光纤及光纤通信系统的测量

论述光纤及光纤通信系统的测量方法,主要介绍光纤测量：单模光纤模场直径,光纤损耗、光纤色散与带宽的测量,光纤通信系统测量,光发射机发送光功率、源消光比、光接收机灵度、光接收机动态范围,眼图的测量。     

光纤及光纤通信系统的测量

本对光纤以及光纤通信系统的测量方法作了一些简单介绍,主要介绍了光纤测量：单模光纤模场直径、光纤损耗、光纤色散与宽带的测量;光纤通信系统测量;光发射机发送光功率、光源消光比、光接收机灵敏度、光接收机动态范围、眼图的测量。     

光纤通信系统的色散补偿

本文介绍光纤通信系统几种常用色散补偿技术的基本原理及性能特点，并结合实际给出具体的使用方法。     

光纤通信系统中的PMD补偿技术

偏振模色散(PMD)已成为高速光纤通信系统中限制单信道传输速率的主要障碍之一.首先介绍了PMD补偿的重要性,随后讨论了现阶段比较可行的主动均衡和补偿PMD的方案,最后介绍了一些抑制PMD效应的新技术.     

高速光纤通信系统的色散调节技术

随着光缆通信系统传输速率的急剧提高，对已大量敷设的Ｇ．６５２光缆，系统越来越受限于色散，如何解决这一问题成了人们关注的焦点。本文在色散对系统影响进行深入分析的基础上，详细介绍了各种色散调节方法，并对它们的特点进行了分析比较。     

光纤通信的测量技术

对光纤以及光纤通信系统的若干测量方法作了介绍。主要介绍了光发射机、光接收机以及光放大器的测量；光通信系统的传输性能和光通道的测量。     

Error probability in digital fiber optic communication systems

In a digital fiber optic transmission system, during photodetection process, a shot noise is produced that is neither stationary nor independent of the digital message. The evaluation of the average error probability in the presence of such a message-dependent shot noise, of additive Gaussian noise, and of intersymbol interference is considered. Two methods of calculation are outlined: an exhaustive method and a Gram-Charlier series expansion method. The latter is preferred when the number of interferers is moderately large. Some numerical examples for binary independent-symbol transmission are presented.     

Line coding plan for fiber optic communication systems

Problems in fiber optic digital communication systems are enumerated and a line coding plan that solves these problems is investigated. This plan utilizes a two-level pulse train that has the same features as the conventional three-level alternate mark inversion sequence. An efficient repeater powering scheme is discussed in connection with the coding plans.     

无中继海底光缆通信系统概述

首先对无中继海底光缆传输系统的构成进行了简要叙述，然后详细阐述了无中继系统用光纤光缆、海缆用连接器和接头、光纤放大器以及光接收机的研究现状，接着论述了其相关技术（波分复用和前向纠错）的发展，最后对无中继通信系统的发展趋势进行了分析与展望。     

Coherence and intersymbol interference in digital fiber optic communication systems

Because of the quadratic relation between optical power and optical field, the transmission of optical power through an optical fiber is, in principle, nonlinear. Under usual conditions, random fluctuations of the incoherent source field and mode mixing tend to linearize the system. Previous assessments of the effect of intersymbol interference (ISI) on the performance of digital fiber optical communication systems are based on the assumption of linearity. This paper examines the effect of ISI on error rates in the other limit of complete coherence where fields are additive but powers are not. It is found that in this nonlinear regime and for weak dispersion, ISI may reduce the error rates slightly, whereas strong dispersion augments it considerably.     

一种LDPC码在光纤通信系统中的性能分析

针对超强前向纠错(FEC)技术在光纤通信系统中的应用,文章提出了一种构造简单、编码容易实现的低密度奇偶校验(LDPC)码的构造方法,并仿真验证了该LDPC码在光纤信道环境下的译码性能.与常用的RS(255,239)码相比,在相同的码效率下,所构造的码长为4 080的LDPC码能够获得比RS码高2 dB的编码增益.     

An IIR adaptive electronic equalizer for polarization multiplexed fiber optic communication systems

An electronic digital equalizer for polarization multiplex coherent fiber optic communication systems is designed to compensate polarization mode dispersion (PMD) and residual chromatic dispersion (CD) of transmission channel. The proposed equalizer is realized with fraction spaced infinite impulse response (IIR) butterfly structure with 21 feedforward taps and 2 feedback taps. Compared with finite impulse response (FIR) structure, this structure can reduce implementation complexity of hardware under the same condition. To keep track of the random variation of channel characteristics, the filter weights are updated by least mean square (LMS) algorithm. The simulation results show that the proposed equalizer can compensate residual chromatic dispersion (CD) of 1600 ps/nm and differential group delay (DGD) of 90 ps simultaneously, and also can increase the PMD and residual CD tolerance of the whole communication system.     

光子晶体光纤在光纤通信中的应用

文章综述了光子晶体光纤的结构、导光原理和特性及其在光纤通信中的应用前景。     

Intrusion-alarmed fiber optic communication link using a planarwaveguide bimodal launcher

This paper summarizes the results of our study of a point-to-point, intrusion-alarmed, graded-index, multimode optical fiber communication system. In this intrusion-alarmed system, data light is transmitted in the lowest order modes of a graded-index multimode fiber and intrusion alarm monitor light is simultaneously transmitted in high-order modes. An attempted intrusion to extract data light by bending the fiber results in attenuation of the monitor light in high-order modes, thereby sounding an alarm at the receiver. However, the data light in the fundamental mode, or in the lowest order modes, propagates along or near the fiber axis where the refractive index is highest and is exceptionally difficult to extract from the fiber. Even for severe bending of the fiber, light in the lowest order modes remains trapped in a set of lowest order modes. Additional benefits of data light transmitted in the lowest order modes are capabilities for wider bandwidths and lower modal noise. The performance of four fabricated planar waveguide bimodal launchers for simultaneously launching data light into the fundamental mode, or into the lowest order modes, and monitor fight into high-order modes of graded-index multimode fiber is described. The configuration, construction, and performance of a laboratory prototype alarmed system are described     

Numerical analysis of intermodal delay in few-mode fibers for mode division multiplexing in optical fiber communication systems

In order to achieve higher spectral efficiency, mode division multiplexing (MDM) in few-mode fibers is a new research area. The idea faces lots of technical issues including intermodal delay and mode coupling which limit the achievable length of the system. This paper is designated to complete the analysis of intermodal delay in step-index few-mode fibers. We analyze numerically all the parameters of fiber, which could impact intermodal delay in few-mode fibers and identify the conditions which can increase the number of multiplex modes without significant increase in maximum intermodal delay.     

Software-synchronized all-optical sampling for fiber communication systems

This paper describes a software-synchronized all-optical sampling system that presents synchronous eye diagrams and data patterns as well as calculates accurate Q values without requiring clock recovery. A synchronization algorithm is presented that calculates the offset frequency between the data bit rate and the sampling rate, and as a result, synchronous eye diagrams can be presented. The algorithm is shown to be robust toward poor signal quality and adds less than 100-fs timing drift to the eye diagrams. An extension of the software synchronization algorithm makes it possible to automatically find the pattern length of a periodic data pattern in a data signal. As a result, individual pulses can be investigated and detrimental effects present on the data signal can be identified. Noise averaging can also be applied. To measure accurate Q values without clock recovery, a high sampling rate is required in order to establish the noise statistics of the measured signal before any timing drift occurs. This paper presents a system with a 100-MHz sampling rate that measures accurate Q values at bit rates as high as 160 Gb/s. The high bandwidth of the optical sampling system also contributes to sampling more noise, which in turn results in lower Q values compared with conventional electrical sampling with a lower bandwidth. A theory that estimates the optically sampled Q values as a function of the sampling gate width is proposed and experimentally verified.