Invention of optical fiber

We have been used to the idea of transmitting information in different ways. When we use the landline telephone to speak, the cable transmits the voice to the wall socket, and the other cable transmits it to the local telephone exchange. Mobile phones work differently: they use invisible radio waves to send and receive information. This technology is called wireless because it does not use cables. Optical fiber is the third transmission mode, which was originally developed for endoscopes. In the 1960s, engineers discovered a way to transmit signals at the speed of light using the same technology.

Optical technology

Optical fiber cable is an extremely thin wire made of glass or plastic. A cable can be composed of two or hundreds of harnesses at most. The thickness of each thread is less than one tenth of the human hair.

Fiber optic cables use full optical technology to transfer information between two locations. Suppose you want to use optical fiber to send information from your computer to your friend's home. We can connect a computer to a laser, which converts electronic information from the computer into a series of optical pulses. The laser is then fired along the fiber optic cable. After moving down the cable, the beam will shoot out at the other end. Your friend needs an electronic message that converts light pulses back to his computer.

How Optical Fiber Works

The light bounces from the wall repeatedly and travels down the optical cable. Each tiny photon slides down the pipe like a sledge. From this, we can understand that the light beam travels in the transparent glass tube. If the light hits the glass at a very shallow angle (less than 42 degrees), it will reflect back again, just like a mirror. This phenomenon is called total internal reflection.

Another thing that keeps the pipe transparent is the structure of the cable, which consists of two independent parts. The main part of the cable (in the middle) is called the core, which is the part through which the light passes. Wrapped outside the core is another layer of glass, called the covering layer. The work of the covering layer is to keep the optical signal inside the fiber core.

Type of optical fiber

Optical fiber transmits optical signal downward in a so-called mode. This sounds very technical, but it only means different modes of propagation: the mode is just the downward path of the light beam along the optical fiber. One mode is to move directly down the middle of the fiber. Another method is to make the fiber rebound at a shallow angle.

The simplest fiber is called single-mode fiber. It has a very thin core, about 5-10 microns in diameter. In a single-mode fiber, all signals travel directly down the middle without bouncing to the edge. Cable TV, Internet and telephone signals are usually carried by single-mode optical fibers and bundled into a large bundle. Such cables can send information over 100 kilometers.

Another type of optical cable is called multimode. Each fiber in a multimode cable is approximately 10 times larger than each fiber in a single-mode cable. This means that the beam can pass through the core in many different modes by following a variety of different paths, in other words paths. Multimode cables can only send messages over relatively short distances.

Even thicker fibers are also used as a medical tool called an endoscope. An endoscope is a thick optical fiber cable composed of many medical optical fibers. At the top of the endoscope, there is an eyepiece and a lamp. The lamp illuminates part of the cable into the patient's stomach. When the light reaches the stomach, it will be reflected from the stomach wall to the bottom of the cable in the lens. Then, it goes into the doctor's eyepiece along another part of the cable. Other types of endoscopes work in almost the same way and can be used to examine different parts of the body. There is also an industrial version of the tool, called a fiberglass, which can be used to check mechanical parts that are not accessible in the engine.