Optical attenuator is a very important passive component of fiber optics. It can attenuate the optical signal energy as expected according to the user's requirements. . At present, serialized optical attenuators have been widely used in the field of optical communication, which brings convenience to users. An optical device inserted into an optical path can attenuate optical signal power according to set requirements. It is used to adjust the power of the optical signal transmitted by the optical communication system or the test system, so that the system can achieve a good working condition. It is also commonly used to detect the sensitivity and dynamic range of optical receivers.
Optical attenuators can be divided into fixed attenuators, graded adjustable attenuators, continuously adjustable attenuators, continuous and graded combined attenuators, etc. Its main performance parameters are attenuation and accuracy. Attenuators are usually made by evaporating or sputtering metal films on glass substrates or using doped glass with high absorption. The required attenuation can be obtained by controlling the thickness of the coating or controlling the amount of doping of the glass and its thickness. The attenuator is also made of the coupling loss when the two optical fibers are butted.
Common optical attenuator mechanical VOA principle
This type of VOA also has a variety of specific implementations. Figure 1 is a schematic diagram of a light-blocking optical attenuator. The light-blocking element is driven to be trapped between two collimators to achieve attenuation of optical power. The light-blocking element can be in the shape of a plate or a cone, the latter can be propelled by rotation, while the former needs to be pushed flat or a certain mechanical structure can be used to realize the conversion from rotation to flat action. The light-blocking optical attenuator can be made into an optical fiber adapter structure or an in-line structure as shown in FIG. 1 .
Similar to the light-blocking VOA mentioned above, there is also an EVOA solution in the form of a mechanical-potentiometer. The principle is to use a stepper motor to drag the neutral gradient filter. When the light beam passes through different positions of the filter, its output optical power will change according to the predetermined attenuation law, so as to achieve the purpose of adjusting the attenuation. There is also a mechanically polarized light attenuator. The basic principle is that the light beam emitted from the input port is reflected by the reflection sheet to the output port, and the reflection coupling efficiency between the two ports is controlled by the tilt angle of the reflection sheet, so as to realize the adjustment of light attenuation. The tilt of the reflector is controlled by a number of different mechanisms. The mechanical optical attenuator is a more traditional solution. So far, most of the VOAs that have been used in the system use mechanical methods to achieve attenuation. This type of optical attenuator has the advantages of mature technology, good optical characteristics, low insertion loss, small polarization-related loss, and no need for temperature control; however, its disadvantages are large size, multiple components, complex structure, low response speed, and difficulty in automated production. , is not conducive to integration, etc.
performance
At present, the market of optical attenuators is getting bigger and bigger, and its output is second only to connectors, couplers, etc. in passive devices. Because the fixed optical attenuator has the advantages of low price, stable performance and easy use, its market is larger than that of the variable optical attenuator. The market demand for optical variable attenuators is still growing steadily due to their flexibility. Attenuator is one of the indispensable and important passive devices in optical communication system, and has a wide range of application prospects. In recent years, some large foreign optical device companies are still developing various new high-performance optical attenuator products in order to obtain optical attenuators with higher performance, smaller size and more suitable price.
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