Keysight 81618A Single-Channel Optical Head Interface Module for 8162x Optical Power Heads

Keysight 81618A Single-Channel Optical Head Interface Module

The Keysight 81618A is a single-channel optical head interface module designed to connect one compatible external optical power head to a supported Keysight lightwave measurement mainframe. Originally manufactured under the Agilent Technologies brand, the module supports modular optical power measurement systems used in fiber optic laboratories, production facilities, calibration environments, and telecommunications test applications.

The 81618A operates when installed in a compatible 8163 Series Lightwave Multimeter, 8164 Series Lightwave Measurement System, or 8166 Series Lightwave Multichannel System. It provides the electrical and communication link between the mainframe and one supported 8162x Series optical head.

The module does not contain an optical detector and does not measure optical power independently. Measurement capability is provided by the external optical head connected to the interface module. Detector material, wavelength range, optical power range, linearity, noise, return loss, fiber compatibility, and open-beam capability therefore depend on the selected optical head.

Compatible optical heads include models for general-purpose power measurement, high-sensitivity applications, high-power measurements, single-mode fiber, multimode fiber, connectorized fibers, bare fibers, and open-beam optical inputs. This modular approach allows one mainframe and interface module to be used with different detector heads according to the measurement requirement.

Features and Benefits of the Keysight 81618A

• Single optical head channel: Connects one compatible external 8162x Series optical power head to a supported lightwave mainframe.
• Modular measurement configuration: Allows the detector head to be selected according to the required wavelength, power range, fiber type, and optical input.
• Broad optical head compatibility: Supports compatible 81622B, 81623B, 81624B, 81626B, 81627B, and 81628B optical heads.
• Mainframe integration: Operates in compatible 8163, 8164, and 8166 Series lightwave measurement platforms.
• External detector placement: Allows the optical head to be positioned near the device under test while the interface module remains in the mainframe.
• Flexible optical interfaces: Compatible optical heads support interchangeable adapters for connectorized fiber, bare fiber, and open-beam measurements.
• Mainframe-controlled operation: Measurement configuration, wavelength, range, averaging, zeroing, and displayed results are managed through the compatible host platform.
• Professional test integration: Suitable for optical power measurement, component testing, stability monitoring, alignment, production testing, and calibration systems.
• Functional self-test support: The interface module can be evaluated through the compatible mainframe’s startup and self-test process.
• Modular serviceability: Separates the optical detector head from the mainframe interface for flexible system configuration and maintenance.

Single-Channel Optical Head Interface

The 81618A provides one external optical head connection. This single-channel configuration is appropriate when one remotely positioned detector head is required for the measurement setup.

The module receives information from the connected optical head and communicates with the host mainframe. The mainframe supplies the user interface, measurement controls, result display, application functions, and system communication capabilities.

For applications requiring two optical heads through one module, the related 81619A provides a dual-interface configuration. The 81618A itself supports one optical head.

Compatible Lightwave Mainframes

The Keysight 81618A is designed to operate in supported lightwave measurement mainframes, including compatible models from the following platform families:

• 8163 Series Lightwave Multimeter
• 8164 Series Lightwave Measurement System
• 8166 Series Lightwave Multichannel System

The host mainframe provides electrical power and control for the interface module. Mainframe firmware, available slot capacity, module recognition, and operating condition should be verified before installation.

The 81618A is not a standalone meter. It requires both a compatible mainframe and a supported external optical head to create an operational optical power measurement channel.

Compatible 8162x Series Optical Heads

The 81618A supports a selection of external optical heads with different detector materials and measurement ranges. Choosing the appropriate head allows the measurement system to address general-purpose, high-sensitivity, high-power, single-mode, multimode, and open-beam applications.

• 81622B: Germanium high-power optical head for supported single-mode and multimode measurements.
• 81623B: Germanium optical head for general-purpose power measurements.
• 81624B: InGaAs optical head for high-sensitivity measurements.
• 81626B: InGaAs high-power optical head.
• 81627B: InGaAs optical head with a 3 mm detector for supported single-mode and multimode applications.
• 81628B: InGaAs high-power optical head with an integrating sphere.

The connected head must be selected according to the optical wavelength, expected power level, numerical aperture, fiber size, beam diameter, detector sensitivity, and required measurement uncertainty.

Modular Optical Power Measurement

The 81618A separates the mainframe electronics from the optical detector head. The external head can be positioned close to the optical source, fiber output, component, or free-space beam being measured.

This arrangement can reduce the need to route the optical signal directly to the mainframe. It is useful for optical benches, alignment stations, equipment racks, production fixtures, and setups requiring convenient detector positioning.

Compatible optical heads measure power from connectorized single-mode or multimode fiber, bare fiber, or an open parallel beam when the selected head and adapter support the intended input.

Measurement Capability Depends on the Optical Head

The 81618A does not establish the wavelength or power specifications of the completed system. These characteristics are determined by the optical head connected to the module.

Supported head configurations cover wavelength ranges extending from 750 nm to 1800 nm. Available optical power ranges extend from high-sensitivity measurements down to -90 dBm through high-power measurements up to +40 dBm. These are family capabilities and do not apply simultaneously to every head.

Buyers should select and verify the optical head according to the required application. Specifications from one optical head must not be assigned to another model.

Interchangeable Optical Adapters

Compatible optical heads support interchangeable connector adapters for common fiber optic interfaces. Available adapter families include options for FC, SC, ST, LC, MU, DIN, E-2000, Diamond HMS-10, bare fiber, ribbon connectors, and other supported formats.

The exact adapter family depends on the optical head. Some heads use threaded adapters, while others use adapters with an integral D-shaped magnetic interface.

The appropriate connector adapter must be installed for the patch cord or bare fiber being measured. Connector family, ferrule polish, fiber type, numerical aperture, and adapter compatibility should be confirmed before connection.

Optical Head Analog Output

Compatible optical heads provide a rear-panel BNC analog output. The analog signal is proportional to the measured optical power within the selected power range.

The analog output varies from 0 V to 2 V when unterminated. A 2 V output corresponds to full-scale optical power in the active range, while 0 V corresponds to no applied optical signal.

Because the full-scale relationship changes during autoranging, manual range selection should be used when the analog output is connected to an oscilloscope, feedback system, data-acquisition device, or other external equipment.

Potential applications include monitoring laser power, assisting with optical alignment, and closing a feedback loop that controls the current supplied to a laser.

Typical Applications

• Fiber optic power measurement
• Single-mode and multimode optical testing
• High-sensitivity optical power measurements
• High-power optical measurements with a compatible head
• Connectorized fiber testing
• Bare fiber power measurement
• Open-beam optical measurements
• Laser source verification
• Optical component characterization
• Fiber alignment and coupling optimization
• Production testing and quality assurance
• Laboratory and calibration systems

Product Overview

Brand	Keysight
Legacy Brand	Agilent Technologies
Model	81618A
Product Category	Optical Head Interface Module
Number of Channels	One optical head interface
Compatible Optical Heads	Supported 81622B, 81623B, 81624B, 81626B, 81627B, and 81628B models
Compatible Mainframes	Supported 8163, 8164, and 8166 Series lightwave mainframes
Optical Detector	Not included in the interface module
Standalone Operation	Not supported
Primary Application	Connecting an external optical power head to a compatible lightwave measurement mainframe

 

Compatible Optical Head Overview

Optical Head	Detector	Wavelength Range	Power Range
81622B	5 mm germanium	850 nm to 1650 nm	Up to +27 dBm, with lower limit depending on wavelength
81623B	5 mm germanium	750 nm to 1800 nm	+10 dBm to -80 dBm
81624B	5 mm InGaAs	800 nm to 1700 nm	+10 dBm to -90 dBm
81626B	5 mm InGaAs	850 nm to 1650 nm	Up to +27 dBm, with lower limit depending on wavelength
81627B	3 mm InGaAs	800 nm to 1700 nm	+10 dBm to -90 dBm
81628B	3 mm InGaAs with integrating sphere	800 nm to 1700 nm	+40 dBm to -60 dBm

 

Operating Requirements

Requirement	Details
Host Mainframe	Compatible 8163, 8164, or 8166 Series lightwave mainframe
External Optical Head	One compatible 8162x Series optical power head
Module Power	Supplied by the compatible host mainframe
Operating Environment	Must remain within the limits specified for the host mainframe and connected optical head
Storage and Shipment Temperature	-40 °C to +70 °C
Condensation Protection	Protect the module from temperature changes that can cause internal condensation

 

Interface Module Performance

The 81618A is an interface module rather than a calibrated optical detector. Published optical accuracy, linearity, noise, wavelength range, return loss, and polarization-dependent response specifications belong to the connected optical head.

The documented performance test for the 81618A is a functional test. The interface module is installed in a compatible mainframe, an optical head is connected, and the platform is powered on. If the interface module passes the supported self-tests, it is considered functional.

Optical performance testing should identify both the 81618A and the connected optical head. Calibrated optical measurement results cannot be assigned to the interface module alone.

Installation and Configuration

The 81618A should be installed in a compatible mainframe slot using the correct module guides and retaining mechanism. The mainframe should recognize the module after startup.

A compatible optical head should be connected to the interface module using the optical head’s attached cable. The connector should be aligned and secured without applying excessive force.

The appropriate connector adapter should be installed on the optical head. Measurement wavelength, averaging time, power unit, range mode, calibration factor, and zeroing should then be configured through the mainframe.

The interface module, optical head, and mainframe should be allowed to complete the required warm-up period before precision measurements are recorded. The specified warm-up time for the supported optical heads is 40 minutes.

Optical Head and Connector Care

Optical connector adapters and detector windows should be inspected regularly. Dust and other particles can be transferred through an adapter opening and collect on the detector’s protective window, causing inaccurate or unstable measurements.

All optical sources must be disabled before connector adapters, fibers, or detector surfaces are inspected or cleaned. Users should never look into an optical cable or output connected to an active source.

Protective caps should remain installed whenever an optical head or adapter is not in use. Only cleaning procedures suitable for the specific head, adapter, detector window, and optical surface should be used.

Comprehensive Functional and Performance Testing

The Keysight 81618A receives comprehensive functional testing before shipment. Evaluation may include installation in a compatible lightwave mainframe, module recognition, startup self-tests, communication with one supported optical head, channel display, range selection, averaging control, wavelength entry, zeroing, and response to an applied optical signal.

When a compatible optical head is available, testing may also include verification of head identification, live optical power readings, manual and automatic ranging, and access to the optical head’s analog output.

The module connector, faceplate, retaining hardware, optical head interface, enclosure, labels, and identification markings may be inspected for physical damage, contamination, corrosion, excessive wear, or mechanical problems.

The exact testing scope depends on the available mainframe, connected optical head, mainframe firmware, optical source, connector adapters, patch cords, and measurement equipment.

Calibration and Performance Verification

The Keysight 81618A interface module is tested for functionality because optical measurement specifications are established by the external optical head. Calibration should therefore be performed on the complete system consisting of the compatible mainframe, 81618A interface module, and selected optical head.

When technically applicable and selected, system performance can be verified before shipment using a compatible optical head. Evaluation may include optical power accuracy, linearity, noise, return loss, polarization-related uncertainty, interference-related uncertainty, range operation, and analog output response, depending on the connected head and available calibration equipment.

Calibration documentation should identify the mainframe, 81618A interface module, and optical head by model and serial number. It should also identify the optical source, wavelength, power levels, adapters, reference equipment, test procedure, measured results, environmental conditions, and applicable measurement uncertainty.

Buyer Considerations

Buyers should confirm that the required compatible lightwave mainframe and optical head are available. The 81618A does not function as a standalone optical power meter and does not contain an optical detector.

The exact measurement capability depends on the optical head. Buyers should verify detector material, wavelength range, power range, fiber compatibility, optical adapter type, analog output requirements, calibration status, and physical condition of the complete measurement system.

The product listing should identify whether an optical head, head cable, connector adapters, protective caps, mainframe, power cord, manuals, calibration records, or other accessories are included.

Only the 81618A interface module and accessories specifically identified in the product listing should be considered included.

Why Buy from AssetRelay?

AssetRelay supplies professional equipment and product solutions for fiber optic, telecommunications, optical testing, photonics, laboratory, production, electronic testing, RF/microwave, inspection, cleaning, and technical research applications. The Keysight 81618A provides a practical interface for integrating one compatible external optical power head into supported modular lightwave measurement systems.

Buyers should review the complete model label, mainframe compatibility, optical head requirements, interface condition, module recognition, functional test results, calibration requirements, and included accessories before purchase.