Single mode means the fiber allows for the transmission of one form of light wave at a time. While multimode means multiple modes can be propagated by the fiber. The differences between single mode and multimode fiber optic mainly relate to fiber core diameter, wavelength & light source, bandwidth, sheath of color, distance and cost.
The core diameter of single mode fiber is much smaller than the multimode fiber. The signature core diameter is 9 μm, it is available in different sizes too. And the main multimode fiber diameter is usually 50 μm and 62.5 μm, which allows for higher “light gathering” capabilities and simplifies connections. Single mode and multimode fiber optic cladding diameter are 125 μm.
Due to its greater core diameter the attenuation of multimode fiber is higher than single mode fiber. The fiber core of a single mode cable is very narrow, so the light that passes through these optical fiber cables is not reflected too many times, thus minimizing the attenuation.
For the multi mode fiber, it can be categorized into two groups which are
- Step-Index Multimode Fiber
Many of the light rays that make up the digital pulse will follow a direct route because of its large core, while others zigzag while bouncing off the cladding. Such alternate paths allow the various classes of light rays, called modes, to arrive separately at the point of reception. The pulse, an aggregate of numerous modes, starts to spread and loses its well-defined form. This type of fiber is best suited for transmission over short distances.
- Graded-Index Multimode Fiber
Contains a core in which the refractive index slowly diminishes towards the cladding from the middle axis. The higher refractive index in the middle makes the luminous rays traveling down the axis move quicker than those near the cladding. Light in the center curves helically rather than zigzag off the cladding because of the graded index, which decreases its travel speed.
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