In today’s communications, various optical devices are used to enlarge the capacity of transmitting information. However, in some cases, the level of optical power should not be enlarged but to be reduced, since too much strong input optical power may damage the optical receivers. And then the optical attenuators are required to solve such kind of problems. This article is to give a basic introduction of optical attenuator in detail.
What is an Optical Attenuator?
An optical attenuator, or fiber attenuator is comprised of an input fiber, collimating lens, blocking device, focusing lens, and output fiber. It is designed to reduce the power level of an optical signal in a fiber optic cable by up to 30 dB. A fiber attenuator is usually applied in fiber optic communications to reduce the optical fiber power at a certain level. And it also can be used on a more permanent basis in order to match the signal with a transmitter and receiver's specific power levels.
Generally, the power reduction is done by such means as absorption, reflection, diffusion, scattering, deflection, diffraction, and dispersion, etc. Fiber optic attenuators usually work by absorbing the light within the signal, which is similar to sunglasses absorbing extra light rays that enter our eyes. What we should make sense is that fiber optic attenuator absorbs the light rather than reflect it. In addition, optical attenuators can provide both fixed and variable attenuation.
What Types Does Optical Attenuator Have?
Optical attenuators have a number of different forms, and they can be divided into different types according to different standards. Here gives an overview of the different classifications.
According to the form of reducing power levels, optical attenuators are typically classified as fixed and variable attenuators.
Fixed optical attenuator is a device used to reduce power levels of a signal by a fixed amount with little or no reflections. For example, a 10dB fiber optic attenuator will reduce the optical power by 10 dB. The output signal is attenuated relative to the input signal while the input and output impedance is maintained close to 50 ohms (or 75 ohms) over the specified bandwidth. Hence, this device is often used to improve interstage matching in a circuit. Generally, fixed fiber optic attenuators are applied in optical fiber communication systems and optical fiber CATV (Community Antenna Television).
Variable fiber optic attenuators, sometimes also called adjustable fiber optic attenuator, have adjustable attenuation range. They usually are inline type, and their appearance like fiber optic patch cord. It is with an adjustable component in the middle of the device to change the attenuation level to a specified figure. With the development of optical communication, the demand for attenuators varies from place to place. Hence, there are also attenuation fiber optic patch cables available in the market. Their function is as same as attenuators and is used inline. Besides, there are also handheld variable fiber optic attenuators. They can be used as test equipment.
In addition, according to the connector types, fiber optic attenuators can be classified as LC, SC, ST, FC, MU, E2000, etc. As their names imply, each attenuator needs to joint to the corresponding connectors such as LC to LC, SC to SC, FC to FC, etc. This is a common classified way.
What an Optical Attenuator Do?
Optical attenuators are widely 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. Now, we have known the classification of fiber optic attenuators, but when to use an optical attenuator? Let’s imagine a scene, when the received optical power is so strong that it saturates the receiver. If the optical power cannot be reduced properly, the receiver cannot detect the signal correctly. In this case, fiber optic attenuator is necessary. As optical communication technologies advanced, optical attenuators have proven to be an important component of fiber optic networks. By introducing an attenuator, the transmission signal can be adjusted into the dynamic range of the receiver. This increases the life span of more expensive optical equipment and ultimately provides a clearer transmission signal, which can save money for people.
Conclusion
In a word, fiber optic attenuator plays a key role in controlling the power of the optical signal precisely. Getting some basic knowledge about them can help us to select the fiber optic attenuators for required applications.
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