VIAVI OCC-55 CWDM Optical Channel Checker and OCC-56 DWDM Optical Channel Checkers are compact and low-cost test alternative solutions to optical spectrum analyzers (OSA) for field service groups tasked with the installation, maintenance and upgrades of WDM systems testing. These selective power meters scan the WDM channels according to ITU-T wavelength grid and automatically record wavelength/frequency and related power level.