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Browse Prior Art Database

Parallel Optical Fiber Cable for Optical Transceivers with a Gap between Groups of Fibers within the Cable

IP.com Disclosure Number: IPCOM000117268D
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 189K

Publishing Venue

IBM

Related People

Kuchta, DM: AUTHOR

Abstract

Disclosed is a method which applies to full duplex parallel optical buses with more than one optical channel in each direction. This invention solves the problem of having to use two separate parallel fiber cables to make a full duplex connection when using optical buses by making a single cable with a gap between the two sets of fibers in the cable.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

Parallel Optical Fiber Cable for Optical Transceivers with a Gap
between Groups of Fibers within the Cable

      Disclosed is a method which applies to full duplex parallel
optical buses with more than one optical channel in each direction.
This invention solves the problem of having to use two separate
parallel fiber cables to make a full duplex connection when using
optical buses by making a single cable with a gap between the two
sets of fibers in the cable.

      When constructing optical transceivers (whether serial or
parallel) there exists a physical limitation on how close one can
physically position the receiver photodiode next to the transmitter
optical emitter.  This limitation arises because of the requirement
to some amount of semiconductor material around the emitter (and
photodiode) for purposes of reliability, dicing, and handling.  There
is also a physical limation on how close the emitter and detector
chips can be place before the epoxy fillet (the epoxy is used to at
these chips to the package) from each chip runs together and creeps
too high up the side walls of the chips.  There are also limitations
which are a little harder to quantify which are due to crosstalk
between the transmitter and receiver due to both electrical and opt
sources.  Because of these three physical limitations, optical
transceivers are always built with the receiver and transmitter
separated by a fairly large distance (many mm or even cm).
(Actually, there is a fourth reason which is that optical ribbon
cables are also not manufactured with enough fibers in them for even
to smallest of optical transceivers.  Currently the ribbon with the
largest number of  fiber that is commercially available has 18 fibers
while the smallest useful optical transceiver requires 20 fibers.
This is soon to change, though.)  As a result of this large
separation, transceiver cables are constructed by using two
previously constructed fiber ribbons the number of channels and
bundling them together.  Fig. 1 illustrates this concept by showing
two ribbons of 10 fibers each that have been bundled together by an
extra sleeve to form a duplex transceiver cable.  The problems
associated with this are the added cost of bundling, the need to mark
the cable in some manner so as to not confuse one side with the
other, and the need to have two separate connectors for each half.
It is possible to make a wider single cable or a transceiver which
contains extra fibers in the center  when...