An optical network including multiple nodes is subject to intermittent faults that may raise alarms in the system. The invention focuses on an optical network based on the Any rate architecture. A single fault such as a client failure at a node in such a network can give rise to a loss of client signal leading to multiple alarms detected at multiple points. To alleviate this problem this invention provides switching in a special Signature signal in place of the lost client signal. By detecting the Signature signal containing a specific code, the fault on the any rate-based architecture can be uniquely identified. In addition to fault identification, the Signature signal on the network makes it possible to maintain Clock and Data Recovery Locks at downstream nodes. The Signature signal serves also as a vehicle for carrying a special optical tag called Wavekey provided by the Wavelength Tracker technology developed by the Applicant. This optical tag includes a low frequency modulation of one or more dither tones onto an optical channel, which is uniquely identified by the tag. Maintaining the Wavekey is important for tracing the end-to-end path and power level of the signal on each wavelength. A method and a Field Programmable Gate Array-based system for the generation and identification of such a Signature signal that not only identifies the fault that has occurred on the optical network but also provides for the maintenance of the Wavekey, are described.