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What is the full name of SMF and MMF? What is its definition?

The full name of SMF is Single Mode Fiber.

Single Mode Fiber is a fiber that can only transmit and insert one mode at a specified wavelength. The central glass core is very thin (the core diameter is generally 9 or 10 μm). Therefore, its intermodal dispersion is very small, which is suitable for long-distance communication. Due to material dispersion and waveguide dispersion, single-mode fiber has higher requirements on the spectral width and stability of the light source, that is, the spectral width is narrower and the stability is better. Later, it was found that at the wavelength of 1.31 μm, the material dispersion and the waveguide dispersion of the single-mode fiber are positive and negative, and the magnitudes are exactly the same. In this way, the 1.31μm wavelength region has become an ideal working window for optical fiber communication, and it is also the main working band of the practical optical fiber communication system. OK, so this fiber is also called G652 fiber. Single-mode fiber can be divided into 652 single-mode fiber, 653 single-mode fiber and 655 single-mode fiber.

The full name of MMF is Multi Mode Fiber.

Multimode fiber transmits multiple modes of fiber at a given operating wavelength. According to the distribution of its refractive index, it is divided into abrupt type and graded type. The numerical aperture of ordinary multimode fiber is 0.2±0.02, the core diameter/outer diameter is 50μm/125μm, and its transmission parameters are bandwidth and loss. Since there are hundreds of modes transmitted in multimode fiber, the propagation constants and group rates of each mode are different, which makes the bandwidth of the fiber narrow, the dispersion large, and the loss also large. It is only suitable for short-to-medium distance and small-capacity optical fiber communication systems .

Multimode fiber allows light of different modes to be transmitted on one fiber. Due to the large core diameter of multimode fiber, cheaper couplers and connectors can be used. The core diameter of multimode fiber is 50 μm to 100 μm.