Singlemode vs Multimode Fiber Optic Cable

Fiber optic cables are being widely used in telecommunication and data networks around the world. Small networks like branch offices and large corporate offices having multiple campuses are making use of the fiber optic technologies to provide their users a reliable and efficient network.

 

Fiber optic cables use light as the medium to transfer the data signals from one end to the other end. Unlike the copper or coaxial cables, there is no electric pulse or current involved in the transmission of signal through a fiber optic cable. Fiber optic cables are available in two main categories, i.e. single-mode fiber and multimode fiber. This article will look into the details of the two types of fiber optic cables and portray the differences, benefits and use cases for both types of fiber.

 

Single-mode Fiber Optic Cable

 

Single-mode fiber optic cables are designed in such a way that it allows light to travel straight down the fiber core with least amount of diffraction and reflection. The light travels from source to the destination in a straight line. The core of the single-mode fiber optic cable is very thin, usually in the range of 8.0 - 10.5 micrometers. Single-mode fibers, due to their thin core and less reflection characteristics, are able to carry the signals over longer distances and achieve very high data transfer rates as compared to the multimode fiber optic cables.

 

The above-mentioned characteristics are beneficial for transmission networks that cover a very large geographical area, however, the increased efficiency is required in the transceivers of the single-mode fiber optic cables. Usually, a very precise and high intensity laser beam is used as a source of light in single-mode fiber optic transceivers. This results in higher costs of the transceivers. On the other hand, the thin core proves to be economical as far as the cost of the fiber optic cable is concerned.

 

From the above-mentioned arguments, it can be inferred that the single-mode fiber is useful for those networks where there is a requirement for high bandwidths (typically in the range of 10 Gbps – 100 Gbps), and longer distance links. The cost of installing a single-mode fiber optic network is justified in those cases.

 

Multimode Fiber Optic Cable

 

Multimode fiber optic cables are constructed in such a way that it allows light to travel through different paths inside the core of the fiber optic cable. The reason behind this is that the core of multimode fiber optic cable is thicker than that of the single-mode fiber optic cable. The core of multimode fiber optic cable is in the range of 50 – 100 micrometers. This thicker core allows the light to reflect and refract inside the core of the fiber optic cable and create multiple “modes” of the light.

 

The larger core of the multimode fiber optic cable also allows the use of light emitting diodes (LEDs) to be used as the light source for its transmission. This results in to the lower cost of allied electronics and transceivers for the multimode fiber optic cable.

 

The limitation for multimode fiber optic is the distance and bandwidths. Due to the less precise electronics and losses due to reflection and refraction, the multimode fiber optic cable is unable to carry the data over longer distance links and is also not capable to provide higher bandwidths. Several types of multimode fiber optic cables are available such as OM1, OM2, OM3 and OM4. The widely used 10 Gbps bandwidth is supported by OM4 fiber optic cable up to a distance of 400 meters only.

 

In the light of above facts, it can be concluded that the single-mode and multimode fiber optic cables are equally useful and beneficial if deployed in their relevant use cases. Single-mode fiber optic cable is beneficial for larger networks and multimode fiber optic cable is useful in smaller office networks where the maximum link distance is not a limiting factor. Multimode fiber optic networks are economical and present an excellent use case for such type of networks.