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Voltage Distribution Through Tri-Lead Wires in a 200mb/S, Split, Fiber-Optic Port Sub-Assembly Design

IP.com Disclosure Number: IPCOM000120508D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 85K

Publishing Venue

IBM

Related People

Jordan, RC: AUTHOR [+3]

Abstract

Disclosed is a method for using drain (shield) wires in a tri-lead or other transmission line cables to carry power/ground currents (used by the circuit attached to the cable) without using dedicated twisted pair wires for this use.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Voltage Distribution Through Tri-Lead Wires in a 200mb/S, Split,
Fiber-Optic Port Sub-Assembly Design

      Disclosed is a method for using drain (shield) wires in a
tri-lead or other transmission line cables to carry power/ground
currents (used by the circuit attached to the cable) without using
dedicated twisted pair wires for this use.

      This method provides the flexibility a designer requires when
developing a high-speed cable interface where low or reduced pin
count is essential.  By using the tri-lead ground (drain) wires that
shield the signal conductor to carry both power and ground
requirements; a reduction in connector system size and cost is
realized.

      This article outlines the method and reasons for using the
tri-lead shield wires to carry the voltage requirements in a 200Mb
split fiber-optic port sub-assembly design.  In previous designs,
power and ground currents are carried in separate twisted pair wires
dedicated for just that use. The intention is to keep potentially
noisy power paths isolated from sensitive signal paths.  Some designs
carry the isolation one step further; the tri-lead signal cables are
wrapped within an external shielded jacket with the twisted pair
wires left outside of the shield.  Twisted pair wire power
distribution systems are typically equivalent to a single 19 gauge
conductor (e.g., two 22 gauge conductors in parallel).

      By using the tri-lead drain wires to carry current in this
design (see the Table), a reduction in voltage drop over prior
applications was accomplished.  This design application achieved a
power path equivalent to a 21 gauge wire, a 24 gauge wire and a 30
gauge wire all in parallel.

      There are two considerations when implementing this method.
They are:  (1)  purity of the power supply voltage, and (2) frequency
of the signal to be referenced to the power supply voltage.  These
two design considerations function jointly to determine the
feasibility of using this method in a design.  If the power supply
voltage is not well filtered, this method would be recommend...