基于半导体光放大器和光学滤波器的同相波长转换理论研究

采用半导体光放大器(SOA)级联滤波器的方案可以实现高速全光波长转换,其中,滤波器实质上是对SOA输出信号的光谱进行优化操作.文中利用带通滤波器(BPF)和延时干涉仪(DI)组成的光谱优化器,不仅实现了80Gbit/s同相波长转换,而且基于遗传算法设计光谱优化器的参数,极大地提高了输出信号的质量.同时,也从理论上分析了SOA中超快带内效应对信号光谱的影响以及光谱优化器中BPF和DI的消光比对输出信号质量的影响.     

基于线性光放大器的全光逻辑异或门理论分析

基于速率方程建立了线性光放大器(LOA)的数值模型,模拟了线性光放大器的增益钳制特性。与对称结构马赫曾德尔干涉仪(MZI)的传输矩阵相结合,构建了线性光放大器马赫曾德尔干涉仪全光逻辑异或门模型,实现了两路40Gbit/s信号的异或运算。与传统的半导体光放大器(SOA)构成的马赫曾德尔干涉仪型异或门进行了比较,从器件结构上对两种异或门运算结果的差异给出了解释。结果表明,线性光放大器具有平坦的增益特性,对输入信号的扰动具有不敏感性,垂直光场缩短了载流子恢复时间;线性光放大器马赫曾德尔干涉仪结构可以实现异或运算;利用差分相位法可以解决载流子恢复时间对信号处理速度的限制,合理地选择延迟时间能获得较好的运算结果;输出信号具有眼图张开度大、消光比高、峰值啁啾小、对波长变化不敏感等优点。     

Theoretical and Experimental Study on all-optical Wavelength Converters Based on the Single-port-coupled SOA

We analyze the all-optical wavelength converter (AOWC)-based on cross-gain modulation (XGM) in a single-port-coupled (SPC) semiconductor optical amplifier (SOA). A comprehensive dynamic model is developed by considering longitudinal variations of the carrier density, the residual rear-facet reflectivity of the SOA and the wide-band spontaneous noise emission. The numerical simulations for the novel wavelength conversion at 10 Gbit/s are presented based on the model. The extinction ratio (ER), conversion efficiency and pattern effect of the SPC-SOA-based wavelength converters are investigated, respectively. Compared with the traditional scheme of the double-portcoupled (DPC) SOA, the SPC-SOA scheme has better performance. We have obtained that the ER is higher than 10 dB with the pump wavelength turned over 15nm from experiments. The experimental results are in agreement with the simulation results.     

A NOVEL SCHEME FOR XGM WAVELENGTH CONVERSION BASED ON SINGLE-PORT-COUPLED SOA

A novel scheme for wavelength conversion based on cross-gain modulation (XGM) in single-port-coupled semiconductor optical amplifier (SOA), in which the input and output share one port, is brought forward. Experimental results and theoretical analysis show that this scheme can be achieved with simple implementation, high output extinction ratio and large input dynamic range. Based on this novel scheme, 2.5 Gbit/s wavelength up conversion with 12.8 nm span has been demonstrated with the output extinction ratio as high as 15 dB.     

Study of dual-directional high rate secure communication systems using chaotic multiple-quantum-well lasers

A scheme of synchronized injection multi-quantum-well (MQW) laser system using optical coupling-feedback is presented for performing chaotic dual-directional secure communication. The performance characterization of chaos masking is investigated theoretically, the equation of synchronization demodulation is deduced and its root is also given. Chaos masking encoding with a rate of 5\,Gbit/s and a modulation frequency of 1\,GHz, chaos modulation with a rate of 0.2\,Gbit/s and a modulation frequency of 0.2\,GHz and chaos shifting key with a rate of 0.2\,Gbit/s are numerically simulated, separately. The ratio of the signal to the absolute synchronous error and the time for achieving synchronous demodulation are analysed in detail. The results illustrate that the system has stronger privacy and good performances so that it can be applied in chaotic dual-directional high rate secure communications.     

基于半导体光放大器瞬态交叉相位调制效应的高速反相和同相波长转换的研究

采用半导体光放大器(SOA)中的瞬态交叉相位调制效应是实现高速全光信号处理的有效途径.利用SOA和带宽为0.4 nm的窄带滤波器同时实现了重复频率为10 GHz、脉冲宽度为10 ps的同相和反相全光波长转换.当滤波器的中心波长相对于探测光载波波长蓝移0.25 nm或者红移0.05 nm时，得到反相波长转换；当滤波器的中心波长相对于探测光波长蓝移0.29 nm或者红移0.25 nm时，得到同相的波长转换.同时用数值模拟了从同相到反相波长转换的极性演化过程，理论分析和实验结果基本相符. 关键词： 半导体光放大器 波长转换 瞬态交叉相位调制     

All-optical NRZ-to-RZ format conversion with dual channel wavelength multicasting functions exploiting cross-phase modulation in a dispersion-flattened nonlinear photonic crystal fiber

All-optical single-to-dual channel format conversion from NRZ to RZ at 10 Gbit/s using cross phase modulation (XPM) in dispersion flattened highly nonlinear photonic crystal fiber (DF-HNL-PCF) is demonstrated. Format conversion with dual channels signal multicasting function is achieved by filtering simultaneously the blue- and red-chirped components of broadened optical spectrum induced by XPM between NRZ signal and clock light. Moreover, the wavelength tunability and dynamics characteristics of proposed format converter are also exploited experimentally by using NRZ signal light with different central wavelength and varying input power. Our results show that a wide wavelength operation range of 21.2 nm, extinction ratio (ER) and Q factor of over 10.9 dB and 6.1 are obtained. Furthermore, the influence of central wavelength offset of optical bandpass filter on converted RZ signal quality is investigated. The proposed scheme is simple, robust, and transparent to bit rate, which makes it very potential for application in future photonic networks.     

Analysis of all optical cascaded XGM wavelength converter using CW-holding beam

In this paper, we propose and analyze a wavelength conversion using an cross-gain modulation (XGM) with two semiconductor optical amplifiers and CW-holding beam for improvement of wavelength conversion speed and frequency chirp characteristics. Wavelength conversion characteristics of the cascaded XGM with a CW-holding beam are investigated in time domain. From the simulation, we have observed that the proposed scheme provides a non-inverted efficient wavelength conversion and frequency chirp reduction at higher bit rate operation.     

Performance improvement and wavelength reuse in millimeter-wave radio-over-fiber links incorporating all-fiber optical interleaver

Simultaneous downlink performance improvement and uplink wavelength reuse in a full-duplex millimeter-wave (MMW) radio-over-fiber (RoF) system by using a simple and cost-effective all-fiber optical interleaver are proposed and demonstrated. The MMW RoF downlink performance improvement is based on suppressing optical carrier-to-sideband ratio (OCSR), with which the mechanism is confirmed by theoretic analysis and derived experimental results. Measured results show that, by suppressing OCSR using a fabricated all-fiber optical interleaver, the downlink optical receiver sensitivity is improved about 2.1 dB. The downlink data rate is 1.25 Gbit/s and the carrier frequency is 58.1 GHz; the link consists of 6 km optical single-mode fiber and 1 m wireless connection. On the other hand, with the interleaver suppressing downlink OCSR, simultaneously an optical carrier is recovered from the RoF downlink and is reused for RoF uplink transmission. The uplink is operated at 62.9 GHz and the data rate is the same 1.25 Gbit/s. With the recovered optical carrier, a laser-free remote access point is achieved. The principle, structure, and fabrication of an all-fiber optical interleaver are also presented in this paper.     

基于半导体光放大器交叉偏振调制效应实现正、反相波长变换

利用琼斯矩阵，对基于半导体光放大器中的交叉偏振调制效应实现全光波长变换进行了理论分析.结果表明，利用这种机制可以实现同相与反相波长变换.在实验上同时实现了10Gb/s归零信号的正相与反相波长变换，输出消光比分别达到了6.9 dB和8.1 dB.     

Chaos synchronization and communication of mutual coupling lasers ring based on incoherent injection

A chaos secure communication system of mutual coupling lasers ring based on incoherent optical injection is proposed, in which fine tuning of optical frequency is not required compared with other schemes based on coherent optical injection. Therefore the secure communication scheme is attractive for experimental investigation. The dynamics of semiconductor lasers in the coupling ring are examined. Numerical investigations indicate that zero lag synchronization can be achieved under equal coupling time and strength of mutual coupling. Furthermore, by chaos shift keying (CSK), secure communication is simulated with a random bit stream of 1.0 Gbit/s. The results confirm the possibility of applying incoherent schemes of mutual coupling lasers ring to realize chaotic secure communication.     

Performance improvement of 10-Gb/s XGM wavelength conversion by using polarization control structure

By utilizing the cross polarization modulation effect in semiconductor optical amplifier(SOA), the extinc tion ratio of cross gain modulation(XGM)wavelength conversion was enhanced, the pattern effect was significantly reduced,and the power penalty of wavelength conversion was reduced by 5 dB simultane-ously. Furthermore, by adjusting the settings of polarization controllers, both inverted and non-inverted wavelength conversion can be achieved right in the same wavelength converter.     

基于折叠式超快非线性干涉仪的全光码型转换理论和实验研究

码型转换是实现非归零(NRZ)信号全光时钟恢复的关键技术.提出了一种基于折叠式超快非线性干涉仪的全光NRZ到伪归零(PRZ)信号转换的新型方案.基于半导体光放大器的分段模型和超快非线性干涉仪的传输函数，建立了该方案的理论分析模型，数值模拟了不同速率下的码型转换过程.实验实现了稳定的10，20和40 Gbit/s的NRZ到PRZ信号的码型转换，分析了影响码型转换输出特性的因素，理论分析结果与实验结果基本符合. 关键词： 超快非线性干涉仪 半导体光放大器 全光码型转换     

A novel approach to all-optical wavelength conversion by utilizing a reflective semiconductor optical amplifier in a co-propagation scheme

Nonlinear optical gain modulation in an InGaAsP/InP bulk reflective semiconductor optical amplifier (RSOA) is studied. The differences of the optical properties between RSOAs and conventional SOAs are initially investigated. All-optical wavelength conversion based on nonlinear gain modulation in RSOAs is demonstrated at a bit rate of 2.488 Gbit/s. It is shown that a bit-error-rate of <10⁻⁹ can be achieved and an extinction ratio of >9 dB can be obtained at a bit rate of 2.488 Gbit/s with a 2³¹-1 non-return-to-zero (NRZ) pseudorandom bit sequence (PRBS). In comparison with conventional SOAs, wavelength conversion by RSOAs shows much improved performances in high-speed all-optical wavelength conversions.     

Theoretical Study of SOA-Based Wavelength Conversion with NRZ and RZ Format at 40 Gb/s

We theoretically discuss 40 Gb/s semiconductor optical amplifier （SOA）-based wavelength conversion （WC） using a detuning optical bandpass Jilter based on ultrafast dynamic characteristics of SOA. Both the inverted and noninverted WCs are obtained by shifting the filter central wavelength with respect to the probe wavelength when input data signal is in return-to-zero （RZ） format. However, we can obtain format conversion from nonreturn- to-zero （NRZ） to pseudo-return-to-zero （PRZ） and inverted WC when the input signal is in NRZ format.     

基于半导体光放大器交叉偏振调制的波长转换理论研究

在半导体光放大器中,采用由张应变引起的自身双折射理论模型对交叉偏振调制型全光波长转换器的波长转换特性进行了数值研究,并对数值结果与相关实验进行了对比。结果表明:通过调节系统参量,可以实现同相或反相波长转换;同相和反相波长转换时输出的信号啁啾、消光比和眼图具有不同特性;随着数据传输速率的增加,输出信号的眼图张开度减小,啁啾变大。     

基于高非线性光纤中非线性偏振旋转效应的全光逻辑门研究

提出了一种新型的基于高非线性光纤(HNLF)中非线性 偏振旋转(NPR)效应的全光逻辑门实现方案. 将两路非归零码数据信号A和B以及一路直流光同时注入HNLF, 光功率变化导致的非线性双折射在两个偏振分量上引入非线性相对相移, 从而导致光信号的偏振态旋转. 在HNLF输出端, 通过波分解复用器和偏振分束器同时滤出数据信号和直流光的正交偏振态, 从而同时实现多种基础组合逻辑, 并可以在同一段HNLF中实现较为复杂的半加器、半减器逻辑功能. 理论分析了信号光在HNLF中的偏振态演化, 以及利用HNLF中的NPR效应同时实现多种全光逻辑门的原理. 并在实验中得到了10 Gbit/s全光信号"与”、"非”、"或”、"同或”、"异或”、"A· B”、"A·B”、半加器、半减器等逻辑功能, 验证了方案的可行性.     

Experimental observation of a 1.5 microm band wavelength conversion and logic NOT gate at 40 Gbit/s based on sum-frequency generation

We have experimentally verified a new idea for 40 Gbit/s wavelength conversion within the 1.5 microm band based on sum-frequency generation (SFG) in a periodically poled LiNbO3 waveguide. The spectrum and the temporal waveform of the output pump reveal that the input cw pump is converted to an optical pulse during SFG. Not only wavelength conversion but also a logic NOT gate at 40 Gbit/s are experimentally observed.     

Ultrafast all-optical signal processing with Symmetric Mach–Zehnder type all-optical switches

We present Symmetric Mach–Zehnder (SMZ) type all-optical switches: an SMZ all-optical switch, a polarization-discriminating SMZ (PD-SMZ) all-optical switch, and a delayed interference signal wavelength converter (DISC). These switches are capable of ultrafast, low control power, and low chirp switching, which is not restricted by slow relaxation of highly efficient nonlinearities. High repetition operation unrestricted by slow relaxation is also possible for these switches. This is because of a push–pull modulation scheme or sometimes called a differential phase modulation scheme. These three devices are similar, but different in some important aspects, thus a comparison is made among the three. Then semiconductor optical amplifiers (SOAs) are discussed as a nonlinear phase shifter for these devices. Then, ultrafast all-optical signal processing using SOA based SMZs is demonstrated. Error-free demultiplexing from 168 to 10.5 Gbit/s is presented, in which a hybrid-integrated SMZ (HI-SMZ) is used as a demultiplexer. In pulse regeneration experiment, the signal pulses at 84 Gbit/s are regenerated by the PD-SMZ and the regenerated pulses are demultiplexed to 10.5 Gbit/s by the HI-SMZ to verify error-free operation. The retiming capability of this scheme is quantitatively demonstrated. Also presented is error-free all-optical wavelength conversion at 168 Gbit/s using the DISC. These results represent the fastest error-free operations reported to date in each category.     

基于半导体光放大器平行双抽运对OFDM光信号进行全光波长变换性能研究

研究了基于半导体光放大器平行双抽运对光正交频分复用信号进行全光波长变换的系统.信号光源经2Gb/s电信号直接调制后再和双抽运光耦合,经半导体光放大器后,由于四波混频效应而产生新的波长的信号光.实验结果显示,经半导体光放大器四波混频效应后,产生新的波长的信号光将携带OFDM信号且偏振不敏感,转换效率与双抽运光之间的波长间隔,抽运与信号光波长间距,信号光与泵浦光之间的偏振夹角等有关.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.