Optical modes are simply the path that a ray of light travels along a fiber. One mod goes right in the middle. The other can bounce off the fiber at narrow angles. Other modes bounce off the fiber at different angles.
The simplest fiber type is singlemode. A very thin core (5-10 microns) sends signals directly down the center without bouncing off the shell. Internet, cable TV and telephone signals are most often transmitted over single-mode fibers, which are bundled into a huge package. These cables can carry information over 60 miles.
Each fiber in a multimode cable is almost 10 times larger than in a singlemode cable. This allows light rays to travel through the core in different paths - in multiple modes. The disadvantage of multimode fiber optic cables is that they can only transmit information over short distances. They are mainly used to link computer networks fiber installation.
How are fiber optic cables made?
Fiberglass is surprisingly strong considering that glass is a fragile material. Most optical fibers are made by pulling a glass rod, heated to the melting point, a few centimeters in diameter and about 1 m long, into a thin fiber 125 micrometers in diameter and several kilometers long.
Each of these fibers is wound together with similar fibers to produce a thicker thread. However, additional protection is often needed when fibers are used in an environment where access is open. For laboratory use, where researchers send “light from a telecommunications facility to a diagnostic device,” and in large industrial assemblies, it is convenient to use fiber patch cords, where the actual fiber is surrounded by additional protective layers. While bare glass fiber can have a typical diameter of 125 micrometers, and the polymer buffer and jacket increase it to a few hundred micrometers, the total fiber cable diameter can be several millimeters."
This not only strengthens the cable, but also makes it easier for operators to recognize the fiber for ease of maintenance and repair. And a fiber optic cable can contain multiple fibers. This allows the already enormous data transmission capabilities of a single fiber to be multiplied. There are many optical components that can be made directly from fibers. Some examples include
Fiber connectors that conduct light between two fibers
Optical filters for use in introducing chromatic dispersion into the system
Fiber polarizers made with polarizing fibers to direct light in a specific direction of polarization
Fiber amplifiers that amplify light at specific wavelengths
These are just a few examples of how fiber optics are made and what we can make from them for use in many areas.
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