Cross Channel Interference due to Wavelength Drift of Tuneable Lasers in DWDM Networks

The authors present an investigation of wavelength stability of a tunable laser transmitter and its impact on the performance of a 2.5 Gb/s dense wavelength division multiplexed system. The wavelength drift of the laser after switching between channels is accurately measured by using a self-heterodyning technique and an optical filtering technique. Performance of a DWDM system, employing such a tunable laser, is characterised by examining the inter-channel interference caused by this drift when the channel spacing is set to 12.5 and 25 GHz. Results obtained show that the wavelength drift affects the system performance by introducing a power penalty in the case of 25 GHz spacing and an error floor in the case of 12.5 GHz spacing