Hello, community members.
Fiber optics and fiber optic cables are an integral part of our network, and today single-mode fiber (SMF) and multi-mode fiber (MMF) cable types are widely used in a variety of applications.
But do you know the difference between them? Today, I want to learn and discuss with you.
Single-Mode Fiber
The central glass core of a single-mode optical fiber is very thin (the core diameter is generally 9 or 10 μm) and can transmit only one mode of optical fiber. Therefore, the inter-mode dispersion is small and is suitable for long-distance communication. However, material dispersion and waveguide dispersion still exist. In this case, the single-mode fiber has high requirements on the spectrum width and stability of the light source, that is, the spectrum width should be narrow and the stability should be good.
Multi-Mode Fiber
Multimode optical fibers transmit optical fibers of multiple modes at a given operating wavelength. According to the distribution of refractive index, it can be classified into the abrupt type and gradual type. The numerical aperture of an ordinary multimode fiber is 0.2±0.02, the core diameter/outer diameter is 50 μm/125 μm, and the transmission parameters are bandwidth and loss.
As there are hundreds of transmission modes in a multimode optical fiber, the propagation constants and group rates of each model are different, so the optical fiber has a narrow bandwidth, large dispersion, and large loss. Therefore, the optical fiber is only suitable for medium-short-distance and small-capacity optical fiber communication systems.
Single-Mode vs Multi-Mode
The differences between single-mode and multi-mode optical cables lie in the core diameter, wavelength, light source, bandwidth, color jacket, distance, and cost.
Core diameter
The core diameter of a single-mode fiber is much smaller than that of a multi-mode fiber. Its typical core diameter is 9 μm, even if other core diameters are available. In contrast, multimode fiber core diameters are typically 50 μm and 62.5 μm, giving them higher "light-gathering" capabilities and simplified connections. Single-mode and multi-mode fibers have a cladding diameter of 125 μm.
Wavelength & Light Source
Due to the large size of the core of multimode fibers, some low-cost light sources are used in multimode fibers, whereas single-mode fibers usually use lasers or laser diodes to generate the light injected into the cables. The wavelengths of common single-mode fibers are 1310 nm and 1550 nm.
Bandwidth
The bandwidth of a multimode optical fiber is limited by its optical mode. Currently, the maximum bandwidth is 28000 MHz x km of OM5 optical fiber. The bandwidth of a single-mode fiber is theoretically infinite because it allows only one mode of light at a time.
Color Sheath
Generally, single-mode optical cables are covered with yellow jackets, and multi-mode optical cables are covered with orange or light green jackets.
Distance
In addition, it should be noted that because core sizes of the multimode optical fiber and the single-mode optical fiber are different, transmission optical modules are also different. Therefore, single-mode and multi-mode fibers cannot be used together.
Finally, it can be concluded that the single-mode optical cable system is suitable for long-haul data transmission applications and is widely deployed in carrier networks, metropolitan area networks, and passive optical networks. Multimode fiber cabling systems have short distances and are widely deployed in enterprises, data centers, and LANs.
Thanks for reading!
