Design and performance optimization of fiber optic adaptive filters

Abstract

There is a great need for easy-to-fabricate and versatile fiber optic signal processing systems in which optical fibers are used for the delay and storage of wideband guided lightwave signals. We describe the design of the least-mean-square algorithm-based fiber optic adaptive filters for processing guided lightwave signals in real time. Fiber optic adaptive filters can learn to change their parameters or to process a set of characteristics of the input signal. In our realization we employ as few electronic devices as possible and use optical computation to utilize the advantages of optics in the processing speed, parallelism, and interconnection. Many schemes for optical adaptive filtering of electronic signals are available in the literature. The new optical adaptive filters described in this paper are for optical processing of guided lightwave signals, not electronic signals. We analyzed the convergence or learning characteristics of the adaptive filtering process as a function of the filter parameters and the fiber optic hardware errors. From this analysis we found that the effects of the optical round-off errors and noise can be reduced, and the learning speed can be comparatively increased in our design through an optimal selection of the filter parameters. A general knowledge of the fiber optic hardware, the statistics of the lightwave signal, and the desired goal of the adaptive processing are enough for this optimum selection of the parameters. Detailed computer simulations validate the theoretical results of performance optimization.

Microwave Photonic Signal Processing

“…The very high bandwidth and potentially low delays (5 ns/m) that can be achieved with optical delay lines make them an ideal technology option for the implementation of signal correlators for very high-speed signals [77]. These structures are similar to the photonic filters that will be discussed in this chapter but are designed to operate over the time domain characteristics of the input signals.…”

Generalization of multivariate optical computations as a method for improving the speed and precision of spectroscopic analyses

“…In the pseudo electronics domain, optical computers have been developed to solve well-defined mathematical problems [3][4][5]. Adaptive fiber optic networks have been designed to dynamically optimize the parameters for artificial neural networks [6] and linear discriminants analysis-based adaptive filters [7,8]. The optical computational network serves as an alternative to an electronic central processing unit.…”

Design and applications of optical devices using optical fibers with radiative taps

“…Such taps have several uses in making fiber optic components, sensors, tapped delay lines, signal processors, and add-drop multiplexers. A series of such taps distributed along an optical fiber can create devices such as finite or infinite-impulseresponse filters, equalizers, long period Bragg grating, distributed fiber optic sensors, optical spectrum analyzers, or array illuminators [2,3]. Large-core multimode fibers are more suitable for making devices with multiple radiative taps.…”