Performance of All-optical WDM Network in Presence of Four-wave Mixing, Optical Amplifier Noise, and Wavelength Converter Noise

The article investigates the effect of four-wave mixing (FWM), amplified spontaneous emission (ASE) noise, and wavelength converter noise on the performance of WDM all-optical networks. Analysis for the evaluation of probability of error has been carried out (a) when only thermal and shot noise are present; (b) when thermal, shot, FWM, and ASE noise are present; and (c) when thermal, shot, FWM, ASE, and wavelength converter noise are present. Numerical results are presented in the graphical forms for the practical values of parameters.     

Nonlinear Codirectional Coupler Filter Used in WDM Networks

It is proposed a novel wavelength filter with a narrow bandwidth suitable for WDM networks, which is based upon nondegenerate four-wave mixing(NDFWM) process in the active region of a wavelength selective coupler. By separating the desired wave-mixing product on the basis of the transverse spatial mode of the electric field, a bandwidth (full width at half maximum, FWHM) of subangstrom for the filter is obtained. The selected wavelength can be tuned in the entire semiconductor gain bandwidth (～70 nm). A theoretical analysis for NDFWM effect in the filter is given. The numerical simulation has been done. The influences of configure parameters on the output efficiency, 3 dB bandwidth (FWHM) and frequency shift are discussed.     

A Novel All-optical Wavelength ConverterBased on Self-pump Four-wave Mixing

A novel scheme of all-optical wavelength converter(AOWC) based on dual pump four-wave mixing(DP-FWM) was demonstrated. To suppress the ASE noise of the semiconductor optical amplifier (SOA), one of the two pumps was generated interiorly from a loop laser constructed mainly by tunable optical filter and SOA. The theoretical model and some experimental results were presented.     

A Novel All-optical Wavelength Converter Based on Self-pump Four-wave Mixing

A novel scheme of all-optical wavelength converter(AOWC) based on dual pump four-wave mixing(DP-FWM) was demonstrated. To suppress the ASE noise of the semiconductor optical amplifier (SOA), one of the two pumps was generated interiorly from a loop laser constructed mainly by tunable optical filter and SOA. The theoretical model and some experimental results were presented.     

刻蚀改变InGaN/AlGaN应变多量子阱发光特性

为了分析干法刻蚀对应变多量子阱(SMQWs)发光特性的影响,采用感应耦合等离子体(ICP)刻蚀技术对金属有机物化学气相沉积(MOCVD)生长的InGaN/AIGaN应变多量子阱覆盖层表面刻蚀了约95 nm。通过光致发光(PL)特性表征发现,干法刻蚀后量子阱光致发光强度较未刻蚀量子阱光致发光强度提高了近3倍。干法刻蚀后,量子阱表面呈现高低起伏状形貌,粗糙度提高,出射光在起伏状粗糙形貌表面反复散射,从而逃逸概率增大,有助于光致发光强度增强。理论计算结果得出表面形貌变化引起的量子阱光致发光强度增强因子约为1．3倍。另外,由于所采用的感应耦合等离子体功率较小,刻蚀损伤深度几乎不会达到量子阱阱层,然而干法刻蚀过程中Ar离子隧穿到量子阱阱层内部可能形成新的发光中心,从而使量子阱的发光强度得到提高。     

A Novel Method for Wavelength Conversion with Dual-pump Four-wave Mixing in a Semiconductor Optical Amplifier

Using a semiconductor-fiber ring laser, a novel method for the all optical wavelength conversion based on dual-pump four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) is demonstrated. For the input signal with different wavelengths, only one external pump is needed. This scheme can simplify the dual-pump FWM in SOA and has nearly constant conversion efficiency and signal-to-noise ratio (SNR) over 50nm range of wavelength shifts.     

Tunable Filters with Narrow-Band in Bulk SLA for DWDM Networks

The filter mechanism of a tunable filter with narrow-band in bulk semiconductor laser amplifier (SLA) is analyzed, which is suitable for dense wavelength division multiplexed (DWDM) optical fiber networks. The wavelength selectivity of the filter is derived from nondegenerate four-wave mixing (NDFWM) in semiconductor gain medium. It uses the direction of propagation to separate the desired wave-mixing product from the other light beams. The filters are shown to have very narrow passbands (subangstrom bandwidth) tunable over the entire semiconductor gain bandwidth. We gave the theoretical analysis of NDFWM effect in semiconductor gain medium is given and a set of nonlinear coupled wave equations is deduced, which are processed efficiently by Runge-Kutta method in numerical simulation. The influences of various structural parameters of the filter on the output bandwidth and efficiency were also discussed.     

Quantum interferences in four-wave mixing processes inside a cavity driven by quantized fields

Interferences in the quantum fluctuations of the output fields are demonstrated in four-wave mixing processes inside a cavity,which is driven by two quantized fields at the signal and the idler frequencies.These interferences depend on the phase fluctuations of the input fields and induce mode splitting in the transmission spectra.     

Coherent Interband and Intersubband Dynamics in Terahertz-Driven GaAs Quantum Wells

We theoretically investigate the optical absorption spectra and charge density by subjecting a GaAs quantum well to both an intense terahertz (THz)-frequency driving field and an optical pulse within the theory of density matrix. In presence of a strong THz field, the optical transitions in quantum well subbands are altered by the THz field. The alteration has a direct impact on the optical absorption and the charge density. The excitonic peak splitting and THz optical sideband in the absorption spectra show up when changing the THz field intensity and/or frequency. The Autler-Towns splitting is a result from the THz nonlinear dynamics of confined excitons. On the other hand, the carrier charge density is created as wave packets formed by coherent superposition of several eigenstates. The charge density exhibitsquantum beats for short pulses and/or wider wells and is modulated by the THz field.     

生长温度和结构参数对InGaAs／GaAs量子阱光学特性的影响

研究了不同生长温度下制备的In0.15Ga0.85As/GaAs应变量子阱的PL谱,结果表明,生长温度越高,In偏析和In-Ga互混越严重,同时,导致更多的In脱附,PL谱发光峰蓝移。对不同In含量的和不同InGaAs厚度的InGaAs/GaAs量子阱进行PL谱测试,分析表明In含量<0.2,生长温度低于560℃时,In含量和InGaAs层量子阱的厚度对In偏析、脱附和In-Ga互混基本没有影响。     

基于半导体光放大器四波混频效应的多种调制格式的波长转换实验

实验报道了利用半导体光放大器(SOA)的四波混频(FWM)效应实现多种码型的波长转换.其中对于非归零(NRZ)信号实现了从单信道到三信道的多波长转换.调制速率从10 Gb/s到40 Gb/s均实现多波长转换.对于归零(RZ)信号分别实现了20 Gb/s和40 Gb/s的RZ格式的波长转换和40 Gb/s的载波抑制归零(CSRZ)格式的波长转换,利用光纤布拉格光栅(FBG)作为带陷滤波器消除共轭光和抽运光之间的串扰.对于非归零差分相移键控(NRZ_DPSK)信号分别实现了20 Gb/s和40 Gb/s的波长转换,利用实验室自制的光纤延时干涉仪进行NRZ-DPSK信号的解调.基于FWM效应的转换光的输出消光比大于7 dB,转换后消光比退化约为3 dB.     

Experimental Study of Single- and Multicast Wavelength Conversion at 10 Gb/s Exploiting Four-Wave Mixing in Highly Non-Linear-Photonic Crystal Fiber with Widely Tunable Conversion Range

Abstract

Optical networking applications require the use of all-optical wavelength converters with input and output wavelength tenability as well as large numbers of multicasting channels. This article demonstrates the single-to-multiple wavelength conversion via multiple four-wave mixings between a 10-Gbit/s return-to-zero signal and several continuous waves co-propagating in a dispersion-flattened highly non-linear photonic crystal fiber. For single-to-single channel wavelength conversion, a wide conversion range of 31 nm is achieved with the optimal conversion efficiency of ?21.4 dB. By employing several continuous-wave probe lights, tunable single-to-dual and single-to-triple channel wavelength conversions are experimentally demonstrated, respectively. Moreover, the dynamic characteristics of the designed wavelength converter are studied under the conditions of variable input powers, polarization mismatch, and different lengths of the highly non-linear-photonic crystal fiber. The system is transparent to both bit rate and modulation format. This is very useful for engineering design and applications of optical-fiber-based wavelength converters in future ultra-high-speed photonic networks.     

Nonlinear Codirectional Coupler Filter Used in WDM Networks

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｗａｖｅｌｅｎｇｔｈｄｉｖｉｓｉｏｎｍｕｌｔｉｐｌｅｘｉｎｇ(ＷＤＭ)ｉｓａｖｅｒｙａｔｔｒａｃｔｉｖｅｓｃｈｅｍｅｔｏｉｎｃｒｅａｓｅｔｈｅｃａｐａｃｉｔｙｏｆｆｉｂｅｒｏｐｔｉｃｃｏｍｍｕｎｉｃａｔｉｏｎｓｙｓｔｅｍ?..     

Ultraslow Propagation of Entangled State via Four-Wave Mixing in a Coupled Double Quantum Well

An analytical method based on four-wave mixing （FWM） is here developed to study the generation of entangled state in an asymmetric semiconductor double quantum well structure. It is found that the maximally entangled state of two beams （the probe and four-wave mixing beams） can be achieved in an appropriate condition. Moreover, we also show that the two entangled beams propagate with ultraslow group velocity in the semiconductor medium. This investigation can be used for achieving the entangled beams in the semiconductor solid-state medium, which is much more practical than that in an atomic medium because of its flexible design and the wide adjustable parameters.     

基于半导体光放大器和整形滤波器的40 Gb/s的归零正码波长变换研究

理论上分析了通过整形滤波器方法实现正码波长变换的原理,并讨论了滤波器带宽及偏移方向对正码脉冲效果的影响,解释了目前实验报道中多采用蓝移滤波方案的技术根由。在实验上利用半导体光放大器(SOA)和通带滤波器完成了40Gb/s的归零码波长变换实验,验证了理论分析的结构,证明了整形滤波器加半导体光放大器的方案可以实现正码的波长变换。这对于简化网络的设计,提高信号传输质量都有重要的意义。     

波分复用薄膜带通滤光片的中心波长温度稳定性

讨论了影响波分复用薄膜滤光片中心波长漂移的因素 ,着重分析了滤光片的温度稳定性。根据实验结果 ,借助于高桥模型 ,分析计算了滤光片的折射率温度系数、线膨胀系数和泊松比以及它们对温度漂移的影响。得到了Ta2 O5/SiO2 滤光片薄膜的折射率温度系数、线膨胀系数、泊松比分别为 1× 10 -5℃-1,5× 10 -7℃-1和 0 12 ,指出了这三个参量是影响温度稳定性最重要的因素 ,特别是薄膜的折射率温度系数。对特定的基板热膨胀系数 ,通过调节滤光片的干涉级次和间隔层材料 ,可望得到零温度漂移的稳定滤光片。     

极化子效应对ZnS/CdSe柱型核壳量子点简并四波混频过程的影响

理论计算了带有极化子效应的ZnS/CdSe柱型核壳结构量子点简并四波混频的三阶极化率.在有效质量近似下,采用无限深势阱模型,导出了带有极化子效应的柱型量子点的三阶非线性光学极化率的解析表达式,解三维薛定谔方程得到电子的本征能量和波函数.分析了电子-LO声子和电子-IO声子相互作用对ZnS/CdSe核壳结构量子点简并四波混频的三阶极化率的影响.结果表明,当量子点尺寸一定时,带有极化子效应的χ(3)DFWM比没有极化子时的三阶极化率提高了近3个数量级,并且电子-LO声子的影响比电子-IO声子的影响大得多;当固定核壳量子点的阱宽而内外半径发生变化时,χ(3)DFWM的峰值随之变化,而且极化子效应影响的大小也随之发生变化.     

利用光纤中自发四波混频产生纠缠光子的实验装置

基于三阶非线性Kerr效应在光纤中产生非线性现象的理论,利用零色散位移光纤中的自发四波混频通过两种实验装置产生了纠缠光子：一种是采用脉冲光抽运由光纤构成的Sagnac光纤环;另一种是采用脉冲光直接抽运一段光纤.通过对不同装置下实验结果的比较,总结了产生高纯度纠缠光子所需的实验条件,并指出了两种装置各自的优缺点.这为研制适用于量子通信的全光纤纠缠光源和单光子源奠定了基础.关键词：纠缠光子光纤四波混频量子通信     

Wavelength Conversion in WDM All-Optical Networks and Analytical Models

This paper gives a brief introduction to the various wavelength conversion techniques. In order to explain the applications and benefits of the wavelength conversion techniques in WDM all-optical networks, several analytical models are studied.     

Wavelength conversion in optical transport networks

The introduction of optical technology in the path layer of a transport network is analyzed; in particular, the impact of all-optical wavelength conversion is examined. Two basic optical cross-connect schemes based on space switching and on wave-length switching, respectively, and two types of wavelength converters are considered. The wavelength converters are, respectively, based on four-wave miring (FWM) in semiconductor optical amplifiers (SOAs) and on cross-phase modulation (XPM) obtained by two SOAs put in an interferometric configuration. An analysis of transmission performances of optical transport networks employing both types of wavelength conversion and both the node architectures is reported. The performances are evaluated by means of a system modeling that facilitates considering physical phenomena occurring during transmission and all the important transmission impairments. The analysis reveals that both the types of converters can be employed with different features and limitations, according to the considered network and switching architecture.