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What are the models of multimode fibre? A Beginner's Guide
Industry Dynamic + 2023.11.06

Multi-mode fibre abbreviation MMF (Multi-Mode Fiber ) "OM" stand for optical multi-mode, i.e. optical mode, is a multi-mode optical fibre to indicate the standard of optical fibre grade. Different grades of transmission with different bandwidth and maximum distance, from the following aspects to analyse the difference between them.

First, OM1, OM2, OM3 and OM4 optical fibre parameters and specifications comparison

1, OM1 refers to 850/1300nm full injection bandwidth in 200/ above the 50um or 62.5um core diameter multimode fibre;

2, OM2 refers to 850/1300nm full injection bandwidth in 500/ above 50um or 62.5um core diameter multimode fibre;

3, OM3 is 850nm laser-optimised 50um core diameter multimode fibre, which can reach 300m in 10Gb/s Ethernet using 850nm VCSEL;

4, OM4 is the upgraded version of OM3 multimode fibre, the fibre transmission distance can reach 550m.

TypeFibre diameter(μm)Fibre Type1 Gigabit Ethernet 1000BASE-SX1 Gigabit Ethernet 1000BASE-LX10Gbps Ethernet 10GBASE40Gbps Ethernet 40GBASE SR4100Gbps Ethernet 100GBASE SR4
OM162.5/125Multimode275m550m33mNot supportedNot supported
OM250/125Multimode550m550m82mNot supportedNot supported
Single mode9/125Single mode5km at 1310nm5km at 1310nm10km at 1310nmN/AN/A

To learn more about optical module packaging you can refer to this article:100G QSFP28

Second, OM1, OM2, OM3 and OM4 optical fibre design comparison

1, the traditional OM1 and OM2 multimode optical fibre from the standard and design of the LED (Light Emitting Diode light-emitting diode) mode as the basic light source, while OM3 and OM4 are optimized on the basis of OM2, so that it is also suitable for the transmission of the light source for the LD (Laser Diode laser diode);

2. Compared with OM1 and OM2, OM3 has higher transmission rate and bandwidth, so it is called optimised multimode fibre or 10 Gigabit multimode fibre;

OM4 is optimised on the basis of OM3 and has better performance.

Third, OM1, OM2, OM3 and OM4 optical fibre functions and features comparison

1, OM1: core diameter and numerical aperture is larger, with a strong ability to collect light and anti-bending characteristics;

2, OM2: core diameter and numerical aperture are smaller, effectively reducing the mode dispersion of the multimode fibre, so that the bandwidth increases significantly, the production cost is also reduced by 1/3;

3, OM3: the use of flame-retardant jacket, which can prevent the spread of flames, prevent the emission of smoke, acid gases and poisonous gases, etc., and to meet the needs of the 10 gb / s transmission rate;

4, OM4: developed for VSCEL laser transmission, the effective bandwidth is more than double than OM3.


IV. Comparison of OM1, OM2, OM3 and OM4 fibre applications

1, OM1 and OM2 over the years is widely deployed in the internal applications of the building to support the maximum value of 1GB of Ethernet road transmission.

2, OM3 and OM4 fibre optic cables are usually used in data centre cabling environments, supporting 10G or even 40/100G high-speed Ethernet transmission.

V. When to use OM3 fibre optic patch cables?

OM3 optical fibre is designed to work with VCSELs and conforms to the OM-3 optical fibre specification of ISO/IEC11801-2nd to meet the needs of 10 Gigabit Ethernet applications.OM3 optical fibre is available in a variety of types including indoor, indoor/outdoor universal, etc., with fibre counts ranging from 4 cores to 48 cores. It also supports all applications based on older multimode 50/125 fibre, including support for LED light sources and laser light sources.

1, using OM3 optical fibre system to transmit Gigabit Ethernet transmission distance can be extended to 900 meters, which means that when the distance between the building is more than 550 meters away from the user does not have to use expensive laser devices.

2, in the 2000 m distance, OC-12 (622Mb / s) rate range of various cases can be used in the standard 62.5/125μm multimode fibre, outside of single-mode fibre will be used. However, the emergence of OM3 multimode fiber has changed this situation, as OM3 fiber can improve the transmission distance of Gigabit and 10 Gigabit systems, the use of 850nm wavelength optical modules and VCSEL supporting the use of the most cost-effective cabling solutions.

3, when the link length of more than 1,000 m, single-mode fibre is still the only choice, single-mode fibre in the Gigabit system can be achieved in the 1310nm wavelength of the transmission distance of 5km, in the 10Gigabit system to achieve the transmission distance of 10km.

When the link length is less than or equal to 1000m, OM3 50μm multimode fibre can be used in Gigabit system, while single mode fibre should be used in 10G system.

5, when the link length is less than 300 m, OM3 multimode fibre can be used in any Gigabit and 10 Gigabit system.

VI. When to use OM4 fibre optic patch cords?

For a typical link, the cost of optical modules is about expensive. Although single-mode fibre is cheaper than multimode fibre, the use of single-mode fibre requires very expensive 1300nm optical modules, which cost about 2-3 times as much as 850nm multimode optical modules. Taken together, a multimode fibre system costs far less than a single-mode fibre system.

When investing in fibre optic cabling, if you can consider increasing the initial investment in cabling and using better multimode fibre, such as OM4 fibre, you can ensure that you make full use of the current multimode fibre technology and reduce the overall cost of the current system; when the system needs to be upgraded to higher speed systems, such as 40G and 100G, OM4 can still be used and will be more cost-effective.

In conclusion, when the transmission rate is greater than 1Gb/s, the use of multimode fibre is a good choice for the system. When higher rates are required, the following are our guidelines for selecting OM4 fibre:

1. For Ethernet users, in 10Gb/s system transmission, the transmission distance can reach 300m to 600m; in 40Gb/s and 100Gb/s system, the transmission distance is 100m to 125m.

For campus network users, OM4 fibre will support 4Gb/s fibre link length of 400m, 8Gb/s fibre link length of 200m or 16Gb/s fibre link length of 130m.


Multimode fibre technology has been developed from OM1 multimode to now support 10Gbps OM4, which will enable the user's investment to get the most effective return, become the backbone cabling or the best choice of fibre to the desktop solution.