A fiber optic attenuator, also called an optical attenuator, simulates losing the could be caused by a long period of fiber. Typically, this device performs receiver testing. While an optical attenuator can simulate the optical loss of an extended period of fiber, it can’t accurately simulate the dispersion that would be caused by a long length of fiber.

Put it simply, for a fiber optic receiver, too much light can overload it and degrade the bit error ratio. In order to achieve the best bit error ratio (BER), the light power should be reduced. Fiber optic attenuators fit the requirement perfectly. This could happen when the transmitter delivers too much power for example once the transmitter is simply too near to the receiver.

How Does a Fiber Attenuator Work?

Attenuators are like your sunglasses, which absorbs the extra light energy and protect your eyes from being dazzled. Attenuators normally have a working wavelength range in which they absorb the sunshine energy equally.

An essential characteristic of a good fiber attenuator is that they should not reflect the light, instead, they should absorb the extra light without being damaged. Because the light power used in fiber optic communications are fairly low, they usually could be absorbed without noticeable damage to the attenuator itself.

Types of Optical Attenuators

Two types of fiber optic attenuators exist: fixed value attenuators and variable optical attenuators.

Fixed value attenuators have fixed values that are specified by decibels. Their applications include telecommunication networks, optical fiber test facility, Lan(LAN) and CATV systems. For instance, a -3dB attenuator should reduce concentration of the output by 3 dB(50%). Fixed value attenuator’s attenuation value can’t be varied. The attenuation is expressed in dB. The operating wavelength for optical attenuators ought to be specified for that rated attenuation, because optical attenuation of a material varies with wavelength. Fixed value attenuators are comprised of two big groups: In-line type and connector type. 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.

Variable optical attenuators come with a variety of designs. They’re general used for testing and measurement, but they also possess a wide usage in EDFAs for equalizing the sunshine 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.

Other types of variable optical attenuators include air gap, clip-on, 3-step and more.

Source: http://www.fiberstore.com/