Browse Prior Art Database

DC Laser Safety Interlock

IP.com Disclosure Number: IPCOM000109454D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 1 page(s) / 51K

Publishing Venue

IBM

Related People

Hayward, C: AUTHOR [+2]

Abstract

Disclosed is a laser interlock for fiber-optic communication systems. A low optical power DC signal is used to detect closed-loop continuity, and control the laser power output.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 70% of the total text.

DC Laser Safety Interlock

      Disclosed is a laser interlock for fiber-optic communication
systems.  A low optical power DC signal is used to detect closed-loop
continuity, and control the laser power output.

      The laser transmitter has three output states: 1) Off; 2)
Normal operation; and 3) DC low optical level.  The DC low level is
selected to be below the class I laser safety emission limit.

      The optical receiver has a DC coupled detector with a low-pass
filter.  The pass band is selected to be below the lowest data
transmission frequency.  The receiver will detect the presence or
absence of data, and the DC optical signal.  The receiver controls
the state of the local transmitter as shown in the table.

      When the duplex connector is disconnected from the optical
transmitter and receiver, the receivers detect no signal, and put the
lasers in DC optical mode.  When the connector is inserted, and a
complete closed optical path is created, the lasers are put into
normal operating mode.

      The DC coupled portion of the optical receiver is more
sensitive than the data portion of the optical receiver since the DC
coupled receiver has a much smaller noise bandwidth.  For a serial
bit rate of 200 Mbps, and a low-pass filter cutoff of 1 KHz, the DC
coupled portion of the receiver is 25 dB more sensitive.  This more
than makes up for the reduction of optical power output from the
laser in the DC mode versus normal operating mode.

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