What Is an Optical Attenuator?

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An optical attenuator decreases the
strength of an optical signal passing through it to a fiber optic cable or open
air. The intensity of the signal is described in decibels over a specific
distance the signal travels. It is the strength, or amplitude of the signal
that changes and not the overall waveform or frequency, so the optical signal
remains undistorted for use in the desired application. Optical
attenuators are often used in optical communication systems, in which
the attenuation, also called transmission loss, helps with the long-distance
transmission of digital signals. The most common optical attenuator types
include fixed and continuously variable attenuators.

 

Optical Attenuator

Often installed where signals are
transmitted from, an optical attenuator can apply the principle of gap loss so
the signal intensity is lowered to the optimal level over a given distance.
Attenuators installed elsewhere along the optical fiber will not lower the
signal strength enough, but some devices utilize signal absorbing or reflecting
components to compensate. An optical fiber connector is often attached to the
optical attenuator which typically has an adapter with a female configuration.
The attenuator itself usually has a cylindrical or even box-like structural
shape which determines the type of equipment in which it can be installed.

 

The fixed variety of optical attenuator,
sometimes found in an electronic circuit, does not reflect light signals to
reduce their intensity. It is generally used where the transmission of data
needs to be highly accurate. The device’s function is determined by the amount
of power it can handle in addition to important variables such as performance
versus temperature and frequency range. Most optical attenuators utilize
resistors, but a variable optical attenuator uses metal semiconductor field
effect transistors or other solid state components. Attenuation intensity is
adjustable so the signals in a fiber optic communication system can be changed
to accommodate fluctuating power levels, protecting the system from damage.

 

A variable optical attenuator can be
mounted on a printed circuit board, or used in test devices such as an optical
power meter. Many attenuators are installed in-line with an optical fiber cable
in order to adjust the transmitted signal accordingly. They are sold by many
retailers and manufacturers online so one can assess their characteristics by
reading the product specifications. Aspects to consider include the average and
peak power the device can tolerate, how much attenuation it provides, as well
as its overall dimensions and the type of environment it can operate in.