National reference standards for determining optical-fibre power maintained
by the National Institute of Standards and Technology (NIST, USA) and the
All-Russian Research Institute for Optophysical Measurements (VNIIOFI, Russ
ian Federation) were compared at wavelengths near 1300 nm and 1550 nm at a
power level of 0.5 mW. Instruments from both laboratories are based on ther
mal detectors capable of electrical calibration. The comparisons indicate r
elative differences of 2 parts in 10(3) or less, which is easily within the
combined uncertainty of the two laboratories.