Atec Agilent-8156A User Manual
Agilent 8157xA Optical Attenuators
Technical Specifications
March 2006
Agilent’s 8157xA Variable Optical Attenuators are
instruments that attenuate and control the optical
power level of light in optical fibers.
As plug-in modules for Agilent’s Lightwave Solution
platform (8163A/B, 8164A/B, 8166A/B) they allow you
to set the attenuation factor and/or power level
manually, or remotely via a common computer
interface.
Their high accuracy combined with their flexibility
makes them ideal as test and measurement equipment
for the modern telecommunication industry.
Modular Design for Lightwave Solution Platform
Agilent’s 8157xA variable optical attenuators are a family
of plug-in modules for Agilent’s Lightwave Solution
Platform 8163A/B, 8164A/B and 8166A/B. The attenuator
modules 81570A, 81571A and 81578A occupy one slot,
while modules 81576A and 81577A occupy two slots. With
17 slots, the Agilent 8166A/B Lightwave Multichannel
System can host up to 17 single slot modules or up to 8
dual slot modules.
Variable Optical Attenuators
Attenuators with Power Control
Agilent’s 81576A and 81577A attenuators feature power
control functionality that allows you to set the output
power level of the attenuator. The attenuator module uses
the feedback signal from a photodiode after a monitor tap,
both integrated in the module, to set the desired power
level at the output of the module. When the power control
mode is enabled, the module automatically corrects power
changes at the input to maintain the output level set by the
user. After an initial calibration for the uncertainties at
connector interfaces, absolute power levels can be set
with high accuracy. The absolute accuracy of these power
levels depends on the accuracy of the reference power
meter used for calibration.
The Agilent 81570A, 81571A and 81578A are small, costeffective attenuator modules with high resolution. They
feature excellent wavelength flatness and can handle high
input power levels. Combined with their low insertion loss,
they are ideal for optical amplifier test, such as
characterization of EDFAs and of Raman amplifiers, as
well as for other multi-wavelength applications, such as
DWDM transmission system test. Various calibration
features allow the user to set a reference power. Both the
attenuation and the power level, relative to the reference
power, can then be set and displayed in the user interface.
An integrated shutter, which can be used for protection
purposes, or to simulate channel drops, is included.
The multimode 81578A brings this performance to
multimode test and can be ordered for 50 µm or 62.5 µm
fiber.
These modules also feature high power handling capability
and excellent wavelength flatness for DWDM applications.
To set a total power level of a multi-wavelength signal, it is
necessary to determine the convolution of the signal’s
spectrum with the sensitivity of the photodiode over
wavelength. An enhanced calibration feature supports this
process and enables setting the integral power of a
DWDM signal with a known spectrum.
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Calibration Processes
Comprehensive offset functionality in the firmware
enhances the calibration of the optical path in various test
set-ups. There is an offset for the attenuation factor, and
an independent offset for the output power level, to
calibrate for losses due to the patch cords and connectors.
Additionally, wavelength and offset value pairs can be
stored in a table to compensate for wavelength dependent
effects in the optical path of the set-up. This allows you to
set the optical power level at your Device Under Test.
Calibration is even easier and more convenient if the
reference power meter and the attenuator are hosted by
the same mainframe: All power related offsets can be
determined by a firmware function that reads a value from
the reference power meter. The difference between the
power value read by the reference power meter and the
actual value of the attenuator is automatically stored as
the offset.
Key Features
• High input powers up to 2 Watt
• Excellent wavelength flatness: typical ± 0.05 dB
• Low insertion loss: typical 0.7 dB
• Wide wavelength range: 1200 nm – 1700 nm (SM),
700 nm – 1400 nm (MM)
• High resolution: 0.001 dB
• Modular design allows up to 17 attenuators in one
mainframe
• Active power control options to set power levels
directly
• Comprehensive offsets allow easy calibration of the
set-up
• Integrated shutter
• Agilent’s versatile optical connector interfaces for all
common types of connectors
Applications
• Bit error ratio test
• Characterization of transceivers, receivers,
transmitters and line cards
• Test of single channel transmission systems
• DWDM channel equalization
• Loss simulation in fiber optic links
• Testing and calibrating the linearity of power meters
• Optical Amplifier Test
- Characterization of EDFAs
- Test of Raman amplifiers and SOAs
• Multi channel transmission system test
• Loss simulation of DWDM signals in fiber optic links
The Agilent 8157xA modules are produced to the ISO 9001
international quality system standard as part of Agilent's
commitment to continually increasing customer
satisfaction through improved quality control.
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