Measuring absolute spectral radiance using an Erbium Doped Fibre   Amplifier
  We describe a method to measure the spectral radiance of a source in an absolute way without the need of a reference. Here we give the necessary detail to allow for the device to be reproduced from standard fiber-optic components. The device is suited for fiber-optic applications at telecom wavelengths and calibration of powermeters and spectrometers at light levels from 1nW to 1uW. 
Bruno Sanguinetti, Thiago Guerreiro, Fernando Monteiro, Nicolas Gisin   and Hugo Zbinden
physics.optics quant-ph