The difference between a singlemode and a multimode fibre patchcord

All fiber consist of a light carrying core in the center covered by an optical coating called cladding that traps light within the core.
The difference between multimode and singlemode is the diameter of the fiber core. The core diameter is either 50 or 62.5 micron for multimode and 9 micron for Singlemode. Multimode patchcords are primarily used with LED sources for LAN and security systems. Its large core makes it easy to couple lots of light from inexpensive LED’s and it has adequate bandwidth for most premises applications.
Singlemode patchcord has higher bandwidth and low attenuation because of its smaller core. But the smaller core needs expensive laser sources for efficient coupling, generally limiting its use to very higher bandwidth system used over long distances.
Telecom and CATV system all use singlemode patchcords. Singlemode Patchcords have yellow colour jacketing and multimode patchcords have orange or grey colour jacketing.