What Exactly Are Fiber Optic Attenuators

A fiber optic attenuator, also called an optical attenuator, simulates losing the could be caused by a long period of fiber. Typically, this device performs receiver testing. While an optical attenuator can simulate the optical loss of an extended period of fiber, it can’t accurately simulate the dispersion that would be caused by a long length of fiber.

Put it simply, for a fiber optic receiver, too much light can overload it and degrade the bit error ratio. In order to achieve the best bit error ratio (BER), the light power should be reduced. Fiber optic attenuators fit the requirement perfectly. This could happen when the transmitter delivers too much power for example once the transmitter is simply too near to the receiver.

How Does a Fiber Attenuator Work?

Attenuators are like your sunglasses, which absorbs the extra light energy and protect your eyes from being dazzled. Attenuators normally have a working wavelength range in which they absorb the sunshine energy equally.

An essential characteristic of a good fiber attenuator is that they should not reflect the light, instead, they should absorb the extra light without being damaged. Because the light power used in fiber optic communications are fairly low, they usually could be absorbed without noticeable damage to the attenuator itself.

Types of Optical Attenuators

Two types of fiber optic attenuators exist: fixed value attenuators and variable optical attenuators.

Fixed value attenuators have fixed values that are specified by decibels. Their applications include telecommunication networks, optical fiber test facility, Lan(LAN) and CATV systems. For instance, a -3dB attenuator should reduce concentration of the output by 3 dB(50%). Fixed value attenuator’s attenuation value can’t be varied. The attenuation is expressed in dB. The operating wavelength for optical attenuators ought to be specified for that rated attenuation, because optical attenuation of a material varies with wavelength. Fixed value attenuators are comprised of two big groups: In-line type and connector type. In-line type appears like an ordinary fiber patch cable; it has a fiber cable terminated with two connectors which you’ll specify types. Connector type attenuator looks like a bulk head fiber connector, it has a male end and a female end. It mates to regular connectors of the identical type for example FC, ST, SC and LC.

Variable optical attenuators come with a variety of designs. They’re general used for testing and measurement, but they also possess a wide usage in EDFAs for equalizing the sunshine power among different channels. One type of variable optical attenuator is made on the D-shaped fiber as a type of evanescent field device. If your bulk external material, whose refractive index is larger compared to mode effective index, replaces a part of the evanescent field reachable cladding, the mode can become leaky plus some from the optical power could be radiated. If the index from the external material could be changed with a controllable mean, with the effects for example thermo-optic, electro-optic, or acoustic-optic, a device with controllable attenuation is achievable.

Other types of variable optical attenuators include air gap, clip-on, 3-step and more.

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What you need to know before you purchase Fiber Optic Attenuators

So why do We Need a Fiber Optic Attenuator?
Bigger is much better, right? Or so many people believe. Beginners in fiber optic technology are often confused with why optic attenuators should reduce light intensity. Aren’t we using amplifiers to improve the signal electricity? The fact 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.
So how exactly does a Fiber Attenuator Work?
Attenuators usually works by absorbing the sunshine, such as a neutral density thin film filter. Or by scattering the sunshine such as an air gap. They should not reflect the light since that could cause unwanted back reflection within 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 it is 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’s the Most Important Feature Should a Fiber Attenuator Have?
The most crucial spec of an attenuator is its attenuation versus wavelength curve. Attenuators should have the same impact on all wavelengths used in the fiber system or at least as flat as possible. For instance, a 3dB attenuator at 1500nm should also lessen the concentration of light at 1550nm by 3dB or as close as possible, this is also true inside a WDM (Wavelength Division Multiplexing) system.
Different Types of Attenuators
There are two functional kinds of fiber attenuators: plug style (including bulkhead) and in-line. A plug style attenuator is utilized like a male-female connector where attenuation occurs inside the device, that’s, on the light path from one ferrule to another. Included in this are FC fiber optic attenuator, LC attenuator, SC attenuator, ST attenuator and much more. An in-line attenuator is connected to a transmission fiber by splicing its two pigtails.
The key of operation of attenuators are markedly different simply because they use various phenomena to lower the power of the propagating light. The easiest means would be to bend a fiber. Coil an area cable several times around a pencil while measuring the attenuation with a power meter, then tape this coil. Then you definitely got a primitive but working attenuator.
Most attenuators have fixed values which are specified by decibels (dB). They’re called fiber optic fixed attenuator. For instance, a -3dB attenuator should reduce intensity of the output by 3dB. Manufacturers use various light-absorbing material to attain well-controlled and stable attenuation. For instance, a fiber doped with a transition metal that absorbs light in a predictable way and disperses absorbed energy as a heat.
Variable optical attenuator is also available, but it is usually a precision instrument utilized in making measurements. From FiberStore, you can get the best Variable Attenuators Instrument.
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Optical attenuator Wikipedia

An optical attenuator is a device used to reduce the power level of an optical signal, either in free space or in an optical fiber. The basic types of optical attenuators are fixed, step-wise variable, and continuously variable.
Applications
Fiber optic attenuator is used in applications where the optical signal is too strong and needs to be reduced. Optical attenuators are commonly used in fiber optic communications, either to test power level margins by temporarily adding a calibrated amount of signal loss, or installed permanently to properly match transmitter and receiver levels.
For example, in a multi-wavelength fiber optic system, you need to equalize the optical channel strength so that all the channels have similar power levels. This means to reduce stronger channels’ powers to match lower power channels. Another example is when the received optical power is so strong that it saturates the receiver, you need an optical attenuator to reduce the power so the receiver can detect the signal correctly.
Fiber optic attenuators are usually used in two scenarios. The first case is in fiber optic power level testing. Optical attenuators are used to temporarily add a calibrated amount of signal loss in order to test the power level margins in a fiber optic communication system. In the second case, optical attenuators are permanently installed in a fiber optic communication link to properly match transmitter and receiver optical signal levels.
Optical attenuators are typically classified as fixed or variable optical attenuator.
Fixed optical attenuators used in fiber optic systems may use a variety of principles for their functioning. Preferred attenuators use either doped fibers, or mis-aligned splices, since both of these are reliable and inexpensive. Inline style attenuators are incorporated into patch cables. The alternative build out style attenuator is a small male-female adapter that can be added on to other cables.
Variable optical attenuators generally use a variable neutral density filter. Despite relatively high cost, this arrangement has the advantages of being stable, wavelength insensitive, mode insensitive, and offering a large dynamic range. Other schemes such as LCD, variable air gap etc. have been tried over the years, but with limited success.
For precise testing purposes, engineers have also designed instrument type variable optical attenuators. They have high attenuation ranges, such as from 0.5 dB to 70dB. They also have very fine resolution, such as 0.01dB. This is critical for accurate testing.
Variable optical attenuator instrument calibration is a major issue. The user typically would like an absolute port to port calibration. Also, calibration should usually be at a number of wavelengths and power levels, since the device is not always linear. However a number of instruments do not in fact offer these basic features, presumably in an attempt to reduce cost. The most accurate variable attenuator instruments have thousands of calibration points, resulting in excellent overall accuracy in use.