How Fiber Optic Cable Works
Have you ever wonder how you can send or receive information on your devices. The answer to that question is via networking cables and one of those networking cables is fiber optic. How does a thin strand of glass transmit data across long distances?
What is Fiber Optics?
Fiber optic cable is a long cylindrical piece of glass or polymer about 9 to 50 micrometers in diameter that is covered with cladding and protective sheath. To receive light over long distance, light must be directed on the other surface of the cable at an angle so that it will not travel out side of the core. Instead of the light being refracted it is reflected. This phenomenon is called total internal reflection. This phenomenon occurs when a light ray is traveling outward to less dense medium and the angle of the incident ray is greater than the critical angle.
Protective sheath is added to preserve the medium but it would make the phenomenon impossible to occur. Thus, the core is covered with cladding that have refractive index about one percent lower that the core. The difference can be achieved by adding dopants. The added dopants are usually from Germanium Oxide. These dopants makes the molecule structure to be imperfect, bonds will not form making it less refractive. Lastly, smooth surface is key. The fiber optic cables will not be able to transfer data at all if it’s surfaces have flaws. Those flaws will affect reflection. Consequently, the light ray will not be accurate.
Inside fiber optics, light can only travel for so far. This happens due to very long length of cable and imperfections of the silica. Impure silica makes the density lesser. As a result, the light decay exponentially, scatter, and be absorbed by the fiber. Not only that, the light can disperse causing it’s pulse to be unrecognizable. That is why after a certain distance lies a repeater or an amplifier to boost the transmission. Repeaters are used to regenerate the light if it is weak and amplifiers are used to amplify the light. Repeaters and/or amplifiers are put just right, near visible regions. They are necessary to solve those attenuation.
Before Fiber Optics
Before fiber optic cables are used, copper cables are used to transmit data. They have few disadvantages such as the transmission could be easily corrupted by electromagnetic (EM) interference because the data are sent using electric current, which induce EM waves. If that EM waves is disrupted so can the current. Other than that, copper can be corroded. Fiber optic will not have those disadvantages as it is using light. Light have significantly faster travel speed than electrons ergo larger bandwidth, more secure data, faster communication or internet speed.
Transmissions and Potential
To maximize the potential of fiber optic cables, there are two ways to increase it’s capacity to transfer data. Firstly, by transmitting different signal in a consistent alternating pattern, multiple signals can be transmitted simultaneously. This is called Time Division Multiplexing. Lastly, by transmitting signals with light at multiple wavelengths. This method is called Wavelength Division Multiplexing or WDM for short. Typically the light wavelengths that are used are around, 850, 1300, and 1550 nanometers. EM wave at those lengths are not visible light but infrared (IR). IR is used since attenuation of the fiber is lesser at those wavelengths.
We can communicate and exchange complex information using fiber optics since the data being transmitted is converted into binary sequence. The data with high binary value or simply one will make light transmitter turn on and vice versa. In order to increase transmission speed, the transmitter have turn off and on so rapidly at a whopping speed of 10 Gbps (Giga bit per second). On the other, receivers will have to be able to receive as fast as the transmitter. To avoid light dispersion at shorter distance, an intricate light source is used. The light source emit focused IR ray with the help of lenses. In addition, filters and scramblers are used to filter out higher order light wave. There scramblers are often used so that the IR wave will remain stable over long distance.
Using Fiber Optics for Networking
One of the applications of fiber optic cables are for connecting the internet world wide. In order to achieve that is by putting many high-grade optical fiber cables across the ocean. To endure the depths of the ocean, fiber optic cables need thick and many layer of protective coverings. These cables are stabilized and secured using steel rods and/or cores, sometimes with Kevlar and other additions. Without protective coverings, these cables will easily break for sure. To prevent that from happening, every network should have multiple and diverse route for backup. Fiber optic cables can also be used for networking in your neighborhood or even directly to your personal devices. If you want to broaden bandwidth and the high speed of your connections, you need to use proper setup ups modem or router and connectors. Improper router can lower the speed because of latency. Mind you, you can’t use fiber optic network at your home if your neighborhood is not connected or does not have fiber optic network as different networking cables as the speed would be capped.
In the early days of fiber optics, it is used for medical imaging tools. Now, it is an essential part of our daily life. Yay internet!
Sources:
Anonymous. 2020. Tutorial: Fiber Optic Basics. Accessed on July 27 2020. <https://www.newport.com/t/fiber-optic-basics>
Mitschke, Fedor. 2009. Fiber Optics Physics and Technology. Germany: Springer
Pal, Bishnu P. 2006. Guided Wave Optical Components and Devices Basics, Technology, and Applications. Elsevier Inc.
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