Optical fiber

An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can send light from one end to the other. These tiny tubes are amazing because they can carry information over long distances faster and more clearly than old metal wires. This makes them very important for things like the internet and phone calls.

Fibers are used instead of metal wires because the signals lose less strength and are not disturbed by electricity or radio waves. They are also used to shine light into tight spaces or to take pictures inside places that are hard to see, like inside machines or the human body with a special tool called a fiberscope.

Making optical fibers usually starts with turning glass or plastic into very thin strands. Inside each fiber, there is a small center part called the core surrounded by another layer called the cladding. When light enters the core, it bounces along the fiber due to a science idea called total internal reflection. This helps the light travel far without escaping.

There are two main types of fibers: multi-mode fibers with a wider center, used for shorter distances, and single-mode fibers, thinner and used for longer distances, like in most internet connections. Joining these fibers together without losing the signal is tricky and needs special techniques, like heating the ends together in a fusion splice or using a mechanical splice. Special optical fiber connectors are used when a connection needs to be changed or moved. The science and technology around these fibers is called fiber optics, a field started by scientist Narinder Singh Kapany.

History

See also: Fiber-optic communication § History

Daniel Colladon and Jacques Babinet showed how light can be guided by bending it in Paris in the 1840s. Later, John Tyndall explained how light reflects inside a material at a certain angle.

In the late 1800s, doctors used bent glass rods to shine light inside the body. By the 1950s, scientists made bundles of tiny glass fibers that could carry images. In 1965, a system for sending data with fiber optics was created, and NASA used fiber optics in cameras sent to the moon.

In 1965, Charles K. Kao and George A. Hockham suggested that pure silica glass could make fibers good for communication. This idea led to better fibers with less loss of signal, making long-distance communication possible.

Uses

Communication

Main article: Fiber-optic cable

For broader coverage of this topic, see Fiber-optic communication.

Optical fiber is used to send information over long distances. It is better than regular wires because light can travel farther without getting weak. This makes it great for telephone and internet services. Each fiber can carry lots of information at once, making it very fast.

Military

Fiber optic drones have been used in the Russo-Ukrainian War. These drones are safe from interference and special electronic attacks.

Sensors

Main article: Fiber-optic sensor

Fibers can help us measure things like temperature, pressure, and movement. They can be used in places that are hard to reach, like inside machines or faraway locations. These sensors are very useful for keeping things safe and working properly.

Power transmission

Optical fiber can also be used to send power using light. This is helpful in places where regular wires can’t be used, like near strong magnets.

Other uses

Optical fibers are used to shine light where it’s needed, such as in medical tools called endoscopes. They can also bring sunlight into different parts of a building or make pretty lights for decorations. Fibers are important in many scientific tools and can even help make lasers stronger.

Principle of operation

An optical fiber is a thin tube made of glass or plastic that can carry light from one end to the other. It works by keeping the light trapped inside through a process called total internal reflection. This means the light bounces back and forth inside the fiber instead of escaping out.

Because optical fibers do not use electricity, they are great for places where electrical signals could cause problems, like near powerful electricity or lightning. They also do not pick up unwanted signals from the environment, making them very reliable for sending information over long distances.

Mechanisms of attenuation

See also: Transparent materials

Attenuation in fiber optics, also called transmission loss, is when the strength of a light signal gets weaker as it travels through the fiber. This happens because the light gets weaker over distance. Scientists measure this loss in units called dB/km. Most fibers are made from a special type of glass called silica, which helps keep the light inside the fiber.

One type of fiber, called single-mode fiber, can have very little loss. For example, a fiber made by Corning called Vascade® EX2500 loses only a tiny amount of light over long distances. This makes it great for sending information over long cables.

Attenuation happens mainly because of two things: scattering and absorption. Scattering is when light bounces off tiny changes in the glass. Absorption is when the glass takes in some of the light. In silica glass, scattering is usually the bigger problem. This is why scientists work hard to make fibers with as little loss as possible.

Manufacturing

Optical fibers are thin strands of glass or plastic that can carry light signals far away. They are made from materials like silica glass, which is very clear and lets light pass through easily. Other materials, such as plastic, can also be used, but they might not work as well for very long distances.

To make an optical fiber, a special rod called a "preform" is made first. This preform has the right mix of materials so that when it is stretched into a thin fiber, it can guide light properly. The preform is then heated and pulled to form the fiber, which can be as thin as a human hair. A protective coating is added to keep the fiber strong and safe from damage.

Practical issues

Fiber cables are flexible but can have problems if bent too tightly, especially with older types of fibers. Special bendable fibers have been made to be easier to install in homes, letting them bend tighter without losing the signal.

Connecting optical fibers to devices uses special connectors or a process called splicing, where tiny pieces of glass are melted together. Newer connectors make this process simpler and faster than older ways.