Causes of Fiber Attenuation

The main factors that cause fiber attenuation are: intrinsic, bending, extrusion, impurities, unevenness and butt joint, etc.

Intrinsic: It is the inherent loss of the fiber, including: Rayleigh scattering, inherent absorption, etc.

Bending: When the fiber is bent, part of the light in the fiber will be lost due to scattering, resulting in loss.

Squeeze: The loss caused by the slight bending of the optical fiber when it is squeezed.

Impurities: Impurities in the optical fiber absorb and scatter the light propagating in the optical fiber, resulting in losses.

Inhomogeneity: The loss caused by the inhomogeneity of the refractive index of the fiber material.

Butt joint: the loss generated when the fiber is docked, such as: misalignment (the concentricity of single-mode fiber is required to be less than 0.8 μm), the end face is not perpendicular to the axis, the end face is uneven, the butt core diameter does not match, and the welding quality is poor.

As light enters one end of the fiber and exits the other, the intensity of the light decreases. This means that after the optical signal propagates through the optical fiber, a part of the optical energy is attenuated. This shows that there are certain substances in the optical fiber or for some reason, blocking the passage of optical signals. This is the transmission loss of the fiber. Only by reducing the fiber loss can the optical signal be unimpeded.

Classification of Fiber Loss

Optical fiber loss can be roughly divided into the inherent loss of the optical fiber and the additional loss caused by the use conditions after the optical fiber is made. The specific breakdown is as follows:

Optical fiber loss can be divided into intrinsic loss and additional loss.

Intrinsic loss includes scattering loss, absorption loss and loss caused by imperfect fiber structure.

Additional losses include microbending losses, bending losses, and splicing losses.

Among them, the additional loss is artificially caused during the laying process of the optical fiber. In practical applications, it is inevitable to connect the optical fibers one by one, and the optical fiber connection will cause loss. Microbending, extrusion, and stretching of the optical fiber will also cause loss. These are the losses caused by the conditions of use of optical fibers. The main reason is that under these conditions, the transmission mode in the fiber core changes. Additional losses can be avoided as much as possible. Below, we only discuss the inherent loss of optical fiber.

Among the intrinsic losses, scattering loss and absorption loss are determined by the characteristics of the fiber material itself, and the intrinsic losses caused by different operating wavelengths are also different. It is extremely important to understand the mechanism of loss and quantitatively analyze the loss caused by various factors for the development of low-loss optical fibers and the rational use of optical fibers.