What is the difference between Single Mode Fiber (SMF) or Multimode Fiber (MMF) exactly?

From a physical standpoint, MMF has a bigger core compared to SMF which allows for a longer wavelength of light. MMF typically uses Light-Emitting Diodes (LEDs) to launch the optical signal.

SMF’s core diameter is much smaller than MMF.  Also, SMF uses lasers to launch light in a more concentrated fashion with a narrower wavelength compared to that of LED in MMF.

MultiMode Fiber Single Mode Fiber

SMF is a much better option for transmitting data over long distances. Typical applications for SMF include college campuses and cable TV networks.

MMF cannot support longer distance. However, due to the lower overall system cost (both transceiver modules and equipment), it is widely used for data applications in local area networks.

With the emerging demand for 40G and 100G network, we are seeing more customers install SMF (lower loss and higher bandwidth) and using them even in shorter distance connections because SMF allows for single pair upgrade to 40G, 100G and possible 400G in the future. Therefore, these customers will not need to retrofit their fiber infrastructure to migrate to future high speed technologies.

Below is a quick comparison to compare the two modes.

MultiMode Fiber Single Mode Fiber Chart

Article content by King Leung, Project Engineer at Mirapath. Connect with King on LinkedIn.