All-Optical Format Conversion From RZ to NRZ Utilizing Microfiber Resonator

We propose an all-optical return-to-zero (RZ) to nonreturn-to-zero (NRZ) format converter utilizing a microfiber knot resonator and an optical bandpass filter. The operation principle is numerically simulated and analyzed. By adjusting the diameter of microfiber knot, the format conversion from RZ to NRZ is successfully demonstrated at different bit rates. The bit-error-rate measurements show the good performance of the proposed format converter.      

All-Optical Format Conversion From NRZ to BPSK Using a Single Saturated SOA

All-optical format conversion from nonreturn-to-zero (NRZ) to binary phase-shift keying format is experimentally demonstrated at 8 Gb/s using a single semiconductor optical amplifier (SOA). The conversion is based on the gain and phase modulations of the SOA on an input NRZ signal of finite extinction ratio     

20-Gb/s All-Optical Format Conversions From RZ Signals With Different Duty Cycles to NRZ Signals

An all-fiber delay interferometer and narrowband filter based an all-optical format conversion scheme, which can convert return-to-zero (RZ) signals with variable duty cycles to nonreturn-to-zero signals, is proposed and demonstrated. The passive converter is independent of wavelength and input power. The operation principle is analyzed and simulated. Experimental results of 20-Gb/s RZ signals with three different duty cycles accord well with the simulation results. The bit-error-rate measurements show the good performance of the proposed scheme. The conversion performances of different wavelengths and parameters are also discussed.     

40-Gb/s Multichannel NRZ to CSRZ Format Conversion Using an SOA

An all-optical converter from nonreturn-to-zero (NRZ) to carrier-suppressed return-to-zero modulation format is proposed and experimentally demonstrated. The converter is based on cross gain and phase modulation in a semiconductor optical amplifier. Single- and multichannel operation is experimentally assessed at 40 Gb/s. In single-channel operation, the required optical signal-to-noise ratio for a bit-error rate of $10^{-9}$ is improved by 3 dB, in comparison to the input NRZ. Considering multichannel operation with two and four channels, this improvement decreases by only 0.6 and 1.5 dB, respectively.      

On-the-Fly All-Optical Contention Resolution for NRZ and RZ Data Formats Using Packet Envelope Detection and Integrated Optical Switches

We present a packet-by-packet contention resolution scheme that combines packet detection, optical space switching, and wavelength conversion performed in the optical domain by integrated optical switches. The packet detection circuit provides the control signals required to deflect and wavelength-convert the contending packets so that all the packets are forwarded to the same output without any collision or packet droppings. We demonstrate the compatibility of the scheme with both nonreturn-to-zero (NRZ) and return-to-zero (RZ) modulation formats by recording error-free operation for 10-Gb/s NRZ and 40-Gb/s RZ packet-mode traffic     

利用SOA和OBPF的40Gb/s RZ到NRZ全光码型变换

全光码型转换技术是实现未来全光网络的关键技术之一,为此提出了一种利用半导体光放大器（SOA）和光带通滤波器（OBPF）的归零（RZ）码到非归零（NRZ）码的信号转换方案。利用通信软件数值模拟了基于40 Gb/s的码型转换,仿真实现了稳定的不同占空比的RZ码到NRZ码的码型转换以及波长转换。     

All-Optical Analog-to-Digital Conversion Using Split-and-Delay Technique

We propose a simplified configuration of all-optical analog-to-digital (A/D) conversion using nonlinear optical loop mirrors (NOLMs). While the conventional scheme of such all-optical A/D conversion requires encoders and threshold, for -bit resolution, the proposed configuration realizes an -bit resolution only using a single encoder and threshold, based on a split-and-delay technique, in which the encoder and the threshold operate more than times as fast as the sampling speed. After discussing detailed design issues of the NOLM-based encoder with particular emphasis on the so-called counterpropagating effects, all-optical 3-bit A/D conversion at 10 GS/s is experimentally demonstrated using the proposed configuration.     

Optical Reshaping of 40-Gb/s NRZ and RZ Signals Without Wavelength Conversion

We experimentally demonstrate a scheme for all-optical reshaping at 40 Gb/s that is wavelength preserving and transparent to both nonreturn-to-zero and return-to-zero on-off keying signals. Eye-diagram reshaping is confirmed by means of bit-error rate versus threshold measurements on both modulation formats. The scheme is based on cross-gain compression in an semiconductor optical amplifier (SOA) and uses two SOAs that are not in interferometric configuration. Due to its working principle, this method is polarization-independent and suitable, in principle, for higher bit rates.     

双通道全光NRZ/RZ格式转换器设计

提出了一种双通道全光非归零码/归零码调制格式转换的方案.该方案中,非归零码信号与同步的时钟抽取光共同注入到高性能非线性光纤中,由高性能非线性光纤构成的参量放大器把非归零码信号转换为归零码信号,同时不改变信号光的波长.实验论证了10Gb/s非归零码双通道的码型转换器.转换后的归零码信号的光信噪比略低于输入光信噪比,其脉冲...     

RZ码和NRZ码的偏振模色散自适应补偿特性比较

建立了自适应偏振模色散补偿系统,利用偏振度作为反馈信号,对40 Gb/s的RZ和NRZ码分别进行了PMD补偿的数值模拟,结果显示,采用DOP作反馈信号、用二段补偿器和三段补偿器对二种码型的PMD补偿均是有效的.但由于高阶PMD的影响对NRZ码的补偿效果要优于RZ码,特别是存在偏振相关色散的影响时,对RZ码的补偿的影响在明显大于NRZ码,这说明,对于RZ码补偿偏振相关色散是必要的.     

注入锁定半导体激光器全光波长转换技术

波长转换器是光通信网络中的一个重要器件。而除半导体光放大器（SOA）外，半导体激光器也是进行波长变换的一种很好选择。基于半导体激光器的注入锁定波长变换技术具有转换带宽较大、啁啾小、消光比特性好、结构简单、成本低廉等诸多优点。将探测光与信号光同步注入法布里-珀罗（F-P）半导体激光器，可以通过信号光功率的变化控制激光器锁模与失锁，导致腔内纵模变化，探测光随之被共振放大或减弱，从而将信息由信号光转换到探测光频率上。从静态实验入手，对半导体激光器的注入锁定现象及光信号控制法布里-珀罗纵模移动等问题分别进行了研究。分析了动态转换激光器工作点的选取问题，在动态实验中实现了较宽范围的正相与反相波长转换，转换速率达到了10Gb／s。     

Four WDM channel NRZ to RZ format conversion using a singlesemiconductor laser amplifier

Multiwavelength channel NRZ to RZ format conversion using a single semiconductor laser amplifier is proposed and experimentally demonstrated. Bit-error-rate measurement of four 10 Gbit/s converted RZ signal channels has confirmed that no noticeable error floor existed     

Dynamic Switching Response of Semiconductor Ring Lasers to NRZ and RZ Injection Signals

Dynamic response of semiconductor ring lasers (SRLs) to external optical injection with nonreturn-to-zero (NRZ) and return-to-zero (RZ) waveforms is investigated using a model including linear and nonlinear mode coupling. The switching characteristics are simulated under various device sizes, injection power levels, and frequency detuning. For NRZ, the switching time reduces with decreasing SRL radius, which has a reasonable agreement with the current experimental results. It is also demonstrated that RZ pulse with duration of several picoseconds can reliably switch 6-mum radius SRL over a detuning range of more than 100 GHz, with the end state self-sustained after switching.     

Comparison of RZ Versus NRZ Pulse Shapes for Optical Duobinary Transmission

This paper presents an experimental study and comparison of return-to-zero (RZ) versus nonreturn-to-zero (NRZ) pulse shapes for optical duobinary systems. Surprisingly, and contrary to the case of on-off keying, we find the NRZ pulse shape to be superior, compared with RZ, for duobinary transmission in all the cases that were studied, including systems that are limited by amplified-spontaneous-emission noise, fiber chromatic dispersion, and self-phase modulation.     

All-Optical AGC of EDFA Based on SOA

We propose a novel all-optical method for automatic gain controlling of transients in erbium-doped fiber amplifiers (EDFAs) using a semiconductor optical amplifier (SOA)-based negative feedback loop for adjusting the EDFA pump power. A dynamic model for the EDFA-SOA system is developed and used for numerical simulation of the transient behavior of this system. Simulation results for EDFA-SOA performance of the proposed method are presented. It is shown that using this method, it is possible to significantly reduce the transient effects, without producing power oscillations on the surviving channels     

Analytical Solution for SOA-Based All-Optical Wavelength Conversion Using Transient Cross-Phase Modulation

All-optical wavelength conversion (WC) based on transient cross-phase modulation (T-XPM) of semiconductor optical amplifier (SOAs) is a promising approach to accelerate the gain recovery of SOAs. An analytical solution is deduced to explain the polarity variation of WC based on T-XPM of SOAs from the viewpoint of the impulse response functions. We conclude that both inverted and noninverted WCs can be realized when the central wavelength of the optical bandpass filter is either blue-shifted or red-shifted with respect to the wavelength of the probe signal. We are able to validate the formula against our experimental results recently published     

Tunable All-Optical Wavelength Conversion of 160-Gb/s RZ Optical Signals by Cascaded SFG-DFG Generation in PPLN Waveguide

We report, for the first time, tunable all-optical wavelength conversion of 160-Gb/s return-to-zero (RZ) optical signals based on cascaded sum- and difference-frequency generation in a periodically poled LiNbO₃ waveguide. The distorted signals due to limited phase-matching bandwidth during conversion were compensated by spectral reshaping. We achieved error-free tunable wavelength conversion with a bit-error rate of less than 10^-9 for 160-Gb/s RZ signals in a 23-nm tuning range over the C-band     

Relationship of Q penalty to eye-closure penalty for NRZ and RZ signals with signal-dependent noise

The relationship between Q penalty (QP) and eye-closure penalty (ECP) is examined for distorted signals in the presence of signal-dependent noise. A simple model is developed to describe the behavior of return-to-zero (RZ) modulation formats and is compared with a model for nonreturn-to-zero (NRZ) formats. The accuracy of the analysis is investigated with extensive simulations, and the numerical results from analysis and simulation are found to be in generally good agreement. Experimental measurements of distortion caused by uncompensated dispersion also show agreement with the simulation results and model predictions. The simplified models allow a means to budget QPs from distortion effects in a straightforward manner during network design for different modulation formats. The analysis predicts a smaller Q penalty as a function of ECP for RZ modulation formats in comparison with NRZ and smaller relative penalties for RZ formats with narrower pulsewidths.     

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。     

NRZ versus RZ in 10-40-Gb/s dispersion-managed WDM transmissionsystems

We compare nonreturn-to-zero (NRZ) with return-to-zero (RZ) modulation format for wavelength-division-multiplexed systems operating at data rates up to 40 Gb/s. We find that in 10-40-Gb/s dispersion-managed systems (single-mode fiber alternating with dispersion compensating fiber), NRZ is more adversely affected by nonlinearities, whereas RZ is more affected by dispersion. In this dispersion map, 10- and 20-Gb/s systems operate better using RZ modulation format because nonlinearity dominates. However, 40-Gb/s systems favor the usage of NRZ because dispersion becomes the key limiting factor at 40 Gb/s