What Fiber Attenuator Do You Use? LC Attenuator or SC?

Fiber optic attenuator is an essential passive component in the optical communication system. With the advancement of DWDM technology, as well as the potential to flexibly upgrade the reconfigurable optical add-drop multiplexer (ROADM), the demand for optical attenuator is sure to soar, especially for optical variable attenuator.

Types of Fiber Optic Attenuators

Optical attenuator takes a number of different forms. They are typically grouped as fixed optical attenuator and optical variable attenuator.

Fixed Optical Attenuator

Fixed attenuator, as the name of which has indicated clearly, is designed to have an unchanging level of attenuation, expressed in dB, such as 1dB, 5dB, 10dB, etc. Fixed value attenuators consist of in-line type and connector type. In-line type looks like a plain fiber patch cable. It has a fiber cable terminated with two connectors which you can specify types. Connector type attenuator looks like a bulk head fiber connector, with a male connector interface on one end and a female interface connector on the opposite end. It mates to regular connectors of the same type such as FC, ST, SC and LC. Their applications include telecommunication networks, optical fiber test facility, Local Area Network (LAN) and CATV systems.

Optical Variable Attenuator

Optical variable attenuator, or variable optical attenuator, generally uses a variable neutral density filter. It has advantages of being stable, wavelength insensitive, mode insensitive, and offering a large dynamic range. Variable optical attenuator is generally used for testing and measurement, but it is also widely adopted in EDFAs (Erbium-Doped Fiber Amplifier) for equalizing the light power among different channels. Basically, there are two types of optical variable attenuator: stepwise variable attenuator and continuously variable attenuator. Stepwise variable attenuator can change the attenuation of the signal in known steps such as 0.1 dB, 0.5 dB or 1 dB. Continuously variable optical attenuator produces precise level of attenuation with flexible adjustment. Thus, operators are able to adjust the attenuator to accommodate the changes required quickly and precisely without any interruption to the circuit.

How to Use Fixed Fiber Attenuator?

As shown in the figure below, fixed fiber optic attenuators should be always installed at the receiver end of the link (X in the drawing). This is because it’s more convenient to test the receiver power before and after attenuation or while adjusting it with your power meter at the receiver, plus any reflectance will be attenuated on its path back to the source.

For female to male fixed fiber optic attenuators, we can plug the patch cord to the female fiber optic adapter of the attenuator. And then plug the male plug connector of the attenuator to the equipment directly. For female to female fixed fiber optic attenuators, we should plug the two patch cords to the two female fiber optic adapter of the attenuator (shown in the figure below).

Conclusion

Fiber optic attenuator is a passive device used to reduce the power level of an optical signal because too much light can overload a fiber optic receiver and degrade the bit error ratio (BER). To achieve the best BER, the light power must be reduced by using fiber optic attenuator. Fiber-MART provides optical attenuators with various connector types, such as FC/SC/ST/LC/E2000, available with APC or UPC polish. Any question pls feel free to contact me at [email protected]