Holographic code division multiple access
AssigneeBell Communications Research, Inc.
InventorsEung G. Paek, Jawad A. Salehi
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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.
Claims2
A decoder for decoding an incoming temporal information-bearing light signal encoded with an optical two-dimensional spatial random encoding mask to produce a decoded original temporal light signal, the decoder comprising
- a Fourier Transform lens for converting the incoming light signal to produce a transformed light signal,
- a hologram, located at the optical focus distance from said Fourier Transform lens, for generating a holographic light signal from said transformed light signal, said hologram representative of the optical random encoding mask,
- an outgoing focusing lens, aligned along the reference beam direction when making said hologram, for generating the decoded light signal, and
- a fiber located at the focal point of said outgoing focusing lens.
A method for decoding an incoming information light signal encoded with an optical random encoding mask to produce a decoded light signal, the method comprising the steps of
- converting the incoming light signal through a Fourier Transform lens to produce a transformed light signal,
- generating a holographic light signal from said transformed light signal with a hologram located at the optical focal distance from said Fourier Transform lens, said hologram being representative of the optical random encoding mask,
- generating the decoded light signal by an outgoing focusing lens, aligned along the reference beam direction when making the hologram, and
- applying the decoded light signal to a fiber located at the focal point of the outgoing focusing lens.
Dependencies are inferred from the claim text.