What is an optical attenuator? What are the types of optical attenuators?

- Sep 22, 2020-

The working principle of optical fiber attenuator


Fiber optic attenuators usually produce attenuation by absorbing light.

The fiber optic attenuator has a working wavelength range that can absorb light energy. At this wavelength, it should not reflect light because this may cause unnecessary echo reflection in the fiber optic system.


APC Fixed attenuator


Another type of optical fiber attenuator uses a certain length of high-loss optical fiber to reduce its input optical signal power, and operates in such a way that its output signal power is less than the input signal power.

Reduce the optical power through the absorption, reflection, diffusion, scattering, deflection, diffraction and dispersion of the optical signal.


male and female  attenuator


Optical technology involved in optical attenuator


(1) Air isolation technology: The transmission of light in the optical fiber is restricted by the law of total reflection, and cannot be scattered, and the intensity is relatively stable. Once it is separated from the optical fiber and an air gap is added between the optical fiber and the optical fiber, the light will scatter out, causing light attenuation.

(2) Displacement and dislocation technology: This method is to move the cores of two optical fibers to a small amount of translation and dislocation to achieve the effect of power loss.

(3) Attenuation fiber technology: According to the absorption effect of metal ions on light, the attenuation fiber doped with metal ions is developed. The attenuation fiber is inserted into the ceramic ferrule, and after a special process, it can be made into a positive and negative fixed attenuator.

(4) Absorption glass method: Optically polished neutral absorption glass sheet can also be used in the production of optical attenuators.


UPC attenuator


When will the optical attenuator be used?

When the optical power received by the optical receiver is relatively large and exceeds its bearing range, when saturation distortion occurs.

Application fields of optical fiber attenuator:

Optical fiber communication network

Light Data Network

Fiber CATV network

High-power optical device measurement

Line evaluation

Connection, adjustment, etc. between devices.

Attenuation range of optical attenuator

The attenuation range of the optical attenuator is 0-65dB.

Among them, the attenuation range of the small variable attenuator is 0-25dB, and the adjustment range is small.


MU attenuator


Advantages of optical fiber attenuator test system


Repeatability of attenuation

Good interchangeability

High precision

Light weight, small size, good reliability

The attenuation varies little with the wavelength, the additional loss is low, and the stability is good.

What is the additional loss of an optical attenuator?

The inherent loss of the optical attenuator is usually composed of attenuation caused by the loss of the optical fiber connector and the unclean end face of the connector.


male and female  attuator



Classification of optical fiber attenuators


1. Variable fiber attenuator

The variable fiber attenuator is made of attenuating fiber doped with metal ions, which can adjust the optical power to the required level.


2. Fixed fiber attenuator

The principle that fixed optical attenuators may use multiple functions for fiber optic systems.

It has two major categories, namely line type and plug type.

The line type looks like an ordinary fiber optic jumper, which consists of a fiber optic cable connecting two connectors of a specified type.

The plug-type attenuator looks like a large-head optical fiber connector, it has a male and a female, and the same type of ordinary connectors, for example, FC, ST, SC and LC.

The fixed optical attenuator is generally made in the form of a movable connector, which can realize the connection with the optical fiber line.

In addition, the end face of the optical fiber will be plated with a metal film of a certain thickness, and an air gap of several microns is left in the optical path to obtain a fixed attenuation.


3. Female and Male optical fiber attenuator

This is a male-female device for different connector designs (LC/SC/FC/ST/MU), PC, UPC or APC grinding (APC can choose tapered or stepped ferrules), attenuation value: 1~30dB.

Wavelength: single mode 1310um, 1550um or dual wavelength; multimode 850um or dual wavelength, equipped with dust cap.

Feature of Yin-Yang optical fiber attenuator: metal ion-doped attenuation fiber achieves the attenuation effect, high power resistance, light source, small size, high precision, good stability, multiple forms, and easy to use.


Attenuator


The last point is the application range of optical fiber attenuators: optical distribution frames, optical fiber network systems, high-speed optical fiber transmission systems, cable television (CATV) systems, long-distance trunk dense wavelength division multiplexing (DWDM) systems, optical add/drop multiplexers ( OADM).