By szrollball | 20 June 2017 | 0 Comments
What are the differences between Single-mode fiber and multimode fiber?
Single Mode Fiber
Single-mode fiber has only one (in most applications for two shares) glass fiber, core diameter of 8.3μm ~ 10μm. As the core diameter is relatively narrow, single-mode fiber can only transmit the wavelength of 1310nm or 1550nm optical signal, and the optical device coupling is relatively difficult. The bandwidth of the single-mode fiber is higher than that of the multimode fiber, meanwhile, it also demands a higher width and stability of the light source: the spectral width is narrower and the stability is better.
As the single-mode fiber dispersion is small, only the transmission of a mode of light, so can achieve large capacity, long-distance transmission. In 100Mbps Ethernet and 1G Gigabit network, single-mode fiber can support more than 5000m transmission distance. Because the single-mode fiber core diameter is too small, it is difficult to control the beam transmission, so the need for extremely expensive laser as a light source, coupled with its transmission rate than the multi-mode fiber, transmission distance higher than the multi-mode fiber at least 50 times, The cost of fiber is higher than that of multimode fiber.
For single-mode optical modules, the general use of LD or narrow spectrum of the LED as a light source, the coupling component size and single-mode fiber to match, can achieve high-speed transmission.
Compared with multimode fiber, single-mode fiber core diameter is much smaller, small core and single-mode transmission characteristics of the single-mode fiber in the transmission of optical signals will not be because of light pulse overlap and distortion. In all fiber types, single-mode fiber has the lowest signal decay rate and maximum transmission speed.
Single-mode fiber is widely used in multi-frequency data transmission applications such as WDM (Wave-Division Multiplexing). The multiplexed optical signal only needs to use one single-mode fiber to realize data transmission.
Multi Mode Fiber
Multimode fiber is another common type of fiber, the core diameter of 50μm ~ 100μm, the working wavelength of 850nm or 1310nm, with the optical device coupling is relatively easy. It can transmit multiple modes at a given operating wavelength.
Compared to twisted pair, multimode fiber can support a longer transmission distance, in 10mbps and 100mbps Ethernet, multi-mode fiber can support up to 2000 meters transmission distance. The common multi-mode fiber has a core diameter of 50 μm, 62.5 μm and 100 μm.
As the multi-mode fiber transmission mode up to hundreds of each mode of the propagation constant and group rate is different, so that the fiber bandwidth narrow, large dispersion, loss is also large, which limits the transmission of digital signal frequency, In the short distance, small capacity optical fiber communication system, generally only a few kilometers.
Different from the single-mode optical module, multi-mode optical module generally use the lower price of the LED as a light source, coupling parts and multi-mode multi-mode fiber to achieve the desired transmission effect.
Compared with single-mode fiber, multimode fiber cost is low. Based on the actual needs, most of the local area network fiber used in multi-mode fiber.
Single-mode fiber for long-distance transmission, high prices; multi-mode fiber for short-distance transmission, low prices. In the choice of fiber jumpers, can not blindly choose, we must first clear their own needs, for what kind of wiring system and how far away the transmission distance, according to the needs of their own choice of fiber.
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