An optical network adapted for determining a fault condition therein, the optical network comprising a controller and a plurality of reconfigurable optical add-drop multiplexers, ROADM, wherein each ROADM comprises: a controller interface for receiving instructions from the controller; a wavelength selective switch, WSS, for receiving a combined input optical signal and for outputting a WSS output signal; an amplifier for amplifying the power level of the output optical signal; and an add-drop bank for receiving at least one single optical signal from the combined input optical signal; wherein a light source is integrated in at least one of the WSS, amplifier and add-drop bank for sending a pilot optical signal; wherein the plurality of ROADMs comprises a first ROADM and a second ROADM, wherein the first ROADM and the second ROADM are optically coupled via an optical link, and the controller is specifically configured for: instructing at least a first light source corresponding to the first ROADM and at least a second light source corresponding to the second ROADM to respectively send a first pilot optical signal and a second pilot optical signal along the optical link extending between the first and the second ROADMs, wherein the first pilot optical signal and the second pilot optical signal have different wavelengths; obtaining from the first ROADM, an output characteristic value of the first pilot optical signal and an input characteristic value of the second pilot optical signal, and further obtaining from the second ROADM, an output characteristic value of the second pilot optical signal and an input characteristic value of the first pilot optical signal; and determining the condition of a domain network section comprising the first ROADM, the second ROADM and the optical link based on the characteristic values. a controller interface for receiving instructions from the controller; a wavelength selective switch, WSS, for receiving a combined input optical signal and for outputting a WSS output signal; an amplifier for amplifying the power level of the output optical signal; and an add-drop bank for receiving at least one single optical signal from the combined input optical signal; wherein a light source is integrated in at least one of the WSS, amplifier and add-drop bank for sending a pilot optical signal; wherein the plurality of ROADMs comprises a first ROADM and a second ROADM, wherein the first ROADM and the second ROADM are optically coupled via an optical link, and the controller is specifically configured for: instructing at least a first light source corresponding to the first ROADM and at least a second light source corresponding to the second ROADM to respectively send a first pilot optical signal and a second pilot optical signal along the optical link extending between the first and the second ROADMs, wherein the first pilot optical signal and the second pilot optical signal have different wavelengths; obtaining from the first ROADM, an output characteristic value of the first pilot optical signal and an input characteristic value of the second pilot optical signal, and further obtaining from the second ROADM, an output characteristic value of the second pilot optical signal and an input characteristic value of the first pilot optical signal; and determining the condition of a domain network section comprising the first ROADM, the second ROADM and the optical link based on the characteristic values. instructing at least a first light source corresponding to the first ROADM and at least a second light source corresponding to the second ROADM to respectively send a first pilot optical signal and a second pilot optical signal along the optical link extending between the first and the second ROADMs, wherein the first pilot optical signal and the second pilot optical signal have different wavelengths; obtaining from the first ROADM, an output characteristic value of the first pilot optical signal and an input characteristic value of the second pilot optical signal, and further obtaining from the second ROADM, an output characteristic value of the second pilot optical signal and an input characteristic value of the first pilot optical signal; and determining the condition of a domain network section comprising the first ROADM, the second ROADM and the optical link based on the characteristic values.