Nortel Optical Multiservice Edge 6130, Руководство по планированию, Страница: 70 / 292

6-10 OAM&P description
Optical Multiservice Edge 6130 NT6Q92MA Rel 1.0 Iss 1 Standard September 2006
Timing distribution
Timing distribution is the ability of the OME6130 to provide a synchronization
reference to external devices. The OME6130 supports the following timing
distribution reference signals:
• CLKOUT and DATAOUT ports on the ESI port located on the faceplate of
the OAM circuit pack
• one or two STM-1/4 ports on the 2x155/622M aggregate circuit pack
• one or two STM-1 ports on the 2x155M circuit pack
The following items need to be considered when using the OME6130 as a
timing source.
• the signal format of the external timing source (E1 or 2.048 MHz for SDH)
• the connector type/impedance of the ESI port (120 ohm balanced or 75
ohm unbalanced)
• the reference sources to be used for timing distribution and the hierarchy
Synchronization operating modes
The OME6130 synchronization operating modes describe the state that the
synchronization hardware is operating in. These modes are not provisionable
by the user and consists of the following:
• freerun
• locked
• holdover
Freerun mode
In freerun mode, the system clock is not locked to a timing reference and runs
at its natural frequency. The synchronization hardware on the 2xSTM-1/4
aggregate circuit pack provides timing references quality as specified in
internal G.813 Option 1 (4.6 ppm). The OME6130 is in this mode if the user
has provisioned the shelf timing as internal or the holdover period has expired
in which case a warning condition is raised to advise the user.
Locked mode
In locked mode, the system clock is locked to a timing reference. The
OME6130 is in this mode when a timing reference is active and working
during trouble free operations.
Holdover mode
The synchronization hardware enters holdover mode automatically if the
target mode is locked but all timing references have become unavailable. The
system clock in the synchronization hardware holds within a certain frequency
range of the last locked-in timing reference in which case a warning condition
is raised to advise the user.