直接调制光发射机原理与故障分析

光发射机按照调制方式划分为调幅、调频和数字调制等多种光发射机,但目前用的最多的是多路调幅光发射机。按照强度调制的方式不同,多路调幅光发射机又可分为直接调制光发射机和外调制光发射机两种。以DFB直接调制光发射机为原型,对光发射机的电路原理与常见故障进行了分析和探讨,并提出了解决方案。     

CATV的反向光发射机

在C ATV的光纤舆传输系统中,正向光发射机用于系统前端向光节点发送信号,反向光发射机用于系统光节点向前端发送光信号。由于目前的C ATV传输系统具有非对称性,即下行频带宽,上行频带窄。正向光发射机与反向光发射机有着明显的不同之处,附表为正、反向光发射机工作频带及所传输的业务内容,图1为反向光发射机系统示意图。由于反向光发射机带宽窄,调制度可以大一些。反向光发射机比正向光发射机的光功率要小,一般在10m W以下,对激光器的要求也较低。只传数据的反向光发射机激光器,可以使用谐振腔半导体激光器,如FP-LD(Fabry Perot-Lase…     

CATV光发射机原理及应用(3)

第三章光发射机的射频激励功能电路 光发射机的任务是把从前端送来的高频电视信号变成光信号,使其能在光导纤维中传输.光发射机按照调制方式来划分有调频、调幅和数字调制等多种.目前用得最多的是多路调幅光发射机,在调幅光发射机中按照强度调制的方式不同又分为直接调制光发射机和外调制光发射机.直接调制光发射机是利用高频电视信号(将信号电流叠加到激光器的偏置电流上)来控制半导体激光器的偏流,进而控制激光器的输出光强;外调制光发射机是在激光器输出激光之后,让其通过一个外调制器,使激光的强度随多路调幅信号电压而改变.无论哪种形式的光发射机都具有射频激励单元电路,在光发射机中,射频激励功能电路是最重要的单元电路.此功能电路的好坏直接决定着光发射机的指标的优劣.鉴于目前市场上直接调制光发射机占大多数,此处RF驱动电路的介绍偏重于直接强度调制光发射机.     

CATV光发射机原理及应用（3）——第三章 光发射机的射频激励功能电路

光发射机的任务是把从前端送来的高频电视信号变成光信号，使其能在光导纤维中传输。光发射机按照调制方式来划分有调频、调幅和数字调制等多种。目前用得最多的是多路调幅光发射机，在调幅光发射机中按照强度调制的方式不同又分为直接调制光发射机和外调制光发射机。直接调制光发射机是利用高频电视信号(将信号电流叠加到激光器的偏置电流上)来控制半导体激光器的偏流，     

CATV外调制光发射机原理及应用（2）

2外调制光发射机原理及结构与1310nm直接强度调制光发射机相比较,1550nm外调制光发射机不存在Chirp效应,光纤系统二次失真和三次失真小,光发射机还可以有两路光信号输出,外调制光发射机配备光纤放大器,输出功率可以超过200mW,因而外调制光发射机得到广泛应用,大中型网络系统几乎全用外调制光发射机。     

CATV光网络设备原理及应用：第六讲 光发射机的射频激励功能电路

(上接第14期) 光发射机的任务是把从前端送来的高频电视信号变成光信号,使其能在光导纤维中传输.光发射机按照调制方式划分为调频、调幅和数字调制等多种.目前用得最多的是多路调幅光发射机,在调幅光发射机中按照强度调制的方式不同又分为直接调制光发射机和外调制光发射机.直接调制光发射机是利用高频电视信号(将信号电流叠加到激光器的偏置电流上)来控制半导体激光器的偏流,进而控制激光器的输出光强.外调制光发射机是在激光器输出激光之后,让其通过一个外调制器,使激光的强度随多路调幅信号电压而改变.无论哪种形式的光发射机都具有射频激励单元电路,此功能电路的好坏直接决定着光发射机指标的优劣.鉴于目前市场上直接调制光发射机占大多数,此处RF驱动电路的介绍偏重于直接调制光发射机.     

光发射机的选择与使用

光发射机是光缆传输系统的核心设备,它的作用是用输入的射频有线电视电信号调制光信号,实现电—光转换(E/O),并向光缆系统发送连续、稳定、可靠的光信号。市场上销售的光发射机按调制方式分为直接调制光发射机和外调制光发射机两种,直接调制光发射机多用于1 310 nm光纤系统,外调制光发射机多用于1 550 nm光纤系统,它们的核心部分都是激光器组件。1直接调制激光发射机1.1组成这种光发射机除核心部件DFB激光器组件外,还有电源、激光器偏置电路、激光器慢启动电路、过载保护电路和驱动保护电路、功率控制和致冷控制电路、失真补偿电路、光检…     

基于MSP430单片机的光发射机监控系统设计

设计并实现了一个基于MSP430的光发射机监控系统,该系统通过使用光发射机控制,来完成光发射机工作状态数据的监测、采集和存储.针对异常情况对光发射机进行控制.     

CATV光网络设备原理及应用第十讲外调制光发射机结构及原理

(上接第22期) 与1 310 nm直接强度调制光发射机相比较,1 550 nm外调制光发射机不存在Chirp效应,光纤系统二次失真和三次失真小,光发射机还可以有两路光信号输出,外调制光发射机配备光纤放大器,输出功率可以超过200 mW,因此外调制光发射机得到广泛应用,大中型网络系统几乎全用外调制光发射机.     

谈光发射机的选择与使用

本文通过介绍光发射机的组成,工作原理,性能参数,谈如何合理选择光发射机,正确使用光发射机,以便搞好对光发射机的维护,确保HFC光纤有线电视网高质量的运行。     

Demonstration of Wavelength Packet Switched Radio-Over-Fiber System

The authors present a novel concept of employing optical wavelength packet switching in radio-over-fiber access networks. In such a system, the tunable laser (TL) would be employed as a transmitter in the central station. The optical carrier generated by this device would be externally modulated with the data signal upconverted to an RF frequency before being sent to the appropriate base station (BS). If each of the BSs is assigned a unique wavelength, the addressing and routing of traffic could be performed on a packet-by-packet basis with the TL switching between the wavelength assigned to different BSs     

Analog direct-modulation behavior of semiconductor lasertransmitters using optical FM demodulation

In this paper, we report a theoretical investigation of the analog modulation performance of a semiconductor laser transmitter which employs the direct optical FM demodulation. This analysis is based on the rate equations in which Langevin noise functions are included. The optical FM response has firstly been derived using a chirp-power relation deduced from the rate equations. The chirp-to-power ratio (CPR) has secondly been computed and illustrated showing the effect of the novel damping parameter phenomenologically introduced in the rate equation for the optical phase. The curves show that the conventional CPR can be notably reduced using FM demodulation. Beside this, the comparison of the FM responses with prior studies show that our model may be more appropriate to describe optical FM behavior of many types of single-mode lasers. The relative-output noise (RON) at the transmitter has also been determined and subsequently used to calculate the carrier-to-noise ratio (CNR) available. It is shown that the transmitter inherent noise would significantly degrade as a result of the conversion of the optical frequency noise into intensity noise. Consequently, intrinsic noise is expected practically to contribute the most to CNR at high powers. This feature can be more easily appreciated through curves illustrating CNR and is in contrast to previous studies in which the receiver shot noise was assumed to be the main noise term     

Compact and 10-Gb/s $times$ 12-Channel Optical Transmitter for Optical Interconnection With High Heat-Dissipation Capability Using Alumina Substrates

A compact 10-Gb/s $times$ 12-channel optical transmitter was developed for very short-reach optical interconnections. The 10-Gb/s/ch operations were achieved without employing the heat pipes or heat sinks typically required to keep vertical-cavity surface-emitting lasers at a low temperature under 85 $^{circ}$C. Alumina ceramic substrates with high heat dissipation capability are incorporated in order to maintain the low temperature operation. The optical transmitter is designed to be as compact as a standard mechanically transferable (MT) optical connector. To enhance usability, the transmitter can be directly connected with the MT-type optical connector with guide pins assembled in the alumina substrate. The compactness and usability of the optical module is effective in intrabox and interbox optical interconnections.      

光纤CATV传输系统的结构和应用

光纤CATV传输系统包括光发射机、光接收机、光纤和必要的光通路器件（如光分路器、光纤连接器）等。该系统采用光纤／同轴电缆混合网（HFC）结构，是一种宽带、低成本的实现方式。结合实际开发工作，简要介绍了光发射机、光接收机及相关器件的工作原理。     

光链路损耗参数的定义和分光比的计算

说明光链路中器件“损耗”的定义,并据此定义推导分析“光纤损耗”、“分光损耗”的定义和计算式,以及光链路所需光发射机输出光功率的计算式。     

15 Gb/s multichannel optical interconnect laser array transmitteroperating at λ=1.3 μm

We have fabricated and measured detailed bit error rate experiments on a 12 channel optical interconnect transmitter operating at rates up to 1.25 Gb/s per channel, using InGaAsP/InP λ=1.3 μm lasers. The lasers are highly uniform, the channel crosstalk is less than 1 dB, and the mode selective losses are low (<1 dB). This transmitter has been demonstrated in an architecture which would allow the transmission of 120 channels of 100-Mb/s uncompressed video signals     

Characterization of an optical frequency-shift-keying transmitter based on carrier-suppressed phase modulation

We experimentally characterize an optical frequency-shift-keying transmitter based on optical carrier-suppressed phase modulation. Only one laser source is needed to generate an optical FSK signal. The demonstration of 10-Gb/s FSK signal generation and 50-km transmission verified the improved performance of the proposed transmitter, compared with the previous two-laser schemes. To further reduce the complexity of the transmitter, the phase modulator is omitted and a single MZM modulator is used for both optical carrier-suppression (OCS) and phase modulation. This simplified structure is verified by simulation, implying the feasibility that a FSK transmitter can be constructed with only one laser source and one modulator.     

Prechirp technique as a linear dispersion compensation forultrahigh-speed long-span intensity modulation directed detectionoptical communication systems

Prechirp technique, as a linear dispersion compensation for intensity modulation direct detection (IM-DD) optical transmission systems, has been investigated theoretically and experimentally. This technique is based on a predistortion technique in an optical transmitter. Implementation to the ordinary IM-DD optical transmitter, which uses an external intensity modulator, is easily realized merely by adding a small injection current modulation to a semiconductor laser diode, allowable optical transmission fiber dispersion will be more than doubled with this technique, modified prechirp technique, which utilizes a time division superimposing prechirped bit streams, has also been investigated to achieve greater dispersion compensation capability     

EML-Based Optical Single Sideband Transmitter

We present a novel optical single sideband (SSB) transmitter comprised of an electroabsorption modulated laser. The transmitter exploits the hybrid or compatible SSB structure wherein the directly modulated laser diode and the electroabsorption modulator function as phase and amplitude modulators, respectively. The theoretical analysis and experimental demonstration confirm the feasibility of optical SSB transmitter for radio-over-fiber applications by using this small semiconductor device.