METRODATA NetTESTER FAMILY USER MANUAL
76-02-107 Rev.A
Page 50 of 133
11 OPTICAL TIME-DOMAIN REFLECTOMETRY (OTDR) TESTING
The unit can be used with a range of special SFP single-mode fibre modules,
supplied by Optical Zonu [9], which have an integrated Optical Time-Domain
Reflectometry (OTDR) measurement facility. With an OTDR SFP module fitted, the
unit can assist with the job of locating a fault on the fibre link (such as a damaged or
disconnected cable) by measuring the time taken for light pulses to reflect off the
fault point and return to the unit.
The OTDR SFP module integrates these diagnostic functions alongside the normal
SFP optical transceiver. Under normal conditions, it operates as a regular fibre
module. But whenever the link fails, the device will automatically switch to OTDR
mode and identify the fault location. The unit maintains a log of faults and can
generate SNMP trap messages when they occur.
MetSfpOTDRFaultStart
This trap is generated when an OTDR fault is first
detected. The trap parameters include the
distance in metres to the fault.
MetSfpOTDRFaultClear
This trap is generated when the OTDR fault is
cleared. The trap parameters include the system
up time for both start and clearance of the fault
condition.
Note
: When used with short fibres, insufficient attenuation of the OTDR pulse can
cause the device to see multiple reflections, and a cable length of a multiple of the
real length to be reported. To counter this, where fibre runs of less that 10km are
used, the use of a 10dB attenuator is recommended.
Distance measurement are accurate to /-10m.
OTDR modules cannot be fitted in SFP+ interfaces.
