Optical Power Sensor Module, InGaAs 800 to 1700 nm The HP (now Keysight) 81531A is an optical power sensor module for the 8153A lightwave multimeter mainframe. Sensor element: InGaAs Wavelength range: 800 to 1700 nm Power range: +3 to -90 dBm Application fiber type: 9/125 µm - 100/140 µm, NA ≤0.3 Noise (peak to peak), averaging time 1 second: <1.5 pW (1200-1600 nm)