Different Application of Single-mode Fiber and Multi-mode Fiber

Optical fiber has the characteristics of fast transmission speed, long distance, safety and stability, anti-interference, and convenient expansion. We often see the long-distance data transmission requirements in building intelligent projects, basically using optical fiber transmission. In the process of use, I found that there is a difference between single-mode fiber and multi-mode fiber in optical fiber. What is the difference between multi-mode and single-mode fiber, and what kind of occasions are they suitable for? :
Both single-mode fiber and multi-mode fiber are used for long-distance high-quality transmission of data. The difference is that light is transmitted in different ways. Light in single-mode fiber propagates along a straight line without reflection, so its propagation distance Very far. The multimode fiber can carry the transmission of multiple optical signals.

Single-mode fiber is an optical fiber with only one strand (two strands in most applications) of glass fiber, with a core diameter of 8.3 μm to 10 μm, and only one transmission mode. The bandwidth of single-mode fiber is higher than that of multimode fiber, but it has higher requirements on the spectral width and stability of the light source, that is, the spectral width should be narrow and the stability should be good. The transmission rate of single-mode fiber is higher than that of multi-mode fiber, and the transmission distance is more than 50 times higher than that of multi-mode fiber. Therefore, its price is also higher than that of multi-mode fiber.

Compared with multimode fiber, the core diameter of single-mode fiber is much smaller. The characteristics of small core diameter and single-mode transmission make the optical signal transmitted in single-mode fiber not be distorted due to the overlapping of optical pulses. Among all fiber types, single-mode fiber has the lowest signal attenuation rate and the highest transmission speed.

Multimode fiber has a thicker central glass core (50 or 62.5 μm) and can transmit light in multiple modes. Multimode fiber can support a transmission distance of up to 2000 meters. The core diameters of common multimode fibers are 50 μm, 62.5 μm and 100 μm. 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. , has been slowly replaced by single-mode fiber, and is basically rarely used. Price: multi-mode is cheap, single-mode is expensive; distance: multi-mode is less than 2KM, single-mode can transmit 100KM; left and right wavelengths: multi-mode 850/1310NM, single-mode 1310/1550NM.

In actual application, if the transmission distance is generally long, use single-mode fiber, and if the distance is short, use multi-mode fiber. The single-mode ones generally have two cores, one core for receiving and the other for transmitting; there are also single-fiber bidirectional ones that use one core, and realize bidirectional transmission on the same core through WDM technology. Single-mode optical fiber wavelength division multiplexer WDM, multi-mode has two cores, there is no single-core, because multi-mode optical cables cannot be used for WDM. Transceivers for single-mode fiber are more expensive than transceivers for multimode fiber.

Single-mode optical fiber has basically replaced multi-mode optical fiber. The relevant optical fiber for communication and weak current is basically single-mode optical fiber. Unless the owner has special requirements, multi-mode optical fiber will basically not be used.