An optical transport system comprising an apparatus 102), the apparatus comprising: an optical output and an optical input; a first optical transmitter connected to the optical output and configured to transmit therethrough a first modulated optical signal carrying light spectrally located within a bandwidth of a first wavelength channel, wherein the first modulated optical signal constitutes a supervisory signals; a first optical receiver connected to the optical input and configured to receive therethrough a delayed portion of the first modulated optical signal; and an optical transmitter for payload transmissions (110 1) connected to the optical output and configured to transmit therethrough a plurality of payload-carrying modulated optical signals, each carrying light spectrally located within a bandwidth of a respective one of payload-carrying wavelength channels, wherein the first wavelength channel is reserved for the supervisory signal and is not used by the optical transmitter for payload transmissions (110 1), wherein the first wavelength channel is spectrally located at an edge of the spectral range occupied by the payload-carrying wavelength channel, wherein the optical transport system further comprises an optical repeater optically connected to the optical output of the apparatus and the optical input (140 1b) of the apparatus, the optical repeater including an optical circuit configured to direct toward the optical input of the apparatus a portion of the first modulated optical signal received from the optical output of the apparatus characterized in that the first optical transmitter comprises: a first light source configured to generate light comprising amplified spontaneous emission; a first band-pass filter configured to generate a first optical beam by passing through a spectral portion of the amplified spontaneous emission located within the bandwidth of the first wavelength channel; and a first optical modulator configured to generate the first modulated optical signal by modulating the first optical beam. an optical output and an optical input; a first optical transmitter connected to the optical output and configured to transmit therethrough a first modulated optical signal carrying light spectrally located within a bandwidth of a first wavelength channel, wherein the first modulated optical signal constitutes a supervisory signals; a first optical receiver connected to the optical input and configured to receive therethrough a delayed portion of the first modulated optical signal; and an optical transmitter for payload transmissions (110 1) connected to the optical output and configured to transmit therethrough a plurality of payload-carrying modulated optical signals, each carrying light spectrally located within a bandwidth of a respective one of payload-carrying wavelength channels, wherein the first wavelength channel is reserved for the supervisory signal and is not used by the optical transmitter for payload transmissions (110 1), wherein the first wavelength channel is spectrally located at an edge of the spectral range occupied by the payload-carrying wavelength channel, wherein the optical transport system further comprises an optical repeater optically connected to the optical output of the apparatus and the optical input (140 1b) of the apparatus, the optical repeater including an optical circuit configured to direct toward the optical input of the apparatus a portion of the first modulated optical signal received from the optical output of the apparatus characterized in that the first optical transmitter comprises: a first light source configured to generate light comprising amplified spontaneous emission; a first band-pass filter configured to generate a first optical beam by passing through a spectral portion of the amplified spontaneous emission located within the bandwidth of the first wavelength channel; and a first optical modulator configured to generate the first modulated optical signal by modulating the first optical beam.