optical power.Band is circular, square in Fig. 3 The solid line of shape corresponds to 50km DFF and 50km NZDSF situations respectively（Before transmission, signal is by the adjustable image intensifer of luminous power EDFA has carried out light amplification）.Can be obtained by Fig. 3, in the case of linear transfer, as input optical power increases, through DFF and NZDSF EVM after transmission is down to 12.30% and is down to 16.05%, i.e., the 4QAM signals after being transmitted through DFF from 21.01% from 18.37% respectively 3-4%s of the EVM better than situation after being transmitted through NZDSF；EVM is smaller to show that characteristics of signals is better.

Fig. 4 is changes of the Q-Factor after 4QAM signals are transmitted through linear with input optical power.In figure band it is circular, Foursquare solid line corresponds to 50km DFF and 50km NZDSF situations respectively（Before transmission, signal is by the adjustable light amplification of luminous power Device EDFA has carried out light amplification）.Can be obtained by Fig. 4, the 4QAM signals Q-Factor after being transmitted through DFF and NZDSF is with input light Power increases and increases, and the Q-Factor changes of correspondence NZDSF are slow；Signal Q-Factor after then being transmitted through DFF is better than The situation of correspondence NZDSF.

In a word, the present invention proposes a kind of Front-haul Transmission systems based on Dispersion Flattened Fiber, realizes speed For 56Gbps, modulation format are the signal transmission of 4QAM.In the case of linear transfer, the system high speed rate, 4QAM signals Transmission characteristic is better than the transmission characteristic in NZDSF and SSMF systems；Transmission system link is more long more obvious；The system transfers are at a high speed The best performance of rate 4QAM signals, is the optimal alternative of Front-haul long spans transmission, is that special applications scene is moved down Dynamic communication Front-haul long spans transmission provides new approaches and experiment is ensured.

It should be pointed out that specific embodiment is the more representational example of the present invention, it is clear that skill of the invention Art scheme is not limited to above-described embodiment, can also there is many variations.One of ordinary skill in the art, it is clearly public with institute of the invention Written description open or according to file is undoubted to be obtained, and is considered as this patent scope of the claimed.

Claims (2)

1. a kind of Front-haul Transmission systems based on Dispersion Flattened Fiber, it is characterised in that：Including QAM signals transmitting terminal, Fiber transmission link and QAM receive the functional module of test side 3；Wherein, QAM signals transmitting terminal includes bit mode generator SHF12104A, digital analog converter SHF612A, electric amplifier SHF806, I/Q modulator, laser EXFO IQS-636 and number The direct current biasing DC Bias of weighted-voltage D/A converter SHF612A, electric amplifier SHF806 and I/Q modulator；Optical transmission chain includes 50： 50 shunts, DSA8300 oscillographs, adjustable image intensifer EDFA, DFF transmission link；QAM receives test side includes local oscillator laser Device, light orthogonal mixer, balance reception photodiode, analog-digital converter, data pre-processor, carrier recovery processor, filter Ripple device, balanced device；In QAM signal transmitting terminals, bit mode generator SHF12104A produces two-way 28Gbps two-forty binary systems Digital pseudo noise code signal, the signal respectively enters two digital analog converter SHF612A, postpone and the treatment of level sublevel, Obtain I roads, Q roads electric signal；I roads, Q roads electric signal are amplified into I/Q modulators through two electric amplifier SHF806 respectively； Nm wave bands of wavelength 1550 that laser EXFO IQS-636 send, the continuous laser of power 15dBm enter I/Q modulators；In I/ In Q modulator, continuous laser is modulated on I roads, Q roads electric signal after amplification respectively, obtains 56Gbps, 4QAM modulated optical signal；Its Middle digital analog converter SHF612A, electric amplifier SHF806, I/Q modulator are required for adjustment direct current biasing to proper states, especially It is three direct current biasings for needing to adjust carefully, repeatedly I/Q modulators；Next, 4QAM modulated optical signals enter Optical Fiber Transmission Link；4QAM modulated optical signals are through 50:50 shunts, wherein signal connects DSA8300 oscillographs, observation 4QAM modulation all the way Optical signal eye pattern；Three direct current biasings for adjusting I/Q modulators can obtain good 4QAM eye patterns；Another road 4QAM modulation light letter Number entering optical power tunable optical amplifier EDFA carries out light amplification, it is ensured that the suitable luminous power needed for linear transfer, then passes through DFF transmission links single spanning distance is transmitted；Enter QAM afterwards and receive test side；Test side is received in QAM, is transmitted through DFF transmission links The signal that 4QAM signals and local oscillator laser afterwards is produced enters light orthogonal mixer jointly, then through the pole of balance reception photoelectricity two Pipe coherent reception, then carries out the conversion opposite with transmitting terminal through analog-digital converter, then through data pre-processor, carrier auxiliary at Reason device, wave filter and balanced device recover information source binary data, analysis 4QAM signal constellation (in digital modulation)s figure, Error Vector Magnitude（EVM）、 Q-Factor, eye pattern, bit error rate change.

2. system according to claim 1, it is characterised in that the transmission characteristic of 56Gbps, 4QAM signal is better than in the system In the transmission characteristic of NZDSF and SSMF systems；Transmission system link is more long more obvious.