Things You Should Know about Optical Attenuator

We always utilize an amplifier to improve signal electricity in fiber optic transmission. But what if there is too much light deliver through a fiber optic receiver? At that time, you may need an optical attenuator to reduce the power level. This post will help you get better understanding of optical attenuator.

An optical attenuator, or fiber optic attenuator, is a device used to reduce the power level of an optical signal, either in free space or in an optical fiber.

Working Principle of Optical Attenuator

Optical attenuator usually works by absorbing the light, like sunglasses absorb the extra light energy. It typically has a working wavelength range in which it can absorb the light energy equally. It should not reflect the light since that could cause unwanted back reflection in the fiber system. Another type of attenuator utilizes a length of high-loss optical fiber, that operates upon its input optical signal power level in such a way that its output signal power level is less than the input level. The power reduction is done by such means as absorption, reflection, diffusion, scattering, deflection, diffraction, and dispersion, etc.

Applications of Optical Attenuator
  • Test power level margins by temporarily adding a calibrated amount of signal loss.
  • Installed permanently to properly match transmitter and receiver levels.
  • Sharp bends stress optic fibers and can cause losses.

In terms of different forms, optical attenuator can be classified as fixed attenuator and variable optical attenuator.

Fixed Attenuator

Fixed attenuator is compact adapter style tool that is ideal for attenuating single mode fiber connectors in various applications. It is comprised of two big groups, in-line type and connector type, displaying as following figure from left to right. In-line type appears like an ordinary fiber patch cable; it has a fiber cable terminated with two connectors which you’ll specify types. Connector type attenuator looks like a bulk head fiber connector, it has a male end and a female end. It mates to regular connectors of the identical type for example FC, ST, SC and LC.

fixed attenuator

Variable Optical Attenuator

Variable optical attenuator is general used for testing and measurement, but it is also has a wide usage in EDFAs for equalizing the light power among different channels. One type of variable optical attenuator is made on the D-shaped fiber as a type of evanescent field device. If your bulk external material, whose refractive index is larger compared to mode effective index, replaces a part of the evanescent field reachable cladding, the mode can become leaky plus some from the optical power could be radiated. If the index from the external material could be changed with a controllable mean, with the effects for example thermo-optic, electro-optic, or acoustic-optic, a device with controllable attenuation is achievable.


From this post, we can know the definition, working principle, applications, types of optical attenuators. Fiberstore provides optical attenuators with various connector types. If you want to know more information, you can visit