Browse Prior Art Database

Low Power Optical Data Transmission

IP.com Disclosure Number: IPCOM000110979D
Original Publication Date: 1994-Jan-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Battelle, D: AUTHOR [+2]

Abstract

Standard optical data transmission techniques involve pulsing a light source with serial data. This beam of light is directed to a photoreceptor, which converts the light pulses into electrical signals. Typical light sources are Light Emitting Diodes (LEDs) and lasers, and the receptors are typically photodiodes and phototransistors. Certain applications are power constrained such that the currents required to drive an LED or laser are unavailable. This invention describes a data transmission technique useful when one partner in the communications is so constrained while the other is not.

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Low Power Optical Data Transmission

      Standard optical data transmission techniques involve pulsing a
light source with serial data.  This beam of light is directed to a
photoreceptor, which converts the light pulses into electrical
signals.  Typical light sources are Light Emitting Diodes (LEDs) and
lasers, and the receptors are typically photodiodes and
phototransistors.  Certain applications are power constrained such
that the currents required to drive an LED or laser are unavailable.
This invention describes a data transmission technique useful when
one partner in the communications is so constrained while the other
is not.

      Refer to the Figure, which shows one partner to consist of a
standard optical transceiver, such as an LED/photodiode pair.  The
second partner consists of a photodiode under a reflective coating,
which has an aperture allowing light to reach the photodiode.  Above
the reflector is a Liquid Crystal Display (LCD) element.

      Communications in one direction (referred to in the Figure as
Mode 1) is by conventional means.  The LED of the transmitter is
pulsed by serial data, while the receiving partner's photodiode
detects the pulses of light.  The beam diameter is sufficiently large
to also illuminate the reflector, but only the light passing through
the aperture is used.

      Communications in the opposite direction (referred to in the
Figure as Mode 2) uses a steady beam of light supplied by the
receiving partne...