  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.

Optics;Quantum Physics