Two types of fiber optic attenuators:
1. fixed value attenuators
2. 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 fiber 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.