HP 81522A Optical Head
The HP 81522A is a high sensitivity optical head that connects to the 81533A or 81533B which is a plug-in module that fits the 8153A and 8163 and 8166 Agilent/HP series mainframe. It also connects to the 8152A Optical Average Power meter. The 81522A optical head is made of a 5mm cooled InGaAs sensor element and covers the range of 1000-1650 nm wavelengths in a range of +3 to -100 dBm. Various connector interfaces are available for that head.
Click the PDF Specification for further information.