Optical fiber related knowledge

Optical fibers are made of glass or plastic. Most are about the diameter of a human hair, and they can be many miles long. Light travels along the center of the fiber from one end to the other, and a signal can be applied. Fiber optic systems are superior to metal conductors in many applications. Their biggest advantage is bandwidth. Because of the wavelength of light, signals containing more information can be transmitted than metal conductors (even coaxial conductors). Other advantages include:

Electrical isolation - Fiber optics do not require a ground connection. The transmitter and receiver are isolated from each other, so there are no ground loop issues. In addition, there is no risk of sparks or electric shock.

Immune to electromagnetic interference - Fiber optics are not affected by electromagnetic interference (EMI), and they do not emit radiation themselves to cause other interference.

Low power consumption - This allows for longer cable runs and fewer repeater amplifiers.

Lighter and smaller - Fiber optics weigh less and require less space than metal conductors with equivalent signal carrying capacity.

Copper wire is about 13 times heavier. Fiber optics are also easier to install and require less conduit space.

Applications

Some of the main application areas for optical fiber are:

Communications – Voice, data, and video transmission are the most common uses for optical fiber, including:

– Telecommunications

– Local Area Networks (LANs)

– Industrial Control Systems

– Avionics Systems Military Command, Control, and Communications Systems

Sensing – Optical fibers can be used to transmit light from a remote source to a detector to obtain pressure, temperature, or spectral information. Optical fibers can also be used directly as sensors to measure many environmental effects such as strain, pressure, resistance, and pH. Environmental changes affect the light intensity, phase, and/or polarization in ways that can be detected at the other end of the fiber.

Power Transmission – Optical fibers can deliver very high powers for tasks such as laser cutting, welding, marking, and drilling.

Illumination – A bundle of optical fibers brought together with a light source at one end can illuminate hard-to-reach areas, for example, inside the human body in conjunction with an endoscope. In addition, they can be used as display signs or simply as decorative lighting.

Optical fiber consists of three basic concentric components: core, cladding, and outer coating

The core is usually made of glass or plastic, but other materials are sometimes used depending on the desired transmission spectrum. The core is the light-transmitting portion of the fiber. The cladding is usually made of the same material as the core, but with a slightly lower refractive index (usually about 1% lower). This difference in refractive index causes total internal reflection at the refractive index boundaries along the length of the fiber, allowing light to travel down the fiber without escaping through the side walls.

The coating usually includes one or more layers of plastic material to protect the fiber from the physical environment. Sometimes a metal jacket is added to the coating to provide further physical protection.

Optical fibers are usually specified by their dimensions, such as the outer diameter of the core, cladding, and coating. For example, 62.5/125/250 refers to a fiber with a 62.5 micron diameter core, a 125 micron diameter cladding, and a 0.25 mm diameter outer coating.