Optical Fiber Types

LinkX User Guide for 400Gbps 100G-PAM4 OSFP & QSFP112-based Cables and Transceivers

Single-mode fiber has a tiny 9-um light carrying core. This is small enough to make the light bend inside at a very shallow angle which keeps the data pulse light photon packets together as a group or “singe mode” which can travel over great distances. Single-mode fiber uses 1310nm wavelength and is typically used for long reaches of 50-meters to 2km to link switches together.

  • The fiber cable jacket is colored yellow

Multimode fiber is used for short reaches of less than 50-meters. Multimode fiber has a large 50-um light carrying core and some of the photons in a single data pulse takes steeper angles traveling down the fiber. This causes the light pulse to scatter inside the fiber into multiple paths or “multi(ple)modes” with some parts of the pulse taking longer to arrive at the end at the photodetector. This results in the pulse intensity weakening and spreading out in time enough to collide with the next following data pulse which limits the maximum reach.

  • Multimode fiber is optimized to be most transparent at 850-nm wavelength.

  • Multimode 850nm transceivers cannot operate with 1310nm single-mode fibers and transceivers.

  • The fiber cable jacket is colored aqua.

  • Fiber type is OM4 up to 50-meters and OM3 for <30m.

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