Agilent 8156A Option 221 High-Return-Loss Optical Attenuator with Monitor Output

Agilent 8156A Option 221 High-Return-Loss Optical Attenuator with Monitor Output

The Agilent 8156A Option 221 is a high-performance programmable optical attenuator designed for precise control of optical power in single-mode fiber test systems. This configuration operates across wavelengths from 1200 nm to 1650 nm and provides a 60 dB attenuation range, excluding insertion loss.

Option 221 combines high-return-loss optical performance with an integrated monitor output. It uses angled-contact optical interfaces and provides return loss greater than 60 dB, depending on the performance of the installed external connector interfaces. The monitor output uses a typical 13 dB tap, corresponding to an approximate 1:20 power ratio.

The 8156A supports manual front-panel operation and remote programming through its GPIB interface. Programmable attenuation, wavelength correction, calibration offsets, automatic sweeps, optical-path enable or disable control, and stored settings make the instrument suitable for laboratory, manufacturing, telecom, and automated optical test applications.

Features and Benefits of the Agilent 8156A Option 221

The Agilent 8156A Option 221 provides precise and repeatable optical power control for engineers, laboratories, production facilities, and service organizations working with single-mode fiber optic systems.

• 60 dB attenuation range: Provides broad optical power adjustment for receiver sensitivity tests, component characterization, and system simulation.
• 1200 nm to 1650 nm wavelength coverage: Supports common single-mode telecom and photonics wavelengths across the documented operating range.
• High-return-loss configuration: Provides return loss greater than 60 dB with compatible angled-contact connector interfaces.
• Monitor output: Includes a typical 13 dB optical tap for connecting a compatible optical power meter or monitoring instrument.
• Fine attenuation adjustment: Supports a minimum attenuation step of 0.001 dB.
• High attenuation linearity: Provides attenuation accuracy below ±0.1 dB and typical performance below ±0.05 dB under documented conditions.
• Excellent repeatability: Delivers repeatability below ±0.01 dB, with typical performance below ±0.005 dB.
• Low polarization sensitivity: Provides polarization-dependent loss below 0.1 dB peak-to-peak, with typical performance below 0.03 dB peak-to-peak.
• Programmable attenuation sweeps: Supports automatic up-and-down sweeps with configurable start, stop, step size, and dwell time.
• GPIB automation: Provides SCPI programming and compatibility functionality for integration into automated optical test systems.

Programmable Single-Mode Optical Attenuation

The Agilent 8156A Option 221 provides controlled attenuation across a 60 dB range, excluding the instrument’s insertion loss. The attenuator can be used to reduce optical power delivered to a receiver, detector, device under test, optical amplifier, or other connected component.

The minimum attenuation step is 0.001 dB, allowing fine control over the output optical level. Settling time ranges from approximately 20 ms to 400 ms depending on the selected attenuation setting.

The maximum optical input level is 23 dBm, equivalent to 200 mW. Users should consider both the input-power limit and the maximum allowable power of connected optical components when configuring a test system.

High-Return-Loss Optical Configuration

Option 221 is the high-performance, high-return-loss version of the 8156A with a monitor output. It uses angled-contact connector interfaces and provides return loss greater than 60 dB. Actual return-loss performance depends partly on the quality and condition of the installed external connector interfaces.

High return loss is valuable in applications where reflected optical power can affect laser stability, introduce measurement uncertainty, or influence the behavior of sensitive components. Angled-contact interfaces help direct reflected optical energy away from the source path.

The useful back-reflection range for Option 221 extends from 6.6 dB to 60 dB when the instrument is used with the required compatible back-reflection accessories and operating mode.

Integrated Monitor Output

The Agilent 8156A Option 221 includes an optical monitor output with a typical 13 dB tap, corresponding to an approximate 1:20 power ratio. This output allows a portion of the optical signal to be directed to a compatible power meter or monitoring instrument.

The monitor output can be used to observe source stability, verify power changes, normalize measurements, or monitor the optical signal while the primary output is connected to a device under test.

Three compatible connector interfaces are required for this configuration, covering the optical input, attenuated output, and monitor output. The exact installed connector interfaces and included adapters should be confirmed from the individual instrument.

Attenuation Accuracy and Repeatability

Option 221 provides attenuation accuracy below ±0.1 dB, with typical linearity below ±0.05 dB when measured at a constant temperature. Repeatability is specified below ±0.01 dB, with typical performance below ±0.005 dB.

The documented specifications are measured at 1310 nm and 1550 nm using a Fabry-Perot laser source, single-mode fiber, and compatible Agilent angled-contact or straight-contact connector interfaces.

Narrow-linewidth sources, including DFB lasers, can produce optical power fluctuations caused by coherent interference and reflections. Fiber movement, connector condition, source coherence, polarization changes, and environmental variation should be controlled during precision measurements.

Low PDL and PMD

The Agilent 8156A Option 221 provides polarization-dependent loss below 0.1 dB peak-to-peak, with typical performance below 0.03 dB peak-to-peak. Low PDL helps reduce attenuation changes caused by variations in the input polarization state.

Polarization-mode dispersion is specified at 6 fs. Low PMD helps preserve the temporal characteristics of high-speed optical signals passing through the attenuator.

These characteristics support demanding component qualification, receiver testing, transmission experiments, and automated measurements where polarization sensitivity or waveform distortion must be minimized.

Programmable Operating Modes

The Agilent 8156A provides several operating modes for configuring attenuation and supporting automated optical measurements.

• Attenuation mode: Displays the selected attenuation and allows the value to be adjusted.
• Wavelength entry: Applies typical wavelength-dependent correction values for the entered operating wavelength.
• Calibration mode: Applies an offset factor within a 99.99 dB display range.
• Display calibration: Sets the displayed attenuation value to 0.00 dB for reference measurements.
• Sweep mode: Performs manual or automatic up-and-down attenuation sweeps with configurable limits and step parameters.
• Back-reflection mode: Allows a desired return-loss level to be entered when used with a compatible Agilent 81000BR back reflector.
• Enable and disable: Interrupts the optical path with a shutter providing greater than 80 dB blocking.
• Store and recall: Stores and recalls nine user-selectable parameter configurations and the default settings.

Automated Optical Testing

The GPIB interface allows all supported operating modes and parameters to be programmed remotely. The instrument uses a SCPI command set and includes an Agilent 8157A compatibility mode for integration with applicable legacy test configurations.

Automated control allows the attenuator to be synchronized with optical sources, power meters, receivers, bit-error-ratio testers, optical spectrum analyzers, switches, and other test equipment.

Programmable sweeps can be used to vary received optical power while another instrument records sensitivity, error rate, output response, or other performance data. Stored configurations help technicians and test applications recall commonly used instrument settings.

Typical Applications

The Agilent 8156A Option 221 Optical Attenuator is suitable for professional applications such as:

• Single-mode optical power control
• Receiver sensitivity testing
• Optical component characterization
• Optical amplifier and transmission testing
• Telecom system simulation
• Automated attenuation sweeps
• Optical power margin testing
• High-return-loss measurement setups
• Back-reflection simulation with compatible accessories
• Source-power monitoring through the monitor output
• Production testing and quality control
• Research and development laboratories

Product Overview

Brand	Agilent Technologies
Model	8156A
Installed Option	221
Product Category	Programmable Single-Mode Optical Attenuator
Option Description	High-performance, high-return-loss version with monitor output
Instrument Format	Non-modular benchtop optical attenuator
Fiber Type	9/125 µm single-mode fiber
Connector Contact Type	Angled contact
Remote Interface	GPIB
Primary Application	Precise programmable attenuation and monitoring of single-mode optical signals

 

Option 221 Optical Specifications

Specification	Details
Wavelength Range	1200 nm to 1650 nm
Attenuation Range	60 dB, excluding insertion loss
Fiber Type	9/125 µm single-mode fiber
Connector Contact Type	Angled contact
Typical Insertion Loss	3.3 dB, including the insertion loss of two HMS-10 connectors
Return Loss	Greater than 60 dB, depending on the external connector interface
Attenuation Accuracy	Less than ±0.1 dB
Typical Attenuation Accuracy	Less than ±0.05 dB
Repeatability	Less than ±0.01 dB
Typical Repeatability	Less than ±0.005 dB
Polarization-Dependent Loss	Less than 0.1 dB peak-to-peak
Typical Polarization-Dependent Loss	Less than 0.03 dB peak-to-peak
Polarization-Mode Dispersion	6 fs
Monitor Output	Typical 13 dB tap, approximately 1:20
Useful Back-Reflection Range	6.6 dB to 60 dB

 

Supplementary Performance Characteristics

Characteristic	Details
Minimum Attenuation Step	0.001 dB
Settling Time	20 ms to 400 ms, depending on the selected setting
Maximum Optical Input Level	23 dBm, equivalent to 200 mW
Optical Shutter Blocking	Greater than 80 dB
Calibration Offset Range	99.99 dB display range
Stored User Settings	Nine configurations
Recommended Recalibration Period	One year
Warm-Up Requirement	No warm-up required when previously stored within the operating temperature range

 

Electrical, Mechanical, and Environmental Specifications

Specification	Details
Power Input	100 V, 120 V, 220 V, or 240 V RMS, ±10%
Line Frequency	48 Hz to 400 Hz
Maximum Power Consumption	90 VA
Dimensions	89 mm high x 212.3 mm wide x 345 mm deep
Dimensions in Inches	3.5 in high x 8.36 in wide x 13.6 in deep
Net Weight	5.3 kg
Net Weight in Pounds	11.7 lb
Operating Temperature	0 °C to 55 °C
Storage Temperature	-40 °C to 70 °C
Humidity	Less than 95% relative humidity from 0 °C to 40 °C
Non-Volatile Memory Backup	Maintains current modes and data for at least 10 years after delivery with the instrument switched off

 

Connector Interfaces

The Agilent 8156A uses interchangeable optical connector interfaces. Option 221 requires three interfaces, one for the optical input, one for the primary output, and one for the monitor output.

The installed connector adapters should be verified before compatible patch cords are selected. Option 221 is specified for angled-contact operation, so the appropriate angled-contact interface should be used to achieve the intended return-loss performance.

Angled-contact and straight-contact connectors should not be mated directly. All connector end faces should be inspected and cleaned before connection to reduce insertion loss, backreflection, contamination, and measurement instability.

Back-Reflection Capability

The instrument provides a back-reflection operating mode for entering and controlling a desired return-loss level. This function requires a compatible Agilent 81000BR back reflector and the required optical connector interfaces.

The documented back-reflector kit for Option 221 includes an Agilent 81000SI interface, Agilent 81000FI interface, Agilent 81113PC cable, Agilent 81000UM adapter, and Agilent 81000BR back reflector.

Back-reflection accessories should not be considered included unless specifically identified in the product listing. Compatibility and condition should be confirmed before the instrument is used for controlled return-loss simulation.

Calibration and Testing Before Shipment

When calibration is technically applicable and supported, the Agilent 8156A Option 221 is calibrated before shipment. The calibration process may include verification of attenuation accuracy, linearity, repeatability, minimum attenuation step, insertion loss, return loss, monitor-output tap ratio, shutter operation, wavelength correction, and GPIB control.

Following successful calibration, the instrument may include a calibration label, calibration certificate, and associated measurement data, depending on the selected service and equipment condition.

If formal calibration is unavailable or not applicable, the instrument receives comprehensive functional and performance testing. This testing may include attenuation control across the available range, optical-path enable and disable operation, monitor-output verification, sweep operation, display functions, front-panel controls, stored settings, and remote communication.

The exact calibration scope, installed connector interfaces, supplied data, back-reflection accessories, documentation, and service records should be confirmed before purchase when these items are required for laboratory, manufacturing, regulatory, or quality-management applications.

Buyer Considerations

The Agilent 8156A Option 221 is a configuration-specific programmable optical attenuator. Buyers should confirm that the 1200 nm to 1650 nm wavelength range, 60 dB attenuation range, angled-contact interface configuration, greater than 60 dB return loss, monitor output, and GPIB functionality match the intended application.

Option 221 should not be confused with Option 201, which provides high-return-loss performance without the monitor output, or Option 121, which provides a monitor output with lower return-loss performance. Option 221 combines the monitor output with the high-return-loss optical configuration.

Buyers should review the instrument’s connector interfaces, optical ports, monitor output, attenuator operation, display, controls, GPIB interface, calibration status, and included accessories. Only items specifically identified in the product listing should be considered included.

Why Buy from AssetRelay?

AssetRelay supplies professional equipment and product solutions for fiber optic, telecom, laboratory, production, inspection, cleaning, RF/microwave, electronic test, and photonics applications. The Agilent 8156A Option 221 supports engineers, laboratories, production facilities, procurement teams, and service organizations that require precise single-mode optical attenuation, high return loss, and monitor-output capability.

Buyers should review the available product photographs, physical condition, installed connector interfaces, optical port condition, included accessories, calibration information, and application requirements before purchase.

Only accessories specifically identified in the product listing should be considered included. Optical connector interfaces, patch cords, power meters, back-reflection accessories, GPIB cables, controllers, software, and other supporting test equipment may be required separately.