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Optical fibers may all look like simple glass strands, but appearance has nothing to do with it – it’s what’s on the inside that counts. Knowing the difference between single-mode and multimode fiber, and choosing the right one, can make or break your network’s performance.

All optical fibers are made up of an inner core that’s surrounded by an outer layer of cladding. In the single-mode versus multimode issue, it’s the fiber’s core size, cladding thickness and signal transmission style that set the two modes apart from one another. Here’s a quick rundown on what it means to be single-mode or multimode, and what each mode is best cut out for.

• Singlemode fibers have narrower cores, which average around 9 microns in diameter, and a thick layer of cladding. Because these cores are on the thinner side, they’re not able to carry quite as much data as multimode fibers, but the light signals are sent straight down the core with little to no “bouncing,” or signal reflection. The combination of thick cladding and a thin core cause the light signal to travel straight and true, so it’s able to transmit farther with little to no attenuation, making single-mode the best choice for high-speed or long-distance applications.

• Multimode fibers have much thicker cores than single-mode fibers (typically 50 or 62.5 microns) surrounded by only a thin layer of cladding, and because of this, they’re able to transmit more data at one time, and are ideal for use with broader light sources, like LEDs. However, multimode’s wider core also leaves light signals with a much wider space to bounce around in, meaning that they can travel in a variety of paths. If single-mode data transmission is the equivalent of sending a bowling bowl straight down the center of a lane, multimode can best be illustrated by throwing a super-ball down a hallway, and watching it ricochet off opposite walls until it reaches the other end.

Because of the “bounce” factor involved in multimode cables, modal dispersion, or the separation of light pulses, can occur, meaning that different parts of the same signal can travel in different patterns and arrive at the receiving end at slightly different times. While this doesn’t make multimode fiber any less effective, it does limit the distance that light signals can be transmitted over, making multimode best for shorter-distance applications requiring a higher volume of data transmission, such as LANs.

What’s the difference between Simplex and Duplex fiber optic cables and connectors?
The difference between simplex and duplex is simple: simplex cables and connectors are based on only one fiber, and are typically used in applications where data needs to be transmitted in only one direction. Duplex components are built around two fibers, which are typically run side by side, and are usually used for applications that require data to be sent and received at the time.