An chromatic dispersion monitoring method based on spectral-shift of SOA

A remnant dispersion monitoring method based on spectral-shift of SOA in high speed optical communication system with CSRZ format and single channel speed of 40 Gbit/s is proposed. The system performance can be optimized by careful choosing bandwidth and center wavelength of the optical fiber grating filter. The dynamical monitoring range is ±60 ps/nm and the monitoring precision is about 5 ps/nm. This method can be suitable for the application in dynamical dispersion compensation of high speed optical communication systems.     

Second- and third-order dispersion compensator using ahigh-resolution arrayed-waveguide grating

We have proposed a dispersion compensation scheme that uses a high-resolution arrayed-waveguide grating (AWG). When the diffraction order of the AWG is 59 and the number of waveguides in an arrayed-waveguide is 340, the calculated maximum second- and third-order dispersion compensation range is 18.0 ps/nm and ±6.0 ps/nm² , and 1100 ps/nm and ±937.5 ps/nm², for a 1 ps-pulse and a 12.5 ps-pulse, respectively. In experiments, second-order dispersion (-0.8 to +5.2 ps/nm) is effectively compensated for 1,1-ps pulses; and. Pulse compression by third-order dispersion compensation is successfully demonstrated     

Nonlinearly strain-chirped fiber Bragg grating with an adjustabledispersion slope

In this letter, we demonstrate an adjustable dispersion slope compensator for waveform distortion compensation based on a nonlinearly strain-chirped fiber Bragg grating. The dispersion slope of the device can be tuned up to -18.9 ps/nm² with a bandwidth >2.4 nm. After transmission through a 120-km-long dispersion-shifted fiber, the resulting waveform distortion for a 2.65-ps pulse is successfully compensated by using this device     

Tunable dispersion compensation at 40-Gb/s using a multicavity etalon all-pass filter with NRZ, RZ, and CS-RZ modulation

We present a multichannel tunable dispersion compensator (TDC) based on multicavity all-pass etalons that is capable of operation at 40 Gb/s. The device has a tuning range of +200/-220 ps/nm with a group delay ripple < /spl plusmn/5 ps over a channel bandwidth of 80 GHz, an overall loss of < 5.2 dB, very low insertion loss ripple, and can operate on any channel on a 200-GHz grid over the C-band. In addition, we present system performance results at 40 Gb/s using NRZ, RZ, and CS-RZ modulation, compensating up to 45 km of nonzero dispersion shifted fiber (NZDSF). Our results show that this device introduces very little excess system penalty with signal frequency drifts of up to 20 GHz when operated near the center of its tuning range. For single channel experiments with fiber, the system penalty increase versus signal detuning is more significant, but can be reduced by dynamically optimizing the device dispersion during detuning. Finally, we demonstrate simultaneous compensation of 4 channels across the C-band over 25 km of NZDSF.     

Compensation for chromatic dispersion and nonlinear effect in highdispersive coherent optical repeater transmission system

A design for a chromatic dispersion equalizer that provides 4.4 times higher efficiency in the dispersion compensation characteristics, compared with a conventional equalizer, is proposed. In addition, the amplitude response slope in the frequency domain is less than half of the conventional characteristic. This extends the compensation limit for chromatic dispersion up to 82500 ps/nm for a 2.5-Gb/s heterodyne system, which corresponds to a 4900-km normal dispersion fiber transmission system. A compensation method for modulational instability is also proposed. The method was confirmed by a 2.5-Gb/s continuous-phase frequency-shift-keying (CPFSK) 764-km normal dispersion fiber transmission experiment, with the abovementioned chromatic dispersion equalizer. Employing computer simulations, an over-1000-km normal dispersion fiber optical repeater transmission system with 2.5-Gb/s CPFSK heterodyne detection was shown to be feasible     

Broad-band dynamic dispersion compensation in nonlinear fiber-based device

In this paper we report on the design, numerical simulation and experimental testing of a novel dynamic dispersion compensation device based on self-phase modulation (SPM) in nonlinear fiber. The proposed all-fiber device is inherently simple and presents several unique advantages, most notably the potential for a broad-band operation covering all wave-length division multiplexing (WDM) channels of a system and the ability to address variable amounts of residual dispersion in each individual channel. Dynamic compensation ranges of up to 140 ps/nm for a single-stage and 240 ps/nm for a two-stage device are demonstrated with 40 Gb/s CS-RZ signal. It is shown that the device can operate with a minimum channel spacing of 200 GHz. For a two-stage device with inter-stage spectral filtering, simultaneous dynamic dispersion compensation (130 ps/nm for 1 dB penalty) and 2R regeneration (2 dB receiver sensitivity improvement) are demonstrated.     

Time-interleaved pulse-shrinking time-to-digital converter with reduced conversion time

A silicon-efficient time-interleaved pulse-shrinking time-to-digital converter (TDC) is proposed. The proposed TDC consists of a 16-stage coarse pulse-shrinking TDC with constant per-stage shrinkage 4.8 ns and a pair of 16-stage fine pulse-shrinking TDCs operated in a time-interleaved manner with constant per-stage shrinkage 296 ps. A simple residual time extraction method is proposed to extract the residual pulse of the coarse TDC simultaneously with digitization carried out by the TDC so that the digitization can be carried out by both the coarse and fine TDCs simultaneously to minimize conversion time. The characteristics of the proposed TDC including silicon consumption, power consumption, conversion time, jitter, and mismatch-induced timing errors are investigated. The proposed TDC was implemented in an IBM 130 nm 1.2 V CMOS technology. Simulation results show that the TDC offers 0.296–76.8 ns dynamic range, 850 ps conversion time, 0.285 LSB differential nonlinearity, and 0.78 LSB integral nonlinearity while consuming 7 mW.     

Wide-Band and -Range Tunable Dispersion Compensation Through Parametric Wavelength Conversion and Dispersive Optical Fibers

An intrinsically ultrafast, wide-band, and -range tunable dispersion compensation (TDC) is realized through parametric wavelength conversion in conjunction with fibers with large dispersion slope such as dispersion compensating fibers. The proposed schemes have unique potentials that they can operate with fast response in a truly colorless manner and are capable of producing two orders of magnitude larger bandwidth-dispersion product than conventional ones. After the discussions on the operating principle and design issues, a proof-of-concept experiment is performed to verify the static operations achieving a tunable dispersion range larger than plusmn280.5 ps² for 2.47 ps optical pulses.     

Tunable Optical Dispersion Compensator With Increased Bandwidth via Connection of a Mach–Zehnder Interferometer to an Arrayed-Waveguide Grating

We propose and demonstrate a novel colorless tunable optical dispersion compensator (TODC) consisting of a Mach-Zehnder interferometer (MZI) connected to an ar- rayed-waveguide grating with a thermooptic lens. The MZI approximately doubles the magnitude bandwidth at large dispersion settings. We demonstrate compensation of a 43-Gb/s nonreturn-to-zero signal dispersed over a range of -844 to + 1700 ps/nm. To our knowledge, +1700 ps/nm is the largest demonstrated dispersion compensation amount of a 40-Gb/s signal with a single TODC.     

Chromatic-dispersion compensator using virtually imaged phasedarray

A new method for chromatic-dispersion compensation is proposed and demonstrated. This method can produce a chromatic dispersion practically in a wide range from -2000 to +2000 ps/nm and can compensate simultaneously for the dispersion of over 60 wavelength channels with 100-GHz spacing in a wavelength-division multiplexed (WDM) system that has a total bandwidth of over 50 nm. This method has further attractive features such as very small polarization-state dependence, mechanically variable chromatic dispersion, and potential for small packaging. It was experimentally confirmed that this method compensated for the chromatic dispersion accumulated through 110 km standard single-mode fiber (SMF) at 1.55-μm wavelength and that 10-Gb/s signal quality was clearly recovered after the 110-km transmission     

色散监测技术的研究与发展现状

自适应色散补偿技术是高速光纤通信系统中的核心技术之一,而对光信号色散进行动态实时监测是实现自适应色散补偿的关键。系统地总结了色散监测技术的研究与发展现状,对各种动态色散监测技术的机制、特点及其实现进行了分析比较,并重点介绍了全光色散监测技术和基于数字相干检测的色散监测技术,探讨了其未来的发展方向。     

A novel chromatic dispersion monitoring method for 1 024 QAM fiber-optic system based on asynchronous amplitude sampling

A new chromatic dispersion (CD) monitoring method is proposed, and the CD monitoring is achieved on the whole range of 0—600 ps/nm. A dual-polarization (DP)-1 024 quadrature amplitude modulation (QAM) 400 Gbit/s CD monitoring system is built using OptiSystem14.0 software. With different optical signal to noise ratio (OSNR) values, different filter bandwidths or different duty cycles, the simulations are carried out. The simulation results show that this new CD monitoring method can be less affected by noise and has a high tolerance for different filter bandwidths. At the same time, this method can do effective CD monitoring on the signal with duty cycle greater than 80%. A high sensitivity in 0—200 ps/nm can be achieved using this CD monitoring method. The technique supports a wide range of data traffic and enhances operation flexibility of optical networks. This work has been supported by the National Natural Science Foundation of China (Nos.61274121 and 61574080). E-mail:zhub@njupt.edu.cn      

40Gbit/s WDM系统可调色散补偿的实现

文章介绍了一种用于40Gbit/s波分复用(WDM)系统的可调色散补偿方案,采用啁啾布拉格光栅的多通道色散补偿技术和掺铒光纤放大器的自动功率控制技术,可以对现有40Gbit/s主流调制编码格式的波分复用系统进行高精度的色散补偿,同时能提高接收机的动态范围.     

High-performance 40 Gbit/s fibre Bragg grating tunable dispersion compensator fabricated using group delay ripple correction technique

A recently proposed UV correction method is used to reduce group delay ripple in a chirped fibre grating tunable dispersion compensator. In 43 Gbit/s CSRZ system tests, the corrected grating had less than 0.5 dB OSNR penalty over the tunable dispersion range of 270 to 750 ps/nm.     

All-Optical Vestigial Sideband Generation Using a Semiconductor Optical Amplifier

An all-optical setup to generate vestigial sideband signals based on self-phase modulation in a semiconductor optical amplifier is experimentally demonstrated at 10 Gb/s. Sideband suppressions higher than 15 dB are reported with improved eye opening. Wavelength-independent operation over 26 nm is demonstrated. Increased chromatic dispersion tolerance is verified: a receiver sensitivity penalty of 5.3 dB, relative to back-to-back, is obtained after transmission over 2720 ps/nm; whereas conventional double sideband is penalized by 4.0 dB after 1360 ps/nm     

一种闭环控制的光纤光栅动态色散补偿仪

利用啁啾光纤光栅的应变调谐特性，将色散补偿的啁啾光纤光栅斜贴于悬臂梁的侧面，通过应力实现啁啾量调整而改变其色散补偿量的大小，同时利用固定在同一悬臂梁的均匀布拉格光栅传感器，实现了闭环自动控制色散补偿量，研制出了一种新型的光纤光栅动态色散补偿仪。该色散补偿仪工作在1550nm波段，典型性能数据为：色散动态补偿范围-1000-1680ps／nm，插入损耗小于1．5dB，动态调谐步进响应时间小于50ms，基本上能满足10Gb／s光纤通信系统中色散动态补偿的要求。     

Design and optimization of photonic crystal fibers for broad-band dispersion compensation

Design of photonic crystal fibers (PCFs) for application of broad-band dispersion compensation is investigated by using an improved design model based on combination of a rigorous vector solver for modal properties and a scaling approach for dispersion characteristics. The newly designed PCF is shown to exhibit large normal dispersion up to -474.5 ps/nm/km, nearly five times of conventional dispersion compensating fibers, and compensate conventional single-mode fibers within /spl plusmn/0.05 ps/nm/km over a 236-nm wavelength range. Furthermore, the design model and methodology can be applied to design other dispersion-based devices such as dispersion flattened fibers and dispersion shifted fibers.     

基于FDTD方法的光子晶体光纤色散特性分析

基于电磁场时域有限差分法(FDTD)计算光子晶体光纤(PCF)的方法, 分析了运用该方法时需要注意的一些问题, 特别是关于晶格位置、晶格上各个电磁场分量的分布以及完全匹配层(PML)中在边界处的电磁场的处理。以此为理论依据分析了一种纯石英材料双层芯PCF, 对这种光纤的传输特性进行了详细的数值模拟。通过调整光纤的结构参数, 设计出大负色散值的宽带色散补偿光子晶体光纤(DCPCF)。数值模拟结果显示在1530～1565 nm波长范围内其色散值在-400和-600 ps/(km·nm)之间变化, 达到了具有相同有效模面积的普通色散补偿光纤(DCF)的5倍。在整个C波段可以有效补偿长度25倍以上的标准单模光纤(SMF), 其色散剩余量在±1.0 ps/nm·km以内。该种结构的PCF对于制作高增益和宽带色散补偿于一体的集中式光纤放大器具有十分重要的意义。     

宽带色散补偿模块的开发

文章从理论出发设计了一种色散补偿光纤波导结构,并制备出一种高性能的色散补偿光纤.测试结果表明:该色散补偿光纤在1 525～1 625 nm波长范围内具有较大负色散,1 545 nm波长的色散系数为-141 ps/(nm·km).采用该色散补偿光纤成功制备出宽带色散补偿模块.G.652光纤传输链路经过该色散补偿模块的补偿后,C波段的残余色散小于5.0 ps/nm,C波段色散斜率也实现了100%的补偿.     

40-Gb/s All-Optical Packet Switching With a Distributed-Feedback Laser as All-Optical Flip-Flop

All-optical flip-flops (AOFFs) have recently received increased attention as elements for all-optical packet-switched networks. In this letter, we use a single off-the-shelf distributed- feedback laser as AOFF to switch 40-Gb/s packets with a guard time as low as 150 ps.