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When to Choose Single-mode Fiber and When, Multi-mode Fiber?

Views: 56 views Publish Time: 2022-04-29

Nowadays, optical fibers are widely used in network construction due to their high speed, among which single-mode optical fibers and multi-mode optical fibers are the most common. There are still many questions asked about the differences and application of these two fiber types. In the following, we will analyze the differences between single-mode fiber and multi-mode fiber in depth, in terms of their basic structure, transmission distance and cost.

1.Basic structure comparison

The basic structure of an optical fiber is generally composed of an outer sheath, a cladding, a core, and a light source. The differences between single-mode fiber and multi-mode fiber are as follows:

1.1. Outer jacket color difference

In practical applications, the outer jacket color of the fiber can be used to quickly distinguish single-mode fiber from multi-mode fiber. According to the definition of the TIA-598C standard, single-mode fibers OS1 and OS2 use yellow outer sheaths, while multi-mode fibers OM1 and OM2 use orange outer sheaths, and OM3 and OM4 use aqua blue outer sheaths (for non-military purposes).

1.2. Core diameter difference

The core diameter of multimode fiber and single mode fiber is significantly different, the core diameter of multimode fiber is usually 50 or 62.5µm, while the core diameter of single mode fiber is 9µm. Because of this, a single-mode fiber can only transmit optical signals with a wavelength of 1310nm or 1550nm on a narrow core diameter, but the advantage of a small core is that the optical signal propagates along a straight line in single-mode fiber without refraction, with low dispersion and high bandwidth. In comparison, the core of the multi-mode fiber is wide, it can transmit multiple modes at a given operating wavelength, but at the same time, as there are hundreds of modes transmitted in the multimode fiber, the propagation constants and group rates of each mode are different, making the fiber have narrow bandwidth, large dispersion, and large loss.