Fiber optic cables for commercial uses come in two general sizes: either single mode or multi-mode. The data transmission rates and the total bandwidth available are all functions of what kind of fiber optic cable is being used.
Single Mode Fiber Optic Cable
These kinds of fiber optic cables are in greater use than the multi-modefiber optic cable types. These cables consist of a single strand that is used for transmission. The strand is narrow and allows only one specific mode of transmission. Single mode transmission strands allow the transmission of high data transfer rates over relatively long distances. This possible due to the presence of the single, narrow small core.The presence of single strands allows single mode fiber optic transmission over large distances with practically no loss in quality. The data transfer rates are much higher in comparison to multi-mode fiber optic cables. However, the advantages offered by single mode fiber optic cables are offset at times by the presence of high costs.
Step-Index Multi-mode Fiber
Graded-Index Multi-mode Fiber
Multi-ModeFiber Optic Cable
Multi-modefiber optic cables possess larger diameters in comparison to single mode fiber optic cables. This helps multi-modefiber optic cables to transmit greater bandwidths in comparison to single mode fiber optic cables, but data transfer rates are much higher in single mode fiber optic cables. Another distinct property of multi-modefiber optic cables is that fiber optic transmission occurs over medium distances, in comparison to single mode fiber optic cables where fiber optic transmission occurs over large distances. Over longer distances, the larger diameters of multi-modefiber optic cables often cause distortions in signals. This results from the superimposition of light signals during transmission through multi-modefiber optic cables. At times, the larger diameters of multi-modefiber optic cables cause light signals to travel in differing directions, and this is responsible for distortions in fiber optic transmission.
Fiber Optic Transmission
Fiber optic transmission occurs in the same manner, whether single mode fiber optic cables are used or whether multi-modefiber optic cables are used. The internal surface of a fiber optic cable is coated with a reflective substance. Any light signals that come through the fiber optic cable are reflected internally throughout the cable. This phenomenon is better known as total internal reflection; however, signals must first be converted from one form to another.
Analog signals need to be converted into digital signals before transmission is possible. This is done by analog to digital converters whose feedback is then used to create light signals using laser pulses. These light pulses move through the fiber optic cables with relative ease. An important property of fiber optic cables is the ability for light signals to move seamlessly, no matter which direction they emerge from and no matter which direction they travel to. This enables the fiber optic cable to be twisted, bent and operated on, so as long as the transmission path is not broken down. The continuity of fiber optic cables ensures that light signals, and thus information, is transmitted seamlessly across long distances.