IT Technology: Single Mode versus Multi-Mode Fiber Optic Cable

Fiber Optics is sending signals down hair-thin strands of glass or plastic fiber. The light is “guided” down the center of the fiber called the “core”. The core is surrounded by a optical material called the “cladding” that traps the light in the core using an optical technique called “total internal reflection.”

The core and cladding are usually made of ultra-pure glass. The fiber is coated with a protective plastic covering called the “primary buffer coating” that protects it from moisture and other damage. More protection is provided by the “cable” which has the fibers and strength members inside an outer covering called a “jacket”.


<< Single Mode Fiber Optic Cable >>

Single Mode fiber optic cable has a small diametral core that allows only one mode of light to propagate. Because of this, the number of light reflections created as the light passes through the core decreases, lowering attenuation and creating the ability for the signal to travel faster, further. This application is typically used in long distance, higher bandwidth runs by Telcos, CATV companies, and Colleges and Universities.

Single Mode fiber is usually 9/125 in construction. This means that the core to cladding diameter ratio is 9 microns to 125 microns.


<< Multimode Fiber Optic Cable >>

Multimode fiber optic cable has a large diametral core that allows multiple modes of light to propagate. Because of this, the number of light reflections created as the light passes through the core increases, creating the ability for more data to pass through at a given time. Because of the high dispersion and attenuation rate with this type of fiber, the quality of the signal is reduced over long distances. This application is typically used for short distance, data and audio/video applications in LANs. RF broadband signals, such as what cable companies commonly use, cannot be transmitted over multimode fiber.

Multimode fiber is usually 50/125 and 62.5/125 in construction. This means that the core to cladding diameter ratio is 50 microns to 125 microns and 62.5 microns to 125 microns.


Reference:
Single Mode vs. Multi-Mode Fiber Optic Cable
http://www.multicominc.com/training/technical-resources/single-mode-vs-multi-mode-fiber-optic-cable/