具有纯频率调制和啁啾抑制的幅度调制的三电极DFB LD

二电极和三电极(多电极或多节)分布反馈激光器是超长传输距离和超大传输容量光纤通信系统的关键器件。本文详细地讨论了三电极分布反缋(DFB)激光器的重要特性,其中包括调谐理论、频率调制响应以及纯频率调制和啁啾抑制的辐度调制。     

单段式分布式反馈半导体激光器光学锁相环研究

单段式分布式反馈(DFB)半导体激光器的频率调制相位响应曲线在0.1~5 MHz之间,且具有180°的相位反转,其作为从激光器的光学锁相环(OPLL)结构难以实现锁相。为解决单段式DFB半导体激光器的锁相问题,在单环反馈回路中加入可调超前移相功能电路和可调增益功能单元,并优化相移参数,实现MHz量级线宽DFB激光器相位的锁定。改进后OPLL在锁相状态下的残余相位噪声为0.012rad2,激光器线宽从2 MHz压窄到10kHz。研究了反馈环路的环路增益对OPLL锁相性能的影响,并给出了最优的环路增益控制参数。     

半导体相移分布反馈激光器模式及调制相应特性的研究--牛顿-矢量方法的应用

给出了适于分析DFB激光器稳态特性的数值模型和分析振幅及频率调制响应特性的解析模型.研究了3相移DFB激光器的调制响应特性,并提出了一种能够快速精确得到DFB激光器多个模式解的新方法--矢量牛顿法.该方法将稳定的矢量法与精确的牛顿法结合,保证了求解质量.实践表明该方法非常适合于求解高度非线性方程的多解问题.用此方法,研究了3相移及简单DFB激光器的纵向光子浓度分布,纵模及调制响应特性.结果表明,3相移DFB具有与简单的DFB激光器同样好的调制响应特性,相移的引入在一定程度上抑制了纵向空间烧孔效应,并且有利于DFB激光器的单模输出.     

半导体相移分布反馈激光器模式及调制相应特性的研究--牛顿-矢量方法的应用

给出了适于分析DFB激光器稳态特性的数值模型和分析振幅及频率调制响应特性的解析模型.研究了3相移DFB激光器的调制响应特性,并提出了一种能够快速精确得到DFB激光器多个模式解的新方法--矢量牛顿法.该方法将稳定的矢量法与精确的牛顿法结合,保证了求解质量.实践表明该方法非常适合于求解高度非线性方程的多解问题.用此方法,研究了3相移及简单DFB激光器的纵向光子浓度分布,纵模及调制响应特性.结果表明,3相移DFB具有与简单的DFB激光器同样好的调制响应特性,相移的引入在一定程度上抑制了纵向空间烧孔效应,并且有利于DFB激光器的单模输出.     

调谐二极管激光吸收光谱技术中的线形误差与校正

在调谐二极管激光吸收光谱(TDLAS)技术中,谱线线形的检测精度受激光器调谐非线性和调制幅度的影响,本文针对近红外分布反馈(DFB)激光器,通过激光器的调谐特性曲线定量分析了调谐非线性和调制幅度对吸收线形的影响,提出了调谐非线性校正和调制幅度补偿方法,并通过实验验证了方法的有效性.实验结果表明,调谐非线性校正可以提高谱...     

半导体激光器的调频特性

本文讨论了半导体激光器(LD)的直接调频(FM)特性,指出随着偏置电流的增大,FM响应降低,伪强度调制(IM)响应增大,并给出了一种新的描述FM能力的方法.     

高速直调激光器组件异常光学特性的研究

报告了1.25Gb/s速率下采用光强度直接调制DFB激光器组件所观测到的异常动态光学特性.分析表明,直调激光器的光学特性与激光器结构、调制速率、驱动电流、管芯温度等因素紧密相关.讨论了激光器调制速率、光谱带宽等对光数字信号传输距离的限制.提出了高速光通信系统选用直调激光器光源的建议.     

分布式反馈激光器调制特性研究

为了深入了解分布式反馈激光器（DFB）的发光机理与调制特性,通过理论分析和实验对DFB的调谐特性进行了研究。得到FITEL和JDS Uniphase两款激光器调制电流与输出中心波长的对应关系和两种确定系数不同的拟合方程,证明了这两款DFB激光器在实际应用中存在非线性关系。结果表明,FITELFRL15DCWD-A82激光器的3dB带宽与驱动电流幅值关系为3.715pm/mA;该调制结果优化了该激光器的可用相干长度,并验证了驱动信号频率变化不影响3dB光谱宽度。对DFB激光器低频调制特性的定量分析结果可为相干检测系统驱动电路设计提供实验依据。     

基于膜片式EFPI光纤麦克风的声源定位系统

提出一种采用激光器频率调制准连续相移干涉实现膜片式光纤声传感器阵列同时解调的技术。通过调制光栅Y分支(MG-Y)可调谐激光器的快速频率调谐引入相移,4个具有π/2相位偏置的光频率按顺序切换,产生准连续的正交相移信号。基于五步相移算法,任意5个相邻相移信号用于相位恢复,由于没有机械运动部件,实现了高速稳定的相位解调。该系统的相位采样率(600 kHz)取决于频率调制速度。实验结果表明,通过调整激光器输出频率,可以正确解调宽腔长范围的非本征Fabry-Perot干涉(EFPI)传感器。此外,构建了一个紧凑的多点声传感阵列系统,实现了声源定位应用。     

TDLAS氧气检测中谐波信号特性研究

可调谐半导体激光吸收光谱(TDLAS)技术是一种具有高灵敏、高分辨、快速响应等特点的气体检测技术,利用半导体激光器可调谐、窄线宽特性,通过检测气体的一条吸收线实现气体浓度的准确检测.阐述了基于波长调制TDLAS技术的氧气检测方法,选择DFB激光器作为光源,通过检测760 nm附近氧气分子的一条吸收线实现了氧气在线监测,主要分析了谐波信号的特性及系统的线性响应.     

Tunable two-segment distributed feedback lasers

The authors describe a two-segment distributed feedback laser at 1.3 mu m with a tuning range of 12.8 AA (209 GHz) and an FM response of 7 GHz/mA. The observed tuning behaviour is in qualitative agreement with an earlier theoretical model. Such two-segment DFB lasers are useful in frequency-multiplexed, frequency-modulated optical networks.<>     

FM response of InGaAsP buried heterostructure distributed feedbacklasers and their applications in incoherent FSK systems

Measurements are reported of the frequency modulation (FM) response of InGaAsP buried heterostructure distributed feedback (DFB) lasers and the system performance of a 1.7-Gb/s and 622-Mb/s incoherent frequency-shift-keyingn (FSK) system using these lasers. The measured lasers include 1.55-μm conventional DFB lasers and quarter-wave shifted DFB lasers. The thermal dips in the FM response of quarter-wave shifted DFB lasers usually occur at the lower frequencies, compared with that of conventional (250-μm-long) DFB lasers. A receiver sensitivity of -32.5 dBm (-39.5 dBm) for a 1.7-GB/s (622-Mb/s) incoherent frequency-shift-keying (FSK) system was achieved using a quarter-wave shifted DFB laser     

FSK heterodyne transmission experiments at 560 Mbit/s and 1 Gbit/s

Optical frequency-shift-keying (FSK) signals are obtained from directly modulated distributed feedback (DFB) semiconductor lasers. Experimental studies of the direct frequency modulation (FM) characteristics of the DFB lasers show a nonuniform FM response due to the competing effects of thermal modulation of the laser active region and carrier density modulation. Equalization of the signal current to the laser is employed to produce a flat FM response from 30 kHz to 1 GHz. Optical FSK transmission and heterodyne detection experiments at 560-Mbit/s and 1-Gbit/s are conducted at a wavelength of 1497 nm. Receiver sensitivities of -39 dBm at 560 Mbit/s and -37 dBm at 1 Gbit/s are obtained. Transmission through 100 km of single-mode fiber at 1 Gbit/s is achieved with no degradation in receiver sensitivity.     

Effect of nonuniform laser FM response on the performance ofmultichannel heterodyne FSK systems using optical amplifiers

A theoretical analysis is provided to evaluate the performance of optical frequency division multiplexed systems taking into considerations the combined effect of receiver noise, laser phase noise and nonuniform FM response characteristic of a practical DFB laser. To overcome the effect of nonuniform frequency modulation characteristic of semiconductor lasers, two different linecoding schemes are used for the laser driving signal. The crosstalk penalty due to the combined effect of nonuniform FM response and phase noise of lasers is evaluated. The improvement in receiver sensitivity due to optical preamplifier is also estimated. The computed results show that the performance of the system is highly degraded due to the effect of laser nonuniform fm response and can be reduced substantially by using linecoding. Further, there is considerable improvement in receiver sensitivity due to the use of an optical preamplifier in the absence of phase noise. In the presence of phase noise there is a reduction in receiver sensitivity     

Optically coherent direct modulated FM analog link with phase noisecanceling circuit

This paper demonstrates a new phase noise canceling (PNC) circuit for use with an optically coherent analog frequency modulation (FM) link employing directly modulated distributed feedback (DFB) lasers. Direct frequency modulation of a semiconductor laser is a highly efficient optical-to-electrical conversion process, which can lead to very low noise figure (NF) and high dynamic range (DR). However, the large laser phase noise found in semiconductor lasers significantly degrades the FM link performance. The PNC circuit is a simple means for canceling the laser phase noise while extracting the modulated signal and taking advantage of the high FM conversion efficiency of semiconductor lasers. The theoretical performance of the PNC PM link is discussed in terms of the signal-to-noise ratio (SNR), NF, and DR, and is compared to a Mach-Zehnder modulated link which uses high-power, solid-state lasers. Phase noise cancellation is demonstrated in an experimental PNC FM link. Comparison of a PNC FM link to an externally modulated AM (coherent) link shows a 31 dB improvement in the NF of the FM link, and a 10 dB improvement in DR. However at higher received optical powers phase-to-intensity noise limits the performance of both links to well below the theoretical calculations     

Dynamic properties of push-pull DFB semiconductor lasers

Using the spatially dependent multimode rate equations, we present a systematic study of small-signal dynamics of push-pull DFB lasers. The various spatial effects such as the longitudinal spatial hole burning, nonlinear gain compression, side-mode contribution, and push-pull modulation are all analyzed in a self-consistent manner. With the closed form expressions for the AM and FM responses, we show explicitly that the resonance frequency and the first cut-off frequency of push-pull DFB lasers are determined by the frequency spacing and the threshold gain difference between the lasing mode and its closest antisymmetric side mode, respectively. Numerical results reveal that a high modulation speed with a very low frequency chirp can be achieved with the push-pull DFB lasers