Agilent/Keysight 81633B,Germanium Optical Head

The Agilent/Keysight 81633B is a Germanium optical power sensor head engineered for precision optical power measurements across the near-infrared spectrum. This 5 mm diameter detector module operates from 800 nm to 1700 nm and delivers absolute accuracy of ±0.15 dB with 0.001 dB resolution. The sensor accepts input power levels from -80 dBm to +10 dBm, with linearity of ±0.006 dB across the CW range (+10 dBm to -60 dBm).

Rise and fall times measure less than 3.5 ns each, supporting fast transient measurements. Noise equivalent power reaches 10 pW/√Hz, enabling detection of weak optical signals. The module connects via FC/PC optical connector and outputs an analog signal (0-2V range) through a rear-panel BNC connector proportional to detected power.

Responsivity is specified at 0.9 A/W. The sensor head measures 70 mm × 120 mm × 30 mm, weighs 0.2 kg, and operates from +15 V to +24 V at 3 W power consumption. A 20-minute warm-up period is required before measurement.

The 81633B integrates with Agilent/Keysight mainframe instruments including the 8163A, 8163B, 8164A, 8164B, 8166A, 8166B, and 8153A, with interface modules 81618A or 81619A required for certain mainframe configurations. Operating temperature range is 0°C to 55°C; storage extends from -40°C to 70°C in non-condensing environments. Maximum input power is 100 mW.

Calibration is valid within one year; an additional 0.3% uncertainty applies in the second year following calibration.

Technical Specifications

• Sensor element: Germanium (Ge), 5 mm diameter


• Wavelength range: 800 nm to 1700 nm


• Power range: -80 dBm to +10 dBm


• Absolute power accuracy: ±0.15 dB


• Power resolution: 0.001 dB


• Linearity (CW +10 dBm to -60 dBm): ±0.006 dB


• Noise equivalent power: 10 pW/√Hz


• Rise time: < 3.5 ns


• Fall time: < 3.5 ns


• Maximum input power: 100 mW


• Responsivity: 0.9 A/W

Key Features

• FC/PC optical connector for industry-standard fiber coupling


• Analog voltage output (0-2V, BNC connector) for direct instrumentation integration


• Fast transient response enables sub-nanosecond timing measurements


• Operates across extended near-infrared wavelength band


• Low noise floor supports weak-signal detection applications

Compatibility & Integration The 81633B works with operation with Agilent/Keysight mainframe units: 8163A, 8163B, 8164A, 8164B, 8166A, 8166B, and 8153A. Interface modules 81618A or 81619A may be required depending on mainframe model.