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fiber optics1
Enterprise Network

How to Realize Multimode to Single-Mode Fibre Conversion?

How to Realize Multimode to Single-Mode Fibre Conversion?

FS Official 2016-12-05

Fibre optics are mainly used for data transmission due to its efficiency and high transmission capacity. And fibre optic cables provide an effective transmission as they are less affected by internal and external interference. The transmission can be done by multimode fibre or single-mode fibre depending on the communication requirements.

Fibre mode conversion, especially multimode to single-mode fibre conversion (MMF-to-SMF conversion) is required when the distance is an important parameter to consider in optical applications. In this tutorial, three methods will be introduced to support mode conversion from multimode to single-mode fibres.

When Is Multimode to Single-Mode Conversion Required?

If you must know one thing about fibre optic cable, it's the difference between single-mode and multimode fibres. Because of different fibre diameter of their cores, they have different applications. Single-mode fibre cable is preferred to use in long distance, high bandwidth runs, and multimode fibre cable is often used for short distance applications. However, a fibre optic network is not as simple as using only one type of fibre. Thus, we usually need mode conversion, especially MMF-to-SMF conversion during the transmission. Mode conversion between multimode and single-mode fibre is typically required when network distance exceeds the limit of multimode fibre. In addition, MMF-to-SMF conversion is also required depending on the equipment and connectivity type in the network. For instance, lower cost legacy equipment uses multimode port, and connectivity is required for single-mode equipment; or a building has multimode equipment, while the connection to the service provider is single-mode, etc.

Multimode fiber cable and single-mode fiber cableFigure 1: Multimode fibre cable and single-mode fibre cable

How to Realize Multimode to Single-Mode Fibre Conversion?

Since mode conversion in the optical network is universal, here are three methods that can realize multimode to single-mode fibre conversion.

Fibre to Fibre Media Converter for MMF-to-SMF Fibre Conversion

As we know, fibre optic media converter supports multimode to single-mode fibre conversion, dual fibre to single fibre conversion and wavelength conversion. Here we mainly talk about the conversion between multimode to single-mode fibres. A fibre-to-fibre media converter can extend a MM network across SM fibre with distances up to 140km in a cost-effective way. For example, a 550m/20km 850nm/1310nm SFP Gigabit Ethernet MMF-to-SMF fibre media converter can support mode conversion from multimode fibre (up to 550 m) to single-mode fibre (up to 20 km) for Gigabit Ethernet (1000 Mbps).

In the application of extending fibre network distances, two Ethernet switches equipped with multimode fibre ports are connected utilising a pair of MMF-to-SMF converters which convert the multimode fibre to single-mode fibre and enable network connectivity across the distance between the switches, as shown in the picture below.


Fiber-to-fiber media converter for MMF-to-SMF conversionFigure 2: Fibre-to-fibre media converter for MMF-to-SMF conversion

WDM Transponder for MMF-to-SMF Fibre Conversion

Similar to fibre-to-fibre media converter, WDM transponder also has the capability to convert multimode to single-mode fibre. As its name shows, transponder is often used in WDM systems, especially in DWDM systems. Because in long runs of DWDM transmission, MMF to SMF or SMF to MMF conversions are usually needed.

WDM transponder for MMF-to-SMF conversion Figure 3: WDM transponder for MMF-to-SMF conversion

Mode Conditioning Fibre Cable for MMF-to-SMF Fibre Conversion

Compared with the two methods mentioned above, mode conditioning fibre cable is different in the conversion between multimode and single-mode fibre. Not able to convert signals into electrical ones as WDM transponder, mode conditioning patch cable launches the laser at a precise offset from the centre of the multimode fibre. This causes the laser to spread across the diameter of the fibre core, reducing the effect known as differential mode delay (DMD) which occurs when the laser couples onto only a small number of available modes in multimode fibre. In addition, mode conditioning fibre cable is limited to be used in applications that using Gigabit 1000BASE-LX (or 10-Gigabit Ethernet 10GBASE-LRM and 10GBASE-LX4) equipment.

Mode conditioning cable for MMF-to-SMF conversion Figure 4: Mode conditioning cable for MMF-to-SMF conversion

FS Multimode to Single-Mode Conversion Solution

FS offers a wide range options of MMF-to-SMF conversion for Fast Ethernet and Gigabit Ethernet, supporting extension up to 120 km for MAN (metropolitan area network) applications. In addition, we offer the matching SFP transceiver modules and high-quality fibre patch cables, which help you deploy the network in the most cost-effective way. For more information, please visit the following product categories or contact us over

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