Holographic code division multiple access

• US 5,438,440 A
• Filed: 01/15/1993
• Issued: 08/01/1995
• Est. Priority Date: 01/15/1992
• Status: Expired due to Term

• Current Assignee: Telcordia Technologies Incorporated (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Bell Communications Research, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Paek, Eung G., Salehi, Jawad A.
• Primary Examiner(s): Ben, Loha
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US08/006,008
• Time in Patent Office: 928 Days
• Field of Search: 359/10, 359/11, 359/29, 359/559, 359/560, 359/561, 364/822, 364/827, 382/31, 382/42
• US Class Current: 359/11
• CPC Class Codes: G03H 1/0005 Adaptation of holography to specific applications holographic optical element G02B5/32; holographic scanner G02B26/106; recognition using holographic mask G06V10/88; holographic memories G11B7/0065, G11C13/042
• CPC Class Codes: G03H 1/041 Optical element in the object space affecting the object beam, not otherwise provided for
• CPC Class Codes: G03H 1/16 using Fourier transform G03H1/10, G03H1/12, G03H1/14 take precedence; analogue computers G06G, e.g. G06G7/19
• CPC Class Codes: G03H 2001/0066 for wavefront matching wherein the hologram is arranged to convert a predetermined wavefront into a comprehensive wave, e.g. associative memory recognition using holographic masks G06V10/88
• CPC Class Codes: H04J 14/005 Optical Code Multiplex

Abstract

A technique for all-optical Code Division Multiple Access (CDMA) system based on optical holography is disclosed. In this technique the energy of an incoming information light signal is spread over a spatial domain by a two-dimensional spatial encoder which includes a mask having regions of first and second transmission characteristics corresponding to the unique code assigned to a particular source. Subsequent decoding, which is accomplished by an optical matched filter through the use of a hologram, spatially despreads the energy of the information light signal and produces a focused light beam which serves as input to a code division detector.

Claims

1. An encoder for encoding a plurality of incoming temporal information-bearing light signals to produce a plurality of spatially modulated light signals, the encoder comprising:

light source means for generating a plurality of temporally modulated information-bearing light signals,

a plurality of fibers, each of said fibers for guiding an associated one of said temporally modulated information-bearing light signals from said light source means,

a plurality of input collimating lenses, each optically coupled to a respective one of said fibers, for spatially spreading the associated incoming temporally modulated light signal to produce an associated spread light signal, and

a plurality of encoding masks, each of said masks optically coupled to a respective one of said input collimating lenses, for modulating said associated spread light signal to produce a spatially modulated light signal, each of said masks including first regions having a first transmission characteristic and second regions having a second transmission characteristic, said first and second regions arranged according to a preselected pattern from a set of two-dimensional code patterns having at least pseudo-random arrays and wherein said patterns correspond to sequences with predetermined correlation properties.

2. A method for encoding a plurality of incoming temporal information-bearing light signals to produce a plurality of spatially modulated light signals, the method comprising the steps of:

generating a plurality of temporally modulated information-bearing light signals and transmitting the temporally modulated information-bearing light signals on individual optical fibers,

spatially spreading the temporally modulated incoming light signals received from each of the optical fibers with individual input collimating lenses to produce spread light signals, and

modulating each said spread light signal with an encoding mask uniquely associated with each said spread light signal to produce the spatially modulated light signals, each said mask including first regions having a first transmission characteristic and second regions having a second transmission characteristic, said first and second regions arranged according to a preselected pattern from a set of two-dimensional patterns having at least pseudo-random arrays and wherein said patterns correspond to sequences with predetermined correlation properties.