A Transfer Standard for Optical Fiber Power Metrology

We have developed and evaluated a transfer standard for the calibration of optical fiber power meters over the wavelength range from 750–1800 nm. The transfer standard is an optical-trap detector consisting of two germanium (Ge) photodiodes, and a spherical mirror. The photodiodes and mirror are contained in a package that is thermally stable and accepts a variety of optical fiber connectors. Spatial uniformity measurements indicate that the variation of detector response as a function of beam position is less than ±0.15%. Comparison of the absolute responsivity for three different input conditions indicates that the detector responsivity is nearly the same for collimated beams transmitted through air, as for diverging input from an optical fiber. Small measurement-result differences between collimated and diverging inputs still remain and are discussed briefly.