Research of all-optical ultra-wideband triplet signal source based on a single semiconductor optical amplifier

A novel scheme for all-optical ultra-wideband triplet signal pulse generation based on the cross-gain modulation (XGM) in a single semiconductor optical amplifier (SOA) is demonstrated. In this scheme, only one optical source and one SOA are needed, so the configuration is simple. Due to only one wavelength is included in the generated triplet pulse, no time difference between output signal light and probe light is introduced during the transmission process. By using the software of Optisystem 7.0, the impacts of the input signal width, the optical power and the wavelength of the optical source on the generated triplet pulse are numerically simulated and studied. The results show that the proposed scheme has better triplet signal pulse when the input signal pulse width is larger, and it is insensitive to the wavelength change within a certain range.     

All-optical ultra-wideband doublet signal source based on the cross-gain modulation in a semiconductor optical amplifier

We propose a novel scheme to generate the ultra-wideband (UWB) doublet signal pulse based on the cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA). In the scheme, only an optical source and an SOA are needed. As there is only one wavelength included in the output doublet signal pulse, no time difference between the upper and down pulses is introduced during the transmission process. By using the software of Optisystem 7.0, the impacts of the optical power, the SOA current, the wavelength and the input signal pulse width on the generated doublet pulse are simulated and tudied numerically. The results show that when the pulse width of the input signal pulse is larger, the output signal pulse is better, and is insensitive to the change of wavelength. In addition, the ultra-wideband positive and negative monocycles can be generated by choosing suitable optical source power and SOA current.     

基于半导体放大器实现多功能超宽带调制的研究

基于半导体放大器(SOA)的增益饱和效应,提出了一种简单的实现多功能超宽带(UWB)调制的方案。方案采用一个光源和单个SOA,可以实现脉冲波形调制(PSM)、脉冲幅度调制(PAM)和脉冲极性调制(BPM),因此实现容易、结构简单和成本低。利用OptiSystem软件对方案进行了仿真研究,分析了各参数对调制信号的影响以及信号的传输特性。结果表明,本方案对光源的波长和光源的光功率的变化不敏感,仿真输出的调制信号在单模光纤(SMF)中可传输35km。     

基于并联SOA的全光广播式超宽带脉冲形状调制技术

基于半导体光放大器(SOA)中交叉增益调制(XGM)效应,采用SOA的并联结构,提出了一种全光产生广播式超宽带(UWB)脉冲形状调制(PSM)信号的方案。该方案同时产生三路超宽带PSM信号,具有多用户传输数据的能力,可为多址通信作理论基础;采用相向的工作方式可以改善输出信号的消光比。利用OptiSystem7.0软件对方案进行仿真,分析了输入信号脉冲宽度、输入光功率和波长对产生的超宽带PSM信号的影响,对信号的传输特性进行了研究。结果表明,本文方案对输入信号脉冲宽度和输入光波长具有良好的容忍度,并且给出了输入光功率的优化范围。     

Continuously wavelength-tunable MQW fabry-perot laser diode pulse source with a fiber-based external cavity

A simple continuously wavelength-tunable fiber ring laser pulse source is demonstrated. Such a source employs a gain-switched multiple quantum-well Fabry-Perot laser diode in a self-seeding scheme and the output pulse wavelength can be tuned continuously via a tunable optical filter. The optical pulses generated exhibit a pulsewidth of 92 ps at the frequency of 2.6 GHz. Within a wide wavelength tuning range of 46 nm, the side-mode suppression ratio and the average power of the output optical pulses obtained are higher than 50.1 dB and 3.3 dBm, respectively, and the pulse spectral stability can be maintained in the whole wavelength tuning range.     

Cascadability Performance Evaluation of a New NRZ SOA-MZI Wavelength Converter

We evaluate the cascadability performance of a new semiconductor optical amplifier (SOA) Mach-Zehnder interferometer-based nonreturn-to-zero wavelength converter in a loop experiment. We use the bidirectional data injection control scheme with an additional continuous-wave signal to optimize the gains and phases imparted by the SOAs. The scheme has been shown to be capable of eight cascaded, error-free wavelength conversions at 10 Gb/s.     

全光超宽带正相和反相monocycle信号源的研究

基于半导体光放大器( SOA)中交叉增益调制(XGM)效应,同时全光实现超宽带(UWB)正相、反相高斯单边信号(monocycle).输出的monocycle脉冲只包含一个波长分量,在光纤传输过程中monocycle上下脉冲不会引入时间差.利用光通信系统软件OptiSystem对方案进行仿真,分析了光源波长对输出monocycle脉冲的影响,结果表明输出的monocycle脉冲具有对光源变化不敏感的优点.     

基于SOA中XGM效应全光超宽带高斯单边信号源的研究

提出了一种基于半导体光放大器（SOA）中交叉增益调制（XGM）效应产生高斯单边信号（monocycle）脉冲的方案。该方案只需要单个外部光源和单个SOA,结构简单;采用相向的工作方式可以改善输出信号的消光比;输出的monocycle信号光只含有一个波长,在光纤传输过程中上下脉冲不会引入时间差。利用Optisystern...     

Quantum-Dot Semiconductor Mode-Locked Lasers and Amplifiers at 40 GHz

Mode-locked lasers (MLLs) and semiconductor optical amplifiers (SOAs) based on quantum-dot (QD) gain material will impact the development of next-generation networks, such as the 100 Gb/s Ethernet. MLLs presently consisting of a monolithic two-section device already generate picosecond pulse trains at 40 GHz. Temperature dependence of pulsewidth for p-doped devices, a detailed chirp analysis that is a prerequisite for optical time-division multiplexing applications, and data transmission experiments are presented in this paper. QD SOAs show superior performance for linear amplification as well as nonlinear signal processing. Using cross-gain modulation for wavelength conversion, QD SOAs are shown to have a small signal bandwidth beyond 40 GHz under high-bias current injection. This makes QD SOAs much superior to conventional SOAs.      

基于PM 的多功能超宽带调制技术的研究

基于相位调制器(PM)级联高斯带通滤波器,提出了一种超宽带(UWB)多功能调制方案,可以实现通断键控(OOK)、脉冲极性调制(PBM)和脉冲形状调制(PSM)。该方案结构简单,只需单个光源,利用率较高,仅改变比特序列发生器(BSG)的编码就可实现三种UWB调制格式间的灵活切换;产生的三种信号只包含一个波长,在光纤中传输时无需复杂的非线性控制和色散管理。使用光通信软件Optisystem进行模拟,研究了光源功率、调制速率以及两支路PM和滤波器系统误差的影响,对OOK、PBM和PSM信号的传输性能进行了分析。结果表明,光源功率和调制速率在一定范围内变化时,可以获得性能最佳的UWB调制信号。     

基于半导体光放大器的组播实验研究

提出了一种基于半导体光放大器(SOA)的组播实验方案,首先利用谱展宽和谱切片得到多波长脉冲源,将其作为探测光并与信号光共同注入到SOA中,利用SOA的交叉增益调制(XGM)效应,信号光与每一个波长的脉冲光发生作用,在SOA输出端通过可调光带通滤波器(TBDF)得到每一波长的变换后信号,实现光信号的组播过程。在实验中,10 Gb/s的归零(RZ)码作为信号光,而由多波长脉冲源产生的4波长脉冲光作为探测光,在探测光波长附近分别得到了与编码信号光逻辑取"非"的信号。     

Analytical Solution for SOA-Based All-Optical Wavelength Conversion Using Transient Cross-Phase Modulation

All-optical wavelength conversion (WC) based on transient cross-phase modulation (T-XPM) of semiconductor optical amplifier (SOAs) is a promising approach to accelerate the gain recovery of SOAs. An analytical solution is deduced to explain the polarity variation of WC based on T-XPM of SOAs from the viewpoint of the impulse response functions. We conclude that both inverted and noninverted WCs can be realized when the central wavelength of the optical bandpass filter is either blue-shifted or red-shifted with respect to the wavelength of the probe signal. We are able to validate the formula against our experimental results recently published     

Increasing input power dynamic range of SOA by shifting thetransparent wavelength of tunable optical filter

Gain-saturation-induced self-phase modulation (SPM) leading to pulse distortion in a semiconductor optical amplifier (SOA) is overcome by shifting a tunable optical filter (TOF). A recovered or broadened pulse can be obtained after filtering the amplified pulse in the SOA even if the short pulse is only 2-3 ps long. The input power dynamic range (IPDR) can be strongly increased by shifting the TOF and the direction of the shifted transparent wavelength is different for 10 Gb/s return-to-zero (RZ) or nonreturn-to-zero (NRZ) signals. The transparent wavelength of the TOF should be shifted to a longer wavelength for RZ signals and to a shorter for NRZ signals. 80-Gb/s optical time division multiplexing (OTDM) signal amplification in the SOA is demonstrated for the first time. We also demonstrate that a large IPDR for the 80-Gb/s OTDM signal can be obtained by shifting the TOF     

全光波长转换器噪声变换的小信号分析方法

本文利用小信号模型对基于半导体光放大器（SOA）交叉增益调制（XGM）波长转换器的噪声变换进行了理论分析和数据计算,结果表明,泵浦光功率和探测光功率的大小以及光放大器的增益对噪声变换有直接的影响,在适度的输入功率范围内,噪声得到了有效的抑制。     

High-Speed Mode-Locked Quantum-Dot Lasers and Optical Amplifiers

Recent results on GaAs-based high-speed mode-locked quantum-dot (QD) lasers and optical amplifiers with an operation wavelength centered at 1290 nm are reviewed and their complex dependence on device and operating parameters is discussed on the basis of experimental data obtained with integrated fiber-based QD device modules. Hybrid and passive mode locking of QD lasers with repetition frequencies between 5 and 80 GHz, sub-ps pulse widths, ultralow timing jitter down to 190 fs, high output peak power beyond 1 W, and suppression of Q-switching are reported, showing the large potential of this class of devices for O-band optical fiber applications. Results on cw and dynamical characterization of QD semiconductor optical amplifiers (SOAs) are presented. QD amplifiers exhibit a close-to-ideal noise figure of 4 dB and demonstrate multiwavelength amplification of three coarse wavelength division multiplexing (CWDM) wavelengths simultaneously. Modelling of QD polarization dependence shows that it should be possible to achieve polarization insensitive SOAs using vertically coupled QD stacks. Amplification of ultrafast 80 GHz optical combs and bit-error-free data signal amplification at 40 Gb/s with QD SOAs show the potential for their application in future 100 Gb Ethernet networks.     

Improving the all-optical response of SOAs using a modulated holding signal

A method for increasing the all-optical modulation bandwidth of semiconductor optical amplifiers (SOAs) by use of a cross-gain-modulated (XGM) holding signal is suggested and analyzed. The bandwidth improvement is numerically demonstrated by studying wavelength conversion in an SOA-based Mach-Zehnder interferometer (MZI) at 160 and 40 Gb/s. The new scheme is predicted to improve the extinction ratio and the minimum mark output power, as well as to reduce the amplitude jitter of the wavelength converted signal.     

Analysis of optical phase-conjugate characteristics of picosecondfour-wave mixing signals in semiconductor optical amplifiers

We have analyzed for the first time the optical phase-conjugate characteristics of picosecond four-wave mixing (FWM) signals in semiconductor optical amplifiers (SOAs) using the finite-difference beam propagation method (FD-BPM). We show that the optical phase-conjugate characteristics of the FWM signals are strongly dependent on input pump pulsewidths. As a typical example, we have demonstrated that SOAs act as an ideal phase-conjugator, within the confines of reversing the chirp of optical pulses, for a 10-ps input pump pulse and a ~2.2-ps linearly chirped input probe pulse. When the pulsewidth of pump pulse becomes short, the minimum compressed pulsewidth is obtained by using a fiber shorter in length than the input fiber, but having the same group velocity dispersion as the input fiber. For a much shorter pump pulse such as 1 ps, the short FWM signal can be obtained via the gating characteristics of the FWM. However, only a part of the phase information is copied to the FWM signal due to such gating characteristics. The phase information is also degraded due to the fast nonlinear effect in the SOA. Thus, the pulsewidth is not compressed by propagation through a dispersive medium     

Characterization of the chirp and intensity modulation propertiesof an SOA-MZI wavelength converter

Wavelength converters based on cross-phase modulation in semiconductor optical amplifiers (SOAs) in the arms of a Mach-Zehnder interferometer (MZI) provide a key network element for reconfigurable optical networks that incorporate wavelength routing. For system design purposes, the properties of the intensity and phase (chirp) modulation of the wavelength-converted signal for an SOA-MZI wavelength converter are important. In this paper, the small-signal α parameter, which characterizes the converter chirp, and the conversion frequency response are characterized experimentally for an integrated all-active SOA-MZI wavelength converter. For both co- and counterpropagating signals, the variation of the a parameter along the interference and conversion curves is considered in detail. Three optical modulators with quite different chirp properties are used to generate the modulated input signal to the wavelength converter. The results demonstrate that the chirp of the wavelength-converted signal is primarily determined by the device properties and the intensity of the modulated input signal. The a parameter of the wavelength-converted signal is negative for noninverting operation and positive for inverting operation. An important contribution of the paper is the detailed assessment of this key device characteristic. The experimental characterization of the wavelength converter is incorporated into a device model that can be used to obtain the pulse response. Calculated and measured results for the time dependence of the intensity and chirp of the wavelength-converted signal are in good agreement. The conversion frequency response for the intensity modulation is also measured along the conversion curve. The 3-dB bandwidth is found to be generally about 8-10 GHz     

Transmission performance analysis of 8/spl times/10 Gb/s WDM signals using cascaded SOAs due to signal wavelength displacement

We have analyzed the transmission performance of 8/spl times/10 Gb/s wavelength division multiplexing (WDM) signals due to crosstalk in cascaded conventional semiconductor optical amplifiers (SOAs). Using two different methods, the crosstalk over the whole gain bandwidth in SOAs is calculated to be 2-5 dB lower for the positive detuning. Then, transmission performance of 8/spl times/10 Gb/s WDM signals up to 6/spl times/40 km span in terms of receiver sensitivity is estimated over various transmission distances using cascaded SOAs for the positive signal wavelength displacement of 30, 40, and 50 nm. Especially for 50 nm detuning, transmission performances with and without using a reservoir channel are similar to each other. Our results suggest that SOAs can be used as an optical amplifier for displacement larger than 50 nm without using the reservoir channel.     

High-Bit-Rate Dense SS-WDM PON Using SOA-Based Noise Reduction With a Novel Balanced Detection

The major drawback of incoherent broadband sources (BBSs) is their inherent intensity noise. Semiconductor optical amplifiers (SOAs) can be exploited at the transmitter to mitigate this noise. Optical filtering at the receiver, however, leads to the return of most of suppressed noise. Wider filtering at the receiver is the best known strategy to maintain performance gains, at the price of reduced spectral efficiency due to the tradeoff between noise cleaning and adjacent channel crosstalk. We introduce a novel balanced receiver for wavelength division multiplexing (WDM) systems that maintains greater noise cleaning and leaves spectral efficiency unchanged. Unlike standard receivers, our balanced scheme does not filter the desired signal. In this paper, we first demonstrate that the newly proposed receiver is equivalent to standard WDM receivers when no SOA for noise cleaning is present at the transmitter. Although a 2.9-dB power penalty is incurred, network capacity is unchanged, i.e., bit error rate (BER) floors due to intensity noise are the same. When SOAs are employed to mitigate severe intensity noise, we show that our receiver outperforms the wide filtering strategy by two orders of magnitude. Dense WDM capacity is demonstrated up to 10 Gb/s using a thermal source, a saturated SOA, and the balanced detection scheme. A BER of 10^-6 is achieved at 10 Gb/s; further improvement is possible using low overhead forward error correction or a better SOA design. This demonstrates the ability of spectrum-sliced wavelength division multiplexing (SS-WDM) passive optical networks (PONs) to operate at 10 Gb/s at good spectral efficiency. Error performance better than 10^-9 is achieved up to 8 Gb/s with 30-GHz optical channel bandwidth and 100-GHz spacing.