About Fiber Optics

What is fiber optics? The word fiber conjures images of strings, strands, threads, etc. With fiber optics, the fiber is an internally reflective tube that is narrow enough to appear as a strand. Tube composition varies depending on application, but most fibers are made of glass, silica, plastic, or a combination thereof. Glass is most commonly used for data transmission over significant distances. Silica is used for high power transmissions over shorter distances. Plastic fibers can be used to isolate systems from high voltages, or for the more commonly known application of lighting.

The appearance of some fiber optic cables can be misleading. A cable can be an inch in diameter, which may negate the imagined "strand" connotation. But most fiber optic cables consist of several protective layers, and contain more than one fiber. For example, a 1-inch thick cable could house 24 protective buffer tubes, each individually housing 12 fibers. That's a total of 288 fibers in one cable! Even a cable the width of a common copper electrical wire could hold 6 to 12 fibers.

Fibers can have extremely small diameters. A fiber freed of its layers of protection is visible to the naked eye, but what you actually see is the fiber's final layer of protection, often called the buffer region. Buffer regions are usually colored to distinguish fibers from one another. Using finely tuned fiber strippers to remove the buffer reveals yet another layer called the cladding, which assists with internal reflection. This appears as a very thin glass tube. Finally, the core of the fiber itself rests in the center. Depending on the type of fiber, the core can be small as 7 to 9 microns. That's about 1/8 the size of a human hair.

The word optics relates to light, and light is the power behind fiber optics. Light is not electricity, so fiber optic cables are not electrical conductors. Light travels faster than electricity. Light is not susceptible to electromagnetic interference. Light's motion generates little to no heat. The list goes on, but what is important to realize is that light is a more pure method of transmission than electrical pulses in a copper wire.

There is less room for error as fewer problems can arise.

Distinguishing between multimode and singlemode fiber:
The core of a multimode fiber is thicker than that of a singlemode. Multimode is usually either 50 or 62.5 microns while singlemode is usually 7 to 9 microns. The difference is that with multimode, light rays may travel the length of the fiber and bounce within the core in many paths, whereas with singlemode, the smaller core allows only rays perpendicular to the core to be transmitted. Also, a much higher power laser light source is employed in singlemode transmission. Multimodes can use LED's as light sources. Otherwise, both multi- and singlemode fibers have the same diameter cladding: 125 microns.