Agilent/Keysight 81623C Optical Power Head

The Agilent/Keysight 81623C is a germanium-based optical power head engineered for precision measurements across the near-infrared spectrum. It connects to the Keysight N7749C optical head interface for remote positioning and delivers measurement uncertainty of ±2.2% at 1000 nm to 1650 nm under reference conditions. The 5 mm detector accommodates parallel beams up to 4 mm in diameter and supports standard single-mode fiber, multi-mode fiber with core diameters to 100 µm (NA = 0.3), bare fibers, and open beams.

Technical Specifications

• Detector: Germanium, 5 mm diameter


• Wavelength Range: 750 nm to 1800 nm


• Power Range: +10 dBm to −80 dBm


• Beam Diameter Acceptance: Up to 4 mm


• Measurement Uncertainty: ±2.2% at 1000 nm to 1650 nm; ±2.5% at 800 nm to 1000 nm (optional calibration: ±1.7% at 1000 nm to 1650 nm)


• Linearity: 50 dB (typically > 55 dB)


• Polarization Dependence: < ±0.01 dB relative uncertainty (typically < ±0.005 dB)


• Spectral Ripple: < ±0.006 dB relative uncertainty (typically < ±0.003 dB)

Key Features

• Analog output configured for linear or logarithmic response across multiple decades


• Magnetic D-shaped adapters enable rapid fiber or beam coupling without disturbing attached connections


• Optional adapters available for standard connector types, bare fibers, and open-beam geometries

Typical Applications

• Optical communication system characterization


• Laser power and spectral performance validation


• Optical component testing and alignment

Compatibility & Integration Integrates with the Keysight N7749C optical head interface, which provides LAN and USB readout, SCPI command control, dual 1 M sample buffers per head, and averaging times from 100 µs to 10 s. Supports internal and external triggering with simultaneous measurement and readout.