What is the Fiber Optical Attenuator?

A fiber optical attenuator is an optical device that reduces the energy of an optical signal. It is used to attenuate the input optical power and avoid the distortion caused by the optical receiver due to the strong input optical power.

The fiber optical attenuator is used as an optical passive device for debugging optical power performance in optical communication systems, calibration calibration of debug fiber optic instruments, and attenuation of optical fiber signals. The product is manufactured using an attenuating fiber doped with metal ions to adjust the optical power to the required level.

The working principle of fiber optical attenuator

Attenuators are like sunglasses that protect your eyes from glare by absorbing excess light energy. Fiber optic attenuators protect the fiber by working in a specific wavelength range like sunglasses. The standard for a good fiber attenuator is to replace the reflective fiber by absorbing additional fiber. Because in fiber-optic communication, it is necessary to use lower optical power without damaging the fiber attenuator.

The Types of fiber optical attenuator

1.According to the way of use

Fixed fiber optical attenuator
The attenuation power is fixed (such as 1dB, 5dB, 10dB, etc.), such as a -3dB fiber attenuator with an attenuation power of 3dB. Such fiber attenuators are typically used in telecommunications networks, fiber optic test equipment, local area network (LAN) and cable television (CATV) systems. Fixed fiber attenuators usually have two interfaces, a male connector interface and a female connector interface.

Adjustable fiber optical attenuator
The optical communication device can be adjusted according to its own needs. Its small size, light weight, high attenuation accuracy, wide range and strong stability, adjustable range of 1~60dB. The port can be connected to ST, FC, SC, and LC connectors, and is mainly used in fiber-optic communication networks, fiber-optic data networks, fiber-optic CATV networks, and fiber-optic test systems.

2.According to the interface type

SC fiber attenuator
It’s applied to the SC fiber interface, it looks similar to the RJ-45 interface, but the SC interface appears flatter.

LC fiber attenuator
it’s applied to the LC fiber interface, the connector that connects the SFP module is made with a convenient modular jack (RJ) latch mechanism. (used by routers).

FC fiber attenuator
It is applied to the FC fiber interface. The external reinforcement method is a metal sleeve, and the fastening method is a turnbuckle. Generally used on the ODF side (the most used on the patch panel).

ST fiber attenuator
It is applied to ST fiber interface, and is often used in fiber distribution frame. The outer casing is round and the fastening method is screw buckle. (For 10Base-F connections, connectors are usually of the ST type. Commonly used in fiber distribution frames).

Usage of fixed fiber attenuator

A fixed fiber attenuator is always used at the receiving end of the fiber link, which is convenient for people to test the optical power before and after the attenuation.

Performance indicators of fiber optical attenuator

1.Insertion loss IL
At the minimum loss, the ratio of the input optical power Pi to the output optical power Po.

The reduction in the optical power of the operating wavelength at the specified output port relative to the total input optical power.

3.Return loss RL
The ratio of the light energy incident on the optical attenuator to the energy reflected in the attenuator along the incident optical path. WDL wavelength dependent loss: the amount of change in the insertion loss value at each wavelength in a certain wavelength band. The amount of change in the insertion loss value over a range of temperatures.

4.PDL polarization dependent loss
The ratio of the maximum transmission to the minimum transmission of the optical attenuator in all polarization states.


With the continuous development of optical communication, the application of fiber attenuators is also increasing. In order to ensure high-speed error-free transmission of the line, the optical power of each channel signal reaches a certain value, and an optical attenuator with high precision and high return loss is indispensable. The use of attenuators can be well matched to common fiber optic connectors, and the ultra-wideband uniform attenuation ensures that the product is now fully compatible with DWDM, CATV and other communication systems, and is now widely used.