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Method for Preventing Excessively High Optical Radiation Levels in Active Stars

IP.com Disclosure Number: IPCOM000100784D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 85K

Publishing Venue

IBM

Related People

Cheng, T: AUTHOR [+2]

Abstract

Disclosed are methods to prevent the leakage of excessive amounts of optical radiation in the event of the failure of an optical star network. They are designed to alert stations to the possibility of the leakage of optical radiation. In a passive network (refer to Fig. 1), no processing of the light signal is performed at the central hub. A node can tell if a fault potentially exists by sensing the light returned to it when it transmits. If no light is sensed on the return path, the node shuts itself down.

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Method for Preventing Excessively High Optical Radiation Levels in Active Stars

       Disclosed are methods to prevent the leakage of excessive
amounts of optical radiation in the event of the failure of an
optical star network.  They are designed to alert stations to the
possibility of the leakage of optical radiation.  In a passive
network (refer to Fig. 1), no processing of the light signal is
performed at the central hub.  A node can tell if a fault potentially
exists by sensing the light returned to it when it transmits.  If no
light is sensed on the return path, the node shuts itself down.

      With active networks (refer to Fig. 2), however, the situation
is more complex.  Four possibilities exist:
1.   The fiber leading to the hub breaks or is disconnected.
2.   The fiber from the laser to the splitter breaks or is
disconnected.
3.   The fiber from the splitter breaks or is disconnected.
4.   A combination of the above possibilities.

      In the first case the hub can sense the loss of light on an
incoming fiber, and issue a command for the node to shut itself down.
Two separate problems present themselves in the second case.  The
first is that a break in the fiber leaves the hub unable to
communicate.  The second is the escape of laser radiation from the
break in the fiber.  The first problem is resolved by ensuring that
there is a signal on the fiber from the hub at all times.  This is
achieved by transmitting an idle sequence when nothing is being
transmitted.  In the absence of a signal, nodes power themselves
down.

      To...