Optical fiber is the flexible transparent fiber made from silica or plastics, slightly thicker than the human hair. Optical fiber is one of the most common tools of transmitting light at both ends, and widely used in optical fiber communication. Optical fiber is usually composed of a transparent core with low refractive index and a transparent cladding material.

Generally speaking, there are two kinds of fiber: MMF and SMF. What are the differences between them? This article will give you the answer.

The differences:
1.Core diameter
The diameter of MMF is larger than SMF, usually is 50 or 62.5µm, while the SMF is 9µm, both cladding diameter are 125µm.

2. Optical source
Usually lasers and LED are used as optical sources. The laser optical source is more expensive than the LED optical source, because of its light can be precisely controlled and has a high power. While the LED optical source is more dispersed, these optical source is much used in MMF patch cord. And the laser optical source is usually used in SMF patch cord.

3. Bandwidth
Single-mode fiber has a higher bandwidth than multimode fiber.

4. The color of sheath
The sheath color is sometimes used to distinguish between single-mode patch cord and multimode patch cord. According to the TIA-598C standard, non military use, single mode patch cord uses yellow outer sheath, multi mode patch cord uses orange or aqua outer sheath. According to different types, some manufacturers use purple to distinguish high performance OM4 fiber and other types of fiber.

5. Transmission distance
MMF mainly used for short-distance optical communication, such as in a building or on a campus. Typical transmission speed is 100M/s, transmission distance is up to 2km（100BASE-FX）, 1 G/s can up to 1000m，10 G/s can up to 550m.

Compared with multimode fiber, single-mode optical fiber can support longer transmission distance, from 100Mbps Ethernet to 1G gigabit ethernet, single-mode fibers can support transmission distance more than 5000m.

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