Simplex fiber optic cable is the basic type fiber cable, simplex means: first, this cable has only one single strand of optical fiber; second, it has one single outer jack. You may wonder what is the cable structure, the fiber core usually refer to the central part of the fiber strand, together it is with necessary stuff surrounding it for protection. To make it clear we have the below picture to illustrate the structure of a basic type simplex fiber optic cable.

When talk about simplex fiber optic cable, we need to note that simplex is totally different with another common seen phrase “single mode”. Simplex means the cable’s physical structure as described above, single mode generally is related to the fiberglass itself, and it means this fiber support only one light transmission mode, that is, one beam propagating along the fiber centerline. Simplex fiber cables can be single mode type or multimode type. Simplex also has nothing to do with cable length or outer diameter; simplex only describes a simple fiber optic cable structure.