声光技术在光纤系统中的应用

本文简要介绍了在光纤通信、光纤传感和光纤信号处理枝术等各种光纤系统中可能开发应用的固体声光技术和光纤声光技术。     

声光频谱分析器的信号处理

集成光学声光频谱分析器是由半导体激光器、导波声光调制器、波导短程透镜和CCD探测器阵列所构成。CCD探测器把接收的光信号转换成电信号,再由TMS32010系统与IBM-PC机组成的主从工作机的信号处理中心进行处理。微机系统中的CPU采用TMS-32010。CCD视频信号采集用循环间隔采样方式。此样机达到的指标:系统带宽为100MHz,分辨率为8MHz,动态范围为20dB。     

Optical processing using outer-product concepts

A row vector when left-multiplied by a column vector produces a two-dimensional rank-one matrix in an operation commonly called an outer product between the two vectors. The outer product operation can form the basis for a large variety of higher order algorithms in linear algebra, signal processing, and image processing. This operation can be best implemented in a processor having two-dimensional (2-D) parallelism and a global interaction among the elements of the input vectors. Since optics is endowed with exactly these features, an optical processor can perform the outer product operation in a natural fashion using orthogonally oriented one-dimensional (1-D) input devices such as acoustooptic cells. Algorithms that can be implemented optically using outer-product concepts include matrix multiplication, convolution/correlation, binary arithmetic operations for higher accuracy, matrix decompositions, and similarity transformations of images. Implementation is shown to be frequently tied to time-integrating detection techniques. These and other hardware issues in the implementation of some of these algorithms are discussed.     

Coherent optical fibre delay-line processor

The operation of an optical fibre tapped delay line with a long coherence length source is described. Optical phase is retained; thus the system can perform bipolar (or in general complex-valued) signal processing operations. Experimental results are presented that illustrate the operating characteristics and capabilities of the system for simple time-domain processing operations.     

Signal processing for optical communication

Optical communication plays a significant and increasing role in our society. The public demand for higher network speed requires an optical backbone network with larger capacity. Accompanying high transmission-rate optical communications system are severe technical specifications for optical devices and systems. Many popular optical devices could be represented with a digital filter model as described in this article. Use of well-developed signal processing techniques and algorithms to design these optical devices is a wise use of existing technology. The wavelength division multiplexing (WDM) system, which is the dominating optical communication system, is introduced in this article. Three signal processing application examples for optical communications are presented: optical wavelength interleaver, an all-pass filter for chromatic dispersion compensation, and an electronic equalizer. As demonstrated in this article, signal processing could play an important role in the development of advanced optical communication systems. However, as demonstrated in the case of an electronic equalizer, some optical system characteristics may require special attention if signal processing techniques are to be applied successfully. Therefore, interdisciplinary cooperation between researchers in optics and signal processing will be crucial for optical communications to fully benefit from signal processing.     

声光器件及其在军事方面的应用

通过声光器件原理、结构和特性的回顾,着重介绍体波声光器件在实时信息处理、光纤传感技术及光计算技术等军事领域的应用.     

用于扩频通信的时间积分声光相关处理系统

本文研究用声光器件实现实时相关的处理方法，推导了声光信号处理器的数学模型，提出了一种能对长码扩频信号进行相关处理的宽带时间积分型声光信号处理系统，并对其设计和性能进行了分析，实验结果表明，应用本系统能够获得５７ｄＢ的的处理增益和６２ＭＨｚ的系统带宽。     

Cascaded acoustooptic/fiber Fabry-Perot filter with finesse over2000

A compound optical filter consisting of an integrated acoustooptic filter in series with a fiber Fabry-Perot filter possesses a very high effective finesse of over 2000 as well as the unique multichannel passband capability of the acoustooptic filter. The fine-grain element in this pair is a narrow (0.5-Å) passband Fabry-Perot filter, and the coarse-grain element is a wide tuning range (130-nm) polarization-independent integrated acoustooptic filter. The composite device has the narrow passband of the Fabry-Perot, the wide tuning range of the acoustooptic filter and the tuning speed of the faster acoustooptic filter (5 μs)     

一种基于声光Bragg衍射的信号处理系统

设计了一种基于声光Bragg衍射的信号处理系统,给出了相应实验框图和说明,分析了其主要性能。本系统最大的优点还是可以方便地产生高精度的、能连续可调的延迟信号,在目标模拟、雷达干扰系统等方面有着极大的应用价值,同时还可以作为一个组件,应用于其他信号处理器件中。     

Acoustooptic algebraic processing architectures

A new generation of optoelectronic signal processors, many exploiting acoustooptic technology, has been developing during the past several years. These processors are designed to perform algebraic operations like matrix-vector and matrix-matrix multiplication. Major architectures are reviewed, including one that performs with digital accuracy. Processor capabilities are assessed in terms of fundamental limitations, and certain practical limitations are discussed.     

Acoustooptic interactions and devices

A review of recent advances in the understanding of the interaction of light and ultrasonic waves in solids and liquids is presented, emphasizing the Bragg diffraction regime wherein the diffracted optical energy is confined near one angular direction. The usefulness of optical beam probing techniques, using laser light sources, for investigating such subjects as ultrasonic attenuation and diffraction, acoustic nonlinear phenomena, magnetoelastic interactions, and photoelastic properties of materials is described. The application of the acoustooptic interaction for the design of devices intended to perform optical information processing functions is also mentioned. Present applications include optical modulators, switches, sequential scanners (such as are useful for television display), random access optical deflectors, and optical correlators. An attempt is made to describe the assets and liabilities of acoustooptic devices and to speculate concerning their future in the practical world.     

Incoherent optical correlators

The use of optical systems in signal processing applications can offer significant advantages over an equivalent electronic approach. These advantages stem chiefly from the high-speed analog multiply and parallel processing capability inherent in an optical system. This can be used to advantage in application areas requiring large quantities of data to be processed in near real time. Presented in this paper is a review of a variety of incoherent optical analog techniques for performing correlation and linear transform operations. Both scanning and nonscanning systems using spatial and/or temporal inputs are considered.     

相位敏感光时域反射仪的振动全程敏感研究

研究相位敏感光时域反射仪振动检测时, 高功率激光脉冲的入射使得光电探测器产生饱和现象而导致光纤前端振动传感不敏感, 低功率又满足不了远距离检测的需求。为了解决这一问题, 采用一种新型传感结构的方法进行了理论分析和实验验证。根据入射功率的高低对光纤分段检测, 通过相应的数据处理, 实现了光纤振动全程敏感的结果。同时, 为了进一步提高该系统的振动灵敏度和信噪比, 对比分析了雪崩二极管检测与利用低噪声光电二极管检测的结果, 并比较了声光调制器与半导体光放大器的实验效果。结果表明, 当测量距离为38km时, 相比雪崩二极管检测, 利用低噪声光电二极管与掺铒光纤放大器有更高的信噪比; 相比声光调制器, 利用半导体光放大器能得到更高信噪比。该新型传感结构为光纤传感器领域的科学研究和工程应用提供了很好的参考。     

声光可调滤波器在光纤通信系统中的应用进展

声光可调滤波器以其宽的调节范围、窄的滤波线宽、多信道并行滤光等特点,在光纤通信系统中作动态增益均衡器具有很多优点。用声光可调滤波器实现ＥＤＦＡ级联的ＷＤＭ系统的动态增益均衡,可扩展增益带宽（～５２ ｎｍ）,提高传输距离 （～ ２４００ ｋｍ）。     

Real-time digital signal processing-based optical coherence tomography and Doppler optical coherence tomography

We present the development and use of a real-time digital signal processing (DSP)-based optical coherence tomography (OCT) and Doppler OCT system. Images of microstructure and transient fluid-flow profiles are acquired using the DSP architecture for real-time processing of computationally intensive calculations. This acquisition system is readily configurable for a wide range of real-time signal processing and image processing applications in OCT.     

All-fiber wavelength-tunable acoustooptic switches based on intermodal coupling in fibers

In this paper, we demonstrate a novel all-fiber wavelength-tunable acoustooptic switch utilizing intermodal coupling in a two-mode fiber (TMF). Its all-fiber configuration consisting of a fiber acoustooptic tunable filter and a mode-selective coupler results in the low loss (<2 dB) operation. The operating bandwidth >50 nm, the switching time of 40 /spl mu/sec, and the crosstalk of 20 dB were achieved. By controlling the design parameters of the two-mode fiber, the 3-dB bandwidth of the switched signal was varied from 2.5 nm to >35 nm. A novel all-fiber dynamic optical add-drop multiplexer is also demonstrated using two acoustooptic switches in series.     

用于雷达信号处理的连续可调声光延迟线

在雷达信号处理中常常要用到延迟时间可调的延迟器件 ,但目前大多数延迟器件都不能满足要求。本文设计了一种新型声光延迟装置。它与以往的延迟器件相比 ,其优点在于延迟时间可连续变化。因此 ,它可以方便地应用在运动雷达目标模拟系统中以及其它高精度的信号处理中     

Tunable acoustooptic reflection filters in LiNbO3without a Doppler shift

A proposal is presented for an acoustooptic filter in LiNbO₃ without the Doppler shift, which is normally present in acoustooptic filters and which is undesirable as an intracavity element. This tunable filter has a significantly wider tuning range than previously demonstrated electrooptic filters. A structure incorporating an interdigital acoustic transducer, polarization filter, and single-mode optical waveguide is shown. The design presented works by cascading two acoustooptic filters with an intermediate polarizer, where the Doppler shift experienced in the first filter is precisely compensated for in the second filter. Hence, the output light of the two cascaded acoustooptic filters is not shifted in frequency, thus making the device suitable for applications inside a laser cavity. The filter with intermediate polarizer can be integrated with a single-mode waveguide and requires only a single interdigital acoustic transducer. Crystal symmetry and acoustic power considerations are treated in detail     

30 km远程分布光纤拉曼温度传感器系统的实验研究

研制成功一套 30km远程分布光纤拉曼温度传感器 (DOFRTS)系统 ,采用了新的光纤放大的反斯托克斯背向拉曼自发散射测温原理和 15 5 0nm掺铒光纤激光器作为抽运源及高速瞬态波形采样技术 ,累加平均等信号处理技术 ,提高了信噪比 ,解决了弱信号检测问题。使用智能化恒温技术 ,使主要元器件在恒温条件下工作 ,解决了工程应用中环境的适应性问题。经鉴定 ,远程分布光纤拉曼温度传感器系统的主要技术指标如下 :光纤长度为 31km ,测温范围为 0～ 10 0℃ (可扩展 ) ,温度测量不确定度为± 2℃ ,温度分辨率为 0 1℃ ,测量时间为 4 32s,空间分辨率为 4m。最后给出了远程分布光纤温度传感器系统性能的国内外对比表     

Coherent optical processing

The principles of communication theory were applied in the 1950's to optical imaging systems and to the analysis of images. Optical systems were analyzed in much the same way as linear systems (modulation transfer functions and channel capacities) and images were characterized in ways analogous to time signals (space-bandwidth products, spatial frequency content, etc.). Both coherently and incoherently illuminated optical systems can be treated using these concepts. Coherently illuminated systems are most useful for performing operation such as convolution, cross correlation, and spectral analysis because the Fourier transform of an optical signal physically exists and can, therefore, be measured or modified. The basic Fourier transform relationship for coherently illuminated systems is developed in this paper. It can be detected directly and used to estimate the distribution of spatial frequencies contained in the signal. Methods for constructing complex-valued spatial filters are described; these filters can be used to realize such operations as convolution or cross correlation, addition or subtraction, and differentiation or integration. Experimental results are given to illustrate the concepts and to susgest potential applications. To extend the range of applications, interface devices are needed to allow optical processing of two-dimensional raster-scanned time signals, wide bandwidth electrical signals, and incoherent optical signals. Interface devices are often needed to convert the output optical signal to an electrical signal for post-processing by a digital computer. For some applications, interface devices are needed to construct spatial filters in real time, so different operations can be performed on a given signal. The desired characteristics of these three interface devices and the current state of their development are briefly reviewed.