Understanding Optical Attenuators

Posted on by FS.COM

Optical attenuators are used to reduce the power level of optical signal, either in free space or in an optical fiber. They are often used in optical communication systems where the optical signal is too strong and needs to be reduced, in which the attenuation, also called transmission loss, helps with the long-distance transmission of digital signals.

Optical attenuators can take a number of different forms and are typically classified as fixed or variable optical attenuator. Fixed attenuators can be broken down into either build out style or incorporated into a patch cord. The build out variety is a small (~ 1.25 inch long) attenuator with a male connector interface on one end and a female interface connector on the opposite end. The build out style is typically fabricated with either air gap attenuation or doped fiber attenuation.

Fiber optic attenuators can be designed to use with various types of fiber optic connectors. Commonly used fiber optic attenuators are the female to male type, which is also called a plug fiber attenuator. Another type inline fiber optic attenuator is designed with a piece of fiber optic cable at any length and connectors are installed as the customers request. Fixed value fiber optic attenuators can reduce the optical light power at a fixed level, for example, a 10dB SC fiber optic attenuator will reduce the optical power 10dB and utilize a SC male to female attenuator. Variable fiber optic attenuators are with adjustable attenuation range. There are also attenuation fiber optic patch cables available, their function is the same as attenuators and are used inline.

Variable Attenuator (or ajustable fiber optic attenuator) is a need to provide different under construction decline. The reduction of precision devices for a wide variety of fiber optic transmission lines to carry out scheduled, the amount of light intensity attenuation. There are also handheld variable fiber optic attenuators which are used as test equipment.

Typical attenuation values are between 3 and 20 dB. It is used in optical systems where the optical power from a source is too high for the test equipment in use. Fixed plug type fiber attenuator provides a connector plug (male) and an adapter socket (female) to connect between fiber patch cord and fiber adapter. Fixed plug type optical attenuator introduces an in-line fixed loss that will reduce the source power to an acceptable detection level. The attenuation level should be stable with temperature and wavelength for a stable reliable system.

An optical attenuator uses a segment of attenuating fiber interposed in the optical path. The attenuating fiber is produced by using a solution doping technique to introduce transition or rare earth elements into the fiber’s core. The dopant reduces the transmission of the fiber. The degree of attenuation depends upon the material used as the dopant, the dopant level, and the length of the attenuation segment. In a specific embodiment, an optical attenuator is provided having a first and second signal carrying optical fibers and an attenuating fiber segment, each of which has a core, a cladding substantially coaxial with the core, and a substantially planar end face. The attenuating fiber segment is fusion spliced between the first and second signal carrying optical fibers. In a second embodiment a portion of the cladding of the attenuating fiber is chemically etched.

Wide range variable & inline fiber optic attenuator and the inline fiber optic attenuator are with more accurate attenuation compared with traditional connector type fiber optic attenuators. Variable optical attenuators from FiberStore are specifically designed for use in DWDM networks with individual channel source elements such as optical add drop multiplexer.


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