Optical arbitrary waveform generation and characterization using spectral line-by-line control

This paper demonstrates optical arbitrary waveform generation (O-AWG) and its characterization using spectral line-by-line control with high-resolution grating-based pulse shapers. Such integrated capabilities are the enabling techniques for high-fidelity O-AWG.     

Broadband arbitrary waveform generation based on microwave frequency upshifting in optical fibers

An interesting method for broadband arbitrary waveform generation is based on the frequency upshifting of a narrowband microwave signal. In this technique, the original microwave signal is imaged into a temporally compressed replica using a simple and practical fiber-based system. Recently, it has been shown that the conventional limitations of this approach (e.g., bandwidth limitations) can be overcome by exploiting a temporal self-imaging (Talbot) effect in fiber. This effect can be used whenever the signal to be imaged is a quasi-periodic waveform (e.g., microwave tones or any arbitrary periodic waveform). This paper provides a comprehensive study of the microwave frequency upshifting technique with special focus on the Talbot-based approach. Following a theoretical analysis of the design constraints of the conventional approach, the Talbot-based solution is theoretically investigated in detail. In particular, the design specifications of a Talbot-based microwave upshifting system are derived, and the practical capabilities and constraints of these systems (e.g., in terms of achievable bandwidth) are stated and examined. The theoretical findings are confirmed by means of numerical simulations. Moreover, a numerical study of the influence of higher-order (second-order) dispersion terms on system performance is presented, and some additional design rules to minimize the associated detrimental effects are given. The results show that microwave frequencies up to a few hundreds of gigahertz over nanosecond temporal windows can be easily obtained with the described technique using input optical bandwidths in the terahertz range. This has been experimentally confirmed.     

二元相位取样光纤Bragg光栅型光分插复用器方案

结合马赫-曾德干涉仪(MZI)和二元相位取样光纤布拉格光栅(BP-SFBG)构造出了一种具备多信道处理功能的光分插复用器(OADM).首先利用传输矩阵法建立了OADM的理论模型,再结合传输矩阵法和Chebyshev恒等式实现对BP-SFBG的快速分析和计算;最后给出了一个仿真设计的实例,数值结果表现出了良好的性能,为具体器件的研制提供了有益的参考.     

N/spl times/N multiwavelength optical cross-connect based on tunable fiber Bragg gratings

We propose a highly channel-scalable multiwavelength optical cross-connect (OXC) based on tunable fiber Bragg gratings (TFBGs), which is suited for metropolitan or access networks. N/spl times/N OXC of this architecture is constructed by cascading independently operating routing modules, and each routing module consists of fiber Bragg gratings (FBGs) with fixed center wavelength and a TFBG-based N/spl times/N routing block. The group velocity dispersion (GVD) and intraband crosstalk (IXT) are the main signal-degrading factors arising from the operation of the proposed OXC, and the effectiveness of each factor is individually investigated numerically for 10-Gb/s nonreturn-to-zero (NRZ) systems. Then, a routing experiment of the proposed OXC is carried out in a 3/spl times/3 routing block configuration, using OC-192 signals with channel spacing of 0.8 nm. Finally, the installable size of the proposed OXC and network scale are estimated by resorting to a comprehensive numerical simulation of 10-Gb/s NRZ signal transmission.     

Single and tunable dual-wavelength operation of an InGaAs-GaAsridge waveguide distributed Bragg reflector laser

The design and operation of an InGaAs-GaAs asymmetric cladding ridge waveguide (RW) distributed Bragg reflector (DBR) laser that can be operated in both a single-wavelength mode and a stable, dual-wavelength mode with tunable mode pair separation are reported. The asymmetric cladding RW-DBR laser consists of a conventional DBR laser with an additional, separate tuning contact pad over a part of the grating. The laser operates on a single-wavelength with no current applied to the tuning DBR pad, and dual-wavelength operation is achieved when current is applied to the tuning DBR pad. Tunable mode pair separations as small as ~13 nm and as large as ~17 nm can be achieved in various tuning conditions     

Temperature and polarisation insensitive Bragg gratings realised onsilica waveguide on silicon

A new technique based on the use of polymer to drastically decrease the temperature sensitivity of Bragg gratings realised on planar silica waveguides deposited on silicon is proposed. Moreover, this technique suppresses the polarisation dependence of the Bragg filters     

Code reusuable optical CDMA system using an array of superstructured fiber Bragg gratings

We have proposed a user extensible optical CDMA system which employs a repeated use of codes in the encoders and the decoders. In this study, we report the user-extension effect by using an array of superstructured fiber Bragg grating (SSFBG) as an encoder and a decoder through the simulations and the experiments. We performed the experiments by using 4 SSFBGs in each encoder and decoder. We have shown that the capable number of users can be increased up to ₆₃C₁?₆₃C₁?₆₃P₂ when 63 orthogonal codes are used.     

基于光纤Bragg光栅的光纤水听器

简单介绍了基于光纤Bragg光栅的光纤水听器的原理以及几种新型的结构和解调方法.与传统的光纤水听器相比,基于光纤Bragg光栅的水听器的实现更加简单方便,在民用和军事方面都有广泛的应用前景.     

Central wavelength tunable mechanism for temperature compensatedpackage of fiber Bragg gratings

The central wavelength of fiber Bragg grating (FBG) must be located in the specified channel band of wavelength division multiplexer (WDM) in optical communication network. Furthermore, the central wavelength also must he stable in the ambient temperature. A temperature compensated fixture Is therefore essential for the application of FBG. By the strength of materials, a theoretical model of the fully temperature compensated fixture can he derived for zero shift of central wavelength of FBG in ambient temperature. Besides, a microtunable mechanism for the pre-pulling force on the FBG is synthesized to adjust the central wavelength to a certain channel band. By this tunable mechanism one can calibrate effectively and efficiently the FBG in mass production of FBG based products     

基于SOPC的多函数发生器设计

结合运用NIOSⅡ嵌入式处理器的SOPC技术,选用CycloneⅡ系列的EP2C35F672C6N作为目标芯片,对函数发生器进行设计,完成Tsoec片上系统以及片外处理电路的构建,用VHDL设计了DDS模块,用C语言程序进行波形参数的读取及显示,用QuartusⅡ设计软件,实现函数信号发生器的功能。不仅可以产生用户通常需要的波形信号,而且波形的频率和幅度在范围内可调,用户还可自行通过对自定义组件的添加和系统进程的添加来实现系统功能的扩展。更好地实现了设计的数字化、集成化、微型化、智能化。     

FPGA实现的任意波形发生器的设计

运用DDS原理,进行任意波形发生器的设计,使得任意波形发生器兼顾DDS的优点.设计中通过实现DDS模块与单片机接口的控制部分将频率控制字由单片输入到输入寄存器模块,由相位累加器模块对输入频率控制字进行累加运算,输出作为双口RAM的读地址线,读数据线上即输出了波形幅度量化数据.其中双口RAM的内容由单片机进行更新,从而实现任意波形的发生.本设计中的相位累加器采用了8级流水线结构借助前5级的超前进位的方法,使得编译的最高工作频率由317.97 MHz提高到336.7 MHz,实现了任意波形的发生,节约了成本,提高了开发周期,具有可行性.     

Optical DPSK demodulator based on /spl pi/-phase-shifted fiber Bragg grating with an optically tunable phase shifter

We propose and demonstrate a novel optical differential phase-shift keying (DPSK) demodulator with an optically tunable phase shifter. The proposed DPSK demodulator is implemented by using a /spl pi/-phase-shifted fiber Bragg grating and an Yb/sup 3+/-Al/sup 3+/ codoped optical fiber. A 10-Gb/s DPSK signal was successfully demodulated by the proposed demodulator, showing clearly open eye diagrams as well as bit-error-free performance. Moreover, the phase of delayed optical signal can be tuned by the phase shifter that is controlled by a pumping light at around 980nm.     

基于DDS的任意波信号发生器设计

任意波形发生器己成为现代测试领域应用最为广泛的通用仪器之一,代表了信号源的发展方向。直接数字频率合成（DDS）技术的发明和应用是频率合成领域里的一次革命。基于DDS的任意波信号源利用FPGA所具有的高集成度、高速度、可实现大容量存储器功能的特性,有效地实现了DDS技术,极大地提高了函数发生器的性能,降低生产成本。     

High-sensitivity optical chemsensor based on etched D-fibre Bragg gratings

A novel and simple optical chemsensor concept based on cladding etched Bragg gratings UV-inscribed in D-fibre is reported. The sensitisation process of the Bragg structure to the refractive index of surrounding-medium under HF-etching has been investigated. Two etched devices were used to measure the concentrations of sugar solution, giving sensitivity as high as 0.02 nm/%.     

Wavelength-switching fibre laser based on multimode fibre Bragg gratings

A multimode fibre Bragg grating (MMFBG) based wavelength-switching erbium-doped fibre laser is reported. With a simple singlemode fibre to MMFBG structure, a novel wavelength-selection technique is developed to achieve the wavelength-switching by changing the mode coupling condition in the multimode fibre. 31 discrete lasing wavelengths are obtained over a wide wavelength range.     

基于Delphi的DDS可视化新型任意信号发生器

以FPGA为核心,TFT实现图形与菜单界面,USB1.1与Delphi7.0完成与上位机接口及图形操作界面,对低频段采用时钟分段分频法,在MCU的控制下实现DDS低频高精度双通道±8 V,0.01 Hz～10 MHz正弦波等常规波形外,还能输出数码流、调制信号、随机噪声、扫频信号及时域/频域自定义波形,信号参数均可步进在线可调.实验表明该设计是行之有效的,在介绍系统设计思想的同时,重点讲述FPGA设计、信号输入方法及提高低频段时域精度的措施等.     

基才Delphi的DDS可视化新型任意传号发生器

以FPGA为核心,TFT实现图形与菜单界面,USB1.1与Delphi7.0完成与上位机接口及图形操作界面,对低频段采用时钟分段分频法,在MCU的控制下实现DDS低频高精度双通道±8 V,0.01 Hz～10 MHz正弦波等常规波形外,还能输出数码流、调制信号、随机噪声、扫频信号及时域/频域自定义波形,信号参数均可步进在线可调。实验表明该设计是行之有效的,在介绍系统设计思想的同时,重点讲述FPGA设计、信号输入方法及提高低频段时域精度的措施等。     

Tunable waveguide transmission gratings based on active gain control

Mode loss or gain can have a significant effect on the operation of waveguide transmission gratings as optical filters. Taking for example a long-period grating (LPG), we present a computer simulation that accounts for these effects. We show that cladding loss or gain result in qualitatively different LPG spectral behavior that can be used as a tuning mechanism in guiding structures where cladding mode properties can be controlled. One possible control mechanism is to have pump-driven gain in a doped cladding, which can perform gradual loss compensation and eventually gain excitement. Based on simulation results, we propose new approaches to tuneable amplifying filter designs in special fibers, as well as grating assisted co-directional couplers for integrated optics platforms.