Multimode fiber

Update:14 May 2018
Summary:

Fibers that have multiple modes by operating the fiber […]

Fibers that have multiple modes by operating the fiber at the same time as its propagation mode are called multimode fiber (MMF:

MUlti ModeFiber). Core diameter is 50μm, due to transmission mode up to several hundred, compared to SMF transmission

Bandwidth is dominated by modal dispersion. Historically used for short-distance transmission of cable television and communication systems. from

From the appearance of SMF fiber, it seems that a historical product has formed. But in fact, because MMF is larger than SMF's core diameter and LED

The light source is easy to combine and has advantages in many LANs. Therefore, MMF is still in the field of short-range communications

It is valued.

When MMF is classified according to the refractive index profile, there are two types of gradient (GI) and step (SI). GI type

The refractive index is highest at the center of the core and gradually decreases toward the cladding. From the perspective of geometric optics, in the core

The advancing light beam appears to mean snakes. Because the time required for each path of light is about the same. So, pass on

The transmission capacity is larger than the SI type.

The refractive index profile of the SI type MMF fiber and the distribution of the core refractive index are the same, but the interface with the cladding

Stepped. Due to the reflection of the SI type light wave in the optical fiber, the time difference of each light path is generated, resulting in

Ejection of light wave distortion, large color shock. As a result, the transmission bandwidth becomes narrower. Currently, there are fewer SI MMF applications.

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