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Optical Channel Monitor (OCM) and Optical Performance Monitor (OPM)
The former measures power, or power and OSNR while the latter usually looks at power,
wavelength, and OSNR. The OCM emphasizes the information (power) at given channels, rather than
monitoring wavelength and its variation. OCMs commonly use Demux-type components as its spectral
elements. Since a Demux-type component, such as AWG, gives a set of fixed discrete channels with a predefined
frequency interval (channel spacing), such OCMs can only provide power measurements at the
wavelength positions corresponding to the DWDM channels. It is obvious that the measurements will be
biased when there is thermal-wavelength drift of the spectral element. It seems that OPM can provide more
network information than OCM since an OPM not only measures power and OSNR, but also monitors
wavelength and its variation. However, as more and more such network monitoring devices are employed,
the difference between OCM and OPM is evolving to be ambiguous. And |
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