Optical communications have become a part of everyone’s life without many people realizing it. We hear from Verizon about their high optical speeds but unless you’re in the telecommunications industry you don’t really know what exactly they are talking about. Optical communications are communicating using light to transport information. In this paper, we will look at when optical communications were established and how it exactly works and the costs of implementation.
Optical communications are using light to portray information. Optical communication wasn’t only used for internet purposes it was also used in Morse code. According to the History channel Morse code was invented in 1836 by Samuel Morse, along with Joseph Henry and Alfred Vail. Morse code was before the invention of the telephone and it was established using pulses of electricity to signal a machine to make marks on a moving paper tape. (Alwayn, 2004) Later, Morse code was evolved and used in the Navy with the implementation of light. The Navy installed huge lamps on their ships and flashed them on and off to indicate a message to other ships. So, optical communications started with the invention of the Morse Code. (History.com Staff, 2009) The invention of fiber optic technologies dates back further to the 1790’s to the optical semaphore telegraph invented by Claude Chappe. (Alwayn, 2004) Following Claude’s invention Alexander Graham Bell patented an optical telephone system which was called the Photophone. (Alwayn, 2004) The photophone was never put into production but the telephone as we know it today was invented afterwards. Following many inventors and research in 1977 a company called General Telephone and Electronics implemented the world first live telephone traffic through fiber-optic system running at 6 mbps, in Long Beach California. (Alwayn, 2004) Today more than 80% of the worlds long distance data and voice traffic is transported over optical fiber. (Alwayn, 2004)
Fiber optic communication is used through fiber optic cabling. Fiber optic cabling was invented by Robert Maurer, Donald Keck, and Peter Schultz. Fiber optics is the transmission of light through long fiber rods of either glass or plastics. The process that the light uses to travel is called internal reflection. (Bellis, 2016) “The core medium of the rod or cable is more reflective than the material surrounding the core. That causes the light to keep being reflected into the core where it can continue to travel down the fiber.” (Bellis, 2016) A fiber optic system consists of light sources, fibers, and light detectors. (Morikawa, 2017)Light sources convert electrical signals into optical signals. Light detectors convert optical signals back into electrical signals. Optical fibers are made with core and cladding. Since optical fibers are used for long distances optical repeaters are needed to overcome attenuation. Attenuation is the loss off signal over a long distance, basically the signal becomes weaker the longer the distance without a repeater to strengthen the original signal. (Morikawa, 2017) There are two principals behind fiber optics Snell’s law and Total Internal Refraction. Snell’s Law is a formula used to describe the relationship between the angles of indices and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air. (Metz, 2014) Fiber optics works by light traveling through optic cables by bouncing repeatedly off the walls. If the light hits the glass at an angle less then 42 degrees, it reflects which is what total internal reflection is. Total internal reflection keeps the light inside the fiber optic cabling and makes sure the light doesn’t leak out. (Woodford, 2016) The other thing that keeps the light from leaking out is the core and cladding. The middle portion of the fiber optic cabling is the core it is where the light travels through. The other portion is the cladding which wraps around the outside of the core and is made up of glass. The cladding keeps the light signal inside the core. It keeps the light inside because it is made up of a different type of glass then the core portion which in turn means that it has a lower refractive index. (Woodford, 2016) There are different types of fiber-optic cables being used today which are single mode fiber and multimode fiber. Multimode fiber is used for short distances and has a lower speed then single mode fiber. The problem with multimode fiber is that it has modal dispersion which is when a signal is spread in time because the propagation velocity of the optical signal is not the same for all modes.
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