New Micro Fibre Optic Cable to Help BT Openreach’s UK Network Capacity

Openreach (BT) looks set to further boost capacity on their UK fibre optic network and harness spare space in some existing cable ducts by overblowing a new-ish type of super small fibre optic cable (72-fibre at 5mm diameter), which could save a bit of time and money.

Overblowing additional fibre cable through a cable duct that already has a large COF200 style fibre spine cable inside (sizes vary), such as those used to serve a local NGA Aggregation Node, is not a new practice but the traditional COF205 “micro-fibre” or “mini-cable” (e.g. 96-fibre cable of 7mm diameter) is sometimes just a little too big to push alongside.

Occasionally the only solution is to build space for a new cable duct, which obviously attracts the problem of costly and time consuming civil works. But successful field trials of the new 5mm fibre cable have shown that Openreach may soon have a much cheaper and simpler fix for certain congested spine routes (those containing Sub-Duct Mono-Bore 5).

Related sub-ducts (SDMB5) have been used since 2000 and according to the operators internal engineering magazine, Openreach could start to blow the new 5mm cable by around Q1 of 2016/17. Going forwards there are also options for small diameter high-capacity fibre micro cables that could be used as a replacement for COF200 spine cables.

For example, Openreach suggests that a 144-fibre cable could be reduced in diameter from 13mm to 8.5mm and a 276-fibre cable might be reduced from 15.5mm to 10.5mm. Obviously this is just one small part of how such networks are managed and maintained, but it’s an interesting little insight. Other operators are also doing similar work.

“Such smaller cables would enable sub-ducts smaller than SDMB5 to be used, thereby providing more space efficient duct usage. Further work is also being focused on micro cable usage closer to end user premises. Again improved duct utilisation is key to reducing our cost base, shortening installation time and limiting the civils works,” said the magazine.