Semiconductor optical amplifier used as regenerator for degraded differential phase-shift keying signals

Phase and amplitude regeneration are necessary for degraded differential phase-shift keying communication systems.This paper proposes a regenerator based on semiconductor optical amplifier for differential phase-shift keying signals.The key regeneration mechanism is theoretically analysed.The effectiveness of semiconductor optical amplifier based regenerator is demonstrated by comparing the bit error rate and eye diagrams before and after regeneration for 40-Gbit/s differential phase-shift keying 1080-km transmission systems.The results show that regeneration effects are very well.Bit error rate is less than 10 12 with the regenerator.     

Dispersion compensation by a tunable all-optical signal regenerator

The effect of dispersion on an NRZ signal in 120 km of SMF28 fiber is partially compensated by a tunable all-optical signal regenerator (TASR). The TASR is comprised of a semiconductor optical amplifier incorporated in an asymmetric Sagnac loop. It is shown theoretically that the primary mechanism underlying dispersion compensation in the TASR relies on its ability to control the optical phase of the carrier. Our results are supported by numerical simulations and experimental results.     

The suppression of optical regenerator employing semiconductor laser amplifier loop mirror on the additive noise

In this paper, transmission properties of the regenerator employing a semiconductor laser amplifier loop mirror (SLALOM) are discussed. The ability of the regenerator to suppress the additive noise in the input data train is calculated. It’s shown that the regenerator can greatly suppress noise in communication system and improve their communication capacity by choosing suitable semiconductor laser amplifier(SLA) and the power of injected continuous wave.     

一种测量GaAs-GaAlAs行波激光放大器增益特性的实验方法

本文报导了一种测量光耦合效率η的新实验方法。这个方法是建立于p-n结短路光电流原理上的。本文推导出适合于行波激光放大器的光耦合效率的公式。短路光电流用一检流计测量,利用公式获得光耦合效率的实验值。利用实验所测光耦合效率,测量了行波激光放大器的增益随注入电流变化的规律,其结果和实验符合。另外本文还介绍了在脉冲注入电流条件下测行波半导体激光放大器增益的实验方法。     

Extinction ratio improvement by an all-optical signal regenerator with a semiconductor optical amplifier and a Sagnac loop

In this paper, we present the operation of an all-optical signal regenerator (AOSR). The AOSR is based on a semiconductor optical amplifier (SOA), which is incorporated in an asymmetric Sagnac loop (ASL). We show experimentally that the AOSR is capable of improving the input signal extinction ratio (ER) considerably. We present a theoretical model, which explains this improvement, and we illustrate a qualitatively similar behavior with a simulation.     

A Multi-Section Quantum-Dot Semiconductor Optical Amplifier for Ultrabroad-Band Gain-Flattened Low-Noise Amplification

We propose an ultrabroad-band 1R regenerator utilizing a multi-section quantum-dot semiconductor optical amplifier.Due to the reduced electron states, quantum dot is beneficial in broadening the gain spectrum and lowering the noise figure. Combining this with a multi-section structure drastically improves the gain equality among the different bound states, leading to an increase in the maximum output power and an improvement of the noise figure.     

40 Gb/s信号全光3R再生实验

提出一种新型40 Gb/s全光3R再生器方案。采用高精细度法布里-珀罗滤波器进行时钟提取。时钟提取前,通过高稳定光源对输入信号光波长变换实现信号光波长和法布里-珀罗滤波器梳状窗口对准;时钟提取后,接半导体光放大器(SOA)进一步消除时钟信号噪声。全光判决中,采用双半导体光放大器串联增大非线性性能,提高了判决门的响应速度。判决输出接窄带滤波器去除脉冲啁啾拖尾,减小码型效应。实验中,恶化40 Gb/s光脉冲信号通过全光3R再生器可以得到再生脉冲。输入恶化信号时间抖动大于5 ps,脉冲宽度大于16 ps,再生得到的信号时间抖动小于1.5 ps。再生信号相对于输入信噪比改善14 dB。连续稳定工作记录大于15 h。通过实验验证,这种全光3R再生器方案成功地实现了40 Gb/s信号的再生。     

All-optical phase and amplitude regeneration of return-to-zero differential phase shift keying data

We report a novel implementation of an all-optical rephasing, reshaping, and reamplification differential phase shift keying (DPSK) regenerator. The rephasing is based on converting phase noise into amplitude noise by using an interferometric configuration and then eliminating the amplitude noise by using a semiconductor optical amplifier (SOA). The reshaping is performed using gain competition and gain compression in a saturated SOA. The scheme was tested using 10Gbit/s, 2(23)-1 pseudorandom bit sequence return-to-zero DPSK data. The measurement shows removal of the degraded data error floor with a 6 order-of-magnitude improvement in bit-error rate. The measured negative power penalty is about 4dB. Mathematical analysis shows a reduction in DPSK phase-noise power by half.     

All optical alternative approach of conducting NAND and NOR logic gates with phase encoding principle

All optical logic gates are the most important building blocks for conducting all optical digital and analog signal processing and computing. It has several uses in the high speed communication system. In last few years various non-linear properties of semiconductor optical amplifier have been utilized for realization of all optical logic gates exploiting different type's optical modulations. In such connection optical phase encoding technique drew more attention in last few years as it shows higher receiver sensitivity and extended tolerance limit in long-haul fiber transmission systems. In this communication the authors have proposed an alternative approach for conducting all optical logic gates with phase encoded inputs by the exploitation of the four wave mixing (FWM) property in semiconductor optical amplifier (SOA).     

An all optical method of implementing a wavelength encoded simultaneous binary full adder-full subtractor unit exploiting nonlinear polarization rotation in semiconductor optical amplifier

Full adders and full subtractors are the basic circuit elements of any digital data processor in electronics as well as in the all optical domain. Again the wavelength dependent encoding/decoding techniques have established itself as a very promising and efficient tool having some inherent and unique advantages relative to the other well known intensity or polarization or phase dependent optical data encoding mechanisms. In this communication, the authors therefore propose a new scheme of implementing a wavelength encoded complete binary full adder-full subtractor unit in the all optical domain using the wavelength conversion by the nonlinear polarization rotation in a single semiconductor optical amplifier. The interacting signals are counter propagating in the semiconductor optical amplifier and hence can be set at the same wavelength. To realize the binary logic wavelength dependent encoding/decoding mechanism is exploited in our proposed scheme of full adder-full subtractor unit. Also the optical add/drop multiplexing employing the special filtering property of the semiconductor optical amplifier is utilized for the designing of the all optical system.     

An integrated circuit subsystem of quantum dot semiconductor optical amplifier coupled with electro-absorption modulator and its application in wavelength conversion

A multi-section circuit model of quantum dot semiconductor optical amplifier is proposed by employing the standard rate equations. Using this model, gain spectra, saturation property, and occupation probability of quantum dot semiconductor optical amplifier are analyzed by PSPICE simulation. An integrated circuit subsystem of quantum dot semiconductor optical amplifier cascaded with electro-absorption modulator is also derived to investigate the patterning effect reduction in wavelength conversion.     

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

Properties of four-wave mixing (FWM) in the semiconductor laser amplifier are studied experimentally in this paper. The optical phase conjugation of the mixing wave is applied to compensate the chromatic dispersion of transmission fiber. It is presented experimental results of the transmission of short optical pulses with 12-ps width over 204 km standard single mode fiber. The results confirm that mid-span spectral inversion (MSSI) employing FWM in a semiconductor laser amplifier is one of potential dispersion compensation techniques for optical transmission over standard single mode fiber with bit rate beyond 40Gb/s.     

Fiber optic loop buffer switch incorporating 3R regeneration

In this paper, an all-optical regenerator based, photonic packet switch architecture, which consists of fiber loop for the storage of the contending packets, is proposed. In the loop buffer, the available buffer space may not be fully utilized due to the re-circulation limit (maximum number of re-circulations that data can take before it can be correctly received at the output). The re-circulation limit arises due to the accumulated ASE (amplified spontaneous emission) noise of the optical amplifier and crosstalk of the optical components. This limit can be counteract by placing a pool of regenerators inside the buffer, which regenerates the signal after some fixed number of re-circulations. As optical regenerators are costly devices, hence they should be placed optimally in the buffer. To do so, in this paper an expression is presented to evaluate the minimum number of required regenerators, to be placed optimally in the buffer for different buffer configurations (B) and re-circulation limits (K), such that full buffer capacity can be utilized without any re-circulation constraints. The simulation results in terms of packet loss probability are presented by considering the detrimental effect of re-circulation limits. Finally, advantages gain due to the regenerator placement inside the buffer are shown.     

A method of developing wavelength encoded all-optical S–R flip-flop by the uses of semiconductor optical amplifier based Mach–Zenhder interferometer and phase conjugation system

A scheme for a high-speed wavelength encoded all-optical S–R flip-flop (or a digital memory cell for storing of optical bits) based on wavelength conversion (MZI) in semiconductor optical amplifier (SOA) and phase conjugation system (PCS) is proposed. The switching action of semiconductor optical amplifier (SOA) does not give too high operational speed because of electrical pumping power. But optical phase conjugation mechanism gives us ultrahigh operational speed. So, joint use of them gives rise to a more high speed system comparatively to only SOA based switches. Here two logic states of the whole system is encoded by two wavelengths as well as frequencies, since the information in the bit is unaffected throughout the communication not having regard to the loss of light energy due to reflection, refraction polarization, etc.     

锥形脊结构半导体光放大器的有限元分析

为提高半导体光放大器与单模光纤耦合效率，建立了半导体放大器的锥形脊结构模型。在该模型下利用有限元数值模拟方法分析，计算了波导区折射率、锥尖宽度、条形波导尺寸、渐变折射率波导层对锥形脊结构模式扩展的影响。通过完善锥形脊结构参量的设计，获得了锥形脊结构半导体光放大器与单模光纤95％的耦合效率。     

直接扣除法测量半导体光放大器频率响应

在光电子器件散射参量定义的基础上建立了基于直接扣除法的半导体光放大器频率响应测量系统,测量中通过扣除激光器和探测器系统的频率响应,得到放大器固有的频率响应。对InGaAsP体材料行波腔半导体光放大器样品进行了测量,得到了放大器在不同注入光功率和不同偏置电流下的频率响应曲线。这些曲线很好地反应了半导体光放大器的增益饱和和噪声特性,进一步分析发现半导体光放大器对低频调制信号的放大能力弱于对高频信号的放大能力,分析认为其原因在于半导体光放大器的载流子寿命有限导致低频信号长时间消耗载流子时,载流子数量无法及时恢复,从而使得增益降低。     

有源光纤环等效时间脉冲复制研究

对利用半导体光放大器有源光纤环为光等效时间采样提供低失真脉冲序列的方法进行了研究。分析了提高复制精度的辅助直流光非线性增益抑制方法,并给出基于递推方式,可进一步提高采样精度的后处理算法。通过实验验证了辅助直流光注入对复制器非线性增益的抑制作用;以及在不充分辅助直流光注入条件下,利用后处理算法抑制非线性误差的效果。结果显示利用半导体光放大器有源光纤环结合后处理算法可以有效地为光等效时间采样提供特性一致、误差可处理的时序脉冲序列。     

All-optical sampling exploiting nonlinear polarization rotation in a single semiconductor optical amplifier

An all-optical sampling scheme using a single semiconductor optical amplifier is proposed for analog signal processing. The analog optical signal is sampled by the probe pulse train through the nonlinear polarization rotation arising in the semiconductor optical amplifier. Conversion efficiency and total harmonic distortion are presented to evaluate the sampling linearity. In the experiment, 40 GSa/s all-optical sampling for 2.5 GHz analog optical signal is successfully demonstrated with commercially available fiber-pigtailed components. The results show that the fundamental conversion efficiency and the total harmonic distortion are 1.35 and 2.01% at the operating power of 5 mW, respectively. The proposed all-optical sampling requires only one semiconductor optical amplifier and has low power consumption, which is simple and has potential for photonic integration.     

Loss-coupled distributed-feedback lasers with amplified optical feedback for optical microwave generation

Multisection semiconductor lasers for optical microwave generation have been fabricated that consist of a loss-coupled distributed feedback (LC-DFB), a phase control, and an amplifier section. High-frequency self-pulsations are generated according to the concept of a single-mode laser with short optical feedback. The effect of the optical feedback via the phase control and the amplifier section on the self-pulsation is apparently shown as a result of the superior single-mode characteristic of the LC-DFB section. Continuous frequency tuning is achieved in the range of 17-35 GHz.