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Fault Detection and Isolation in Optical Networks using Wavelength Routers

IP.com Disclosure Number: IPCOM000115427D
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 99K

Publishing Venue

IBM

Related People

Li, CS: AUTHOR [+2]

Abstract

The next generation of all-optical networks with wavelength reuse will use wavelength routers so that each wavelength can be utilized simultaneously in different areas of the network. A fault detection and isolation system must be provided as part of any such network system. Performing this task in normal electronic switching systems is fairly straightforward because such links operate using a given well-known protocol, such as Synchronous Optical Network (SONET). In such systems, the output of the switch ports looks at the bits in the signal injected by the input of the switch ports to determine and isolate faults.

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Fault Detection and Isolation in Optical Networks using Wavelength
Routers

      The next generation of all-optical networks with wavelength
reuse will use wavelength routers so that each wavelength can be
utilized simultaneously in different areas of the network.  A fault
detection and isolation system must be provided as part of any such
network system.  Performing this task in normal electronic switching
systems is fairly straightforward because such links operate using a
given well-known protocol, such as Synchronous Optical Network
(SONET).  In such systems, the output of the switch ports looks at
the bits in the signal injected by the input of the switch ports to
determine and isolate faults.  However, such schemes cannot be used
in an all-optical systems because the electronic signal cannot be
monitored and changed at the wavelength router, and secondly the
actual protocol being used on the link may not be known and hence the
monitoring system will not know the specific formats being used in
the signal.

      Detecting a fault inside a wavelength router is somewhat
complex.  Assume that the only components that fail are the optical
switches, one of which is present for each wavelength.

      If a switch fails, at least one of the lightpaths flowing
through the switch will be affected.  This will result in a loss of
light condition being detected at the ends of the lightpath.  The end
nodes then communicate with each node along the path of that
lightpath to determine whether it is a link failure.  If it is not a
link failure, then the next step is to determine the switch that has
failed.  The mechanism to determine this fault must be as
non-intrusive
as possible, i.e., other lightpaths must not be affected.

      Two approaches are listed that can be used to identify a switch
fault.  Both approaches require a local controller to be able to
monitor the output from each switch port by using a monitor
photodiode,
as shown in Fig. 1.  Thu...