Theoretical investigation of optical wavelength conversion techniques for DPSK Modulation formats using FWM in SOAs and frequency comb in 10 gb/s transmission systems

We have investigated the wavelength conversion techniques for differential phase-shift keying (DPSK) modulation formats in 10 Gb/s transmission systems, compared with the non-return-to-zero (NRZ) modulation format. For the wavelength conversion of DPSK modulation formats, we employed the wavelength converters based on the four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) and the frequency comb generated by phase modulation. The power penalty at 10/sup -9/ bit error rate was used as a measure of the system performance degraded by the wavelength conversion. Our simulation results show that the DPSK modulation formats have a smaller power penalty than the NRZ modulation format for the wavelength conversion using the FWM effect in an SOA due to a much lower pattern effect. However, as the wavelength conversion uses the frequency comb generated by phase modulation, it has a similar power penalty compared with the NRZ modulation format. It is also shown that the DPSK modulation formats are possible to obtain the power penalty less than 0.4 dB for both wavelength conversion techniques.     

Board-level optical-to-electrical signal distribution at 10 gb/s

An opto/electrical prototype for on-board optical-to-electrical signal broadcasting operating at 10 Gb/s per channel over an interconnect distance of 10 cm is demonstrated. An improved 1/spl times/4 multimode interference (MMI) splitter at 1550 nm with linearly tapered output facet is heterogeneously integrated with four p-i-n photodetectors (PDs) on a silicon (Si) bench. The Si bench itself is hybrid integrated onto an FR-4 printed-circuit board with four receiver channels. A novel fabrication/integration approach demonstrates the simultaneous alignment between the four waveguides and the four PDs during the MMI fabrication process. The entire system is fully functional at 10 Gb/s.     

NRZ码和CSRZ码在40 Gbit/s单通道系统中传输性能分析

文章仿真了非归零码(NRZ)和载波抑制归零码(CSRZ)在40 Gbit/s单通道系统中G.652光纤上传输6×80 km的性能.比较了两种码型对接收端光滤波器和电滤波器带宽的要求、不同的入纤功率下功率代价以及残余色散对比.结果表明,在高速传输系统中,CSRZ码的传输性能明显优于NRZ码.     

Improvement of dispersion tolerance using phase-Modulated NRZ signals in 40-gb/s transmission systems

Compared with the conventional nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed return-to-zero, and chirped RZ signals by numerical simulation, a higher dispersion tolerance in the presence of fiber nonlinearities and amplifier noise has been obtained in this letter by using the phase-modulated NRZ signals. This scheme aims to improve resistance to residual dispersion by an adapted phase modulation at the transmitter.     

Uncooled DBR laser directly Modulated at 3.125 gb/s as athermal transmitter for low-cost WDM systems

An uncooled three-section tunable distributed Bragg reflector laser is demonstrated as an athermal transmitter for low-cost uncooled wavelength-division-multiplexing (WDM) systems with tight channel spacing. A /spl plusmn/0.02-nm thermal wavelength drift is achieved under continuous-wave operation up to 70/spl deg/C. Dynamic sidemode suppression ratio of greater than 35 dB is consistently obtained under 3.125-Gb/s direct modulation over a 20/spl deg/C-70/spl deg/C temperature range, with wavelength variation of as low as /spl plusmn/0.2 nm. This indicates that more than an order of magnitude reduction in coarse WDM channel spacing is possible using this source.     

Electronic precompensation of intrachannel nonlinearities at 40 gb/s

Digital electronic precompensation of intrachannel nonlinearities is studied in a transmission system which consists of 100% dispersion-compensated spans. Different Mach-Zehnder-based transmitter structures are compared. Simulation results demonstrate that using a triple Mach-Zehnder modulator achieves effective compensation of intrachannel nonlinear effects at large launch powers.     

10 Gbit/s NRZ global transmission using optically amplifiedelectronic regeneration

10 Gbit/s NRZ error-free fibre transmission over distances exceeding 400000 km is demonstrated using an optically amplified regenerator with a 160 km span. Direct modulation of a DFB laser raises the stimulated Brillouin scattering power threshold while maintaining system simplicity and robustness     

10 Gbit/s, 138 km uncompensated duobinary transmission overinstalled standard fibre

The first field demonstration using optical duobinary signalling at 10 Gbit/s over installed fibres is reported. Transmission over 138 km of standard fibre is demonstrated without repeaters or dispersion compensation and with a penalty of only 2.5 dB. This technique significantly increases the bit rate distance product without changing any specifications of the existing fibre network. The influence of fibre nonlinearity on system performance is also investigated     

All-optical logic xor gate at 80 gb/s using SOA-MZI-DI

All-optical xor operation has been demonstrated using a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) and delayed interferometer (DI) at 80 Gb/s. The DI is based on a polarization maintaining loop (PML) mirror. The results show using the PML-DI in series with the SOA-MZI improves the pulse quality of the xor result.     

利用SOA交叉增益调制实现2.5 Gbit/s非归零码的全光波长变换

采用半导体光放大器 (SOA)的交叉增益调制进行了 2 5Gbit/s的非归零码光脉冲的波长变换。向下波长变换间距大于 2 0nm ,向上波长变换间距大于 10nm。对变换信号测量了接收机入纤功率和误码率的关系。实验中采用同向变换的方式 ,信号光中心波长固定 ,探测光采用外腔半导体激光器 ,中心波长连续可调。对变换信号进行了至少 1h的测量 ,误码为零。为其在波分复用(WDM)网络中的应用奠定了基础。     

Analysis of feedback for higher order polarization-mode dispersion mitigation of NRZ 40-Gb/s optical transmission

First-order polarization-mode dispersion (PMD) compensation by means of a polarization controller and a differential delay line is not sufficient to guarantee error-free transmission for 40-Gb/s channels when higher order effects severely increase signal distortion. Higher order mitigation is possible by cascading more than one first-order block. However, only two-stage or three-stage devices remain simple enough to be actually controlled. The performance of such higher order PMD compensators is evaluated by means of numerical simulations. Two different feedback signals have been used, demonstrating that first-order and higher order PMD distortion of nonreturn-to-zero (NRZ) pulses at 40 Gb/s can be strongly mitigated for instantaneous values of the differential group delay (DGD) up to the bit slot, when the compensator is properly controlled.     

Characteristics of optical duobinary signals in terabit/s capacity,high-spectral efficiency WDM systems

Optical duobinary signals have been applied to dense wavelength division multiplexing (WDM) systems with high-spectral efficiency to fully utilize a limited gain bandwidth of about 35 nm (4.4 THz) for an erbium-doped fiber amplifier (EDFA). These signals are one type of partial response signals and have narrower bandwidth than conventional intensity modulation (IM) signals. Thus, the use of these signals should make possible to attain ultradense WDM systems. In this paper, characteristics of optical duobinary and IM signals in ultradense WDM systems are compared through experimental evaluations at 20 Gb/s. High-spectral efficiency of 0.6 b/s/Hz was reached in this demonstration     

Field transmission of 8 /spl times/ 170 gb/s over high-loss SSMF link using third-order distributed Raman amplification

This paper reports on the field transmission of N/spl times/170-Gb/s over high-loss fiber links using third-order distributed Raman amplification (DRA) in a commercially operated network of Deutsche Telekom. It gives an overview of the key technologies applied for the realization of an 8 /spl times/ 170 Gb/s (1.28 Tb/s) dense wavelength division multiplexing (DWDM) system demonstrator and summarizes long-haul transmission experiments with terabit-per-second capacity over European fiber infrastructure. Third-order DRA enabled repeaterless transmission of 1 /spl times/ 170 Gb/s and 8 /spl times/ 170 Gb/s over links of 185- and 140-km field fiber, respectively. Including an additional 25 km of lumped standard single-mode fiber (SSMF) at the end of the span, a total loss of 61 and 44 dB, respectively, was bridged.     

40Gb/sWDM系统中RZ&NRZ调制格式的性能比较

利用数值计算的方法对40G WDM系统进行了仿真.在考虑了光纤群速度色散(GVD)、三阶色散(TOD)、自相位调制(SPM)、交叉相位调制(XPM)、四波混频(FWM)和偏振模色散(PMD)的前提下,通过对比眼图和Q因子,对归零码(RZ)和非归零码(NRZ)调制格式的传输性能进行了研究.     

Performance degradations of 2.4 Gbit/s NRZ/RZ lightwave systems dueto reflection-induced phase-to-intensity-noise conversion

Performance degradations in 2.4-Gb/s NRZ (nonreturn to zero) and RZ lightwave systems due to phase-to-intensity-noise conversion between two connectors have been evaluated using computer simulation techniques. Both NRZ and RZ systems have approximately the same penalty if the roundtrip time delay between the two connectors is an exact integer number of bits. If the roundtrip time delay is slightly offset, however, the RZ system penalty is significantly reduced. For example, the RZ system penalty is reduced from 3 dB (roundtrip delay between the two connectors=40 b) to 1.5 dB (roundtrip delay=40.5 b) for two connectors with 8-dB return loss each     

Semiconductor light sources for 40-Gb/s transmission systems

The status and prospects of semiconductor light sources for 40-Gb/s transmission systems are reviewed in regard to the following three topics: direct modulation, external modulation, and pulse sources for return-to-zero format. Included are discussions on direct modulation of a 1.3-/spl mu/m distributed feedback laser for 40-Gb/s very-short-reach optical links, progress made in developing external modulators based on electroabsorption of multiple quantum wells, and mode-locked lasers for carrier-suppressed return-to-zero modulation format.     

10 Gbit/s based NRZ DWDM systems using polarisation switching in single wavelength channel

It is experimentally demonstrated that the nonlinear tolerance of 10 Gbit/s/ch NRZ based DWDM systems over 1500 km standard singlemode fibre can be significantly improved through the use of orthogonal polarisation switching between adjacent bits in a single wavelength channel.     

新型改进光双二进制传输的编解码方案

提出了改进型光双二进制信号在高速率（≥10Gbit／s）传输时预编码的一种新方案。通过分析编解码过程，证明该信号传输时不易受码间干扰影响，能用二进制强度调制一直接检测的系统接收信号。仿真产生了该信号的2种码型。结果表明，采用色散补偿技术能使MD-NRZ和MD-RZ信号在长距离传输后克服眼图失真，MD-RZ信号比MD-NRZ信号在传输后有更低的误码率。     

Fiber nonlinearity and dispersion mitigation in 40-Gb/s NRZ WDM transmission using a multichannel optical equalizer

We investigate the mitigation of distortion due to self-phase modulation and dispersion in 40-Gb/s nonreturn-to-zero wavelength-division-multiplexed transmission using a multichannel optical equalizer. The ability of the equalizer to reduce the signal degradation due to fiber nonlinearities was demonstrated. We achieved 21-channel transmission at BER <10/sup -9/ without forward error correction over 750 km of true wave reduced slope fiber with 107-km amplifier span lengths.