fiber attenuation

There are many factors that cause fiber attenuation, but the cause is nothing more than the inherent loss of the fiber or when the fiber is bent, part of the light in the fiber will be lost due to scattering, resulting in loss. So, what are the reasons for fiber attenuation? Let's take a look down together!

ZR Cable analyzes fiber attenuation

What are the reasons for the weakening of optical fibers?

1. Absorption loss of materials

Optical fibers are made of materials that absorb light energy. After the particles in the fiber material absorb the light energy, they vibrate and generate heat, and dissipate the energy, thus resulting in absorption loss. In an optical fiber, when electrons of a certain energy level are irradiated with light of a wavelength corresponding to the energy level difference, electrons located in the orbits of lower energy levels will transition to orbits of higher energy levels. This electron absorbs light energy, resulting in light absorption loss.

2. Scattering loss

How does scattering occur? The tiny particles such as molecules, atoms, and electrons that make up matter vibrate at certain natural frequencies, and can emit light with wavelengths corresponding to the vibrational frequencies. The vibration frequency of a particle is determined by the size of the particle.

The larger the particle, the lower the vibrational frequency, and the longer the wavelength of the light emitted; the smaller the particle, the higher the vibrational frequency, and the shorter the wavelength of the emitted light. This vibrational frequency is called the natural vibrational frequency of the particle. But this vibration is not self-generated, it requires a certain amount of energy.

Resonance occurs when a particle is exposed to light of a certain wavelength at the same frequency as the particle's natural vibration.

The electrons in the particle start to vibrate at this vibrational frequency. As a result, the particle scatters light in all directions, the energy of the incident light is absorbed and converted into the energy of the particle, and the particle re-emits the energy in the form of light energy. Therefore, for those who observe from the outside, what they see is that the light hits the particles and scatters in all directions.

3. Congenital deficiency

The fiber structure is not perfect, such as air bubbles, impurities, or uneven thickness in the fiber, especially the core-cladding interface is not smooth. . This loss can be overcome, that is, to improve the fiber manufacturing process.

Scattering makes the light radiate in all directions, and a part of the scattered light is reflected back in the opposite direction to the propagation of the fiber, and this part of the scattered light can be received at the incident end of the fiber. The scattering of light causes a portion of the light energy to be lost, which is undesirable.

However, this phenomenon can also be used for us, because if we analyze the intensity of the received light at the transmitting end, we can check the breakpoint, defect and loss of the fiber. In this way, through human ingenuity, bad things are turned into good things.

4. Optical fiber scattering loss

The scattering inside the fiber will reduce the transmitted power and cause loss. The most important of scattering is Rayleigh scattering, which is caused by changes in density and composition inside the fiber material.

5. Waveguide scattering loss

This is scattering due to random distortion or roughness at the interface, and it is actually mode switching or mode coupling caused by surface distortion or roughness. One mode will give rise to other modes of transmission and radiation due to the fluctuation of the interface.

Due to the different attenuation of various modes transmitted in the fiber, in the process of long-distance mode conversion, the mode with small attenuation becomes the mode with large attenuation. After continuous transformation and inverse transformation, although the loss of each mode will be balanced, but The mode generally produces additional loss, that is, additional loss due to mode conversion, and this additional loss is the waveguide scattering loss. To reduce this loss, it is necessary to improve the optical fiber manufacturing process. For well-drawn or high-quality fibers, this loss is essentially negligible.

6. Radiation loss caused by fiber bending

Optical fibers are flexible and can be bent, but after bending to a certain extent, although optical fibers can guide light, the transmission path of light will change. The transmission mode is converted into a radiation mode, so that a part of the light energy penetrates into the cladding or passes through the cladding as a radiation mode that leaks out and is lost, resulting in loss. When the bending radius is greater than 5-10cm, the loss caused by bending can be ignored.

What are the reasons for fiber attenuation? Today, ZR Cable will answer you here. I believe that you have also answered your questions about the reasons for fiber attenuation.