Absorptive nonlinearity in Er-doped optical fiber

Optical absorptive nonlinearity in Er-doped optical fiber has been discussed and measured at the window wavelength 1.55 μm for optical communications firstly. It is proposed that the mechanism of this absorptive nonlinearity is the induced absorption. The first order nonlinear absorptive coefficient and the imaginary part and the complex value of the third-order susceptibility at that wavelength are obtained from the measured absorptive nonlinearity. Foundation item: Supported by the National Natural Science Foundation of China (69487007) Biography: Song Qian (1937-), female, Professor. Research direction: nonlinear optics and all-optical communications.     

Er-doped fiber optical bistability without cavity

The observation of increasing absorption nonlinearity and bistability without cavity in Er-doped fiber is reported. The operation power is low (submilliwatts). The operation mechanism is analyzed. Supported by the National Natural Science Fundiation of China Zhang Yuancheng: born in Aug. 1938. Professor     

Nonlinear optical fiber resonator: Optical fiber bistability

The linear and nonlinear charecteristics of verious optical fiber loop resonators have been processed uniformly using transmission matrix method. It is pointed that in nonlinear operation condition each of those optical fiber loop resonators may be used to make an all-optical fiber bistability device. The configuration, charecterictics and threshold of verious Er-doped fiber loop bistability devices have been calculated, analysised and compared, and the design principle of those devices has been given. Supported by the National Natural Science Fundation of China Zhang Yuancheng: born in Aug. 1938, Professor     

E r 3+ -doped fiber optical bistability by Ar+-laser

Under The nonlinear optics condition the all-fiber optical bistability operation has been realized in an all-fiber resonator consisted of Er-doped fiber and optical fiber couplers. The experimental bistability threshold is consistent with the theory. Supported by National Natural Science Foundation of China Song Qian: born in Aug. 1937. associate professor     

光纤孤立子与光孤子通信

光纤的一个重要特征：线性和非线性效应，如群速度色散效应和Kerr非线性效应。首先介绍了光孤子的概念、历史的研究，然后讨论了单模光纤中光孤子形成的物理机制，比较了光孤子通信和光纤通信的优缺点，最后探讨了孤子间相互作用对光孤子通信系统的影响。     

光纤光栅及电色散补偿技术在光纤通信中的应用

制约光纤通信最关键的因素是光纤的色散和非线性效应,采用光域和电域相结合的补偿技术,即在传输链路中采用光纤光栅补偿技术,在接收端采用电色散补偿技术,成功补偿了10GB／sNRZ信号系统中1270kmG．652光纤的色散．在入纤光功率较高的情况下,光电补偿系统抵抗非线性作用的能力明显优于全光补偿系统,同时能保持较高的系统Q值,有利于实现对现有光纤通信系统的升级和扩容．     

Optical fiber grating bistability

It is proposed that a segment of Er-doped fiber with a couple of fiber gratings on the ends may be used as a novel optical bistability device with low power and high speed. Operation and bistability threshold of device are analysed in accordance with the distributed feedback couple-mode theory and the nonlinear characteristic of Er-doped fiber. It is shown that a nanoseconds microwatts bistable operation of a centimeter device is realizable under nowaday technological condition. Supported by the National Natural Science Foundation of China Zhang Yuancheng: born in Aug. 1938. Professor     

光纤色散对波分复用系统的影响

分析了光纤色散对波分复用系统的影响，讨论了在有初始频率啁啾的脉冲、非线性效应、激光器的相位调制噪声时光纤色散对波分复用系统的影响，并分析偏振模色散对系统性能的限制。     

Digital optical signal amplifier using an Er-doped fiber optical bistable device

The principle and charecteristics of verious digital optical signal amplifiers using Er-doped fiber optical bistability devices have been discussed. Optical signal gain and its variation with the parameters of the devices with constant or pulse optical bias have been calculated, and the design principle of those devices has been given. Supported by the National Natural Science Fundation of China Zhang Yuancheng: born in Aug. 1938, Professor     

1.55 μm wavelength operation of E r 3+ -doped optical fiber bistability

An all-optical all-fiber optical bistability operation has been realized in an all-fiber cavity consisted with Er-doped fiber and optical fiber-loop miroors. The experimental bistability threshold is consistent with the theory. Foundation item: Supported by the National Natural Science Foundation of China (69487007) Biography: Song Qian (1937-), female, Professor. Research direction: nonlinear optics and all-optical communication.     

Fiber nonlinearity mitigation by improved zero-interpolation method in coherent optical OFDM systems

An improved zero-interpolation method with signal clipping to improve fiber nonlinearity tolerance in the long-haul coherent optical orthogonal frequency division multiplexing system (CO-OFDM) is presented. The new technique is implemented by interpolating zero subcarriers and selecting the odd subcarriers to carry data and clipping conventional CO-OFDM signal at zero. With such a scheme,the effect of fiber nonlinearity can be miti-gated,and the wanted signal carried on odd subcarriers is or-thogonal to clipping noise,which falls on even frequencies. Simu-lation shows that the system Q value is improved by more than 2 dB at the length of 960 km     

颗粒形状对光学非线性增强的影响

研究了金属／电介质复合物的金属颗粒具有旋转椭球形的形状分布时对有效非线性光学性质的影响;根据一般的Maxwell-Gamett近似方法,采用谱密度来描述,对研究的模型进行数值模拟,分析数值计算结果可知颗粒的形状对光学非线性有明显的增强,并且每一种颗粒的形状其光学非线性随频率变化时都存在一个增强峰．     

高速光纤通信系统中二阶PMD补偿方案的研究

偏振模色散效应严重制约着长距离高速光纤通信的发展,偏振模色散的自适应补偿成为光通信领域研究的焦点。在分析目前高速光通信系统中常用的几种PMD补偿技术局限性的同时,对高阶PMD及其补偿问题进行了分析与讨论,提出了二阶PMD补偿方案,并对该方案进行了推导。     

Hybrid fiber optical bistability and optical signal processing

A hybrid fiber optical bistable device with electrical feedback has been proposed and analyzed. Bistability operation and some applications for optical signal processing have been realized experimentally. Supported by the National Natural Science Fundation of China Song Qian: born in Aug. 1937, Professor     

偶氮聚合物的热致非线性光学特性研究

利用z扫描技术研究了一种偶氮聚合物在连续激光作用下的热致非线性光学特性,并根据实验结果计算了偶氮聚合物的热光系数dn/dT和热致非线性折射率n2.由实验结果,发现样品的热光系数和热致非线性折射率与激发波长及样品在该波长下的线性吸收的强弱有关.     

S波段光纤放大器研究进展

迅速膨胀的数字信息服务量使拓展光纤通讯带宽成为迫切需求，S波段光纤通讯窗口的开发利用已迫在眉睫，本文介绍了掺铥光纤放大器(TDFA)、增益位移掺铥光纤放大器(GSTDFA)、拉曼放大器(RFA)等S波段光纤放大器的工作原理及研究进展情况。     

光通信用塑料光纤的性能及系统应用

随着用户对数据通信需求的日益增大，传输数据容量正在迅速增长，网络运营商都在积极发展高速传输系统，为此急待一种新型传输介质来适合短距离高速传输要求。目前在计算机网络通信中光纤通信具有无可比拟的优势，它具有传输速率高，抗电磁干扰能力强和安全保密性好等优点。但由于石英光纤的易碎性，难以连接和价格高等原因，并不适合在短距离通信中应用。近年来国外一些著名大学和研究机构竞相开发价格便宜、接续简捷、工作可靠的塑料光纤和通信系统。本文通过对新型塑料光纤的性能分析，得出结论，塑料光纤以其较高的性能价格比将广泛应用于短距离通信中。     

一种GLS玻璃中红外光子晶体光纤的双折射和非线性研究

设计了一种适合于中红外波段传输的GLS玻璃高双折射高非线性光子晶体光纤(PCF),利用电磁波传播的多极散射理论数值模拟了该光纤的双折射和非线性特性,并对实验制备这种软玻璃光纤的可行性进行了分析。研究发现,通过调节光纤的结构参数可以将该PCF的双折射最大值调至所需的中红外波段(3~10 m),在波长=8.214 m处模式双折射达到了0.16,且偏振方向非线性系数=0.15m-1-1,即该光纤在中红外波段同时具有高双折射和高非线性。这种光纤有望实现中红外波段超短脉冲展宽,进一步扩展中红外波段的激光源。     

Equivalent noise models in fiber optical communication systems

An equivalent noise model of optical receiver amplifiers as shown in Fig. 1 has been given in many fiber optical communication literatures. It is proved in this paper that this equivalent noise model is neither equivalent to the original one nor measurable. The main reason is that the position of the input impedance in this noise model is not the same with its in the typical noise model, but the sameS _vn,S _in with the typical noise model are used. So the equivalent noise model above is wrong and is not fit to be taken into application. Supported by National Education Board Fang Zhihao: born in May 1941, Professor     

NRZ 码在弱非线性色散光纤中的演化及色散补偿后的非线性研究

随着色散补偿技术的成熟，高速光纤通信中另一个限制因素———非线性将随着光纤链路加长而积累起来，并引起新的波形展宽．就每一段光纤而言，均属弱非线性的色散光纤，因此，有必要对光信号在这种光纤中的演化进行深入研究．本文在前人研究的基础上得出了只考虑一阶初始非线性时ＮＲＺ码在弱非线性色散光纤中传输时域和频谱近似解析式，并且给出了频谱、波形随距离、色散、非线性的变化图．对于由正、负色散光纤组成的光纤链路，得出了色散达到最佳补偿时的非线性干扰系数．