How Clean Is Your Network?

Geoff Day, Technical Manager at CMS plc, highlights the importance of cleaning fibre optic components to prevent network cabling failures.

Today’s network requirements place ever increasing demands on the cabling infrastructure to perform both reliably and consistently. 40G and 100G Ethernet installations are becoming an increasing reality in high speed applications such as data centres and, as such, result in a greater use of fibre optic cabling.

But if the cabling fails in these environments the impact is even more dramatic. Lots more data doesn’t get transmitted, meaning that even the shortest element of downtime prevents essential “transactions” which can cost the data centre owner and end customer significant losses of revenue and profit.

Clearly all potential points of failure need to be eliminated to avoid downtime and all its costly after-effects, and this is why the cleaning of fibre optic connectivity and cabling is so important and shouldn’t be underestimated. The investment in good cleaning practices at the front end of an installation can really pay dividends in the long run.

One of the standard statistics circulated around the structured cabling industry is that up to 50% of network failures are due to connectivity issues and when drilling down further a significant proportion of these failures are due to unwanted dirt and contamination in the fibre optic components.

Contaminants

When fibre works well, it transmit’s great volumes of data at high speed. To achieve this, the glass cores of the fibre need to be perfectly aligned and clean to ensure the signal can be transmitted with minimal loss. Any contaminant can have a significant impact on performance.

Dirty Fibre viewed from a scopeDirty Fibre viewed through a scope

Putting this into context: If we take a single-mode fibre, the actual fibre core is only 8 microns thick. If we compare this with other items such as a human hair which is typically 50 microns or a particle of sand which is 90 microns, we can easily begin to see how very small contaminants can have a serious impact on performance, and, in some cases, can completely obstruct signal transmission.

The existence of particles between two fibre connectors, which should be in direct contact with each other, can cause “back reflection”, where a portion of the original signal is reflected back to the originating laser. The problem can usually be detected using an OTDR and sometimes via visual inspection.

There are numerous contaminants, that exist in the typical workplace environment that can impact on fibre performance and these include: dirt, grease, hand lotion, skin oil, skin cells, food and lint. Putting this another way there are many opportunities for fibres to become contaminated in the course of normal installation activities.

One of the biggest challenges of contamination is that it cannot be seen with the naked eye and a specialist inspection microscope is required to view the cleanliness of the endface and ensure that the connections will perform to their maximum potential.

So for trouble-free network installation and continuous performance it is essential to adopt best practice when handling and cleaning fibre components in order to prevent performance problems due to dirty fibre elements.

Sticklers Fibre Cleaning Kit

The Cleaning Toolkit

Before you can start the cleaning process you need to have your fibre cleaning “toolkit” in place and it makes sense to invest in good specialist fibre cleaning products which are available from a number of suppliers in the marketplace. These products have been widely tested and proven to give the best possible results.

So what do you need in your toolkit?

Canned Air: this is ideal for blowing loose particles from optical fibre connector endfaces or for drying cleaning fluid residue from the endface after wet cleaning.

Dry wipes: these are used to clean exposed connectors (as opposed to ports on hubs) and bare fibres. However if used in isolation they can cause a build up of static which is not desirable so these should be used in conjunction with a cleaning fluid which will dissipate the static

Cleaning fluids: these are used to dissolve oils that may be found on the fibre and dissipate static. However if used in isolation they can leave salt remains behind in the form of a white residue which can be very difficult to remove. It is generally accepted that the best practice is to use a “wet/dry process” to obtain optimum results, more of this later.

Selection of the correct cleaning fluid is critical to the results you will be able to obtain in the cleaning process. You should avoid using aqueous (water-based) solutions as they can be slow to dry and can leave moisture on the endface. In cold ambient temperatures the moisture may actually freeze on the endface and alignment sleeve. If the moisture is not completely removed before the fibre is connected to the sleeve, the laser-energised fibre can vapourise the remaining fluid into a gas causing an explosion. You should avoid the use of IPA (isopropyl alcohol) for cleaning as it is highly flammable and hazardous. It is also slow-drying and hygroscopic (attracts water) which can dilute its cleaning properties.

Swabs: you will need swabs to clean optical ports and devices as these fibres are often recessed. Swabs are available in different sizes to suit different connector types.  They are dry and also need to be used in combination with the cleaning fluid for best results.

You will also need an inspection microscope to examine the results of your cleaning work.

Checklist

A few helpful reminders about fibre cleaning.

  • Plan to clean and inspect fibres as part of the installation process
  • Invest in high quality cleaning products as part of your toolkit
  • Dont use IPA as it is flammable and hazardous and not as effective as specialist fibre optic cleaning fluids
  • Use a wet/dry cleaning process is critical for success
  • Remember to clean both end-faces before mating
  • Try not to touch the end-faces of connectors or leave them exposed.
  • It is best to inspect and clean fibre components before connection
  • Dont forget to clean associated fibre equipment on a regular basis
  • Remember INSPECT>CLEAN>INSPECT and repeat if necessary

The Cleaning Process

When cleaning exposed connections you should take a clean dry wipe and apply a minimum amount of cleaning fluid to it. Next you should place the endface of the connector perpendicular to the wipe. To clean you should move the connector in a wiping action, moving from the wet to the dry area of the wipe using a gentle pressure. You then need to check your work with an inspection microscope and repeat if necessary, but make sure you use a new section of the dry wipe if you repeat the cleaning process.

To clean optical ports that are usually recessed, firstly you need to select the appropriate sized swab for the fibre connector. Then dampen the tip of the swab by applying a small amount of cleaning fluid. Next insert the swab into the optical port and rotate 5 or 6 times in one direction, applying a gentle pressure. Inspect the endface and repeat the process if necessary.

When cleaning bare fibres, take a dry wipe and fold it in two, then dampen the wipe with a small amount of cleaning fluid. Next wrap the wipe around the fibre and squeeze gently, sliding the wipe towards the end of the fibre. You should then be able to hear the fibre “squeak” when it is clean.

To clean bulkhead adaptors you can spray a cleaning fluid into the ports and use canned air to help with drying.

It is also important to ensure that all other associated equipment such as microscope lenses, test heads and adaptors are also regularly cleaned to ensure you are getting an accurate reading of your results.

Summary

Whilst fibre offers superior network performance it is also more susceptible to contaminants that can dramatically reduce its performance. Investing in the right cleaning tools and adopting best practice when cleaning fibre products can mitigate costly failures post installation.