The HP 81522A optical head is specially designed for low PDL, low spectral ripple, and high return loss and is used for optical component tests.
It works with the 81533B interface module.
This unit has has the following specifications:
Optical Wavelength Range: 1000 to 1650 nm
Optical Power Range: +3 to -100 dBm
It is used in Agilent lightwave mainframe models 8153A and 816XA and the HP 8152A Optical Power Meter.