Determination of Er-fibre L-band gain coefficient from measured ASE spectra

We show that the gain coefficient in Er-fibres in the L-band region can be directly determined as a function of wavelength from easily measured ASE output spectra at two different saturation levels. Further, we demonstrate that the tilt-functions T derived from gain and ASE curves are equal, within experimental error, in the region from 1570 to 1610 nm and, then, that the gain coefficient can be determined directly from measured ASE spectra, which is a simpler and faster method than gain measurements.