A method for calibrating an OLTS includes calibrating a first optical power meter of the OLTS using a stabilized light source. The method further includes calibrating a second optical power meter of the OLTS using the stabilized light source. The method further includes setting a power of an internal light source using the calibrated first optical power meter. A calibration cable is connected to a first test port and a second test port during setting of the power level, and a connection of the calibration cord to the second test port is maintained between calibrating of the second optical power meter and setting of the power level.