Browse Prior Art Database

A Method to Improve the Utilization of Optical Star Networks

IP.com Disclosure Number: IPCOM000103186D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 56K

Publishing Venue

IBM

Related People

Cheng, T: AUTHOR [+3]

Abstract

Disclosed is an efficient medium access protocol for a passive optical star. It utilizes two wavelengths, one for data transfer and the other for control. Each station is equipped with a transmitter and receiver for each wavelength. The two wavelengths of light from the transmitters are coupled into a single fiber via a wavelength division multiplexor. This fiber in turn is attached to the star coupler. Similarly, the fiber that leads from the star coupler to the station is attached to a wavelength division demultiplexor, and the two wavelengths of light are then taken to their respective receivers. On the control channel, a token is constantly kept in circulation. Stations transmit on the data channel using a CSMA protocol (preferably a protocol such as Virtual Time CSMA so as to minimize the probability of a collision).

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A Method to Improve the Utilization of Optical Star Networks

      Disclosed is an efficient medium access protocol for a passive
optical star.  It utilizes two wavelengths, one for data transfer and
the other for control.  Each station is equipped with a transmitter
and receiver for each wavelength.  The two wavelengths of light from
the transmitters are coupled into a single fiber via a wavelength
division multiplexor.  This fiber in turn is attached to the star
coupler.  Similarly, the fiber that leads from the star coupler to
the station is attached to a wavelength division demultiplexor, and
the two wavelengths of light are then taken to their respective
receivers.  On the control channel, a token is constantly kept in
circulation.  Stations transmit on the data channel using a CSMA
protocol (preferably a protocol such as Virtual Time CSMA so as to
minimize the probability of a collision).  As soon as a collision is
sensed, the stations switch over to a token passing mode.  The
station that has the token transmits a message and releases the token
simultaneously with the start of transmission.  This is made possible
by the separate control channel.  The token keeps circulating until
it is grabbed by a station with a message to transmit. The station
waits until it sees an End of Transmission frame, and then proceeds
to transmit.  As soon as the token makes one round trip with no
transmissions, stations revert to the CSMA mode of operation.  Note
that the...