Reprogrammable matched optical filter and method of using same

Abstract

A high-speed, high-throughput matched optical filter for processing data that allows for rapid reprogramming to change the reference signal or signals. A coherent time-domain optical memory system includes a coherent time-domain optical storage material (18) and a laser (16) for providing pulses of optical radiation in coherent time-domain optical storage relation with the storage material. One or more reference signals are first stored in the material by modulating one or more of the laser pulses with the reference signals and writing these pulses on the storage material (18) in close succession with their associated write pulses as is customary in coherent time-domain optical memories. The reference signals are phase encoded before they are stored. Another laser pulse modulated with the signal to be processed is then applied to the storage material. The echo signal induced by this signal pulse takes the form of the correlation of the reference pulse with the signal pulse. The use of phase encoded reference signals and a similarly phase encoded signal under analysis greatly enhances the ratio of the main peak to the side lobes in the echo signal when a match occurs. This greatly enhances the ability to detect a match. A plurality of reference signals may be stored in different spatial regions of the storage material (18). A lens assembly (23) is provided to expand the laser pulse modulated with the signal under analysis to cover all the spatial regions storing reference signals. In this manner a comparison may be performed simultaneously with all spatial regions. The echo signal will exhibit a strong correlation in that portion of the signal corresponding to the address of the matched reference signal.