We all know that the purchase price of optical fibre has come down significantly due to huge increases in production capacity and increased efficiency. There are still price pressures on the polymers used in cable products which depend on oil prices and exchange rates but for fibre consumers the picture has been positive. However, the purchase cost of cable for a network is usually less than 10% of the project total so it’s the cost of ownership over the fibre’s life that needs considering
Blown systems allow cable to be provided by a single installer at short notice. Where that cable is a higher fibre count, expanding capacity over a lower count product, the smaller cable can be recovered and used elsewhere. Spliced-in, non-ducted, cable is often difficult to remove and is not usually in a state to be re-deployed. The other main reason to change cable is to improve the fibre type. Fibre types have evolved over the 25-year typical life of external plant, from G.651 (multimode) to G.652 and G.652D singlemode, through the ill-fated G.653 dispersion shifted fibre to G.655 NZDS fibre, to the current G.657 bend resistant types. In the future, multi-core and ‘holey’ fibres are likely to dominate!
Using the ‘tube’ level as a capacity management tool
Underground space is rarely easily won and main ducts (around 100mm in diameter) are often congested with a few heavy cables that makes the installation of smaller cables a challenge. By overlaying a multi-tube bundle the user gets a number of discrete and separately routable pathways. At the tube level routing, can be carried out by simple to apply and low cost push-fit connectors combined with simple duct break-out ‘joints’ with no need for fibre closures. Moreover, in a multi-user shared or dark fibre network, different owners can own different tubes and they can be routed to different chambers to allow connection according to each user’s needs. With a conventional cable network, shared ownership must take place at the cable level. This means that all customers have to share the same joint – giving access issues, or the same cable must be repeatedly broken into, risking its integrity.
For both incumbent and new entrant carriers, planning where to deploy precious resources is always a major issue. Irrespective of the fibre price, it’s a finite resource and in limited supply currently so cannot be mis-allocated. However, forecasting the location of, and uptake percentage amongst, new customers is more difficult than ever because the number of customers and potential providers has never been greater. By building a base tube network – which itself can be easily extended – and populating it with the right number and type of fibres on demand, much of those concerns are eased.
From a purely financial perspective many new operators and funded by venture capital which demands a high and immediate Return on Investment. By deferring fibre costs – and that of associated fittings – money can be saved at all stages of the network life cycle.
Most travellers are familiar with the disruption caused by utility road works closing traffic lanes or entire road sections. Whilst this gas and water construction causes more upheaval, telecoms build is partly to blame. Heavy winching equipment, massive cable reels and a multi-worker team inevitably cause more disturbance than a single worker blowing-in a fibre unit or a relatively lightweight cable. Don’t forget that for the telco, disruption often equals cost as its common to have to pay for closing any kind of highway. Where that highway is a railway, those considerations – and costs – may have to be multiplied several times.
But there are situations where disruption would not only be expensive but it would compromise the location. One example is within hospitals where opening entries between sterile areas or closing treatment areas when conventional cable is laid is prohibited. Because different types of BF tubing can be jointed easily, a seamless path can be created; we will explore that a little more below.
A Unified network
Both owners and users would like a network where there are as few ‘joins’ as possible and where there are joints, it’s for flexibility purposes. Unfortunately, using a cable that transitions between above ground, underground and inside building locations invariably means three different cable types, three splice closures and 3 sets of splicing work. With a tube based system, it’s an easy task to push-fit connect aerial microduct to underground microduct to indoor microduct and blow through one fibre unit or cable with no splices or splice closures at all. In some situations, it’s even easier because the same microduct can be used throughout.
As well as saving the financial budget, this approach saves the network’s power budget and reduces the potential points of failure, because unnecessary, purely in-line, joints no matter how good (and pricey!) are inevitably a potential failure point.
Overall Time and Labour Considerations
It’s worth looking at the physical acts involved with fibre product blowing compared with the actions required to deploy either a direct bury cable or pull a traditional cable into a main duct. Direct burying requires either mole-ploughing in a rural area or in the built environment the use of traditional trenching. Trenching is hugely disruptive (with indirect costs) and has high direct costs whereas mole ploughing works only in certain conditions and in limited applications. When it comes to installing low count fibre products, especially for the ‘drop’ end of the network the ergonomic advantage of deploying extremely small and lightweight blown products is overwhelming. Typically, the installation rate for a 2-12 fibre unit is between 30 and 60 meters per minute and a single person can transport the product and the small blowing head and compressor – and they can do all this using a lightweight vehicle. However, in the literature it’s easy to find comments that it takes at least 4 people a full working day to install 1km of ‘traditional’ cable, when the use of heavy equipment, frequent chamber opening and roadworks preparation is considered. So, it’s little surprise that a network based on a multiple tube deployment, using on-demand, lightweight fibre units and cables not only offers a day-one price advantage but, more importantly, the best whole-life value.