Agilent Keysight 81628B InGaAs High Power Optical Sensor Head 800-1700nm

Agilent Keysight 81628B InGaAs High Power Optical Sensor Head 800-1700nm: High-Power Integrating Sphere Detection for Optical Amplifier and DWDM Testing

The Agilent Keysight 81628B InGaAs High Power Optical Sensor Head 800-1700nm is a high-power optical sensor head built around an InGaAs detector with an integrating sphere, designed to measure optical power from -60 dBm all the way up to +40 dBm across the 800–1700 nm wavelength range. It targets engineers characterizing high-power sources such as EDFAs, Raman amplifiers, and pump lasers, where standard optical power sensors would saturate or be damaged.

Key Features and Benefits of the Agilent Keysight 81628B InGaAs High Power Optical Sensor Head 800-1700nm

• Wide 800–1700 nm wavelength range — Covers visible-adjacent, O-band, E-band, S-band, C-band, and L-band telecom applications from a single sensor head.
• +40 to -60 dBm power range — Handles high-power amplifier outputs and low-level signals in the same instrument, eliminating the need for multiple sensors.
• Integrating sphere design — Distributes incoming light uniformly across the detector, giving accurate readings on high-power sources without hot-spot damage or saturation.
• Return loss typical >75 dB — Minimizes back reflections that would otherwise disturb high-power sources under test.
• ±0.006 dB polarization dependence (typical) — Very low PDL keeps measurement uncertainty small when working with polarized sources.
• ±3.0% uncertainty at reference conditions (970–1630 nm) — Delivers accurate absolute power readings across the primary telecom wavelength range.
• Analog output included — Direct analog signal for data logging, external ADCs, and integration into custom measurement setups.
• Compatible with 81618A/81619A Interface Modules — Drops into standard single or dual head interface modules for use with Keysight lightwave mainframes.
• Wide operating range for open-beam and fiber inputs — Accepts single-mode NA =0.2 and multimode NA =0.4 with a 3 mm center-of-sphere spot.

Advanced Capabilities

The 81628B's integrating sphere design is what makes high-power measurement possible without damaging the sensor. When light enters an integrating sphere, it undergoes multiple diffuse reflections off the sphere's inner coating before reaching the detector — this spreads the optical energy over a large area and integrates over any spatial non-uniformity in the beam. The result is that a +38 dBm (6 W) source that would immediately destroy a direct-illumination photodiode can be measured accurately, with the detector seeing only a small fraction of the total power via calibrated sphere geometry. The head is rated to a damage threshold of 40.5 dBm, giving a small but real margin above the +40 dBm maximum measurement point.

Safety considerations at high power are also worth noting. For optical power higher than 34 dBm, the attached heatsink MUST be used. For continuous or average optical power higher than 38 dBm, the connector adapters will get warmer than permitted according to safety standard IEC 61010-1. The 81628B can handle optical power up to 40 dBm, but operation above 38 dBm is at the operator's own risk. For continuous operation above +30 dBm, the operating temperature is also limited to 35°C rather than the standard 40°C ceiling.

Calibration and Quality Assurance

Every Agilent Keysight 81628B is calibrated prior to shipping to OEM specifications. The order includes a Calibration Certificate, Calibration Label, and full Calibration Data. This means the sensor head arrives traceable, audit-ready, and ready to use straight out of the box — no need to schedule a calibration cycle before putting it into service. The 81628B has a recommended factory recalibration period of 2 years.

Specifications