FIBER OPTIC QUESTIONS
4) WHAT IS THE DIFFERENCE BETWEEN MULTI-MODE (MM) AND SINGLE MODE (SM) FIBER OPTIC CABLE?
Answer: Two commonly used types of fiber used in fiber optic cables are SM (Single Mode) and MM (Multi-Mode). SM fiber uses a single strand of glass fiber to carry the optical signal, whereas MM fiber uses multiple strands. SM fiber is available with a narrower diameter then MM fiber. In addition, SM fiber transmits with less signal degradation than that of MM cable. Therefore, SM cable is used in applications requiring transmission over longer distances. A typical maximum transmission distance for SM fiber is 12.4 miles (20 km) but can extend longer distances, as compared to 1.2 miles (2km) for MM fiber. Note that MM cable is generally more expensive than SM cable of the same length.