SILICON WEDGE-TRAP DETECTOR FOR OPTICAL-FIBER POWER MEASUREMENTS

We have designed and built an optical fibre power detector based on a large-area silicon PIN photodiode and a concave mirror in a wedge-trap configuration. The detector was designed as a high-accuracy transfer standard for near IR (835-865 nm) optical fibre power measurements wit h multimode fibre-ribbon cables in a manufacturing-production environm ent. Additional requirements were that the detector be insensitive to the input beam geometry, and able to accommodate different optical fib re connector types, collimated laser light, and highly diverging light from optical fibres. Four identical copies of the detector were evalu ated at the NIST Laser Sources and Detectors Group calibration facilit y and one was tested in the manufacturing environment. The spatial and angular responsivity was highly uniform and varied less than 1% for a ngles of incidence ranging from 0 degrees to +/-15 degrees:. Absolute spectral responsivity measurements, for collimated and diverging light input wavelengths ranging from 672-852 nm, showed quantum efficiencie s as high as 99%. Linearity measurements from a few nanowatts to a few milliwatts indicated a nonlinearity of only 0.05%.