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Replace reflective fibers by absorbing additional fibers
May 08, 2018

Attenuators are like sunglasses and protect your eyes from intense light by absorbing excess light energy. Fiber optic attenuators can act like sunglasses and protect the fiber by working in a specific wavelength range. The standard for a good fiber attenuator is to replace the reflective fiber by absorbing additional fiber. Because in optical fiber communication, it is necessary to use lower optical power without damaging the optical fiber attenuator.

Its working principle is:

1, air isolation technology

The transmission of light in the fiber is constrained by the law of total reflection and cannot be scattered out, keeping the intensity relatively stable. Once it is separated from the fiber, adding air gaps between the fiber and the fiber will cause the light to scatter and cause light attenuation. Since light is scattered from the ordinary optical fiber incident on the air, it is necessary to control the attenuation within a certain range. It is necessary to ensure the separation distance and maintain the alignment of the optical fibers at both ends. This principle can be used to make flanged fixed attenuators and adjustable attenuators. Flange type fixed attenuator adopts the isolation attenuator, according to the curve diagram to make a certain thickness of the attenuator, insert the attenuator into the flange, it can play the role of fixed light attenuation. Flange type adjustable optical attenuator adopts the principle of mechanical rotation. Adjusting the distance between the connectors at both ends through mechanical rotation can make the light attenuate between 0~30dB.

2, displacement misalignment technology

In this method, the two fiber cores undergo slight translational misalignment so as to achieve the effect of power loss.

Through the use of ordinary pigtails, the cores of the two pigtail fibers are fused in the misalignment process with a fusion splicer, so that the loss of the eccentric core occurs during the transmission, and a connector-type fixed attenuator, also called an in-line fixed attenuator, is obtained. .

3, attenuation fiber technology

According to the absorption of light by metal ions, an attenuated fiber with an impurity metal ion is developed. As with an attenuation coefficient per kilometer of an ordinary fiber, this attenuating fiber also has a fixed attenuation coefficient, but this attenuation coefficient is not calculated in kilometers. Instead, it is calculated in millimeters. The attenuated fiber is inserted into the ceramic ferrule. After a special process, it can be made into a fixed type attenuator.

4, absorption glass method

Optically polished neutral absorption glass sheets can also be applied to the fabrication of optical attenuators. By using the light absorption properties of a substance, a sheet or strip of neutral dark glass is formed and placed on the light path to attenuate the light intensity. The absorption glass is distinguished by the transmittance T and the attenuation rate expressed in decibels. Transmittance T = transmitted light intensity / incident light intensity, attenuation rate η = 1 / T, attenuation rate expressed in decibels β = 10 x log η = - 10 x logT, decibel rate in decibels can be easily estimated The decay rate of the slice combination, the sum of the decibel rate of attenuation of each slice is added as the attenuation rate of the combined attenuation slice group, expressed in decibels. The sheet is made to have a fixed attenuation value, and the strips have different attenuation values at different parts of the dark material, which are continuously increasing inside. Monolithic sheet-shaped light-absorbing glass can be used to make a fixed attenuator. A plurality of sheet-shaped absorption glass can be converted into a step-by-step adjustable attenuator through a disc and the strip-shaped absorption glass can be made into a continuously adjustable attenuator through continuous displacement.

5, solid state light attenuation technology

Adjustable optical attenuators in the form of air-isolation and absorption glass use mechanical methods to achieve attenuation tunability. There are also a small number of solid-state optical attenuation technologies, such as tunable diffraction grating technology, MEMS technology, and liquid crystal technology. , magneto-optical technology, planar optical waveguide technology, etc.

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