Our current Internet connection uses a very common technology called fiber optics. The shape of the optical fiber is actually a long cylinder of transparent soft material.
Optical signals propagate in optical fibers to achieve the effect of spreading information.
But there is a problem, the optical fiber is clearly transparent, light from one end into the, why does not come out of the side?
How is it that light can come in at one end and come out at the other, no matter how the fiber is twisted?
The principle of optical fiber is called total reflection of light. The first thing to understand is the refraction of light: light travels in two different transparent media, and refraction occurs if the light is not perpendicular to the interface of the medium.
For example, a chopstick placed in water looks as if it is bent at an Angle, which is the refraction of light.
If light enters the water from the air at an oblique Angle, draw a straight line perpendicular to the interface through the incident point. This line is called the optical axis. The direction of light incident has an Angle called alpha, and the direction of light entering the water through refraction has an Angle called beta.
If light is emitted from a medium with a small refractive index into a medium with a large refractive index, then β<α; otherwise, β>α.
Air has a smaller refractive index than water, so if light enters water from air, it's alpha > beta.
Suppose we now take a light ray from a medium with a high refractive index and shoot it into a medium with a low refractive index, in which case alpha is less than beta.
Now we adjust the Angle of incidence, which asked alpha increasing, the corresponding beta will be increasing, but when alpha is big enough, the Angle of refraction beta will be 90 degrees, at this time due to the alpha < beta, alpha Angle must not 90 degrees, if this time continue to increase the Angle of incidence of alpha, beta cannot be greater than 90 degrees Angle of refraction, so there is no light refraction.
According to the law of conservation of energy, all light will be reflected back into the incident medium at an Angle equal to the Angle of incidence. This is the phenomenon of total reflection.
The optical fiber is a transparent cylinder made of quartz glass. The refractive index in the center of the optical fiber is higher than that in the edge. As long as the incident Angle of the light is controlled within a certain range, all the optical signals transmitted into the optical fiber will be reflected all the way, and will not escape out of the optical fiber.
In this way, the optical signal can travel through the optical fiber, and this is the principle of optical fiber, called total reflection.
Charles Kao, a Chinese physicist, won the Nobel Prize in Physics in 2009 for his tireless work on optical fiber technology, which has revolutionized communication.
When Dr. Kao first worked on making fiber optics practical, the mainstream community was unconvinced, but the popularity of fiber optics today shows that sometimes one person's persistence is far better than the majority's abandonment.