1. The main factors causing fiber attenuation are: I […]
1. The main factors causing fiber attenuation are:
Intrinsic, bending, squeezing, impurities, unevenness and butting, etc.
Intrinsic: It is the inherent loss of optical fiber, including: Rayleigh scattering, inherent absorption, etc.
Bending: When the optical fiber is bent, part of the light in the optical fiber will be lost due to scattering, causing 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 and cause losses.
Non-uniformity: The loss caused by the non-uniformity of the refractive index of the optical fiber material.
Butt connection: The loss caused by fiber butt, such as: different axis (single-mode fiber coaxiality is required to be less than 0.8μm), the end face is not perpendicular to the axis, the end face is not flat, the butt core diameter is not matched, and the splicing quality is poor.
When light enters from one end of the fiber and exits from the other end, the intensity of the light will be weakened. This means that after the optical signal propagates through the optical fiber, the light energy is attenuated partly. This shows that there are certain substances in the optical fiber or for some reason, blocking the passage of light signals. This is the transmission loss of the optical fiber. Only by reducing fiber loss can the optical signal flow unimpeded.
2. Classification of fiber loss
Fiber loss can be roughly divided into the inherent loss of the fiber and the additional loss caused by the use conditions after the fiber is made. The specific breakdown is as follows:
Fiber loss can be divided into inherent loss and additional loss.
Intrinsic loss includes scattering loss, absorption loss and loss due to imperfect fiber structure.
Additional loss includes micro-bending loss, bending loss and splice loss.
Among them, the additional loss is artificially caused during the laying 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. The micro-bending, squeezing, and stretching of the optical fiber can also cause loss. These are the losses caused by the use conditions of the optical fiber. The main reason is that under these conditions, the transmission mode in the fiber core has changed. Additional loss can be avoided as much as possible. Below, we only discuss the inherent loss of optical fibers.
Intrinsic loss, scattering loss and absorption loss are determined by the characteristics of the fiber material itself, and the intrinsic loss caused by different operating wavelengths is also different. Understanding the mechanism of loss and quantitatively analyzing the size of loss caused by various factors are extremely important for the development of low-loss optical fibers and the rational use of optical fibers.