single mode vs multimode fiber

Single Mode vs Multimode Fiber

Fiber optic cables include single mode and multimode fiber, single mode can only propagate one type of mode, and multimode can propagate multiple modes. Fiber optic cable comprises a core, cladding, and a buffer. The core is the central part of the fiber where the light travels. Single-mode fiber has a smaller core and only one pathway of light or mode of propagation. The smaller core size leads to lower attenuation allowing for longer transmission distances and higher bandwidth. Instead, multimode fiber has a large core that supports multiple simultaneous light modes. This means that more types of data can be transferred. In addition, the larger core leads to higher attenuation than single-mode fiber, limiting bandwidth and transmission distance.

single mode vs multimode fiber

However, multimode fiber is easier to install due to its larger cores, which are easier to align. On the other hand, multimode fiber is less expensive than single-mode fiber optic cable. The differences between single-mode and multi-mode fiber affect bandwidth, transmission distance, cost, installation, etc. So, what is the difference between single-mode and multimode fiber optic cables? What factors should be considered when choosing between these two fiber types? The following is a detailed introduction.

Difference between single mode vs multimode fiber

Fiber Core

Single-mode cable has a small fiber core much smaller than multimode fiber. Its typical core diameter is 8-10 µm. The multimode fiber core diameter is 50 µm and 62.5 µm typically.

Transmission Distance

Single-mode fiber supports long-distance transmission, while multimode optical fiber is designed for short-distance runs. Single-mode fiber can go as far as 40 km or more. The maximum transmission distance of multimode fiber is between 300 and 500 meters. Generally, single-mode fiber is used for lengths greater than 500m, and multi-mode fiber is less than 500m.

Bandwidth

Single-mode fibers have a higher bandwidth capability than multimode fibers. Single-mode fiber can only have one signal/ray of light that can pass through the fiber at a time. So, its bandwidth is unlimited theoretically. On the other hand, multimode fiber bandwidth is limited by its light mode. This caps the bandwidth and leads to five grades of multimode fiber each with different bandwidth and distance capabilities.

Attenuation

Multimode fibers tend to have higher attenuation than single-mode fibers. Single-mode fiber works with lasers at operating wavelengths with less signal attenuation or degradation of a signal. Multimode fibers rely on the transmission of multiple light modes with less brightness and higher attenuation.

Wavelength & Light Source

Single-mode fibers can be classified as the OS1 and OS2 types, fiber wavelength is 1310 nm and 1550 nm. Single-mode fiber often uses a laser or laser diode to produce light injected into the cable. Due to the large core size of multimode fiber, some low-cost light sources that work at the 850nm and 1300nm wavelengths are used in multimode fiber cables.

Sheath Color

According to the TIA-598C standard definition, single-mode fiber is coated with a yellow outer sheath, and multimode fiber is coated with an orange or aqua jacket.

Terminate Fiber

Single-mode fiber is more difficult than multimode fiber to terminate due to its smaller core size.

Cost

Multimode fiber systems are much cheaper than single-mode fiber systems and are considered more cost-effective. Single-mode fibers require more expensive active equipment, such as electronics and laser transmitters. Whereas multimode fibers utilize cheaper electronics, thus leading to lower overall system costs.

In conclusion

Choosing the right fiber cable comes down to what you need for your specific application. Single mode fiber is ideal for long-distance data transmission applications, including CATV, carrier networks, MANs, PONs, etc. Multimode fiber is perfect for lighter-capacity bandwidth and shorter-distance applications like general data and voice applications, such as adding segments to an existing network.

 

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