Novel scheme for ultrafast all-optical XOR operation

A novel scheme for all-optical exclusive-OR (XOR) operating at 160 Gb/s is proposed and analyzed by means of numerical simulations. It consists of a Mach-Zehnder interferometer (MZI) where a semiconductor optical amplifier (SOA) is placed in each of its arms. This SOA-MZI setup is coupled to a delay interferometer, which acts as a signal regenerator. It is shown that error-free operation can be achieved at a data rate of 160 Gb/s, indicating that the proposed scheme is not limited by the SOA recovery time.     

基于半导体光放大器的波长转换新方案研究

分别对基于半导体光放大器(SOA)的交叉相位调制(XPM)型和交叉增益调制(XGM)型波长转换器提出了改进的新方案。采用非对称的马赫-曾德干涉仪(MZI)结构,实现了速率为10 Gb/s转换范围达40nm的XPM波长转换;利用SOA中的交叉偏振调制(CPM)效应,在XGM波长转换器中引入偏振控制结构,大大改善了转换性能,并在同一个波长转换器中实现了正反相的波长转换。     

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     

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.     

Study of polarization-insensitive wave mixing in bulk semiconductoroptical amplifiers

A detailed experimental investigation of polarization-insensitive dual-pump wave mixing in bulk, polarization-insensitive semiconductor optical amplifier (SOA) is reported. Measurements of the phase conjugated, polarization-insensitive four-wave mixing (FWM) efficiency are reported versus: (1) pump-signal wavelength spacing while keeping the wavelength spacing between the two orthogonally polarized pumps constant and (2) wavelength spacing between the pumps while keeping the signal wavelength constant. The achieved wavelength conversion bandwidth of the polarization-insensitive scheme is approximately 60 nm with efficiency between 8 and -20 dB. The obtained results are in good agreement with theoretical predictions     

Noise Transfer Characteristics in a Semiconductor Optical Amplifier With Application to Wavelength Conversion Based on a Delay Interferometer

A theoretical model is presented to analyze the noise transfer characteristics in a semiconductor optical amplifier (SOA) under the excitation of a noisy pump signal and a noise-free probe signal. An analytical expression is derived for the optical signal-to-noise ratio (OSNR) of the output probe signal from the SOA. The influence of the gain saturation of the SOA, and the pump and probe signal powers on the noise transfer characteristics is investigated. The noise transfer model is used to determine the output noise power of a delay interference wavelength converter. An analytical expression is obtained for the nonlinear phase change in the SOA, which determines the output power of the wavelength-converted signal. These results show that the noise transfer in the wavelength conversion can be suppressed by increasing the probe signal power, but that the improvement in the output signal OSNR relative to the input signal OSNR is accompanied by a reduction in the conversion efficiency. This fundamental tradeoff can be readily investigated during the design optimization process using the concise results derived in this paper.     

利用半导体光放大器和滤波器组合实现高速波长转换和码型转换

将半导体光放大器(SOA)和滤波器组合使用是实现高速全光信号处理的有效途径。利用半导体光放大器和带宽为0.32nm的可调窄带滤波器同时实现了40Gbit/s的非归零(NRZ)信号的反相波长转换(WC)和非归零到伪归零(PRZ)信号的码型转换,波长转换和码型转换的结果差异取决于滤波器中心波长相对于探测光波长的失谐量。当滤波器的失谐量为-0.24nm时,输出反相的波长转换,此时滤波器起到加速半导体光放大器增益恢复的功能。当滤波器失谐量为 0.41nm和-0.48nm时,得到非归零到伪归零的码型转换,并且产生的伪归零脉冲分别出现在非归零信号的上升沿和下降沿,此时滤波器的作用是将探测光的相位信息转换为强度信息,并且该码型转换结果兼有波长转换的功能。     

基于半导体光放大器-交叉增益调制波长转换器消光比特性的研究

建立了基于半导体光放大器一交叉增益调制(SOA-XGM)的波长转换理论模型，利用分段方法对交叉增益调制波长转换器同向和相向两种工作方式下消光比(ER)特性作了详细的研究。结果表明，波长转换器的输出消光比随转换速率增加而减小，而且转换速率越高，减小得越快；随着抽运波长的变化，消光比有一个对应于峰值增益波长的最佳抽运波长；波长向下转换(Δλ＜0)时的消光比要明显优于向上转换(Δλ＞0)；输出消光比也随着输入消光比的增大而增大。相同情况下相向工作方式时的输出消光比特性要优于同向工作方式。最后，从物理上对两种工作方式消光比和噪声特性的差异作了解释。     

Waveform shaping of chirp-controlled signal by semiconductoroptical amplifier using Mach-Zehnder frequency discriminator

The optical output waveform of a semiconductor optical amplifier (SOA) is shaped using a Mach-Zehnder interferometer (MZI) as a frequency discriminator in order to suppress its distortion at high SOA input powers. This technique is applied to chirp control of an optical signal using an SOA, and the chirp control with waveform shaping greatly improves the transmission performance of a positively chirped optical signal in standard single-mode fiber over a wide range of SOA input powers. We also demonstrate that the chirp control with waveform shaping can be achieved without changing the drive settings of the SOA and MZI, even when the optical frequency is switched to another channel located on the wavelength-division-multiplexing frequency grid     

Wavelength conversion based on nonlinear polarization rotation in gain transparent SOA

We describe an all-optical wavelength conversion scheme for 1310 nm to 1550 nm based on nonlinear polarization rotation in a gain-transparent semiconductor optical amplifier(GT-SOA) which brings in the assistant light to improve the property of the converted light.From the SOA carrier density equations,the 1310 nm-to-1550 nm wavelength conversion scheme is analyzed by the Jones matrix.The phase shift between TE and TM modes and the converted light are simulated at bit rate of 30 Gbit/s.We also analyze the influence of the input signal power,the injected current and the assistant light power on the extinction ratio of the converted light.     

Broadcasting in colorless WDM-PON using spectrum-sliced wavelength conversion

We propose and experimentally demonstrate a novel wavelength-division-multiplexed passive optical network (WDM-PON) scheme for providing broadcasting service by using an inverted amplified spontaneous emission (ASE) from a semiconductor optical amplifier (SOA). In this scheme, single pump signal is converted into multiple wavelengths signal by spectrum sliced wavelength conversion. We expect it could be very practical and cost-effective solution for broadcasting in WDM-PON due to its simplicity.     

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.     

基于半导体光放大器交叉增益饱和的波长转换的理论分析

建立了基于半导体光放大器交叉增益饱和的波长转换的理论模型。分别讨论了小信号下波长转换特性和大信号下转换波形的畸变情况。结果表明,半导体光放大器的载流子寿命是导致输出波形畸变的主要因素。     

集成光学移相器波长相关性的比较研究

移相器是一种常用的集成光学结构,其相移值的波长相关性决定了移相器的工作波长范围。针对移相器的波长相关性,文中对两种集成光学移相器设计方案（长度差方案和折射率差方案）所设计的二氧化硅基集成光学移相器进行了实验研究。在马赫-曾德尔干涉仪（MZI）的两干涉臂之间,采用两种移相方案分别设计制作180移相器,通过测试MZI的插入损耗与波长的依赖关系对两种移相器的波长相关性进行了比较。研究结果显示,折射率差方案所设计移相器的工作波长范围大约是长度差方案的1.8~1.9倍。这一实验结果与理论计算吻合,证明了折射率差方案设计的移相器的相移值波长相关性更小,因而具有更宽的工作波长范围。     

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.     

NRZ-OOK-to-RZ-BPSK modulation-format conversion using SOA-MZI wavelength converter

A novel all-optical modulation-format conversion from nonreturn-to-zero on-off keying (NRZ-OOK) to return-to-zero binary phase-shift keying (RZ-BPSK) is proposed. A Mach-Zehnder interferometric (MZI) wavelength converter consisting of integrated semiconductor optical amplifiers (SOAs) is utilized to implement the proposed format conversion. Error-free operation at a bit rate of 10.7 Gb/s is experimentally demonstrated in order to show the feasibility of the proposed scheme. The received sensitivity of the converted signal is improved by 2.9 dB compared with a back-to-back NRZ-OOK signal at BER=10/sup -9/. In addition, a reasonable dispersion tolerance of the converted signal up to /spl plusmn/500 ps/nm is observed. The numerical simulation based upon the carrier-rate equation verifies the experimental results.     

Optical label encoding using electroabsorption modulators and investigation of chirp properties

A novel scheme of optical label encoding by wavelength conversion based on electroabsorption modulators (EAMs) is reported. Based on the experimental observations, the chirp properties of the wavelength-converted signal are discussed and a wide dynamic range of the chirp /spl alpha/-parameter is found allowed. Compared with cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA), the EAM has several advantages, which make it attractive for optical label encoding or other applications as a wavelength converter.     

基于半导体光放大器的四波混频效应对正交频分复用光信号进行全光波长变换

实验研究了基于半导体光放大器(SOA)的四波混频(FWM)效应的单抽运光正交频分复用(OFDM)信号的波长变换系统.信号光源和抽运光源分别由两个不同输出波长的可调分布反馈式激光器(DFB-LD)产生.信号光源经2.5 Gb/s OFDM的电信号直接调制后再和抽运光源耦合,经光放大器后在SOA实现波长变换.实验结果显示,耦合信号经SOA四波混频效应后,产生新波长的信号光将携带OFDM信号,且转换效率与信号光和抽运光的功率、波长以及两者的偏振夹角有关.同时也测量了转换的OFDM信号的功率-误码曲线和接收星座图.     

基于半导体光放大器的四波混频型全光波长转换器

本文报道了基于自行研制的半导体光放大器（SOA）的四波混频（FWM）型全光波长转换,采用环型腔掺铒光纤激光器（EDFL）作为泵浦源,实现了转换波长的连续可调。并就波长转换间距、光放大器的小信号增益和输入泵浦光功率对转换效率的影响进行了理论与实验分析,结果表明高的SOA增益和较大的输入泵浦光功率须利于转换效率的提高。     

基于半导体光放大器临界激射状态的同相波长转换

基于半导体光放大器处于放大和激射之间的临界状态 ,实现了同相波长转换 ,转换后光信号与泵浦光信号有相同的比特系列 .运用放大器中存在的自发辐射光子诱发的受激辐射和入射信号光子诱发的受激辐射之间的竞争很好地解释了实验结果 .结果表明 ,此种波长转换结构简单、输出消光比不退化