CN106788741B - 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, system transfer rate 56Gbps, modulation format 4QAM；In linear transfer, the system high speed rate, the transmission characteristic of 4QAM signals are better than the transmission characteristic in NZDSF and SSMF systems；The longer transmission system link the more apparent；The system transmits the best performance of high-speed 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 under special applications scene and experiment ensures.

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 systems, and in particular to a kind of Front-haul biographies based on Dispersion Flattened Fiber Defeated system can be applied to the fields such as fiber optic communication, optical Information Processing.

Background technology

As data communication is continuously increased with multimedia service demand, mobile communication rapid development simultaneously constantly meets people Communication requirement；However, existing mobile communications network generally uses front end delivery interface CPRI (Common Public Radio Interface) or OBSAI (Open Base Station Architecture Initiative), in data speed Rate, bandwidth, in terms of time delay there are 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 units such as China Mobile Communications Research Institute propose Next-generation forward pass interface NGFI (Next Generation Front-haul Interface) [3 China mobile research institute, et al. White Paper of Next Generation Front-haul Interface, v1.0 (2015)] to meet the needs of the 5th third-generation mobile communication (5G) development；NGFI refers to next-generation wireless Forward pass interface in network master between Base-Band Processing function and far end radio frequency processing function provides five kinds of interface division sides Analogue transmission not only may be used in case, but also digital transmission technology can be used to reduce to system parameter requirement, can flexibly accept or reject, 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 has a vast 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 communications demand of geographical environment realizes that the transmission of Front-haul long span optical fiber becomes day It is beneficial urgent.

Dispersion Flattened Fiber (DFF, dispersion flattened fiber) dispersion very little in telecommunication wavelength ranges And dispersion flattene can not only eliminate monochrome signal caused by dispersion and distort, but also can be to avoid the dispersion distortion of wide range signal；? In the case that joint nonlinear effect generates super continuous spectrums, DFF can ensure 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 the superperformance of 10Gbps, 40GHz optical millimeter wave long span equilibrium amplification transmission in nearly Dispersion Flattened Fiber.It can See, DFF is a kind of good transmission medium, there is important application in fiber optic communication, be can be used as under special applications scene The alternative of Front-haul long span optical fiber transmission mediums；There is presently no carry 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 bit codings, multi-system is combined with quadrature carrier technology, is further carried High spectrum utilization, while enhancing interference free performance and ensure that the bit error rate, in addition there are high power spectrum density and low calculating are complicated The advantages that spending；QAM receives much attention as important modulation format, and 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；Spectrum is cut in sound light modulation in simultaneous transmission, multiple light is put 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].Currently, there is not yet QAM signals Transmission experiment report in Dispersion Flattened Fiber；Meanwhile industry communication requirement urgently expects to have biography more better than SSMF characteristic Defeated system is to realize that the longer single spanning distance of QAM signals transmits.

Invention content

In state natural sciences fund (number 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 56Gbps, modulation format 4QAM；High speed within the system 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 ensures.

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

Active demand is transmitted for mobile communication Front-haul long spans under special applications scene, the present invention proposes one Front-haul Transmission system of the kind based on Dispersion Flattened Fiber, system transfer rate 56Gbps, modulation format 4QAM；It should The technical solution that system is taken：The system includes that QAM signals transmitting terminal, fiber transmission link and QAM receive the function of test side 3 Module；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 splitters, DSA8300 oscillographs, adjustable light amplification Device EDFA, DFF transmission link；It includes local oscillator laser, light orthogonal mixer, two pole of balance reception photoelectricity that QAM, which receives test side, Pipe, analog-digital converter, data pre-processor, carrier recovery processor, filter, balanced device；In QAM signal transmitting terminals, bit Mode generator SHF12104A generates two-way 28Gbps high-speed binary digit pseudo noise code signals, which respectively enters Two digital analog converter SHF612A carry out delay and the processing of level sublevel, obtain the roads I, the roads Q electric signal；The roads I, the roads Q electric signal Respectively I/Q modulators are amplified into through two electric amplifier SHF806；The wavelength that laser EXFO IQS-636 are sent out 1550.31nm, power 15dBm continuous laser enter I/Q modulators；In I/Q modulators, the amplified roads I, the roads Q telecommunications Number continuous laser is modulated respectively, obtain 56Gbps, 4QAM modulated optical signal（The signal essence is identical as 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 lights letter all the way Number eye pattern；Good 4QAM eye patterns can be obtained in three direct current biasings for adjusting I/Q modulators；Another way 4QAM modulated optical signals into Optical power is adjustable, and image intensifer EDFA carries out light amplification, it is ensured that then the suitable luminous power needed for linear transfer is passed through DFF and passed Transmission link single spanning distance transmits；Enter QAM later and receives test side；Test side is received in QAM, after the transmission of DFF transmission links The signal that 4QAM signals and local oscillator laser generate enters light orthogonal mixer jointly, then through balance reception photodiode phase Stem grafting is received, and the transformation opposite with transmitting terminal is then carried out through analog-digital converter, then through data pre-processor, carrier auxiliary processing Device, 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 Defeated front and back spectrum situation.

Beneficial effects of the present invention are as follows：

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

2. the longer transmission system link the more apparent；

It is special applications 3. system proposed by the invention is the optimal alternative of Front-haul long spans transmission The transmission of mobile communication Front-haul long spans provides new approaches under scene and experiment ensures.

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 A function module：1 is QAM signal transmitting terminals, and 2 be fiber transmission link, and 3 be that QAM receives test side；Wherein, QAM signals emit 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 packet 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）, filter（31）, balanced device（32）；

Fig. 2 is high-speed 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) are then the obtained 4QAM planispheres after DFF, NZDSF and SSMF of 25km transmission respectively；

Fig. 3 is variations of EVM of the 4QAM signals after linear is transmitted with input optical power, and band is round, square in Fig. 3 The solid line of shape corresponds to 50km DFF and 50km NZDSF situations respectively；

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

Specific implementation mode

With reference to the embodiment and attached drawing technical solution that the present invention will be described in detail, but protection domain is without being limited thereto.

1 Fig. 1 of embodiment is the Front-haul Transmission system installation drawings based on Dispersion Flattened Fiber, which is divided into 3 Function module：1 is QAM signal transmitting terminals, and 2 be fiber transmission link, and 3 be that QAM receives test side；Wherein, QAM signals transmitting terminal Including 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 modulator Direct current biasing DC Bias（8）（9）（10）（11）（12）（13）（14）；Optical transmission chain includes 50：50 splitters（15）, DSA8300 oscillographs（16）, adjustable image intensifer EDFA（17）, DFF transmission links（18）；It includes local oscillator that QAM, which receives test side, 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）, filter（31）, balanced device（32）.In QAM Signal transmitting terminal, bit mode generator SHF12104A（1）Generate two-way 28Gbps high-speed binary digit pseudo noise codes letter Number, which respectively enters two digital analog converter SHF612A（2）（3）, carry out delay and level sublevel processing, obtain the roads I, The roads Q electric signal；Wherein in the control software of digital analog converter, the corresponding interface of setting signal is D3, and level number 2, amplitude is 200mV；In bit mode generator control software, CH4 and CH6 pseudo noise code digital signals are gated；The roads I, the roads Q electric signal are through electricity Amplifier SHF806（4）（5）I/Q modulators are respectively enterd after amplification（6）；Laser EXFO IQS-636（7）The wavelength sent out 1550.31nm, power 15dBm continuous laser enter I/Q modulators（6）；In I/Q modulators（6）In, the amplified roads I, Q Road electric signal modulates continuous laser respectively, obtains 56Gbps, 4QAM modulated optical signal（The signal essence is identical as QPSK）；Its Middle digital analog converter SHF612A（2）（3）, electric amplifier SHF806（4）（5）, I/Q modulators（6）It is required for adjustment direct current biasing （8）（9）（10）（11）（12）（13）（14）To proper states, in particular for carefully, adjust I/Q modulators repeatedly（6）Three A direct current biasing（12）（13）（14）；Next, 4QAM modulated optical signals enter fiber transmission link；4QAM modulated optical signals pass through 50:50 splitters（15）Branch, wherein signal connects DSA8300 oscillographs all the way（16）, observe 4QAM modulated optical signal eye patterns；It adjusts Save I/Q modulators（6）Three direct current biasings（12）（13）（14）Good 4QAM eye patterns can be obtained；Another way 4QAM modulation lights Signal is into optical power tunable optical amplifier EDFA（17）Carry out light amplification, it is ensured that the suitable luminous power needed for linear transfer, so Afterwards by DFF transmission links（18）Single spanning distance transmits；Enter QAM later and receives test side；Test side is received in QAM, is passed through DFF Transmission link（18）4QAM signals after transmission and local oscillator laser（19）The signal of generation enters light orthogonal mixer jointly（20）, Then through balance reception photodiode（21）（22）（23）（24）Coherent reception, then through analog-digital converter（25）（26）（27） （28）The transformation opposite with transmitting terminal is carried out, then through data pre-processor（29）, carrier recovery processor（30）, filter（31） And balanced device（32）Recover information source binary data, analysis 4QAM planispheres, Error Vector Magnitude（EVM）, Q-Factor, eye Figure, the bit error rate（BER）Situation of change.

Fig. 2 is high-speed 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) are then the obtained 4QAM planispheres after DFF, NZDSF and SSMF of 25km transmission respectively.Flat Under the identical input condition that equal luminous power is -0.95dBm, signal has carried out linear transfer (this situation through DFF, NZDSF and SSMF 56Gbps, 4QAM modulated optical signal to be generated in I/Q modulators is 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 Obtained after DFF and NZDSF transmission the point of planisphere than after SSMF is transmitted it is critical it is intensive in it is very much, i.e., transmission performance is well very It is more；QAM signals obtain getting well when planisphere characteristic of the planisphere after transmitting through NZDSF after DFF is transmitted；Back-to-back situation Under 4QAM signals Error Vector Magnitude（EVM, error vector magnitude）It is 7.22%, signal is through three types The output power 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 system performance is poorer；Conversely, EVM is smaller, and planisphere characteristic is better.The result shows that in linear transfer, input optical power is identical, output power is close, The fibre-optical dispersion of DFF, NZDSF and SSMF are sequentially increased, and influence of the fibre-optical dispersion to high-speed 4QAM signals is occupied an leading position； The planisphere characteristic that high-speed 4QAM signals are transmitted in DFF systems is substantially better than transmits situation in NZDSF and SSMF systems.Cause Planisphere characteristic of the 4QAM signals after SSMF is transmitted is very poor, does not further relate to 4QAM signals in discussion below and is transmitted in SSMF Situation.

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

Fig. 4 is variations of Q-Factor of the 4QAM signals after linear is transmitted with input optical power.In figure band it is round, The solid line of square corresponds to 50km DFF and 50km NZDSF situations respectively（Before transmission, signal passes through the adjustable light amplification of luminous power Device EDFA has carried out light amplification）.It can be obtained by Fig. 4, the 4QAM signals Q-Factor after DFF and NZDSF transmission is with input light Power increases and increases, and the Q-Factor variations of corresponding NZDSF are slow；Then the signal Q-Factor after DFF is transmitted is better than The case where corresponding NZDSF.

In short, the present invention proposes a kind of Front-haul Transmission systems based on Dispersion Flattened Fiber, rate is realized The signal transmission for being 4QAM for 56Gbps, modulation format.In linear transfer, the system high speed rate, 4QAM signals Transmission characteristic is better than the transmission characteristic in NZDSF and SSMF systems；The longer transmission system link the more apparent；System transmission high speed The best performance of rate 4QAM signals is the optimal alternative of Front-haul long spans transmission, is moved down for special applications scene Dynamic communication Front-haul long spans transmission provides new approaches and experiment ensures.

It should be pointed out that specific implementation mode is the more representational example of the present invention, it is clear that skill of the invention Art scheme is not limited to the above embodiments, and can also have many variations.Those skilled in the art define public affairs with the present invention Written description open or according to file is undoubted to be obtained, and this patent scope of the claimed is considered as.

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 function 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 mode converter SHF612A, electric amplifier SHF806 and I/Q modulator；Optical transmission chain includes 50： 50 splitters, DSA8300 oscillographs, adjustable image intensifer EDFA, DFF transmission link；It includes local oscillator laser that QAM, which receives test side, Device, light orthogonal mixer, balance reception photodiode, analog-digital converter, data pre-processor, carrier recovery processor, filter Wave device, balanced device；In QAM signal transmitting terminals, bit mode generator SHF12104A generates two-way 28Gbps high-speed binary systems Digital pseudo noise code signal, the signal respectively enter two digital analog converter SHF612A, carry out delay and the processing of level sublevel, Obtain the roads I, the roads Q electric signal；The roads I, the roads Q electric signal are amplified into I/Q modulators through two electric amplifier SHF806 respectively； The continuous laser of 1550 nm wave bands of wavelength, power 15dBm that laser EXFO IQS-636 are sent out enters I/Q modulators；In I/ In Q modulator, the amplified roads I, the roads Q electric signal modulate continuous laser respectively, obtain 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；It connects down Come, 4QAM modulated optical signals enter fiber transmission link；4QAM modulated optical signals are through 50:50 shunts, wherein believing all the way DSA8300 oscillographs number are connect, 4QAM modulated optical signal eye patterns are observed；Three direct current biasings of adjusting I/Q modulators can be obtained good Good 4QAM eye patterns；Another way 4QAM modulated optical signals carry out light amplification into optical power tunable optical amplifier EDFA, it is ensured that line Property transmission needed for suitable luminous power, then pass through DFF transmission link single spanning distances transmit；Enter QAM later and receives test side；? QAM receives test side, and the signal that the 4QAM signals and local oscillator laser after the transmission of DFF transmission links generate is entering light just jointly Mixer is handed over, then through balance reception photodiode coherent reception, is then carried out through analog-digital converter opposite with transmitting terminal Transformation, then information source binary data is recovered through data pre-processor, carrier recovery processor, filter and balanced device, it analyzes 4QAM signal constellation (in digital modulation)s figure, Error Vector Magnitude（EVM）, Q-Factor, eye pattern, the bit error rate variation.

2. system according to claim 1, which is characterized in that the transmission characteristic of 56Gbps, 4QAM signal is excellent in the system In the transmission characteristic in NZDSF and SSMF systems；The longer transmission system link the more apparent.