Special tunable fiber-ring laser, applied as local oscillator in an absolute calibrated spectrometer for WDM systems

A special tunable fiber-ring laser is introduced. With this laser as local oscillator, a calibrated optical spectrometer was realised which allows the supervision of all transmitters of a EDFA-based WDM-system. A special fiber-ring laser was introduced which is quasi single-mode and quasi continuously tunable over the entire EDFA-band. With that as local oscillator, a spectrometer was built up, which allows the monitoring of the frequency and power distributions of all transmitters in the EDFA-band. The absolute frequency accuracy was better than 0.7 GHz. A sensitivity of -45 dBm was achieved, where the sensitivity was mainly limited by the high insertion loss of the Fabry-Perot-interferometer in the ring. A unit, based upon the described set-up, can be used for supervision of any EDFA-based WDM network.