What is the difference between Multimode and Singlemode fibre optic cable?

This article explains the differences between Multi-mode and Single-mode fibre and the maximum distance you can expect for different data rates from 100Mb to 40GbE on OM1, OM2, OM3, OM4 and OS1 fibre types.

Multimode and singlemode fibre

Fibre cables vary enormously, in the type of fibre, the construction and materials and the number of fibres present. Optical fibres are extremely thin strands of very high purity silica (glass), which transmit light from one end to the other with minimal loss.

Types of Fibre
There are two primary types of fibre - multimode and singlemode.

Multimode fibre can carry multiple light rays (modes) at the same time by having varying optical properties at the core; essentially light travelling the shortest path (down the middle) travels the slowest.The larger core simplifies connections and takes advantage of the lower cost LED & VCSEL technologies which operate in the 850nm window. Due to dispersion the range is limited so it tends to be used as premises cabling when less than a kilometre. It comes in two core sizes, 62.5 and 50 microns.

Singlemode fibre has a much smaller core size of 9 microns and has a single light path and can travel much longer distances of up to 100km. These require more expensive electronics which operate in the 1310 and 1550nm windows and are typically used in longer distance LAN's, Cable TV and telephony applications.

Fibre Optic Cable Transmission Distances

These are the industry standard minimum distances achieved with each fibre type, however some cable manufacturers offer enhanced cables which exceed these. It's always best to check the manufacturers specification.  

The table below shows distances for ratified standards only.

Fibre Distances

There are some exceptions to these distances.

1. You can extend the Gigabit transmission distance for all types of multi mode fibre optic cable to 2km with proprietary Gigabit extenders.  This is useful when you already have fibre cabling installed and additional performance is required. 

2. By using singlemode modules and a mode conditioning cable, you can increase the range on OM1 fibre optic cable to 550m.

For a printed version of this page and other Fibre Optic FAQ's, please request a Fibre Optic Guide here and we will post a copy to you. 

For costs and information on bulk fibre cables, assemblies, panels and more see our fibre products section here.

If you need any further help or advice please give us a call on 01488 685800 or fill in our Contact us form

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