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Optical Communications

Optical signal to noise ratio monitoring using interferometric methods

Work is currently related to in-band optical signal to noise ratio OSNR monitoring using interferometric methods. Such measurements are important in fault diagnosis in optical communications networks. The use of reconfigurable optical add-drop multiplexers in communications networks means that the noise level in adjacent channels may be vastly different. This renders current out-of-band noise monitoring next to useless. The in band monitoring scheme uses the coherence difference between signal and noise to measure the noise within the signal channel. The current focus involves observing the effects of various network impairments and modulation formats on the system.

A schematic and photograph of the OSNR monitor.

The result of an OSNR measurement performed on a 10G non return to zero (NRZ) on-off keyed signal with 600ps/nm of chromatic dispersion.


1. E. Flood, W. H. Guo, D. Reid, M. Lynch, A. L. Bradley, L. P. Barry, and J. F. Donegan, "In-band OSNR monitoring using a pair of Michelson fiber interferometers," Opt. Express 18, 3618-3625 (2010)