Agilent/Keysight 81531A – Optical Head

The Agilent/Keysight 81531A is an InGaAs optical power sensor module designed for integration into Agilent/Keysight Lightwave Multimeter mainframes. It delivers high-accuracy optical power measurements across the near-infrared spectrum, serving telecommunications, fiber optics, and laboratory characterization applications.

Technical Specifications

• Sensor Element: InGaAs


• Wavelength Range: 800 nm to 1700 nm


• Power Measurement Range: +3 dBm to −90 dBm


• Measurement Accuracy: ±2.5% (1000 nm to 1650 nm)


• Measurement Resolution: 0.0001 dB/dBm


• Linearity: Linear response from 0 dBm to −70 dBm


• Analog Output Bandwidth: DC to 5300 Hz (range and module dependent)


• Analog Output Voltage: 0 to 2 V into open circuit


• Analog Output Impedance: 600 Ω typical


• Maximum Input Voltage: +10 V

Key Features

• Plug-in module architecture for quick mainframe integration


• Wide spectral coverage from 800 nm to 1700 nm


• Dynamic range spanning six decades of optical power


• High measurement resolution supports precision component testing


• Factory calibrated with traceable calibration certificate

Typical Applications Optical power measurement in fiber-optic test systems, telecommunications component characterization, laser power assessment, and optical system validation in research and production environments.

Compatibility & Integration The 81531A operates in the 8153A and 8163A mainframes, as well as the 8164 mainframe. It is not compatible with the 8166 mainframe. Agilent 81000xI Series optical interface connectors are required separately - available options include 81000FI (FC/PC), 81000VI (ST), 81000KI (SC/PC), and 81000NI (FC/APC).