兰州大学机构库 >物理科学与技术学院
光通信系统中掺铒光纤激光器的研究
Alternative TitleStudy on Erbium-doped Fiber Lasers In Optical Communication Systems
张欣
Thesis Advisor冯博学 ; 祝宁华
2007-03-02
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword光纤激光器 单纵模掺铒光纤激光器 注入锁定 波长调谐 输出波长及功率稳定 线宽 有理数谐波锁模
Abstract

光纤激光器具有许多突出的优点和特点:与光纤元件的天然兼容性;可用带宽较宽;阈值低;与半导体激光器相比,光束质量较好,噪声较低;加之结构紧凑、便携式、精密化等特点,因而它在光纤通信、光纤传感等领域具有重要的应用前景,受到了国际上科技界、产业界的广泛重视,成为研究的热点。本文从理论和实验上对掺铒光纤激光器的若干关键技术进行了研究,如连续光掺铒光纤激光器,脉冲光掺铒光纤激光器等。我们主要开展了以下几方面的研究工作:

根据多模半经典理论,对注入锁定光纤环形腔激光器进行了理论分析与模拟。讨论了在小信号注入情况下,均匀加宽注入锁定光纤环形激光器的单模运转问题;然后逐一分析了注入锁定光纤环形腔激光器的锁定带宽、输出光线宽、输出功率等表征注入锁定特性的关键物理量并作了相应的模拟计算。随后,对掺铒光纤环形腔激光器(EDFRL)的注入锁定技术进行了实验研究,实验结果表明,注入场对腔模的影响与失谐量、泵浦功率、注入强度等参量有关,且如果合理选择环形腔的各参数和注入光功率,则注入光对激光器线宽的展宽可以控制在很小的程度,甚至接近 EDFRL 的本征线宽,实现窄线宽输出。

提出了一种多环形腔结构的单纵模掺铒光纤激光器。首先讨论了使激光器运行在单纵模状态的谐振腔理论。同时实验结果表明,这种激光器通过在主环形腔中插入充当模式滤波器的三个长度不等的无源次级环形腔,并结合腔内光纤布拉格光栅,实现了短时间的单纵模输出,短期线宽小于500Hz。

从理论与实验两方面对单纵模掺铒光纤环形腔激光器的波长调谐和稳定性进行了研究:首先,根据速率方程对可调谐掺铒光纤环形腔激光器的输出功率特性进行了理论分析。采用数值计算方法研究了环形腔各个参数如腔内损耗、铒离子团簇、输出耦合比、增益光纤长度等对EDFRL输出功率特性的影响。结果表明腔内损耗是影响可调谐EDFRL输出功率特性的最重要的因子;而铒离子团簇会导致输出功率平坦性变坏;同时增益光纤长度也存在一最佳值。为光纤环形腔激光器的优化设计提供了依据。随后,实验上提出了一种实现可调谐的单纵模EDFRL输出波长及功率稳定的新方法。即利用注入锁定技术向EDFRL腔内注入低功率连续光,使某一纵模在注入光的基础上起振。此纵模在对增益介质的竞争中可以稳定地占据优势,从而与注入信号发生锁定,实现激光器输出的稳定。实验得到激光器在1527.4-1561.9nm范围内波长连续可调,输出功率>0.6dBm,信噪(SNR)>43dB;输出光波长与功率抖动分别<0.01nm和≤0.02dB,且线宽约为1.4kHz。

采用锁模的频域分析理论和时域分析理论分析了光纤环形腔激光器的有理数谐波锁模现象。并对EDFRL的有理数谐波锁模技术进行了实验研究。通过实验,不仅获得了分子数为一时的高阶有理数谐波锁模脉冲,还发现了分子数不等于1时的有理数谐波锁模现象,突破了传统的有理数谐波锁模的分子数只等于一的局限。此外,理论模拟与实验均发现,通过选择适当的调制器偏置电压(b)和调制深度(M)的值的组合,当调制器工作在非线性区,获得了强度分布均衡的脉冲序列。

Other Abstract

Fiber lasers have a lot of outstanding merits and characteristics, such as good compatibility with fiber components and fiber systems; wide bandwidth; better beam quality and lower noise than semiconductor lasers; in addition, compact structure, portability, and so on. Consequently, there has been considerable interest in developing fiberlasers for optical communication, fiber sensors, spectroscopy, etc. And nowdays fiber lasers have become hot point over the world. In this dissertation, several key technologies of the fiber lasers have been studied theoretically and experimentally, such as
continuous wave fiber laser, pulse wave fiber laser. The main contents of this dissertation are as follows:

The multimode semiclassical Lamb method is applied to the analysis of injection-locked fiber ring lasers. Under weak signal limit, the problem of single-mode operation for homogeneously broadened fiber ring lasers is discussed,
and some key parameters, which determine the performance of injection-locking, such as the locking bandwidth, the linewidth of output laser, and output power are analyzed
and simulated respectively. Whereafter, the injection-locking for Erbium-doped fiber ring lasers (EDFRLs) is studied experimentally, and results show that the influence of
the injected field on the cavity modes has a relation with some parameters such as detuning, pump power, injected intensity, etc. Besides, it is found that the linewidth
broadening due to injection can be minimized if the parameters of the ring cavity and the injected power are chosen properly, thus linewidth narrowing can be realized.

A single-longitudinal-mode (SLM) erbium-doped fiber laser with multiple ring cavities (MRC) is proposed and experimentally demonstrated. The EDFL is structured by inserting three different short passive subring cavities, which serve as mode filters,into the main cavity,and it is combined with a fiber Bragg grating(FBG), the MRC resonator make single-longitudinal-mode lasing. The resonant theory of multiple-ring cavities for SLM operation is discussed. And the experimental result show that a short-term linewidth of less than 500Hz is realized.

The wavelength tuning and output stability of single-longitudinal-mode EDFRL are studied theoretically and experimentally. Firstly the output power characteristics of a tunable EDFRL are analyzed. The effects of total intracavity loss, erbium ion clustering, output coupling ratio, and active fiber length are investigated. The experimental results indicate that minimization of the intracavity lass and erbium ion clustering as well as optimization of the active fiber length are very important. After that, a novel method to stabilize the wavelength and output power of tunable single-longitudinal-mode EDFRL with compound cavity structure is proposed and experimentally demonstrated. One of the longitudinal modes is stimulated by the injected continuous wave(CW),So that this mode is able to win the competition to stabilize the system.The output power of >0.6dBm and the SNR of >43dB within the tuning range from 1527.4 to 1561.9nm can be achieved for this laser ,the wavelength variation of less than 0.01nm and the power fluctuation of less than 0.02dB, and linewidth of about 1.4kHz have also been obtained.

Using the frequency domain analysis theory and the time domain analysis theory of the active mode-locked homogeneous lasers, we study the mechanism of the rational harmonic mode-locking fiber ring laser (RHML-FRL) pulse generation in detail. And the simulated results are in good accord with the experiments. The experimental results indicate that RHML not only can take place when the modulation frequency of the modulator fm =(n+1/p)fc but also can happen when fm=(n+m/p)fc , where m is unequal to 1 but an integer less than p. We call it arbitrary numerator RHML. In addition, a simple technique for the pulse-amplitude equalization of high repetition rate pulses generated from RHML-FRL is demonstrated through both simulation and experiment. Its principle is based on nonlinear modulation. By properly adjusting the bias level and modulation depth of modulator, amplitude equalized short pulses have been obtained.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/229929
Collection物理科学与技术学院
Recommended Citation
GB/T 7714
张欣. 光通信系统中掺铒光纤激光器的研究[D]. 兰州. 兰州大学,2007.
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