Absolute power calibration
The calibration of a power meter is usually achieved by exposing both the meter under test and
a calibrated power meter with known uncertainty (the reference meter) to an optical radiation,
and by transferring the reference meter's measurement result to the test meter.
The allowable spectral bandwidth depends on the test meter's spectral responsivity; the
stronger its wavelength dependence, the narrower the spectral bandwidth. Usual bandwidths
are