How To Choose Fiber Optic Attenuators

Fiber attenuators are used in fiber optic communications to reduce optical fiber power at a certain level. Why do we need fiber attenuators? Bigger is better, right? Or so most people believe. Beginners in fiber optic technology are often confued with why optical attenuators are necessary to reduce light intensity. Aren’t we using amplifiers to increase the signal power level?

The truth is that too much light can overload a fiber optic receiver. Optical fiber attenuators are needed when a transmitter delivers too much light, such as when a transmitter is very close to the receiver.

How Does a Fiber Attenuator Work?

Optical Attenuators usually works by absorbing the light, such as a neutral density thin file filter. Or by scattering the light such as an air gap. They should not reflect the light since that could cause unwanted back reflection in the fiber system.

Another type of attenuator utilizes a length of high-loss optical fiber, that operates upon its input optical signal power level in such a way that its output signal power level is less than the input level. The power reduction are done by such means as absorption, reflection, diffusion, scattering, deflection, diffraction, and dispersion, etc.

What is the Most Important Feature Should a Fiber Attenuator Have?

The most important spec of an attenuator is its attenuation versus wavelength curve. Optical attenuators should have the same effect on all wavelengths used in the fiber system or at least as flat as possible. For example, a 3dB attenuator at 1500nm should also reduce the intensity of light at 1550nm by 3dB or as close as possible, this is especially true in a WDM (Wavelength Division Multiplexing) system.

Different Types of Attenuators

There are two functional types of fiber attenuators: plug style (including bulkhead) and in-line. A plug style attenuator is employed as a male-female connector where attenuation occurs inside the device, that is, on the light path from one ferrule to another. The types of fiber optic attenuators are based on the types of connectors and attenuation level. FiberStore supply a lot of fiber optic attenuators, like FC, SC/APC, ST, PC, LC, UPC, MU, FC/APC, SC, LC/APC, fixed value plug type fiber attenuators with different attenuation level, from 1dB to 30dB. An in-line attenuator is connected to a transmission fiber by splicing its two pigtails.

The principle of operation of attenuators are markedly different because they use various phenomena to decrease the power of the propagating light. The simplest means is to bend a fiber. Coil a patch cable several times around a pencil while measuring the attenuation with a power meter, then tape this coil. Then you got a primitive but working attenuator. Most fiber attenuators have fixed values that are specified in decibels (dB). They are called fiber optic fixed attenuator. For example, a -3dB attenuator should reduce intensity of the output by 3dB.

Manufacturers use various types of light-absorbing material to achieve well-controlled and stable attenuation. For example, a fiber doped with a transition metal that absorbs light in a predictable way and disperses absorbed energy as a heat. Variable fiber optic attenuators also are available, but they usually are precision instruments used in making measurements.

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