For determining whether a configuration of an optical transmission interface of a first device has to be adjusted for transmitting optical signals to a second device via an optical band-pass filter, the second device having an optical reception interface configured to enable receiving optical signals output by said optical band-pass filter and transmitted by the first device on a carrier wavelength when said carrier wavelength is comprised in the passband of the optical band-pass filter, said carrier wavelength and/or said passband of the optical band-pass filter being a priori unknown, a monitoring device performs: monitoring an evolution of a difference level between codewords received by the second device via said optical signals and corresponding codewords transmitted by the first device; and determining whether the configuration of the optical transmission interface of the first device has to be adjusted, on the basis of said monitoring.