
20.9 OPTICAL PERFORMANCE MONITORING
As optical com munication data rates increase from 40 to 160 Gb/s and beyond,
signals become much more sensitive to transmission impairments such as ASE
noise, chromatic dispersion, and polarization mode dispersion (PMD), loss and
others. This has driven significant interest in developing all-optical techniques for
OPM [134] in systems and networks. Without monitoring signal quality, a reduc-
tion in network performance is only discovered once actual data are lost. Perfor-
mance monitoring of the optical signal can provide information about the signal
quality and identify network fault locations and generate failure ...