EVERYTHING YOU NEED TO KNOW ABOUT FIBRE OPTICAL…

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21.04.2021 | Fibre optical, Multimode, Singlemode

The Difference Between Types of Fibre Optical Cables

Fibre optical cables are one of the most reliable and versatile options on the market, sending information through pulses of light. If you’re in the market for fibre optical cables, you’ve probably looked at the options of both single mode and multimode fibre cables. The difference between the two can be confusing to the naked eye, but they fundamentally impact the performance level of each cable. We’re taking an in-depth look at the difference between single mode and multi-mode in terms of construction, cost, and distance.

 

How Do Fibre Optical Cables Work?

Fibre optical cables work by sending light through the cable with photon particles bouncing down the cable due to the internal reflection. This light beam travels down through the core of the cable, which sits at the middle of the cable’s glass structure. Around the core, there is a cladding layer of glass that keeps the light refraction inside the core. 

 

The mode is the path that the light follows through the fibre, which is why you have single mode and multi-mode fibre cable options. The single mode has the simplest structure with the smallest core, leading the signal to travel directly through the core. With a multi-mode fibres optical cable, the core is around ten times the size, and the light travels through multiple paths.

 

We’re taking a look at the differences between single and multi-mode fibre optical cables, which primarily sits in the bandwidth, colour sheath, cost, core diameter, distance, light source, and wavelength. We’re looking at both single and multi-mode options separately, so you can decide which one is best suited for your project.

How fibre otical cables work

 

What Is Structured Cabling?

Structured cabling is a telecommunication cabling infrastructure with different smaller elements, giving it the ‘structured’ name. The purpose of structured cabling is to give you a dependable and predictable performance rate with flexibility for everyday use that allows for maximising the system availability. Structured cabling can help to future proof the usability of your cabling system. 

 

This style of cabling brings organisation to your infrastructure. The patch panels and trunks create a structure within the system that allows hardware ports to be connected to the patch panel, which is connected to another through a trunk (using multi-fibre optic cables) in the main distribution area. The MDA is essential to the structured cabling as it allows for the adds, changes, and moves to occur with the shorter length patch cords. 

 

Structured cabling with multi-mode fibre optic cables allows you to reduce the potential downtime caused by human error and gives you a cleaner look than a point-to-point cabling method. It’s also a time-saving option as it’s quicker to trace cables and ports to make changes.

 

What is Computer Cabling?

For your home or a small office, the computer cabling you’re most likely to be using revolves around single mode fibre optical cables. These are the simplest form of fibre optic cabling as there is a reduced light reflection which allows the signal and transmission to travel quickly through the wires. The data transmission can carry over a larger distance, making it ideal for TVs, internet, and telephone signals. 

For computer networks set up in a larger office or data centre, multi-mode fibre optical cables are used as they carry your data transmission across a shorter distance due to higher light refraction. 

 

What are Single Mode Fibre Optical Cables?

A single mode fibre optical cable uses one type of light mode, while multi-mode cables propagate multiple modes. These single-mode OS2 cables are typically used for long-distance single transmission due to their attenuation. These cables are usually used in carrier networks, MANs and PONs.

 

The core diameter for a single mode fibre is significantly smaller than a multi-mode option. For an OS2 single mode, the diameter is 9um – whereas an OM3 or OM4 multi-mode has a diameter of 50um. With a single mode fibre optic cable, laser or laser diodes product the light that is injected into the cable, typically producing a wavelength of 1310nm and 1500nm.

 

As the diameter in a single mode fibre is smaller, the light which passes through the cable is not reflected in the same way as multi-mode cables, which leaves the attenuation at a minimum. The attenuation for a single mode fibre at 1310nm is 0.36dB/km, compared to OM3 multi-mode fibres having an attenuation of 3.0dB/km at 850nm. As the attenuation is reduced due to the limited internal light ray reflection, single mode fibre optic cables give you a higher speed of data transfer over a larger distance.

 

As single mode cables have one light mode, their bandwidth is unlimited as a result. One of the most noticeable differences between the two is their colour sheath. For a single mode fibre cable, they have a yellow outer sheath.

 

For most people, the difference they care most about is the cost involved in the system and installation. While single mode fibre cables have their benefits, they’re also the most expensive. A typical single mode fibre solution can cost up to five times the price of a multi-mode fibre. 

 

As these cables work on a longer distance, the transceivers require lasers at a longer wavelength with a smaller spot-size and narrower spectral width to work. The increased transceiver and interconnect costs come from the need for higher-precision alignment and tighter connection tolerance. 

 

Although they have a higher system cost, single mode fibre optics have a lower upgrade installation cost. When it comes to upgrading your system, the labour costs for replacing multi-mode OM3 and OM4 cables is higher than the single-mode OS2.

Fibre Diameters

What are Multi Mode Fibre Optical Cables?

Multi-mode fibre optic cables have a larger core with significantly increased reflection, which leads to higher attenuation and dispersion rates, giving a higher bandwidth delivery for shorter distances. Multi-mode cables are typically used for communicating data across a small, localised area where a large volume of data needs to be sent. The number of core cables in the multi-mode determines the data load it can carry. As the multi-mode cables travel a shorter distance, you’ll usually find them in data centres, enterprises, and LANs. 

 

OM3 and OM4 multi-mode fibre cables have a core diameter of 50um, compared to the 9um of an OS2 single mode. The larger diameter size enables the multi-mode fibres to have simpler connections, and they possess a higher ‘light gathering’ ability.

Multi-mode cables have a limited bandwidth due to their light mode – for an OM5 multi-mode fibre, this is currently 28000MHz*km. As multi-mode fibre optic cables have a larger core size, some of their more affordable light sources – such as LEDs – work with an 850nm wavelength.

 

Multi-mode fibres travel a shorter distance due to their larger core size and model dispersion, allowing them to support multiple light modes. While it travels a shorter distance, these cables can carry a larger data load than OS2 single mode cables – which carry a lighter load over a longer distance.

 

In terms of visual differences, a multi-mode fibre optical cable has an outer sheath coating in either blue or orange. The cost difference between the two is the next noticeable difference. Multi-mode optical transceivers cost significantly less than their single-mode counterparts by two or three times the price. The speed will largely determine the cost of the multi-mode optical transceiver. 

 

The system cost of operating multi-mode fibre optics is reduced as they’re easier to manufacture with a more versatile design that works for various devices, with them being produced at a lower cost than OS2 single mode alternatives. The upgrade cost to 100G for standard-based premise applications is also lower for multi-mode fibre optics.

 

What Are the Main Differences Between Single and Multi-Mode?

The OM3 and OM4 multi-mode cables can carry a higher data rate than the single-mode OS2 cable, even though the latter can travel a larger distance. The distance is usually the deciding factor between whether you go with single or multi-mode cables. If you only need a few hundred meters of distance, a multi-mode cable would work best. If you need a significantly higher distance, a single mode cable will be more suitable. You’ll also want to consider the cost of future upgrades when you’re coming up with your budget – as the cost of a single fibre optic upgrade is lower.

 

Which One Is Best for My Project?

Both single and multi-mode fibre optic cables have their benefits, and the differences are what makes them work better for certain projects over others. You’ll want to consider your budget, the bandwidth speed you need, and the distance you want the fibre optic cables to cover. You can’t mix single mode and multi-mode fibres together due to their different core sizes and light modes. Mixing the two would result in an optical loss and reduced efficiency. 

 

Similarly, you can’t use a multi-mode transceiver for a single mode cable as an optical loss will occur. You could use a single mode transfer for certain multi-mode fibre cables if you need to. You want to consider all the factors we’ve mentioned in this article to find the fibre optic cables that will work for your network needs.

 

For more information don’t hesitate in getting in contact with our specialist team.

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