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FDDI I/II Signal Repeater

IP.com Disclosure Number: IPCOM000112812D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 81K

Publishing Venue

IBM

Related People

Bowen, R: AUTHOR [+3]

Abstract

In FDDI I/II networks that use (optical or electrical) By-Pass switches, the X3T9.5 FDDI standard states that the power budget for cable plant is -11 dB. This limits to 3, the number of stations that may be connected in a contiguous sequence in the "power off" mode. This is because when the station is powered off, the By-Pass switch is activated to carry the signal around this station to the next station. This By-Pass switch introduces significant insertion loss. After the signal passes through 3 consecutive By-Pass switches, it is degraded to the point of not being usable by any subsequent nodes (i.e., it exceeds -11 dB).

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This is the abbreviated version, containing approximately 52% of the total text.

FDDI I/II Signal Repeater

      In FDDI I/II networks that use (optical or electrical) By-Pass
switches, the X3T9.5 FDDI standard states that the power budget for
cable plant is -11 dB.  This limits to 3, the number of stations that
may be connected in a contiguous sequence in the "power off" mode.
This is because when the station is powered off, the By-Pass switch
is activated to carry the signal around this station to the next
station.  This By-Pass switch introduces significant insertion loss.
After the signal passes through 3 consecutive By-Pass switches, it is
degraded to the point of not being usable by any subsequent nodes
(i.e., it exceeds -11 dB).

      Thus, the problem to solve is, how to enable any number of FDDI
stations (with by-pass switches) to power down in an unrestricted
manner and to maintain a proper signal level.

      Most FDDI networks are built in a star wired configuration.
The center of the star is a FDDI concentrator.  Each SAS (single
attached station) is attached to a separate port on the concentrator
and the FDDI backbone is connected to a backbone port connection.  A
concentrator is an expensive device and performs many functions.

      The solution to the above stated problem is to replace this
active concentrator with a simple signal repeater.  The repeater
would simply receive the signal from a station, boost it and pass it
to the next station.  Note, that a by-pass switch may or may not be
connected between the station and the repeater.  It does not matter.
The signal is boosted and repeated regardless of the presence of the
by-pass switch.  Thus, because the standards limit the number of
consecutively conected by-pass switches to three, it is required...