M320 Attenuation in SONET/SDH PICs

SONET/SDH transceivers in the different reach classes—such as short reach (SR), intermediate reach (IR), or long reach (LR)—generate different output power levels and tolerate different input power levels. Transceivers that have a longer reach can transmit enough power to saturate the receivers on PICs that have a shorter reach. Specifically, LR transceivers can saturate IR PICs, and both IR and LR transceivers can saturate SR PICs. Transceivers in the same reach class can also saturate one another.

To prevent saturation, you might need to attenuate power at the PIC receiver, particularly if you know that it has a shorter reach than the transceiver that is sending the signal. Determine the amount of attenuation needed by measuring the power level at each receiver. Attenuate the power to bring it within the allowable range; for short lengths of fiber, with fiber and connector loss close to zero, an attenuator of 5 to 10 dB should be sufficient.

For specifications of minimum and maximum input level (receiver sensitivity and receiver saturation) and minimum and maximum output level (average launch power) for the SONET/SDH PICs supported on the M320 router, see the M320 Multiservice Edge Router PIC Guide.