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Optical fibre must be pristine to transmit reliably and to splice properly .
The existing standard for end-face cleaning is confusing . IEC 61300-3- 35 clearly states that IPA is no longer acceptable for end-face cleaning . But IPA commonly is packaged and promoted for fusion splice prep . Far too often splicers and end-face cleaners forget to send each other the memo : do not use this chemical for every fibre cleaning application .
Throughout the 1990s numerous new solvent choices evolved to replace ozone-depleting chemicals , and some of those experiments migrated into the fibre optic industry . Some companies used alcohol in different mixtures . Precision hydrocarbons were tried and tweaked to minimise environmental issues . New chemicals such as hydrofluoroethers ( HFE ) and
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hydrofluorocarbons ( HFC ) entered the market . I even have seen companies using unconventional cleaning fluids , such as dish washing detergent and SimpleGreen . It was a crazy time .
Most of the exotic ( and ineffective ) practices died out due to economic , environmental , performance or worker safety concerns . Today the list has been abbreviated to just a few , proven choices . Amazingly , more as a nod to ‘ tradition ’ than ‘ effectiveness ’ IPA remains on the list . There is another reason : IPA is inexpensive and often purchased from a drug store .
I recall training an important fibre optic distributor and I gently suggested to the owner that IPA was not best choice for cleaning fibre . Coolly , he advised me that he and his mum had started their massive international business transferring IPA from 55 gallon drums into small bottles . Their highly successful enterprise exists to this day and ‘ we ’ re not going to change ’.
But one has to ask , why not ? Why have perceptions of IPA remained unchanged while everything else in the industry has evolved at a furious rate ?
What don ’ t we understand ?
Isopropyl alcohol has many names . On safety data sheets it may be called isopropanol , rubbing alcohol , propan-2- ol , 2-propanol , dimethyl carbinol or just IPA . It is an organic compound with the chemical formula C3H7OH . No matter what the name , on the safety data sheet it will carry the official CAS number of 67-63-0 . It is a colourless , flammable compound with a strong odour . It has a wide variety of medical , industrial and household uses but it has many flaws , as well .
For a start , IPA is neither a very effective nor very versatile cleaner . IPA ’ s cleaning ability is limited to human body oil and ionic salts but not much more . IPA is not effective on mineral oils and most hand lotions . IPA does not clean oils and greases very well . Since fibre optics has now expanded into mining , oil fields , as well as telecom networks and data centres , selecting the right stuff becomes an essential best practice .
Drying speed is another issue with IPA . Slow drying IPA can be trapped inside a fibre optic connector . This once pure liquid may leach out inconveniently and contaminate an end face . A familiar characteristic of any liquid is its boiling point ; the lower the boiling point the faster a liquid will evaporate . Water boils at 100 ° C and dries slowly ; alcohol
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boils at 78 ° C so it dries slowly as well . Many companies have introduced new cleaning choices that boil near room temperature . These cleaners will ‘ flash dry ’ and will not leave contamination or moisture trapped on the fibre .
IPA has another unexpected characteristic : it is hygroscopic which means it attracts moisture to itself . Studies of 99.9 per cent IPA reveal that a bottle of IPA in an open container will lose seven per cent of its strength in as little as 15 minutes . IPA continues to absorb moisture until it reaches equilibrium at about 65 per cent . This is why the rubbing alcohol purchased at a local store is about 30 per cent water . The manner in which the cleaner is packaged is critical to its performance . Water doesn ’ t just dilute IPA ’ s already feeble cleaning power . It also will add residues carried in the air . Those contaminants from the air – and others from those cheap plastic bottles – will be left behind when the IPA dries . This is the source of the ‘ haze ’ that IPA leaves after cleaning . The haze may interfere with transmission of light ( increased insertion loss ) and also may affect the transmission of one wave length verses another wave length , which can be very troubling in DWDM systems .
No matter how pure the IPA may be when purchased , it will become contaminated when it is poured into a pump bottle , dispenser or an uncovered container . Guaranteed . Each time a drop of IPA is squeezed out of a traditional pump-bottle , air enters . This is reality
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Modern , nonflammable fluids – along with the appropriate noncellulose wipers – are the best choice to ensure a clean surface . |
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