How to choose single-mode fiber and multi-mode fiber in integrated wiring project?
1. What is a single-mode fiber
Single-mode fiber (SingleModeFiber): The central glass core is very thin (core diameter is generally 9 or 10 μm), and only one mode of fiber can be transmitted. Therefore, its intermodal dispersion is very small, suitable for long-distance communication, but there are still material dispersion and waveguide dispersion, so single-mode fiber has higher requirements on the spectral width and stability of the light source, that is, the spectral width should be narrow and the stability 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 their sizes are exactly equal. 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 practical optical fiber communication systems. Determined in, so this fiber is also called G652 fiber.
2. What is multimode fiber
A fiber that transmits multiple modes at a given operating wavelength. According to the distribution of its refractive index, it can be divided into sudden type and gradual type. The numerical aperture of ordinary multimode fiber is 0.2±0.02, the core diameter/outer diameter is 50μm/125μnu, and its transmission parameters are bandwidth and loss. Since there are hundreds of modes transmitted in multimode fiber, the propagation constant and group velocity of each mode are different, so the bandwidth of the fiber is narrow, the dispersion is large, and the loss is also large. It is only suitable for short-to-medium distance and small-capacity optical fiber communication systems. .
Multimode fiber allows different modes of light to be transmitted on one fiber. Since the core diameter of multimode fiber is relatively large, cheaper couplers and connectors can be used. The core diameter of multimode fiber is 50 μm to 100 μm.
The selection of single-mode optical cable in the integrated wiring project will consider the following points:
Single Mode Fiber: The central core is very thin (the core diameter is generally 9 or 10 μm), and only one mode of light can be transmitted. Therefore, its intermodal dispersion is very small, suitable for long-distance communication, but there are still material dispersion and waveguide dispersion, so single-mode fiber has higher requirements on the spectral width and stability of the light source, that is, the spectral width should be narrow and the stability better.
It was later found that at a wavelength of 1310nm, the total dispersion of single-mode fiber is zero. From the point of view of the loss characteristics of the optical fiber, 1310nm is just a low loss window of the optical fiber. In this way, the 1310nm wavelength region has become an ideal working window for optical fiber communication, and it is also the main working band of practical optical fiber communication systems. The main parameters of 1310nm conventional single-mode fiber are determined by the International Telecommunication Union ITU-T in the G652 recommendation, so this fiber is also called G652 fiber.
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