Views: 0 Author: Site Editor Publish Time: 2022-10-10 Origin: Site
Before understanding the difference between single mode and multimode, we need to know that light propagates in a fiber as a set of independent beams. These beams that travel at a specific angle to the axis of the fiber are called modes. We can distinguish single-mode and multi-mode by transmission mode, single-mode fiber supports one mode while multi-mode fiber supports multiple modes. The following will analyze the differences between single-mode and multi-mode fibers from five aspects.
1. Different transmission modes
Single-mode fiber transmits in one mode, while multimode fiber tends to have hundreds of transmission modes.
2. Different core sizes
Multimode fibers have a larger core diameter than single-mode fibers, typically 62.5 or 50 um, while single-mode fibers have a core diameter of about 9 um.
3. Relative refractive index difference
The relative refractive index difference between the core and cladding of multimode fiber is much larger than that of single mode fiber, generally ~1%, or ~2%, or higher, while the relative refractive index difference of single mode fiber is generally less than 0.4%.
4. Refractive index profile
The pulse broadening caused by the different arrival times of multiple modes at the receiving end is called modal (intermodal) dispersion, which greatly reduces the bandwidth of the fiber. To solve this problem, multimode fibers use graded index, which enables different modes to reach the receiving end at the same time. And single-mode fiber supports only one mode, so there is no such concern, so it is usually a step index.
5. Application scenarios
The multiple modes of multi-mode fiber will lead to pulse broadening, and its bandwidth is lower than that of single-mode fiber, so it is mainly used for short-distance transmission, such as local area networks, data centers, etc. The single-mode fiber has a long transmission distance and is mainly used in scenarios such as metropolitan area networks and backbone networks.
