C-band DWDM and 18-wavelength CWDM tunable OTDR series for metro Ethernet, remote PHY and passive C-RAN link characterization. The FTBx-740C series includes CWDM and DWDM tunable OTDR modules (e.g., CW18-M18W or DWC) designed to stabilize the central wavelength under test to avoid drift/leakage into adjacent channels and to enable single-ended CWDM/DWDM fiber characterization, test through MUX/DEMUX/OADM, in-service testing using client wavelengths, and technician-friendly channel selection. The configuration described by the provided MCN appears to pair an FTB-1v2 Pro (dual-carrier DC) platform with an FTBx-740C module and the option list shown in the request.