EMD launch
Equilibrium Mode Distribution. In multi-mode fibres, EMD is reached when the distribution of modes is independent of fibre length.

EPON
Ethernet based Passive Optical Network (PON).

Excess loss (EL)
Power lost in an optical coupler or splitter. Proportion of the signal that is present at the input but none of the output ports.

Extrinsic loss
These are losses caused by defects and imperfections that cause the loss to exceed the theoretical minimum loss that is intrinsic, and called intrinsic loss. Examples of causes of extrinsic losses include lateral or axial offset between mating fibres that causes higher insertion loss, lack of physical contact, lack of an angle on fibre ends, imperfections on the fibre`s surface as well as many others that can cause higher reflectance losses.