Nortel Passport 15000, Установка и обслуживание оборудования, Страница: 345 / 874

Chapter 17 Hardware procedures 345
Passport 15000, 20000 Hardware Installation, Maintenance, and Upgrade 5.2S2
Determining if you need to use inline attenuators with
optical FPs
Determine if you need to use inline attenuators with optical FPs prior to
cabling the FPs. Perform this procedure for every pair of optical FPs.
Prerequisites
• You must be familiar with “Safety considerations and best practices”
(page 53).
• Optical function processors (FPs) have different transmit and receive
strengths for short reach (SR), intermediate reach (IR), and long reach
(LR) capabilities. When the maximum transmit (Tx) power is higher than
the maximum receive (Rx) sensitivity, an inline optical attenuator is
required to reduce the signal strength to an acceptable level. Adding an
optical attenuator with the appropriate amount of signal reduction at
either the input or output end of the shared signal cable reduces the
transmit signal strength to be within the range of acceptable receive
sensitivity.
• When connected optical FPs are the same type and have the same reach,
that is, SR, IR, or LR, an attenuator may still be required. For example,
the 1-port OC-12 (NTHR29) requires an attenuator for a loopback.
Procedure steps
1 Identify a pair of optical cards that are intended to be a connected pair, for
example, FP-to-FP or FP to another vendor’s equivalent optical card of
the same type of signaling.
2 Record the location of each pair, that is, floor number, room, aisle number,
node id, slot numbers of the pair.
CAUTION
Risk of damage to equipment by laser strength
When an FP receives a laser signal that exceeds its range
of receive sensitivity, the FP can be damaged or fail. The
ranges for transmit and receive are not always the same on
an optical FP. Always check whether each FP signaling
connection requires an attenuator.