The portable Fibrain FCPM-18/1310 power meter is used for field power measurements in CWDM channels. Its unique features are an automatic identification and measurement of all 18 CWDM channels compliant with ITU-TG.694.2 recommendation, lack of moving and scanning components which have been replaced by built-in passive CWDM filters (which leads to significantly higher reliability), and a possibility of measurements of so-called grey 1310 nm channels. By using the built-in function of offset level setting, the FCPM-18/1310 meter can be successfully applied to approximate the power of CWDM channels in a line with a measurement using a power monitoring port (often called the test port) that is built into CWDM multiplexers and demultiplexers.