Multimode Fibre Types

Introduction.
Multi-Mode Fibre(MMF) has been commercially available via distribution and deployed into simple networks, as far back as the early1970s. In the early days, the choice was quite simple, either 62.5/125um or 50/125um. Needless to say, Multimode was used for short links Data-Comm type applications. However, the demands for speed and data rates continue to escalate from 1Gbit/s and now 100Gbit/s, and we now have 5 multi-mode fibres to choose from all of which are application-specific they are OM1/2/3/4 & 5. Note OM1 is a 62.5/125 OM2-5 inclusive are 50/125 fibres.
We will use this opportunity to help you better understand Fibre types OM1-5, enabling you to make an informed decision on application and Fibre choice.

Multimode Fibre (MMF)
MMF is an optical Fibre with a comparatively large core, either 62.5/125 or 50/125um used in short-distance applications, such as Local Area Networks-LAN / CCTC / Data Centres & Campus environments. Due to the large core and the multiple paths of light, distance in a multi-mode Fibre is restricted, as a typical indicator 10Gbit/s approx. 550mtrs

 


How Many Types of Multimode Fibre?
The International Organisation for Standardisation – ISO 11801 controls and governs how we manage the specifying of the Fibre types. We have drawn up a table to help classify and understand each of the Fibre types from OM1-OM5. See Table 1 & 2 
In the table below we will consider - Cable Sheath Colour / Bandwidth / Distance / Data Rate / Core Size & Light Source.

Colour identifier    Classification    Size um    Fibre Type    Optical Source    Bandwidth MHz/Km    Practical
Application
Orange    OM1    62.5    Legacy    LED    200    Fast Ethernet
Orange    OM2    50    Legacy    LED    500    1GbE
Aqua    OM3    50    LOMMF    VSCEL    2000    10GbE
Magenta    OM4    50    LOMMF    VSCEL    4700    40GbE
Lime    OM5    50    WBMMF    VSCEL    28000    100GbE
Table 1

Typical Distance that Data can Travel. 
     1000BASE-SX    10GBASE-SR    40GBASE-SR4    100GBASE-SR10
OM1    275 m    33 m    Not specified    Not specified
OM2    550 m    82 m    Not specified    Not specified
OM3    Not specified    300 m    100 m    100 m
OM4    Not specified    400 m*    150 m    150 m
OM5    Not specified    400 m*    150 m    150 m
Table 2


OM1 Fibre 
This is a Legacy Fibre with a 62.5um core can normally be identified with Orange sheath typically internal cable. It is a legacy Fibre dating back to mid-1970 from a practical perspective at best a 1GbE. It was commonplace to use this on 100MegBit Ethernet application. If you were to use this on 10GbE, you would get a drive distance of 30mtrs. This uses an LED Light Source.
OM2 Fibre 
This is also a legacy Fibre with a 50um core can normally be identified with an orange sheath typically internal cable. It is a legacy Fibre dating back to mid-1970 from a practical perspective at best a 1GbE. If you were to use this on 10GbE, you would get a drive distance of 82mtrrs. This uses an LED Light Source.

OM3 Fibre
This also has a 50um core and comes with an Aqua sheath. The Fibre is optimised for VSCEL based equipment this Fibre "OM3" supports 10GbE at lengths up to 300mtr. It can be used on 40GbE, but it is more commonly used as the standard on 10GbE.i

OM4 Fibre 
This also has a 50um core, and the Fibre is optimised for Laser-based equipment. It is effectively an enhanced OM3 Fibre and is better able to deal with high bandwidths. The OM4 Fibre is fully backwards compatible with OM3 Fibre. The OM4 was developed specifically to operate with VSCEL based transmission equipment. It can handle 10GbE over 400mtrs & 40/100GbE up to 150mtrs (MTP/MPO connectorisatioin would have to be used)

OM5 Fibre 
The OM5 Fibre is the latest generation within the OM range of fibres. It also shares a 50um core the same as OM4/3/2. The OM5 is a WBMMF – Wideband Multi-Mode Fibre it to is also fully backwards compatible with OM4 fibre.OM5 cables can be identified with Lime green jackets. This Fibre can support 4 x WDM channels at a minimum speed of 28Gbps/Channel. We will shortly issue a specific paper on OM5. 

MMF – Multi-Mode Fibre Connector Types
There is a vast array of connectors available for assembly with MMF. Connectors have evolved over many years, so we have a combination of Legacy & Current standard in the market place.
Typical connector types SMA / ST / SC / FC / LC / MU / E2000 / MTRJ / DIN / MTP & MPO 
The higher the bandwidth / Faster speeds, the more accurate the connector needs to be. So on a 40GbE connection, it is improbable today, to use an SMA/ST or SC. Table 3 below gives typical application:-
Connector    Type of Connector    Application    Ferrule Ø mm
SMA / ST / SC / FC    Large     Legacy system 100mbE / CCTV / Lan / 1GbE     2.5
LC / MU / DIN / E2000    Small Form Factor     Lan 1-10-40GbE / Data centres / High Density     1.25
MTRJ     Special / Tyco         Special
MTP / MPO     Multi-Fibre On/Off    Data Centre preterminated solutions     NA
Table 3

Supply
If you need help on selection and supply, why not visit www.cmwltd.co.uk we are online ready to help.

Advantages of MMF 
Most of the Lan / Data Centre & Enterprise networks' applications are of a comparatively short distance compared with Telecoms / Wide Area Networks (WAN) & Metro. MMF can support all the major transmission protocols – Ethernet / Internet.
MMF is relatively easy to install handle and terminate. The associated active equipment is LED-based significantly cheaper than the Single-mode Laser based equipment. It would be difficult and very costly to use single-mode Fibre and equipment at short distances from a practical perspective. This, combined with an increased skill set needed to handle SMF, makes MMF the most cost-effective solution for the Lan / Data Centre & Enterprise Networks. The performance of MMF continues to develop, given the evolution which has already taken place OM1-OM5 this evolution has been driven by market/system demands this evolution will continue to meet the challenges of the future.

Conclusion
The market is currently driven by application. We have 2 distinct areas Telecom- SMF & Data Comms MMF. The MMF market continues to evolve, making increasing demands on the MMF Fibre, and the Fibre manufactures continue to develop the capability of MMF. The systems and active equipment interfacing with MMF are also moving at a pace. I do not see any point in the future where SMF will be substituted into MMF networks for a reason detailed earlier. These are 2 distinct and mutually exclusive area within the Communications Market. The need for MMF will be with us for many more yrs. To come. 
 
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