Recent Advances in Optical Processing Techniques Using Highly Nonlinear Bismuth Oxide Fiber

We report our recent studies on nonlinear processing of optical signals using a 35-cm highly nonlinear bismuth oxide fiber (Bi-NLF). Our findings are based on self-phase modulation, cross-phase modulation, and four-wave mixing in the Bi-NLF. We demonstrate applications of the nonlinear techniques in optical signal regeneration, tunable optical delay, stabilization of multiwavelength laser source, tunable optical pulse generation, microwave photonic carrier frequency multiplication, and all-optical wavelength conversion.     

MPLS组件与框架——MPLS体系结构解析

从系统上介绍1种新兴骨干网络技术MPLS的体系结构，包括其基本概念、功能特性、结构组成及其内在关系。在MPLS体系结构中，标签是关键的技术手段。所有进入MPLS的包都必须加上标签，所有操作都围绕标签展开，对标签的分析、处理和根据标签内容进行包转发是在标签交换路由器LSR上完成的，LSR综合了传统路由器和交换机的优点，是MPLS的基本单元，带有标签的包在LSR间传输，所经过的LSR序列组成标签交换路径LSP。LSP建立和控制是MPLS体系结构的重要内容。在建立LSP的过程中，MPLS体系结构支持环路检测，以避免环路的产生而降低网络性能。MPLS体系结构能够利用LSP建立隧道，简化了传输控制，降低了设备复杂度，提高了网络性能。     

All-optical processing of time-serial IM/DPSK encoded label and payload packets

We demonstrate an all-optical label and payload processor based on nonlinear optical signal processing with semiconductor optical amplifiers. The processor separates the label and the payload, and generates a synchronization pulse, used to control the label comparison operation in an all-optical routing node.     

脉内调相脉间跳频雷达信号的处理

本文是对非连续谱雷达信号体制的研究,结合了相位编码信号和跳频信号提出一种脉内调相脉间跳频信号。研究了该信号提取信息的处理方法,根据其信号形式,对相同载频频率的不同脉冲,实现脉间多普勒处理,通过对回波信号的频谱变换获得目标的速度信息。根据信号的编码特性应用采样相关进行距离处理。仿真结果表明该方法可获得比较理想的速度、距离信息。     

数字副载波强度调制与光脉冲调制系统误比特率分析

为了分析数字副载波强度调制与光脉冲调制系统的差错性能,本文首先给出了无线光信道通信系统简化模型,在此基础上推导了2种调制方式的信噪比,并分析比较了功率有效性和误比特率.数字副载波强度调制使用二进制移相键控(BPSK),光脉冲调制采用曼彻斯特编码.仿真结果表明,在同等条件下,光脉冲调制系统的功率有效性要优于数字副载波调制系统,误比特率也明显低于数字副载波调制系统.由于光脉冲调制对激光器的线性要求较低,因此在实际应用中一般考虑使用光脉冲系统.但数字副载波调制也有其优势,有利于实现高速数字通信.     

Optical Signal Processing by Phase Modulation and Subsequent Spectral Filtering Aiming at Applications to Ultrafast Optical Communication Systems

This paper describes optical signal processing based on optical phase modulation and subsequent optical filtering, which is applicable to 160-Gb/s optical time-division multiplexed (OTDM) subsystems. Ultrafast phase modulation of an optical signal is done by self-phase modulation (SPM) and cross-phase modulation (XPM) when an optical pulse passes through a nonlinear optical fiber. Such phase modulation induces the spectral shift of the optical signal. Various types of optical signal processing are realized simply by filtering out the spectral-shifted component. Using SPM-based pulse reshaping in a 500-m-long silica-based highly nonlinear fiber (HNLF), we demonstrate highly stable generation of a 10-GHz 2-ps optical pulse train tunable over the entire C band. A phase-locked loop (PLL) can suppress the slow phase drift of the output pulse train induced by fluctuations of the nonlinear fiber length, enabling the application of the pulse generator to a 160-Gb/s OTDM transmitter. Based on XPM in a 2-m-long photonic crystal fiber, optical time-division demultiplexing of 160-Gb/s optical signals is demonstrated. The long-term stability is drastically improved as compared with the device composed of a conventional silica-based HNLF, because the short fiber length reduces the phase fluctuation between the signal and control pulses. Instead of nonlinear fibers, an electrooptic modulator such as a (LN) modulator also performs the phase modulation in a more practical manner. We propose and demonstrate an optoelectronic time-division demultiplexing scheme for a 160-Gb/s OTDM signal, which consists of an LN phase modulator driven by a 40-GHz electrical clock and an optical bandpass filter (BPF). We also demonstrate base-clock recovery from a 160-Gb/s optical signal with an optoelectronic PLL. The phase comparator is simply composed of an LN phase modulator and an optical BPF, ensuring the stable and reliable operation in the 160-Gb/s receiver.     

基于滑模观测器的无位置传感器PMSM控制研究

在无位置传感器的永磁同步电机控制策略中,采用观测器通过电压和电流来观测转子位置而取代位置传感器是一种有效的策略,但这种策略在零速及附近的低速范围内存在观测死区。提出一种将电机的它控和自控方式相结合的控制策略,在零速及附近的低速范围内采用它控方式,电机按照压频比控制并在观测器能够观测出转子位置后切换到自控方式而实现空间电压矢量控制。研究表明这种方式能够解决观测器方式在零速及附近的低速范围内存在预测死区问题,适用于对低速控制性能要求不高的风机以及泵类等的永磁同步电机控制。     

Tunable optical transversal filters based on a Gires-Tournois interferometer with MEMS phase shifters

We present tunable optical filters based on a modified Gires-Tournois interferometer. The back reflection plane of the interferometer is replaced with a one-dimensional micromirror array for phase modulation. Using Gaussian beam optics, we show that the transfer function of the device has the form of the transversal filter in digital signal processing. The design and analysis techniques of conventional digital filters can, therefore, be adapted to tunable optical filters. Both the amplitude and phase of the transfer function can be controlled by reconfiguring the micromirrors. Application examples in dispersion compensation and variable bandwidth bandpass filtering are discussed and experimentally demonstrated.     

有轨电车用永磁电机同步调制技术研究

永磁同步电机相比于异步电机以其自身的明显优势在轨道交通领域有着越来越广泛的应用。本文针对有轨电车用永磁电机脉冲调制方式,分析了现有的永磁电机脉冲同步调制技术的难点及存在的问题。结合有轨电车用永磁电机的特性以及工程实际,提出了一种简单有效的脉冲同步调制方法。该调制方法以空间矢量脉宽调制（SVPWM）的基本理论为基础,低速下采用异步调制模式,高速下采用五段式和七段式混合同步调制的模式,针对不同的调制区间采用不同的载波比构建电压脉冲。实验证明,本调制方式可以实现电机在高速区的同步调制,输出电压脉冲稳定,不同载波比切换过程中无冲击,易于工程化实现。     

基于Hall位置传感器的BLDCM正弦波驱动性能研究

针对稀土永磁无刷直流电机(BLDCM),借助电机本体所固有的三相Hall转子位置传感器,通过空间矢量脉宽调制(SVPWM)控制技术,实现了BLDCM的正弦波电流驱动。实验结果表明,与方波电流驱动相比,采用正弦波驱动可有效减小BLDCM的运行噪声,降低转矩脉动,实现低成本家用电器等领域的静音运行。     

空调压缩机低速无位置传感器控制策略

由于空调压缩机内部含有腐蚀性制冷剂,无法安装位置传感器,传统的恒流频比(I/f)方法在中、高速以下运行时,存在控制精度低、响应慢等问题。针对这一问题,提出了基于脉振高频正弦电压注入策略。通过对电流信号进行处理,获取得到转子位置、磁极方向信息。引用了锁相环(PLL)位置跟踪策略以降低对电机参数与检测精度的依赖性。为检测出转子磁极方向,提出了一种对正、负半轴的直轴高频电流信号分别进行积分、比较的转子磁极方向识别策略。仿真与实验结果表明该方法能在低速条件下对转子位置快速跟踪,鲁棒性强。     

Scaling the modulation bandwidth and phase efficiency of a silicon optical modulator

We present an optimized design and detailed simulation of an all-silicon optical modulator based on a silicon waveguide phase shifter containing a metal-oxide-semiconductor (MOS) capacitor. Based on a fully vectorial Maxwell mode solver, we analyze the modal characteristics of the silicon waveguide. We show that shrinking the waveguide size and reducing gate oxide thickness significantly enhances the phase modulation efficiency because of the optical field enhancement in the voltage induced charge layers of the MOS capacitor, which, in turn, induce refractive index modulation in silicon due to free carrier dispersion effects. We also analyze the device speed by transient semiconductor device modeling. As both optical absorption and modulation bandwidth increase with increasing doping concentration, we show that, with a nonuniform doping profile in the waveguide, balance between the device operation speed and optical loss can be realized. Our simulation suggests that a TE-polarized optical phase modulator with a bandwidth of 10 GHz and an on-chip optical loss less than 2 dB is achievable in silicon.     

Study of hybrid optical burst networks

We propose the hybrid optical burst switching (HOBS), and investigate the HOBS-based ring topology with numerical simulation. Results indicate that the packet loss ratio in HOBS is much less than that in optical burst switching(OBS) and its performance depends on some parameters such as the packet proportion, the electronic buffer size and the processing speed in the node. __________ Translated from Journal on Communications, 2005, 26(11): 7–11 (in Chinese)     

Measurement of 10-fs laser pulses

We report full characterization of the intensity and phase of ~10-fs optical pulses using second-harmonic-generation frequency-resolved-optical-gating (SHG FROG). We summarize the subtleties in such measurements, compare these measurements with predicted pulse shapes, and describe the implications of these measurements for the creation of even shorter pulses. We also discuss the problem of validating these measurements. Previous measurements of such short pulses using techniques such as autocorrelation have been difficult to validate because at best incomplete information is obtained and internal self-consistency checks are lacking. FROG measurements of these pulses, in contrast, can be validated, for several reasons. First, the complete pulse-shape information provided by FROG allows significantly better comparison of experimental data with theoretical models than do measurements of the autocorrelation trace of a pulse. Second, there exist internal self-consistency checks in FROG that are not present in other pulse-measurement techniques. Indeed, we show how to correct a FROG trace with systematic error using one of these checks     

40 Gb/s Field-Modulated Wavelength Converters for All-Optical Packet Switching

We present a high-functionality photonic integrated circuit that performs field-modulated wavelength conversion. This device incorporates an on-chip sampled grating distributed Bragg reflector laser for wide tunability. Wavelength conversion is accomplished using a preamplified semiconductor optical amplifier photodiode receiver interconnected with a traveling-wave modulator to form a high-speed optical gate. This paper discusses the design and performance of this device, as well as its potential for optical packet switching applications. Error-free wavelength conversion is demonstrated at 40 Gb/s with 1–3 dB power penalty compared with back-to-back transmission over 22 nm of input and output tuning. Output extinction in all cases is greater than 9 dB, and conversion efficiency ranges from $-$2 to $-$ 6 dB over the tuning range. This device additionally demonstrates the capability for external 10 Gb/s modulation, which can be used for optical label encoding.      

Photonics for switching and routing

The ongoing growth of data traffic from existing and new applications poses a challenge to the packet-switched network infrastructure. High-capacity transport can be achieved in such networks by using dense wavelength-division-multiplexed systems, and reconfigurable optical add-drop multiplexers allow the optical layer to provision wavelength-based circuits between routing nodes. However, construction of the high-capacity packet routers provides significant scaling issues due to complexity, interconnect, and thermal limits. In this paper we will not seek to cover all aspects of optical packet switching and routing but outline some of the challenges facing the construction of such future routers and describe the role photonics can have in overcoming some of these issues. We will discuss how photonics' primary role will be to provide interconnection between racks of electronic routing elements and describe how fast wavelength switching can provide a high-capacity distributed switch fabric that will allow these packet routers to scale to higher capacities. The fast wavelength switching can be seen as the packet analog of wavelength-based circuit switching of today's transparent optical networks.     

Ultrafast All-Optical Serial-to-Parallel Converters Based on Spin-Polarized Surface-Normal Optical Switches

We describe our recent work on all-optical serial-to-parallel converters (SPCs), from the all-optical switches employed in the SPCs to the application of the SPCs for packet processing. The ability to handle ultrafast optical signals is enabled by types of surface-normal optical switches employing different switching mechanisms: one is based on rapid electron trapping in low-temperature-grown Be-doped quantum wells, and the other is based on differential spin-excitation. With these switches, 1:16 SPCs are demonstrated for 40-Gbit/s, 100-Gbit/s, and 1-Tbit/s optical packets. In addition, the SPC is compact, low power, polarization insensitive, exhibits extremely high on/off ratios, and generates a simultaneous parallel output, and thus, provides a promising interface device allowing the processing of ultrafast, asynchronous optical packets in a highly functional complementary metal-oxide-semiconductor (CMOS) processor. As an application, an optical label swapper that integrates the SPC with a CMOS processor is also demonstrated for 40-Gbit/s asynchronous optical packets     

一种空间矢量的三相逆变器调制方法研究

针对三相逆变器提出了一种基于PID神经网络的空间矢量调制(SVPWM)方法。三相逆变器具有矢量的开关状态,其调制算法的实现非常复杂,在设计的方案中,摒弃传统的神经网络,采用PID神经网络用于SVPWM算法的快速实现,三层前馈PID神经网络以指令电压和角度作为输入信息,借助于一个简单的计时器和逻辑电路,产生三相12路对称脉宽调制波形。最后利用Matlab神经网络信息工具箱依据误差逆变算法使用实测数据对该系统进行了测试,结果证明,在全部线性调制区内,系统性能很好。     

Monolithic Wavelength Converters for High-Speed Packet-Switched Optical Networks

This paper describes the design and demonstration of advanced 40-Gb/s return-to-zero (RZ) tunable all-optical wavelength converter technologies for use in packet-switched optical networks. The device designs are based on monolithic integration of a delayed interference Mach-Zehnder interferometer (MZI) semiconductor optical amplifier (SOA) wavelength converter with a sampled-grating distributed Bragg reflector tunable laser and an on-chip waveguide delay. Experimental results are presented demonstrating error-free wavelength conversion with 1-dB power penalty at 40-Gb/s data rates. By incorporating label modulation functionality on-chip along with a fast tunable 40-Gb/s wavelength converter, fully monolithic packet-forwarding chips are realized that are capable of simultaneous error-free wavelength conversion of 40-Gb/s payloads, remodulation of 10-Gb/s packet headers, and data routing through fast wavelength switching     

基于电光晶体的激光PPM偏振调制设计

调制解调技术是大气激光通信系统中的关键技术。提出一种新的光与电脉冲组合调制方式,对已经进行过PPM（脉冲位置调制）调制的激光信号再用电光晶体进行偏振调制。设计了同一信道四种偏振态（0°、30°、60°和90°方向振动的偏振光束）的PPM偏振调制方案。搭建了硬件时序电路及偏振调制系统,四束偏振光通过同一大气信道,同时被衰减,信道的衰减可以相互抵消。硬件仿真结果表明：采用光与电脉冲组合调制方式可以减少甚至消除大气信道对大气激光通信的影响,而且由于光波的偏振复用可以成倍提高大气激光通信的通信容量。