Agilent/Keysight 81628B,Optical Head (Dual Channel)

The Agilent/Keysight 81628B is a dual-channel optical measurement head for high-power optical signal detection across the infrared spectrum. It integrates with Keysight Lightwave Measurement platform mainframes via 81618A or 81619A interface modules and features a wavelength-dependent calibrated integrating sphere optimized for accurate measurements at power levels up to +40 dBm.

Technical Specifications

• Sensor Element: InGaAs


• Wavelength Range: 800 nm to 1700 nm


• Power Range: +40 dBm to −60 dBm


• Maximum Input Power: +40 dBm (damage threshold 40.5 dBm)


• Aperture Diameter: 8 mm


• Averaging Time: 100 µs to 10 s


• Data Logging: Up to 20,000 samples


• Relative Uncertainty: ≤ ±0.006 dB (typical)


• Return Loss: > 75 dB (typical)


• Noise (peak-to-peak): < 5 nW


• Linearity (CW, 23°C ±5°C, 970 nm to 1630 nm): ±0.03 dB to ±0.10 dB depending on power level


• Reference Uncertainty (970 nm to 1630 nm): ±3.0%


• Analog Output: 0–2 V via BNC connector

Key Features

• Built-in wavelength-dependent calibrated integrating sphere distributes input power over a large surface area for enhanced linearity and thermal stability


• Detachable heatsink for operation above 2 W input power; required for continuous operation between 34 dBm and 38 dBm


• Supports single-mode fiber (NA ≤ 0.2) and multimode fiber (NA ≤ 0.4) via threaded connector adapters


• Automatic power ranging and min/max value monitoring


• 8 mm exposed aperture accommodates open-beam and custom fiber holder configurations

Compatibility & Integration

• Connects to Agilent/Keysight 81618A single-channel or 81619A dual-channel interface modules


• Compatible with threaded-type connector adapters


• Analog output requires autoranging to be disabled


• Operation above 38 dBm proceeds at operator risk; operation above 34 dBm without heatsink may cause connector and hardware temperatures to exceed IEC 61010-1 safety limits (55°C)