Fiber Fun Fact: Multimode Vs. Single Mode

May 1, 2014 at 10:00 AM


Have you ever considered…


What is the difference between multimode and single mode fiber cable?


This is a question our tech support and customer service teams are often asked. Depending on your job function or area of expertise you may already be “in the game,” but for the layman or tech-freshman this is good knowledge to have.


A Single mode fiber cable has a small diametric core that allows a single mode of light to propagate. The most common size is 9/125.  For example, a single mode fiber’s glass core is 9 microns in diameter.  A strand of human hair is typically about 100 microns.  Now that’s small!


On the other hand, a Multimode fiber cable has a core diameter that is much larger than the wavelength of light transmitted.  As the light passes through the core, the number of light reflections created increases, allowing for more data to pass through at a given time. Two common multimode fiber types are 50/125 and 62.5/125.


Fiber specifications list the core and cladding diameters as a ratio. Multimode fiber is commonly 62.5/125 or 50/125 micron, Single mode fiber is commonly 9/125 micron.


For another great fiber optic tip, check out this video!   


In general, a single mode system is more expensive due to the cost of the laser transceivers required to drive the system. As a result, these transceivers provide better signal strength and great reliability over long distances (up to 100km or more). Multimode is much more affordable because the larger core size simplifies connector termination and allows the use of lower-cost transceivers such as LEDs (light-emitting diodes) to drive a system. Multimode can be used in distances up to 2km, depending on the network speed and bandwidth. Single mode cable is most often used by entities such as cable TV/ISP companies for long distances, while multimode is often used for short inter-building wiring and between-building cable runs often found in campus environments. 


Also, don't confuse the two! If you are running multimode cable, you need a multimode Ethernet media converter; a Single mode converter will not work.


Here’s another tip of ours that specifies wavelength and distance limitations for Multimode, Single mode and laser optimized fiber cable.


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