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。     

Multiwavelength fiber ring laser using a gain clamped semiconductor optical amplifier

We demonstrate a novel multi-wavelength fiber ring laser based on a gain clamped semiconductor optical amplifier. The number of lasing lines can be tuned by adjusting the loss inside the cavity. The wavelength interval between the wavelengths is 100 GHz. The proposed laser shows a stable operation with total intensity fluctuation for a single laser line within ±0.02 dB at room temperature for a period of 30-minutes.     

Hybrid flat gain C-band optical amplifier with Zr-based erbium-doped fiber and semiconductor optical amplifier

An efficient gain-flattened C-band optical amplifier is demonstrated using a hybrid configuration with a Zirconia-based Erbium-doped fibre (Zr-EDF) and a semiconductor optical amplifier (SOA). The amplifier utilizes a two-stage structure with a midway isolator to improve flat gain characteristic and reduce noise figure. At input signal power of −30 dBm, a flat gain of 28 dB is obtained from wavelength region of 1530 to 1560 nm with gain variation of less than 4 dB. The noise figure is maintained below 11 dB at the flat-gain region. This amplifier has the potential to be used in the high channel count dense wavelength division multiplexing system due to its simplicity and compact design.     

All-optical frequency multiplication/recovery based on a semiconductor optical amplifier ring cavity

A novel scheme for all-optical frequency multiplication/recovery based on a semiconductor optical amplifier ring cavity is proposed and investigated numerically. The results show, for a 2.5 GHz driving pulse train, it can be generated 5-25 GHz repetition rate pulse trains with low clock amplitude jitter, polarization independence and high peak power. Furthermore, the extraction of the clock signal from a pseudorandom bit sequence signal can be realized based on the proposed scheme.     

Gain-enhanced optical coherence in a high optical gain semiconductor

The propagation of ultrashort pulses in a traveling wave semiconductor amplifier is considered. It is demonstrated that the effective polarization relaxation time, which determines the coherence of the interaction of pulses within the medium, strongly depends on its optical gain. As a result, it is shown that at large optical gains the coherence time can exceed the transverse relaxation time _T2$T_2$ by an order of magnitude, this accounting for the strong femtosecond superradiant pulse generation commonly observed in semiconductor laser structures.     

All-optical ultrawideband monocycle generation utilizing gain saturation of a dark return-to-zero signal in a semiconductor optical amplifier

We demonstrate a simple and compact scheme to generate ultrawideband (UWB) monocycle pulses utilizing gain saturation of a dark return-to-zero (RZ) signal in a semiconductor optical amplifier (SOA). When optical pulses with a dark RZ format propagate through the SOA, the output power at the rising edge will be overamplified compared with that at other durations due to the gain unsaturation. As a result, the output pulses are monocyclelike. The UWB frequency spectra at different injected currents, different input pulse widths, and different input wavelengths are analyzed. Our experiments show that the monocycle generation has good tolerance to the SOA bias current and the input signal wavelength.     

基于半导体光放大器的光控器件中控制光的性能分析

在O-RPR(optical resitient packet ring)光弹性分组环的基础上分析了在双环耦合全光缓存器这一基于半导体光放大器(SOA)的光控器件中要顺利实现数据的读写控制对光控制层功率提出的要求及其影响因素，讨论了由于信号光脉冲形状不是理想方波而造成的啁啾及脉冲压缩现象，分析了控制光功率波动及其信噪比对输出数据造成的影响. 得到的结论对其他基于SOA的光控器件同样具有借鉴意义. 关键词： O-RPR光弹性分组环 基于SOA的光控器件 双环耦合全光缓存器 控制层光功率     

Rapid evaluation of gain spectra from measured ASE spectra of travelling-wave semiconductor optical amplifier

Small signal gain (SSG) spectra of travelling-wave semi conductor optical amplifier (TWA) are usually obtained from the ratio of amplified signal power to the input sig nal power for one by one wavelength at different injec tion currents. This conventional measuring method i not only tedious but also restricted by the wavelength range of external laser source. Amplified spontaneou emission (ASE) spectra are good sources of optical gain information. A method was introduced by Hakki-Paol (H…     

Rapid evaluation of gain spectra from measured ASE spectra of travelling-wave semiconductor optical amplifier

An analytical equation, which directly relates amplified spontaneous emission (ASE) with small signal gain (SSG) of travelling-wave semiconductor optical amplifier (TWA), was derived. It was shown by theoretical analysis and experimental results that calibrated ASE spectra of TWA at different injection currents could be good evaluation and extension of SSG near gain peaks when gain peaks are larger than several decibels.The rapid evaluation method of SSG spectra is very simple, effective and especially applicable to batch measurement.     

Multiwavelength fiber ring lasing by use of a semiconductor optical amplifier

A multiwavelength fiber ring laser obtained by use of a semiconductor optical amplifier (SOA) with a simple laser cavity configuration is reported. A Fabry-Perot filter was used in the fiber laser ring cavity to achieve more than 50 simultaneous wavelength lasing oscillations with a frequency separation of 50 GHz. The resulting stable broadband multiwavelength lasing operation was attributed to broadband and flat gain of the SOA, which has a gain flatness of 0.8 dB for more than 20 nm. The laser has a total output power of -3 dBm and a signal-to-spontaneous-noise ratio of 30 dB.     

Optical pattern recognition by use of a segmented semiconductor optical amplifier

A technique for high-speed, all-optical pattern recognition based on cross correlation in a segmented semiconductor optical amplifier (SSOA) is presented. A counterpropagating pump-probe setup is used to perform cross correlation of the spatial gain-loss pattern in the SSOA with the optical data pattern (pump), and the result is read out with a counterpropagating probe. Cross correlation of 4-bit patterns at 85 Gbits/s is experimentally demonstrated. Simulations show reasonable agreement with experimental measurements and are used to address scalability to higher bit rates and longer data patterns.     

Nonlinear distortion generated by semiconductor optical amplifier boosters in analog optical systems

Closed-form theoretical expressions for the second- and third-order harmonic distortions generated by a semi-conductor optical amplifier (SOA) operating under slight saturation conditions are derived for what is believed to be the first time. The distortion results provided by these expressions agree very well with those obtained by means of simulation and experiments, showing that one should carefully adjust the optical power launched into the SOA to obtain both the good linearity and high dynamic range required by analog optical systems.     

半导体光放大器引起的光控器件中的信号损伤分析

在双环耦合全光缓存器的基础上分析了全光分组交换网络中以半导体光放大器（SOA）为相移器件的反馈型全光缓存器输出的信号损伤,包括SOA的非线性及载流子恢复时间限制引起的脉冲畸变与连续码流中的图样失真和SOA的自发辐射噪声累积引起的信噪比恶化及缓存器结构引起的“漏光”问题.理论分析及实验结果表明,在采用反相控制并注入高功率控制光的情况下,脉冲畸变与图样失真被抑制,由信噪比恶化及漏光决定的光分组的缓存圈数被限制在20—30圈.得到的结果对基于SOA的光缓存器及逻辑器件同样具有借鉴作用. 关键词： 全光分组交换 全光缓存器 信号损伤 半导体光放大器的噪声分析     

Polarization-independent wavelength conversion using a single semiconductor optical amplifier

Polarization-independent wavelength conversion is demonstrated by using four-wave mixing (FWM) in a single semiconductor optical amplifier (SOA). In this scheme, all the incident fields are split into two orthogonal-polarized parts by polarizing beam splitters (PBS). Each of the two parts is then transmitted into one facet of the SOA and they are counter-propagating through the same amplifier. Wavelength conversion with the polarization sensitivity less than 1.3 dB is obtained over a range from 1510 to 1620 nm.     

Interferometric method of suppressing the pattern effect in a semiconductor optical amplifier

A new idea of using change in index of refraction to suppress gain variation in a saturated semiconductor optical amplifier (SOA) is presented. This kind of gain compensation has the advantage of high speed because it involves two phenomena that always accompany each other. This compensation can be achieved with a nonsymmetrical Mach-Zehnder interferometer structure. Calculated results show that with this structure the input and output power of the SOA can be extended to nearly 10 dB from the former small-signal limit when less than 1-dB gain variation is permitted. Numerical simulations with an advanced dynamic model of the SOA agree with the calculated results.     

Dynamic model of slow light in a tensile-strained semiconductor optical amplifier

The slow light effect in semiconductor optical amplifiers has many potential applications in microwave photonics such as phase shifting and filtering. Models are needed to predict the slow light effect in SOAs and its dependence on the bias current, wavelength, and power and modulation index. In this paper we predict the slow light characteristics of a tensile-strained SOA by using a detailed time-domain model. The model includes full band-structure based calculations of the material gain, bimolecular recombination and spontaneous emission, a detailed carrier density rate equation and travelling-wave equations for the amplitude modulated signal and amplified spontaneous emission. The slow light parameters of interest include the beat signal phase shift and amplitude response. The model predictions show good agreement with experimental trends reported in the literature.     

Investigation of gain recovery for InAs/GaAs quantum dot semiconductor optical amplifiers by rate equation simulation

The gain recoveries in quantum dot semiconductor optical amplifiers (QD SOAs) are numerically studied by rate equation simulation. Similar to the optical pump-probe experiment, the injection of double 150 fs optical pulses is used to simulate the gain recovery of a weak continuous signal under different injection levels, inhomogeneous broadenings, detuning wavelengths, and pulse signal energies for the QD SOAs. The obtained gain recoveries are then fitted by a response function with multiple exponential terms to determine the response times. The gain recovery can be described by three exponential terms with the time constants, which can be explained as carrier relaxation from the excited state to the ground state, carrier captured by the excited state from the wetting layer, and the supply of the wetting layer carriers. The fitted lifetimes decrease with the increase of the injection currents under gain unsaturation, slightly decrease with the decrease of inhomogeneous broadening of QDs, and increase with the increase of detuning wavelength between continuous signal and pulse signal and the increase of the pulse energy.     

Placement of optimized semiconductor optical amplifier in fiber optical communication systems

This paper deals with the placement of semiconductor optical amplifier for 10 Gb/s non-return to zero format in single mode and dispersion-compensated fiber link. We investigated post-, pre- and symmetrical power compensation methods for different positions of the SOA in fiber link. The effect of increase in signal input power for the three power compensation methods is compared in terms of eye diagram, bit error rate, eye closure penalty and output received power. It is found that the post-power compensation method is superior to pre- and symmetrical power compensation methods. Further, the effect of variation in length of the standard single mode fiber and dispersion-compensated fiber for three power compensation configurations has also been observed. The impact of eye closure penalty is observed for large transmission distances for different signal input powers.     

Gain recovery in semiconductor optical amplifiers

Pump-probe measurements are presented of gain compression and recovery in a series of four semiconductor optical amplifiers of different lengths but otherwise identical structures. A continuous wave probe beam from a tunable laser is used to measure the wavelength dependence of gain compression and recovery times. A good level of agreement is obtained when these results are compared with numerical simulations using a model that includes the material gain spectrum, saturation effects and the variation of optical intensities with longitudinal position in the device. In addition the experimental results are interpreted in terms of a recent theory that offers approximate analytic expressions connecting recovery time with transmission gain. The spectral dependence of the recovery time and the gain are used to verify the correlations between these quantities and their dependence on device length. The results for recovery time show a strong dependence on probe wavelength with a pronounced minimum which is coincident with the peak of the gain spectrum for each device. A rather weak correlation of speed with length is found.