Guideline for Fixed Fiber Optic Attenuator

Posted on by FS.COM

As a beginner in fiber optic network, I used to think that the optical power should be as strong as possible. Even sometimes we use optical amplifiers to improve the optical signal. So what are the optical attenuators used for? As we know, the source of the single-mode fiber is laser, the power of which is extremely strong. Therefore we can use single-mode fiber to achieve long distance transmission. But, if the transmission distance over single-mode fiber is too short, too much light may overload a fiber optic receiver, which may cause serious high bit error rates. How to solve this? Optical attenuator should be inserted at the receiver end to reduce the power to the proper level. There are fixed and variable two types optical attenuators in the market. The knowledge of fixed fiber optic attenuator will be introduced in this article.

What Is Fixed Fiber Optic Attenuator?
Fixed fiber optic attenuator, also called fixed plug type or fixed build-out fiber optic attenuator, is used in fiber optic communications to reduce the optical fiber power by a certain level. Typical attenuation values are between 1 and 30 dB. Usually, it has a male plug connector at one side to allow the attenuator to be plugged directly into receiver equipment or adapters in patch panel, and has female type fiber optic adapter at the other side to allow the patch cords to plug in. Fixed fiber optic attenuator name is based on the connector type and the attenuation level. LC 5dB fixed fiber optic attenuator means this attenuator uses LC fiber optic connector, and it can reduce the optical fiber power level by 5dB.

Fixed Fiber Optic Attenuator

Fixed Fiber Optic Attenuator Types
Fixed fiber optic attenuators are available in LC, SC, ST, FC and MU style with APC and UPC polish. Generally, multimode systems do not need attenuators as the multimode sources, VCSELs, rarely have enough power output to saturate receivers. Instead, single-mode systems, especially short links, often have too much power and need attenuators. Therefore, fixed fiber optic attenuators are usually single-mode types. The most commonly used type is LC single-mode female to male and female to female fixed fiber optic attenuator. Unlike the common female to male type mentioned above, the female to female fixed fiber optic attenuators have female type fiber optic adapter at the both ends, which are also therefore called fiber optic adapter type attenuators. They can be used as adapters and attenuators at the same time.

Fixed Fiber Optic Attenuator Types

How to Use Fixed Fiber Optic 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.

How to Use Fixed Fiber Optic Attenuator

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).

female to male fixed fiber optic attenuators

FS.COM Fixed Fiber Optic Attenuator Solution
FS.COM provides a wide range of fixed plug type single-mode fiber optical attenuator with optional attenuation value from 1dB to 30dB. They are used directly on the fiber optic connectors and provide a fixed level of optical attenuation. Our fixed fiber optical attenuator has low return loss and works at both 1310nm and 1550nm wavelength range. LC and SC fiber connector types with UPC or APC polish are available, as well as ST and FC types of attenuators.

FS P/N Description
48521 LC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 1dB
48522 LC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 3dB
48523 LC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 5dB
48524 LC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 6dB
48525 LC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 7dB
48526 LC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 10dB
48527 LC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 12dB
48528 SC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 3dB
48529 SC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 5dB
48530 SC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 7dB
48531 SC/UPC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 10dB
52012 SC/APC Singlemode Fixed Fiber Optic Attenuator, Male-Female, 2dB
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