Single mode vs multimode fiber

1. Single Mode Fiber
2. Multi Mode Fiber
3. OM1, OM2, OM3, OM4, OS1

1. Single Mode vs Multimode Fiber

Fibre optic cabling is a very common aspect of most structured cabling installations. Therefore
crossing the correct type of fibre cable is imperative to the successful operation of your technology.
In addition within those types you need to choose the correct category within that cable type
bracket.
Therefore we compare Single Mode vs Multimode Fiber and the differences between them
All fibre cables are constructed of individual cores with which within the light is transported from
transmitter to receiver. This cores are mode of either glass or plastic. Furthermore that consist of the
actual inner core and the cladding surrounding and protecting that tube. In addition fibre cables can
contain numerous cores within a single cable. Thus bundles of 4,8,12,16,24,48 are commonly founds
in a single fibre optic cable.
Further articles on Fibre Optics and FAQ's can be found on our Fibre Optic Knowledge Centre HERE
Singlemode Fiber
The terminology of a singlemode fiber comes from the situation that is transmits a single mode of
light down its cores. The transmission is via a laser from the transmitting device. A single mode of
light its transported directly the core with minimal reflection within
The inner core is smaller than its counter part for this reason and is referred to as 9/125. This is a 9
micron diameter core coated in a 125 micron cladding. Due to the transmission properties there is
less dispersion of light as it travels along the core and therefore there is less loss of the original
signal. Thus singlemode fiber is more suited to higher bandwidth requirements. Furthermore it is
more suited to longer transmission distance applications.
The cable is categorised into 2 sub sections.
 OS1
 OS2
OS1 and OS2 differ mainly in their cable construction. Thus OS1 is commonly a tight buffered
construction and for internal applications. Likewise OS2 is usually a blown fibre or loose tube
construction and for external purposes
They have similar transmission characteristics. However due to less attenuation (transmission loss)
on OS2 cables it can transmit similar speeds over longer distances. For example some
manafacturers will state OS1 transmitting 10GBE up to 2km and OS2 transmitting 10GBE upto 10km
This is due to the attenuation loss on OS1 being 1dB/km and Os2 being 0.4dB/km. Less attenuation
equals greater transmission range
Due to the specialist equipment for transmission the overall cost of a single-mode system is higher
than that of multi-mode. However the cable can cheaper to purchase and is the same cost to install.
Multimode Fiber

2. Multimode receives it names in an opposite way to its counterpart. Multiple / Many modes of light
are transmitted down its core all of which travel are different wavelengths are in a different path.
The light source is usually an LED source
Thus the light is similar to that of shining a torch into the core. Subsequently there is greater modal
dispersion (Loss) of the light as it travels.
For this reason multimode doesn't have the same transmission distance capability as singlemode.
The cores in a multi-mode fibre are considerably larger than single-mode. 4 of the main categories
are 50/125 and the legacy OM1 is 62.5/125. Notice that the cladding for all fibre cables remains the
same and only the internal core size changes
The 5 categories of multi-mode fibre are
 OM1
 OM2
 OM3
 OM4
 OM5
Each category is an improvement on its predecessor. Therefore this results in a greater ability to
transmit greater bandwidth. Further higher grades are able to transmit the same speeds as the
previous grade but over longer distances.
The Chart below compares the different cables and their transmission capabilities

3. Single Mode vs Multimode Fiber Summary
Core Sizes
Singlemode are 9/125 microns
Multimode are 50/125 microns and in the OM1 category 62.5/125
Transmission
Singlemode uses a single mode of light transmitted via a laser light source
Multimode used many modes of light via a LED light source
Distance Limitations
Singlemode are commonly used up to 2km and often beyond to 10km
Multimode are limited to 550m performance and therefore mainly used internally or on small
campus plots
About NM Cabling Solutions - Network Cabling Specialist
NM Cabling is a technology and structured cabling integrator working throughout the United
Kingdom.
We have created a comprehensive Knowledge Centre for our industry which can be viewed
at https://www.nmcabling.co.uk/knowledge-centre/