The core of multimode fiber is thick, the transmission speed is low, the distance is short, the overall transmission performance is poor, but its cost is relatively low, it is generally used in the environment of buildings or adjacent geographical locations. Another type of optical fiber with a diameter of 1310nm or 850nm is easy to work with. It can transmit multiple modes at a given wavelength. Compared with twisted pair, multimode fiber can support longer transmission distance. In 10 Mbps and 100 Mbps Ethernet, multimode fiber can support the longest transmission distance of 2000 meters. The core diameters of common multimode fibers are 50 μ m, 62.5 μ m and 100 μ M.
Single mode optical fiber can only allow one beam of light to propagate, so single-mode fiber has no mode dispersion characteristics. Therefore, the core of single-mode fiber is relatively thin, with wide transmission band, large capacity and long transmission distance. However, due to the need of laser source, the cost is high.
Single mode fiber has only one strand (two strands in most applications) of glass fiber with a core diameter of 8.3 μ m ~ 10 μ M. Due to the relatively narrow core diameter, single-mode fiber can only transmit optical signals with wavelength of 1310nm or 1550nm, so it is relatively difficult to couple with optical devices. The bandwidth of single-mode fiber is higher than that of multimode fiber, but at the same time, it also puts forward higher requirements for the spectral width and stability of the light source: the spectral width should be narrow, and the stability should be good. Due to the small dispersion of single-mode fiber, only one mode of light can be transmitted, so large capacity and long-distance transmission can be realized.
For the single-mode optical module, LD or LED with narrow spectral line is generally used as the light source, and the coupling component size is matched with the single-mode fiber, which can achieve high-speed transmission. Single mode optical fiber is widely used in WDM and other multi frequency data transmission application systems. The multiplexed optical signal can be transmitted with only one single-mode fiber.
Single mode fiber or multimode fiber?
In security applications, the most common determinant of multimode or singlemode is distance. If it's only a few miles, multimode is preferred. Because led emitters / receivers are much cheaper than lasers needed for single mode. If the distance is greater than 5 miles, single mode fiber is the best. Another issue to be considered is broadband. If future applications may include the transmission of large bandwidth data signals, then single mode will be the best choice.
