增益半导体光放大器的特性

为满足半导体光放大器（SOA）在光纤到户FTTH系统接入网中的广泛应用,提出了基于光纤光栅外腔反馈型GC-SOA结构的全光增益机制,窄线宽激光光源经可变衰减器、隔离器和光纤光栅注入到SOA中,SOA的输出光经隔离器和光纤光栅送至光谱分析仪,通过光纤光栅反馈输入SOA形成钳制激光。对GC-SOA的阈值特性、增益特性及开关特性进行分析,结果表明:当注入电流小于GC-SOA的阈值电流时,增益随注入电流的增加而增加;当注入电流大于GC-SOA的阈值电流后,其增益不再随注入电流的变化而变化,实现了SOA的增益稳定,使SOA的饱和输出功率得到了提高。     

基于SFRL的FWM型可调谐波长转换器啁啾特性分析

基于半导体光纤环形腔激光器的四波混频型可调谐全光波长转换器的宽带理论模型,从理论上研究了输入信号光功率、注入电流、两个耦合器的耦合比、激射光波长和半导体光放大器有源区长度对转换光频率啁啾的影响.结果表明:转换光的频率啁啾随着输入信号光峰值功率、注入电流以及SOA有源区长度的增大而增大,随两个耦合器耦合比的增大而减小.     

SOA动态增益特性的理论和实验研究

提出了SOA有效增益恢复时间的概念，同时推导了有效增益恢复时间的解析表达式.针对SOA在交叉增益调制型波长转换方面的应用，从理论上分析了注入电流、探测光功率、有源区长度对增益恢复时间的影响，实验测量了不同条件下SOA的增益恢复时间，实验结果与理论计算结果相符合. 关键词： 半导体光放大器 增益恢复时间 全光波长转换器     

基于半导体光纤环形腔激光器的全光广播式超宽带信号源

提出一种新型的基于半导体光纤环形腔激光器(semiconductor fiber ring laser, SFRL)全光超宽带(ultra-wideband, UWB)信号源的方案,该方案可以同时产生3路高斯脉冲一阶导数脉冲(monocycle) UWB信号.建立了这种全光UWB信号源的宽带理论模型,通过数值模拟的方法研究SFRL中的半导体光放大器(semiconductor optical amplifier, SOA)的注入电流、激射光波长、输入信号光功率和波长对monocycle信号性能的影响.结果表明:SOA的注入电流在200—220 mA时可以获得对称性较好的monocycle脉冲;输出monocycle脉冲平均功率和正、负脉冲振幅随激射光波长增加而增加;较低的输入信号光功率可以获得性能较好的monocycle信号;输入信号光波长对输出monocycle信号有一定的影响,但影响很小.     

对向传输下半导体光放大器的超快动态特性(英文)

通过引入场传输模型对在对向传输方案下的半导体光放大器中增益、相位及啁啾的超快动态特性进行了数值分析.讨论了半导体光放大器中带内效应光谱烧孔与载流子加热,以及带间效应载流子消耗对动态特性的影响.同时分析了半导体光放大器的有源区长度对增益动态特性的影响.结果显示:对向传输下同样可应用蓝移失谐滤波器提高半导体光放大器的工作速率,但与同向传输方案不同的是,在对向传输方案下利用短有源区长度的半导体光放大器更利于实现高速的全光波长变换.理论分析结果可为基于半导体光放大器的超快全光信号处理提供理论指导.     

考虑端面反射率的半导体光放大器增益特性研究

在考虑到端面反射率影响的前提下,从SOA载流子的速率方程和耦合波方程出发,建立了基于SOA的交叉增益调制波长变换理论模型,利用分段模型方法对影响增益特性的几个参数进行了数值模拟。结果发现,注入电流和有源区面积对SOA增益的影响有一个阈值,在阈值范围内,SOA增益的大小随着注入电流和有源区面积的增大而明显的增大,但是超过阈值时,则SOA增益趋向饱和。     

半导体光放大器中光波传输特性研究

根据半导体光放大器(SOA)载流子速率方程和光波在SOA内的传输方程,采用分段的方法计算出光波功率和相位与载流子浓度的关系公式。在泵浦光输入功率分别为5mW和15mW情况下通过仿真得到泵浦光输出波形和归一化转换光波形,其中归一化转换光的波形变化可间接体现不同泵浦光输入功率对SOA内载流子浓度的影响。分析了泵浦光波长和SOA注入电流对探测光的归一化输出、相位和频率啁啾产生的影响。结果表明,随着泵浦光波长的增加,探测光的三种光波特性曲线逐渐趋于平缓。注入电流将会直接影响到SOA的载流子浓度,以此对探测光的输出产生影响,注入电流越大,探测光的频率漂移越远。     

半导体光放大器的稳态增益饱和特性

高速全光逻辑门是实现光分组交换、光计算和未来高速大容量光传输的关键器件,近年来受到广泛的关注。半导体光放大器（SOA）因为具备体积小、工作波长范围宽、响应时间短及良好的非线性特性等优点,成为研制高速全光逻辑器件的首选。采用分段模型分析了SOA的稳态增益饱和特性,通过数值求解载流子速率方程和光传输方程对其特性进行了仿真实现。结果表明,SOA在入射光功率不同时会表现出明显的非线性;在一定范围内增加光功率,SOA增益持续增加,继续增加入射光功率,SOA逐渐进入饱和吸收状态,增益反而降低。     

半导体光放大器亚皮秒量级超快动态特性的研究

通过考虑脉冲频谱的增益色散，提出了一个分析亚皮秒光脉冲在半导体光放大器(SOA)中传输的新思路.分别对超快光脉冲在时域和频域内进行离散化，建立了一个更为合理的传输数值模型.基于该模型，观察到了脉冲频谱的明显漂移，并探讨了漂移量与脉冲载波波长、脉冲能量、脉冲宽度、SOA长度和注入电流等外部条件之间的关系，从理论上解释了文献没有证实的实验结果.同时，基于交叉增益调制原理，利用双光束结构，描述了载流子加热、光谱烧孔效应和双光子吸收等非线性效应引起的增益压缩.理论分析的结果为改善SOA的动态特性提供了指导. 关键词： 半导体光放大器 超快非线性效应 增益色散性     

基于半导体光放大器中交叉增益调制效应的波长转换啁啾特性的分析

对基于半导体光放大器中交叉增益调制效应的波长转换后信号的啁啾特性进行了分析。研究了输入信号光和参考光和功率、波长、转换速率、信号光消光比以及半导体光放大器的偏置电流对转换后信号啁啾的影响。     

基于XGM的SOA波长变换器噪音特性分析及优化设计

利用动态载流子恢复时间可以精确模拟基于交叉增益调制的SOA全光波长变换器的饱和增益效应,本文将SOA分段ASE噪音功率和分段动态模型结合,得到沿长度分布的ASE噪音功率,并讨论了偏置电流、泵浦光和探测光的波长、功率、SOA长度对消光比和信噪比的影响理论计算结果表明,大的偏置电流有利于提高消光比和信噪比;对于一定的输入波长,相对较大的泵浦光和相对较小的探测光变换效果好;SOA的长度存在最佳值.     

多电极半导体光放大器对增益特性的改善

提出了采用多电极实现电流非均匀注入来改变半导体光放大器(SOA)内部的载流子分布,从而改变其增益饱和特性的一种新的方案.用SOA分段模型的计算结果表明,与单电极均匀注入电流的SOA 相比,在同样的总注入电流下,对一个两电极SOA采用前面小后面大的非均匀电流注入,可以提高饱和输出功率和饱和输入功率.而采用前面大后面小的电流注入方式,则将使SOA更容易发生饱和,不仅饱和输出功率与饱和输入功率减小,而且增益谱在饱和后的压缩程度加大,增益谱压缩的对称性提高.对多电极SOA,可以方便灵活地调节各节之间的长度比和注入电流比来满足不同的应用要求.     

Tunable 19 × 10 GHz L-band FP-SOA based multi-wavelength mode-locked fiber laser

We present a multi-wavelength mode-locked fiber ring laser incorporating a semiconductor optical amplifier (SOA) and a Fabry-Perot semiconductor optical amplifier (FP-SOA). Because the gain of the SOA is depleted by an external injection optical signal, the SOA acts as a loss modulator. The FP-SOA serves as a tunable comb filter. The presented laser source can generate 19 synchronized wavelength channels with the extinction ratio of about 21 dB, each mode-locked at 10 GHz, and mode-locked pulse width is about 40 ps. Oscillation wavelengths band can be tuned by adjusting the bias current of the SOA, and wavelength spacing also can be changed by using a tunable optical delay line (ODL) or a temperature controller. The polarization-insensitive devices ensure that the output power is rather stable. This fiber laser has potential applications in longer waveband (L-band) within the low-attenuation window.     

Enhancement in the gain recovery of a semiconductor optical amplifier by device temperature control

We present a numerical investigation on the temperature dependence of gain recovery, of a semiconductor optical amplifier (SOA). It is shown that the decrease in temperature significantly speed-up the gain recovery of the SOA. Under typical operating conditions, a 20 K reduction in temperature of the SOA results in a decrease of 150 ps in the gain recovery time. A comparative estimation of device temperature and assisted-light power requirements for enhancing the gain recovery has also been carried out. It is found that, a decrease of 8 K in the temperature of the SOA, is as effective in enhancing the gain recovery as injection of 25 dBm assisted-light power in the counter-propagating mode. Our study shows that under moderate current biasing conditions, temperature reduction is a better and convenient option to speed-up the gain recovery of an SOA, than the use of external assisted-light injection, which requires an additional laser source and wavelength division multiplexing (WDM) components for coupling and de-coupling, leading to insertion losses in the communication channel.     

Multi-wavelength fiber laser based on nonlinear polarization rotation in semiconductor optical amplifier and photonic crystal fiber

A nonlinear polarisation rotation (NPR) based multi-wavelength laser source is demonstrated using a semiconductor optical amplifier (SOA) and photonic crystal fiber (PCF). The SOA acts as not only the gain medium but also the phase retarder for multi-wavelength oscillation in conjunction with an isolator. The incorporation of PCF improves the NPR effect and thus assists in the multiwavelength generation. The wavelength spacing reduces from 4.82 to 2.76 nm as the PCF length increases from 50 to 100 m. With a 100 m long PCF, the proposed laser produces at least 42 lasing wavelengths with optical signal to noise ratio of more than 10 dB.     

A pump power controlled 1,060 nm multiwavelength fiber ring laser using nonlinear polarization rotation of SOA

We propose and experimentally demonstrate a both channel spacing and wavelength-tunable 1,060 nm multiwavelength fiber laser using nonlinear polarization rotation of semiconductor optical amplifier (SOA). The SOA in the cavity can not only provide the gain but also generate a pump power controlled phase-shift between two orthogonal linear states of polarization. The experimental result shows that the fast and continuous wavelength tuning is achieved with external light injection, while the channel spacing of the multiwavelength laser can be varied by adjusting the length of polarization maintaining fiber. When an external laser source with 13 dBm power is injected into the SOA as a control pump, optically tunable operation of up to 20 wavelength channels, from 1,042 to 1,058 nm, with a wavelength spacing of 0.8 nm has been demonstrated with the signal-to-spontaneous-noise ratio over 40 dB at room temperature. The lasers are stable with a maximum power fluctuation per channel of less than 0.5 dB during 2-h test.     

Lateral Current Injection (LCI) Multiple Quantum-Well 1.55 μm Laser with Improved Gain Uniformity Across the Active Region

A simulation study of lateral current injection 1.55 m laser with strain-compensated multiple quantum-well (MQW) active region (InGaAsP well, InGaAlAs barrier) is presented using self-consistent 2D numerical simulations. The effects of different mesa width and p-doping in the QWs on the carrier and gain uniformity across the active region are explored. A high p-doping in the quantum wells is found to increases the carrier and gain non-uniformity across the active region. The QW region close to the n-contact side does not provide much gain at high optical powers. An asymmetric optical waveguide design is proposed to help reduce the gain non-uniformity across the active region. By shifting the optical modal peak toward the p-side, the modal overlap between the gain region and the optical mode is improved and a more even carrier and gain distribution is obtained. However, due to reduced bandgap of the quaternary InGaAsP p-cladding, an enhanced electron leakage out of the QWs into the p-cladding degrades the laser efficiency and increases the threshold current. Transient time–domain simulations are also performed to determine the small-signal modulation response of the laser promising a simulated high modulation bandwidth suitable for direct-modulation applications.