COMPARISON OF ERBIUM AMPLIFIER CHARACTERISATION USING AN ITU GRID WITH VARYING CHANNEL SEPARATIONS

摘要

100GHz spacing ITU grid source measurements of gain and noise figure of EDFAs are presented. Channel numbers can be halved or quartered giving deltas to the 100GHz measurements of <～0.15dB and <～0.3dB respectively. Recently wavelength division multiplexed erbium doped fibre amplifier (EDFA) designs have progressed from "red band" (～1540-1560nm) to "full band" (～1530-1560nm) and eventually "extended band" (～1570-1600nm). As this happened problems have become apparent with existing methods of EDFA measurement such as the noise-gain profile technique. These methods suffer because they concentrate the power saturating the amplifier into one or a very small number of channels. Spectral hole burning, and the dependence of the amplifier's saturation on the wavelength of the saturating signal, lead to the results obtained to these techniques being unrepresentative of EDFA system performance. For accurate measurements the test source used must accurately represent the multi-channel loading used within the system for which the amplifier is designed. Here we present gain and noise figure results for an amplifier tested with lasers separated by 100GHz at the wavelengths defined by the ITU. Fully populating an ITU grid is expensive. Results have also been obtained using sources with separations of 200, 400 and 800 GHz. These are compared here to the 100 GHz benchmark to investigate cost reduction by the use of sub-populated grids. To the authors' knowledge previous work has only modelled sub-populated grids. It should be noted, that the gains and noise figures are only calculated at the source wavelengths in this technique, so some of the separations may be prohibited by their reduced spectral resolution