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Opto-Electronic Signal Processing Element

IP.com Disclosure Number: IPCOM000034374D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 4 page(s) / 72K

Publishing Venue

IBM

Related People

Heinzmann, P: AUTHOR [+2]

Abstract

Proposed is an opto-electronic signal processing element consisting of fiber-optic delay lines combined with a photodiode matrix. The element allows to logically combine optical pulses of a serial pulse stream. It may, e.g., be used in a time-division demultiplexer having a large line rate achievable without the need for electronic device speeds corresponding to the large bandwidth. The basic circuits, providing for logic AND and OR functions, respectively, are illustrated in Fig. 1. An optical pulse stream arriving at input A is fed, via optical fibers, to photodiode D1 and, delayed in delay element xT, to photodiode D2. The AND function is performed in a series connection of diodes, the OR function in a parallel arrangement.

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Opto-Electronic Signal Processing Element

Proposed is an opto-electronic signal processing element consisting of fiber- optic delay lines combined with a photodiode matrix. The element allows to logically combine optical pulses of a serial pulse stream. It may, e.g., be used in a time-division demultiplexer having a large line rate achievable without the need for electronic device speeds corresponding to the large bandwidth. The basic circuits, providing for logic AND and OR functions, respectively, are illustrated in Fig. 1. An optical pulse stream arriving at input A is fed, via optical fibers, to photodiode D1 and, delayed in delay element xT, to photodiode D2. The AND function is performed in a series connection of diodes, the OR function in a parallel arrangement. With a delay of xT, successive optical signals arriving at input A spaced apart by that amount of time, are logically combined and electric signals representing the logical function performed are provided at outputs B. With these two basic functions, AND and OR, any other logical function can be composed by choosing the appropriate parallel/serial connection of diodes. A receiver, consisting of such opto-electronic circuit elements and operating as demultiplexer for optical signals arriving from a transmitter, is shown in Fig. 2. The incoming signal is split into fibers of different length, i.e., with different delays (xT) and coupled to an array of high-speed photodiodes (D1 to D8). Using a series arrangement of photodiodes to perform a logic AND function between pulse streams with different delays, the incoming signals are demultiplexed whereby the original data are reproduced.

(Image Omitted)

The time diagram of Fig. 3 serves to explain the principle of operation of the demultiplexer arrangement of Fig. 2. For simplicity, a very simple transmission code is used. Other codes with better bandwidth efficiency may be designed at the expense of a more complex decoder configuration. Fig. 3(a) shows the received pulse train consisting of a synchronization pulse S separated by (N-1) zeroes from the N data...