[1] Single-mode fiber (SMF): Consists of a very small core and uses expensive laser tech to send a single ray of light. Popular in long-distance situations spanning hundreds of kilometers, such as those required in long haul telephony and cable TV applications. [2] Multi-mode Fiber (MMF): Consists of a larger core and uses LED emitters to send light pulses. Light from an LED enters the multimode fiber at different angles. popular in LANs because they can be powered by low cost LEDs. It provides bandwidth up to GB/s over link lengths of up to 550 meters.