Experiments on 40 Gb/s Transmission with Wavelength Conversion: Results from the IST ATLAS Project

In this article we report the main experimental results obtained in the framework of the IST ATLAS project regarding the transmission at 40 Gb/s over long terrestrial links, including the frequency conversion of a signal. We report the single-channel 40 Gb/s transmission over a link 500 km long with an amplifier spacing of 100 km, both with G.652 fibers and G.653 fibers by periodically compensating the chromatic dispersion with dispersion-compensating fibers. We report the single-channel transmission at 40 Gb/s, also, after the wavelength conversion of a channel with both PPLN and semiconductor optical amplifier devices. In particular, 500 km distances are obtained with PPLN wavelength conversion and 300 km distances with semiconductor optical amplifiers. Some results have been reported for electronic devices operating at 40 Gb/s.     

Experiments on 40 Gb/s Transmission with Wavelength Conversion: Results from the IST ATLAS Project

In this article we report the main experimental results obtained in the framework of the IST ATLAS project regarding the transmission at 40 Gb/s over long terrestrial links, including the frequency conversion of a signal. We report the single-channel 40 Gb/s transmission over a link 500 km long with an amplifier spacing of 100 km, both with G.652 fibers and G.653 fibers by periodically compensating the chromatic dispersion with dispersion-compensating fibers. We report the single-channel transmission at 40 Gb/s, also, after the wavelength conversion of a channel with both PPLN and semiconductor optical amplifier devices. In particular, 500 km distances are obtained with PPLN wavelength conversion and 300 km distances with semiconductor optical amplifiers. Some results have been reported for electronic devices operating at 40 Gb/s.     

光双二进制传输系统的性能研究

光双二进制信号的谱宽是传统二进制信号的一半,采用双二进制传输比二进制传输色散限制的中继距离可增加一倍.本文对采用传统光接收机的光双二进制传输系统用MATLAB进行了通信仿真.结果表明:在完全消光条件下,10 Gb/s双二进制信号在常规单模光纤上传输可达160 km,40 Gb/s双二进制信号在非零色散光纤上为30 km,均比二进制增加了一倍;详细考察了消光比对传输的影响,只有消光比大于25 dB时,双二进制相对于二进制传输的优越性才呈现出来.     

普通单模光纤传输系统的光纤光栅色散补偿研究

通过系统分析光纤光栅的耦合模理论 ,探索、优化光纤光栅的制作过程 ,研制了满足ITU T建议波长的优质光纤光栅。用双透镜和扫描移动平台结合相位掩膜板研制的光纤光栅分别成功实现了 4× 10Gb/s 4 0 0km和4× 10Gb/s 80 0km普通单模光纤传输系统的色散补偿 ,功率代价均小于 2dB ,且最佳功率代价为负值。同时对4× 10Gb/s 80 0km普通单模光纤传输系统的偏振模色散实施长时间的监测 ,系统偏振模色散小于 10 ps,提出了发展 10Gb/s的光通信系统更符合目前我国国情的见解。     

Transmission of 10 GHz, 3.5 ps Optical Pulses Over 100-km Standard Fiber Using Mid-span Spectral Inversion

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Simulation of high capacity 40 Gb/s long haul DWDM system using different modulation formats and dispersion compensation schemes in the presence of Kerr's effect

In this paper, simulative analysis of 40 Gb/s long haul (500-2000 km) DWDM system with ultra high capacity upto 1.28 Tb/s has been carried out for carrier-suppressed return-to-zero (CSRZ), duobinary return-to-zero (DRZ) and modified duobinary return-to-zero (MDRZ) modulation formats. The DWDM system has been analyzed for the pre, post and symmetrical dispersion compensation schemes for 16 Channels with 25 GHz channel spacing in order to find the optimum modulation format for a high bit rate optical transmission system. The effect of variation in input power and transmission distances is observed in terms of Q value and eye opening for various formats. It is found that symmetrical compensation is superior to pre and post dispersion compensation schemes. It has also been observed that the performance of DWDM system is severely limited by the four-wave mixing (FWM) effect and is determined that MDRZ format seems to be the best choice for the transmission distance beyond 1550 km despite slightly more complex transmitter and receiver configuration. Further, symmetrical compensation scheme has been investigated for 32×40 Gb/s MDRZ format for faithful transmission over 1450 km.     

实现20Gbit/s的OTDM孤子信号56km色散位移光纤的传输

在国内最先采用孤子的方式将8×2.5Gb/s的OTDM信号在色散位移光纤中传输了56.1km,对8×2.5Gb/s的OTDM进行解复用后进行了误码测量,系统功率代价为2.9dB.系统采用增益开关半导体激光器作光孤子源,高Q电滤波方式提取时钟,非线性光学环路镜解复用。孤子脉冲最大半宽度为20ps,传输光纤平均色散1.2ps/nm/km。     

Phase encoded spread in time signals for suppression of propagation non-linearities in 40 Gb/s CDM/WDM communications systems using optical phase conjugation for dispersion compensation

The non-linear degradation along a RZ-WDM 40 Gb/s transmission link is shown to be reduced when a spectral direct sequence bipolar phase shift keying (DS/BPSK) encoding format is used. Standard single mode fibre transmission links are studied which use optical phase conjugation for dispersion compensation in the encoded system. For a WDM system with 100 GHz channel spacing, an improvement of 6 dB is found in the link output power margin at a distance of 300 km after five amplification stages.     

In-Field n × 40 Gb/s Transmission Experiments with In-Line All-Optical Wavelength Conversion

In this work, WDM transmission with 40-Gbit/s per channel bit rate has been experimentally demonstrated over a 500-km link. Different chromatic dispersion conditions have been managed and in-line all-optical wavelength conversion has been carried out with a periodical poled lithium niobate (PPLN) device in a polarization-independent scheme. The link was obtained by connecting the fibers contained in an installed cable between Roma and Pomezia (25 km), encompassing single-mode (G.652) and high-end (G.655, non-zero dispersion with a particular value and flat curve for chromatic dispersion) fibers. Some 40 Gb/s channels were propagated in the link 500 km long and one channel was dropped from the link after 300-km propagation, wavelength converted, and added to the other channels for the next 200 km. The electrical data interfaces exploited a 4 × 10 Gbit/s to 1 × 40 Gbit/s MUX at the transmitter, along with a 1 × 40 Gbit/s to 4 × 10 Gbit/s DMUX at the receiver. Successful transmission of 4 channels, 200-GHz spaced, has been achieved over 500 km along both G.652 and G.655 links. No evidence of penalty comparing converted and unconverted channels has been reported. Transmission experiments of 8 × 40 Gbit/s, with 100 GHz frequency spacing, are also reported. No significant degradation has been observed in the case of the G.652 link.     

Gain Controlling of Erbium-Doped Fiber Amplifier by Samarium Doped Inner-Cladding in the 1.5µm Region

In this work, WDM transmission with 40-Gbit/s per channel bit rate has been experimentally demonstrated over a 500-km link. Different chromatic dispersion conditions have been managed and in-line all-optical wavelength conversion has been carried out with a periodical poled lithium niobate (PPLN) device in a polarization-independent scheme. The link was obtained by connecting the fibers contained in an installed cable between Roma and Pomezia (25 km), encompassing single-mode (G.652) and high-end (G.655, non-zero dispersion with a particular value and flat curve for chromatic dispersion) fibers. Some 40 Gb/s channels were propagated in the link 500 km long and one channel was dropped from the link after 300-km propagation, wavelength converted, and added to the other channels for the next 200 km. The electrical data interfaces exploited a 4 × 10 Gbit/s to 1 × 40 Gbit/s MUX at the transmitter, along with a 1 × 40 Gbit/s to 4 × 10 Gbit/s DMUX at the receiver. Successful transmission of 4 channels, 200-GHz spaced, has been achieved over 500 km along both G.652 and G.655 links. No evidence of penalty comparing converted and unconverted channels has been reported. Transmission experiments of 8 × 40 Gbit/s, with 100 GHz frequency spacing, are also reported. No significant degradation has been observed in the case of the G.652 link.     

Gain Flattening Approach to Physical EDFA for 16 × 40 Gb/s NRZ-DPSK WDM Optical Communication Systems

We are using different approaches to gain flattening in EDFAs without using additional components; i.e., gain flattening filter, dispersion shift fiber, periodic gratings, etc. By using gain flatten approach 3, it is possible to achieve the transmission of sixteen channels at 40 Gb/s wavelength division multiplexing (WDM) over a transmission distance of 490 km by single-mode fiber and dispersion-compensating fiber at a span of 70 km with channel spacing of 200 GHz. We observed the bit error rate less than 10^-9 and power of received signal more than -5 dBm with NRZ-DPSK format.     

Optical phase remodulation for Rayleigh noise mitigation in 10 Gb/s/channel WDM passive optical networks

We investigate the principles of optical phase remodulation and demonstrate its application in a future-proof10 Gb/s/channel wavelength-division-multiplexed(WDM) passive optical network to realize a colorless optical network unit and bidirectional transmission over a single fiber. The modulation depth of downstream differential phase-shift keying is properly reduced to facilitate phase remodulation and Rayleigh noise mitigation. For both downstream and upstream 10 Gb/s signals, error-free transmission via a 20 km single-mode fiber is demonstrated without dispersion compensation operation.     

具有电色散补偿的10 Gb/s脉冲转换器的研制

设计并研制了带电色散补偿功能的10 Gb/s脉冲转换器。电色散补偿通过时域均衡的方法,消除光纤色散带来的码间串扰;将电色散补偿芯片纳入脉冲转换器设计中,从而提高了其传输距离。所研制的样品光发射部分采用分布反馈激光器加电吸收调制器集成光源,接收部分采用带互阻放大器的雪崩光电二极管光电探测器模块,电色散补偿芯片对光电探测器输出的码流执行色散补偿算法。对样品进行的测试结果表明该脉冲转换器背对背接收灵敏度为-24.6 dBm,经过100 km G.652光纤传输后接收灵敏度为-20.8 dBm。未加电色散补偿功能时,采用相同的光源传输距离仅为50 km。     

40 Gbit/s非等幅编码光时分复用传输系统

4× 10Gb s非等幅编光时分复用 (OTDM)传输系统采用增益开关分布反馈式激光器 (GS DFB)产生超短光脉冲 ,通过色散补偿光纤 (DCF)和梳状色散光纤链 (CDPF)实现了脉冲的线性和非线性压缩 ;利用啁啾光纤光栅实现色散补偿 ;在接收端 ,利用电吸收调制器 (EAM)实现了光时分复用信号的解复用 ;同时采用非等幅编码方案提取帧时钟。整个系统经过 12 2km的G .6 5 2光纤传输之后 ,误码率小于 10 - 9。     

利用啁啾光纤光栅进行色散补偿的研究

分析了由于光纤的色散引起的脉冲展宽,并介绍了啁啾布拉格光纤光栅进行色散补偿的基本原理。２－５Ｇｂ／ｓ、１００ｋｍ 色散补偿的实验结果表明,利用啁啾光纤光栅进行色散补偿是一种切实可行的色散补偿方案。     

Gain Flattening Approach to Physical EDFA for 16 × 40 Gb/s NRZ-DPSK WDM Optical Communication Systems

We are using different approaches to gain flattening in EDFAs without using additional components; i.e., gain flattening filter, dispersion shift fiber, periodic gratings, etc. By using gain flatten approach 3, it is possible to achieve the transmission of sixteen channels at 40 Gb/s wavelength division multiplexing (WDM) over a transmission distance of 490 km by single-mode fiber and dispersion-compensating fiber at a span of 70 km with channel spacing of 200 GHz. We observed the bit error rate less than 10^-9 and power of received signal more than -5 dBm with NRZ-DPSK format.     

Transmission of 40 Gb/s × 8 WDM channels with 100 GHz spacing using short-period dispersion-managed fiber

We report on the 320 Gb/s (40 Gb/s × 8 channels) WDM transmission experiment using short-period dispersion-managed fiber. After 320-km transmission, the average Q-factor was measured to be better than 20.4 dB. In addition, we compared the performances of various types of fibers in 40-Gb/s based systems. The results show that the SPDMF was robust to both the intra-channel and inter-channel nonlinearities due to its small average dispersion and large local dispersion.     

Impact of extinction ratio of single arm sin LiNbO3 Mach-Zehnder modulator on the performance of 10 and 20 Gb/s NRZ optical communication system

We investigate the impact of extinction ratio of single arm sin² LiNbO₃ Mach-Zehnder (MZ) amplitude modulator on the performance of 10 and 20 Gb/s single-channel optical communication system. For different fiber lengths, the system performance has been analyzed with the increase in the extinction ratio. The effect of variation in dispersion parameter has also been illustrated. The impact of extinction ratio (ζ), dispersion parameter and length of the fiber has been further optimized with minimum bit error rate (BER) at optimal decision threshold (10⁻⁹) for 10 and 20 Gb/s bit rate. It is found that the system gives optimum performance at extinction ratio (ζ) value 20 dB. The increase in the transmission distance from 468 km for 10 Gb/s to 532 km for 20 Gb/s has been reported, and 8 dB improvement in the Q value has been observed as the value of ζ is increased from 10 to 20 dB. At 20 Gb/s, the system gives optimum performance for dispersion parameter value only up to 4 ps/nm km; however, at 10 Gb/s the system can operate for dispersion values up to 14.3 ps/nm km. Further we investigate the self-phase modulation (SPM) effect for the increase in the input power. It is observed that the SPM effect is negligible below 3 dB m input power and it increases at higher power levels.     

优化调制格式实现2560 km低代价无误码传输

在单级调制器产生非归零码(NRZ)基础上,分析了利用双级调制器产生归零码(RZ)以及载波抑制归零码(CSRZ)的方法和特点。对非归零码,归零码和载波抑制归零码在以掺铒光纤放大器(EDFA)为单一的功率放大、以啁啾光纤光栅(CFBG)为色散补偿器的10Gb/s系统中的传输性能进行了计算机仿真并比较这三种调制码型的传输特性。同时在实际的2560km G.652光纤链路上利用上述三种调制格式以点对点形式进行了8×10Gb/s传输实验,通过适当控制线路的功率分配以及合理安排系统的色散补偿,实现了三种调制格式的无电中继条件下的零误码传输。计算机仿真和实际实验结果进一步表明,载波抑制归零码的采用有利于优化系统的传输性能,降低传输代价,载波抑制归零码在上述配置的实际传输系统中无误码传输2560km功率代价仅为2.5dB。     

Experimental Study of Four Wave Mixing in Semiconductor Laser Amplifier and its Application to Dispersion Compensation in Mid Span Spectral Inversion System

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