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Fibre Optic Cable Transmission Speed

Fiber optic cable transfers data via pulses of light which travel through either plastic or glass cores. Thus fibre optic cable transmission speed will be dependent on several factors such as

  • Category of fibre optic cabling
  • The quality of the installation of the main cable runs
  • The quality of the terminations
  • What type of environment that it is present in

What is Fibre Optic Cable?

Fiber Optic cable differs from traditional data cabling in that it uses pulses of light to transmit signals along a cable constructed of individual plastic or glass cores. Therefore this different from traditional data cabling where signals are sent using electrical signals down copper conductor wires.

Fiber Optic cables are categorised into two main sections

  • Singlemode Fiber Optic Cable
  • Multimode Fiber Optic Cable

These main categories can be further split into sub categories in each cable. Thus singlemode has OS1 and OS2. Furthermore Multimode has OM1 through to Om5

Both categories are similar in that they both work on a send and receive protocol. Therefore transmit signals are sent down one core from A to B and then the return signal is sent back by a second core from B to A

In addition both types of cable can come in multiple cores wrapped in an outer protection sheath. In a single fibre cable its common to find 4, 8, 16, 32, 64 and more fibre cores wrapped into a single cable. This is the same for both singlemode fibre and multimode fibre

The different in the two categories is 1) How the cores and constructed and 2) The transmission hardware used with the cable

Singlemode Fiber Optic Cable

Singlemode consists of a 9 micron diameter inner core and wrapped in a 125 micron outer cladding. The cladding keeps the light within the inner core from escaping and losing signal.

Transmission is undertaken in the 1310 and 1550nm windows and the cable is usually the choice of longer distance or higher speed at distance communications

This type of cable uses a laser technology to transmit a straight laser light down the center of the core. Therefore in this manner a very low loss is achieved as there is little loss of light due to interference from the inner of the glass core. However the hardware to transmit is a higher entry point of technology

Singlemode Fiber Distances

The major of advantage of fiber cabling over copper data cabling is its ability to transmit speeds over a much longer distance.

Singlemode fibre will transmit 1 Gigabit up to 100km and 10Gig Through 100 Gig up to 40Km dependent on the hardware use din transmission and receiving. Multimode is alot more limited in distance when it compares in transmission

Multimode Fiber Optic Cable

Singlemode consists of either a  50 micron or 62.5 micron diameter inner core and wrapped in a 125 micron outer cladding. However the 62.5 micron core type is a legacy cable now and rarely seen in new installations. The 50 micron core categories are OM2, OM3, OM4, and Om5. Om 3 and Om4 are the main installation categories found in 2020 installations

Transmission is undertaken in the 850 and 1300nm windows and the cable is usually the choice of internal and localised external links within buildings.

The transmission in multimode is different to the singlemode laser beam type. Thus in multimode many “modes” of light are flooded into the central cable core. These light signals are travel in separate paths along the same core. As they travel they reflected back and forth within the inner class core. Therefore this creates light signals travelling at different speeds. In addition due to the reflecting signal is lost as it hits little infractions and bends within the cable and core.

Thus due to the different transmission type the transmission speed and distance possible is reduced in comparison. However the hardware and transmission cost is massively reduced. Therefore this type of cable is the choice of the majority of internal fibre optic cabling installations.

Multimode Fiber Distances

The following chart summarises the different categories of cable and their transmission abilities

Fibre Optic Cable Installation Chart












Fibre Optic Cable Transmission Speed – Summary

The choice of fibre optic cabling should always start with your expected transmission requirements. Those requirements should taken into consideration your current and future needs.

A common problem we see is where companies have had fibre cabling installed and either due to lack of knowledge or to save cost the installation isn’t suitable for their requirements. The connections still work and on the surface all looks ok but the infrastructure isn’t able to carry their transmissions without delays, slowness and or loss of signals

Therefore always start with the current and expected requirements and match the required fibre cabling from there. We are able to offer advice and free surveys to help you achieve the correct fibre optic cabling installation whether it is in London, The South or for national projects throughout the UK


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