What is the difference between single mode and multimode fiber?

Single mode fiber  is designed to support only a single propagation mode for a  polarization direction while Multi mode fiber is designed to support multiple transverse guided modes for a polarization. Hence the core diameter (8.2 μm )and the numerical aperture (0.14) of SMF is comparatively lower than multimode fibers. which usually have significantly larger core and  also a higher numerical aperture of about. 0.2–0.3.  Therefore lasers that are operational at  1390nm are used for SMF while LEDs are used for MMF(operational frequency is 1390nm or 1490 - 1625 nm while for  Multi-mode is 850 nm)

Single mode fibre is designed for transmission for a single ray or mode of light. It is used for long distances.

Multi mode Fibre is used for short distances, It has a large light carrying core

Multimode fiber has a relatively large light carrying core, usually 62.5 microns or larger in diameter. It is usually used for short distance transmissions with LED based fiber optic equipment. Single-mode fiber has a small light carrying core of 8 to 10 microns in diameter.

Single Mode fiber optic cable has a small diametral core that allows only one mode of light to propagate. This means that the core to cladding diameter ratio is 9 microns to 125 microns. Multimode Fiber Optic Cable. Multimode fiber optic cable has a large diametral core that allows multiple modes of light to propagate.

. Single mode fiber can only carry one mode of light due to its small core diameter. Thus the light reflection is very small which makes it better for long distances. This application is typically used by Telcoms, CATV companies, and Colleges and Universities.

. Multi mode fiber can carry many multiple modes of light due to the bigger core diameter. Thus the light reflection increases which make it better for short distances. This application is typically used for data and audio/video applications in LANs. RF broadband signals.

Single Mode cable is a single stand of glass fiber with a diameter of 8.3 to 10 microns that has one mode of transmission.  Single Mode Fiber with a relatively narrow diameter, through which only one mode will propagate typically 1310 or 1550nm. Carries higher bandwidth than multimode fiber, but requires a light source with a narrow spectral width. Synonyms mono-mode optical fiber, single-mode fiber, single-mode optical waveguide, uni-mode fiber.

Single-mode fiber gives you a higher transmission rate and up to 50 times more distance than multimode, but it also costs more. Single-mode fiber has a much smaller core than multimode. The small core and single light-wave virtually eliminate any distortion that could result from overlapping light pulses, providing the least signal attenuation and the highest transmission speeds of any fiber cable type.

Single-mode optical fiber is an optical fiber in which only the lowest order bound mode can propagate at the wavelength of interest typically 1300 to 1320nm.

Multimode cable is made of of glass fibers, with a common diameters in the 50-to-100 micron range for the light carry component (the most common size is 62.5).  POF is a newer plastic-based cable which promises performance similar to glass cable on very short runs, but at a lower cost.

Multimode fiber gives you high bandwidth at high speeds over medium distances. Light waves are dispersed into numerous paths, or modes, as they travel through the cable’s core typically 850 or 1300nm. Typical multimode fiber core diameters are 50, 62.5, and 100 micrometers. However, in long cable runs (greater than 3000 feet [914.4 ml), multiple paths of light can cause signal distortion at the receiving end, resulting in an unclear and incomplete data transmission.

It all about how many microwave length (called lambda ) can be sent on a single fiber.  single mode, also called monomode, can only send on lambda. Whereas, Multimode can send multiple ones at the same time.

  Best regards 

Multi Mode Fiber: There are two main sizes for multi mode fiber. these are most widely used in data networks. The numbers 50/125 and 62.5/125 that represent the diameters of the fiber core and cladding,the unit is micron which is the millionths of a metre.

Single Mode Fiber:Single mode cable has a core diameter of 8.3 to 10 microns. which is most commonly used in telecommunication for transmission systems,the number 8.3/125 represents the diameters of the fiber core and cladding.

Note: Both multi and single mode fibers have an outside diameter of 125 microns about 5 thousandths of an inch.

Single Mode fiber optic cable has a small diametral core that allows only one mode of light to propagate.Multimode fiber optic cable has a large diametral core that allows multiple modes of light to propagate.