Agilent/Keysight 81626C,High Power Optical Head

The Keysight 81626C is a high-power optical head designed for precision optical power measurements across the near-infrared spectrum. It features an InGaAs filtered large-area detector with a 5 mm active area, enabling accurate measurements from –70 dBm to +27 dBm across its operational range. The head accepts parallel beams up to 4 mm diameter, standard single-mode fiber, and multimode fiber with core diameters to 100 μm and numerical apertures ≤0.3.

Magnetic D-shaped adapters enable rapid fiber changeover without twisting loads. An analog output port delivers linear or logarithmic voltage feedback proportional to optical signal power, supporting automated alignment and closed-loop optimization. The 81626C interfaces with the N7749C Optical Power Meter Head Interface, which supports two or four measurement heads simultaneously.

Network connectivity via LAN and USB, combined with a built-in web browser GUI and SCPI command compatibility, enables flexible remote and local control. Typical measurement uncertainty is ±2.5% at reference conditions for the 81626X01C variant. Optional enhanced metrology reference calibrations are available for applications requiring working standard quality assurance.

Technical Specifications

• Detector Type: InGaAs filtered large-area detector


• Detector Area: 5 mm


• Wavelength Range: 850 nm to 1650 nm


• Power Range: –70 dBm to +23 dBm (850–1650 nm); –70 dBm to +27 dBm (1250–1650 nm)


• Input Acceptance: Parallel beams to 4 mm diameter, standard SM fiber, MM fiber (≤100 μm core, NA ≤0.3), straight connector (NA ≤0.2)


• Analog Output: BNC connector, 0–2 V (2 V = full-scale input)


• Measurement Uncertainty: ±2.5% typical (81626X01C at reference conditions)

Key Features

• Magnetic D-shaped quick-change adapters minimize fiber handling stress


• Analog feedback port for real-time signal monitoring and automated alignment


• Dual output modes: linear or logarithmic voltage scaling across power decades


• Optional enhanced metrology reference calibrations


• Compatible with current and legacy Keysight optical power meter interfaces

Typical Applications

• High-power fiber and free-space beam characterization


• Automated alignment and closed-loop power optimization


• Working standard metrology for telecom and industrial optical systems

Compatibility & Integration

• Controlled by N7749C Optical Power Meter Head Interface (supports 2 or 4 heads)


• Backward compatible with 81618A (single channel) and 81619A (dual channel) legacy modules


• LAN and USB readout with SCPI command interface


• Optional threaded adapters supported via removable 81624DD adapter