The truth is out there

he field of fibre optics generates some strange myths and legends. To the uninitiated it can seem like alien technology. It's even been suggested that fibre optics were brought to Earth by aliens. If you believe the American tabloids, humans discovered fibre optics inside the flying saucer which is supposed to have crashed near Roswell, New Mexico in 1947 and merely copied the idea.

The truth is much more down to earth (Alexander Graham Bell was experimenting with it in the 1880s), as is the technology when you get to know it. But why should you should think about offering fibre optic installation services?

Well, there is a lot of money to be made by fibre optic installers at present – and most likely in the future too. Demand for both fibre and its installers is at an all-time high.

So, now that you're motivated to at least consider offering fibre optic installation services, let's look at the technology involved.

The actual laying of fibre optic cables bears a striking similarity to laying copper. It's the termination, testing and jointing procedures that are significantly different.

Fibre optics convey information down a glass fibre using light as the medium for the signal. The signal is converted into light at the transmission end, sent down the fibre by laser and turned back into the message at the reception end. That's really all there is to it.

Today, a typical information transmission sequence over fibre optics is: information (voice, data or video) is fed into an encoder which converts it into either analogue or digital data. A light source is then used to send that information via pulses of light through a fibre to a detector. The detector receives the analogue/ digital information and a decoder is used to reconvert the information into a voice, data or video signal.

Installation techniques
In a typical procedure, after the duct cable laying arrangement has been planned off-site, installers begin their on-site work with the rodding and cleaning of the main duct. Shooting/pulling follows, with a rope drawn into the subduct. There then follows the cable drum setting stage, cable pulling in and testing and recording of results. The cable is fixed and jointed in the manhole, and further tests are conducted and recorded.

That probably all sounds quite familiar. It's a cable – and you're laying it. But that said, there are significant differences from cable in the termination, jointing and testing procedures. Fibre must be prepared for termination and jointing, which requires removal of the protective acrylate coating.

This is done using specialist stripping tools. The fibres within then need to be cleaned. Following that, fibres are cleaved using a specialist cleaving tool, which g ensures that the ends are cut perfectly square. Thus prepared, the fibres are joined together by a process called splicing. Splicing also allows damaged cables to be repaired either temporarily or permanently, for fibres to be joined to predetermined connectors, and to provide a low loss connection between two fibres.

There are two methods of splicing – mechanical and fusion. Of the two, fusion splicing is almost universally recognised as the superior method – and it costs less. Aligning the two fibres to be joined is obviously a critical procedure. The less well aligned the fibres, the greater the splice loss ie the amount of attenuation or damage done to the signal.

Splicers employ at least five different methods to align the fibres. The PAS alignment method for fusion splicers is probably the best, not least because it makes the whole process automatic for the operator. In fact, splicers are now so advanced that the whole process is greatly simplified for the operator from start to finish. What could conceivably be one of the greatest areas of difficulty for engineers is now fast, simple and very accurate indeed.

Following splicing, joins are enclosed to protect their integrity and to mechanically strengthen the cable. Again, specialist equipment is needed and different types of enclosure are used depending on the cable type and whether access is required to the joint or not.

Fibre is interfaced to TX or RX equipment using high precision connectors. There are many types, each offering different performance criteria. Fibres are once again stripped and cleaned before being fitted into the connector. An epoxy solution is syringed into the connector body before the connector is placed in a pre-heated oven to cure the epoxy and seal the join. This is a simplification, but the basic procedure.

Either a laser diode or a light emitting diode (led) is used to send a signal through the fibre. At the other end, an avalanche or pin photodiode is used as the receiver.

Of course, all this work with joins and connectors can affect the integrity of the signal. Test and measurement in fibre optics is all about checking that the signal is getting through with the minimum of interference, or else identifying where the signal loss is coming from and repairing it.

Testing
There are several methods of testing. A visible light source/fault locator system injects a visible light source into the fibre to allow any leakage to be easily identified. It can also be used to confirm the continuity of a fibre over distances of 3-5 kilometres.

A light test set comprises a light source and optical power meter – one at either end of the fibre. The optical power meter reads the strength of the signal sent by the light source.

The third method is using an optical time domain reflectometer (OTDR), which injects a pulse of light into the cable and measures both the loss and distance within it. As with splicing, a lot of thought has gone into making these systems simple for the operator.

The cost of starting
So, fibre optics isn't rocket science. A fibre optic installation engineer can be fully trained and qualified in under two weeks, from start to finish for less than £2000. Training is a good idea, because there are both safety and liability issues to think about, just as there are with routine electrical work.

The best recognised form of qualification for training is probably the City & Guilds courses in single and multi-mode fibres, and there are several places in the UK which offering these. Fujikura, for example, offers both courses, as well as a fast track system that enables engineers to qualify within just one week.

The real cost is in tooling up to offer fibre optic installation services. Splicers and OTDRs don't come cheap. However, if you just want to dip your toe in the water or only expect to tackle a few jobs to begin with, why not lease or hire the equipment instead? Several companies offer hire services. There are a choice of packages, and usually a hire-to-buy option.

It is worth seriously considering offering fibre optic installation services. The demand for fibre is growing all the time, and with it the demand for installers. The work can be exceptionally profitable and moving into fibre optics can help to secure your company's future.

The technology really isn't that difficult – if you can master electricity, you can surely master light – and there are ways in which won't break the bank. It's got to be worth thinking about, hasn't it?