Optical fibre and natural disasters
After the horrific events in Christchurch, New Zealand, and Honshu, Japan, I thought it wise to look at the ability of fibre to withstand these types of natural disasters. The glass component of fibre is quite fragile and delicate. However fibre’s light conductor core is always sheathed in a variety of protective coatings, from simple plastic to modern materials like Kevlar.
Ultimately fibre enjoys the same tensile strength as steel of the same diameter. When covered by a protective jacket or armour, it can be treated fairly roughly without damage. It is also more resistant to temperature extremes and corrosion than alternative cable systems (copper, coaxial, etc).
Recent developments have seen ‘bend insensitive’ fibre emerge, which greatly reduces the risk of breakage and signal attenuation when it is bent, even to small radiuses.
Fibre rarely exists commercially as a single fibre. Rather, bundles contain dozens, often hundreds, of single fibres in a cable.
Such cables carry an incredible amount of bandwidth – tens of thousands of phone calls, or hundreds of Gigabits of data per second. Breakage of this cable due to a natural catastrophe or human error can create a massive loss of communications. We have seen this a couple of times in New Zealand when main North-South fibre trunks were broken, causing important internet and phone outages until the fibre links were repaired.
Fibre terrestrial links can travel either underground in ducts or trenches, or aerial attached to existing power or telephone poles. One can easily imagine the comparative survival rates of the two systems in the case of an earthquake or tsunami.
In fact, it has been shown that aerial deployment costs on average four times less than going underground. And after seeing the horrific tsunami damage around Sendai, Japan, I’d suggest that any aerial fibre installations would be wiped out in those areas.
Underground fibre runs should have a much higher survival rate as no power nor active electronics are generally used between headends, or relay sites. Also the fibre carries no electrical power and can be saturated with water, mud, etc, without any negative effect. These networks may go down due to power outages or damaged headend electronics, but the underground fibre network itself has a good chance of remaining intact, thus easier to get back online again.
Two undersea fibre cables were damaged in the Sendai region – not surprising when we read that the island of Honshu has moved 2.4m during the quake.
So we might conclude that fibre offers no major advantages in natural disasters.
I think that what really saves us these days is the development of the Internet Protocol (IP) and other recent data transmission methods. Why? Because these ways of sending data are not reliant on a fixed point-to-point route, but can and will find an alternate route to the destination. The secret of high-availability data communications today is redundancy and alternate network paths. As we increase the number and cover of our high-speed fibre networks, the assurance we gain comes in the ability get IP packets through the cobweb of multiple paths available to the users.
Broken fibre links can be, up to a point, self-healing by finding an alternate traffic path. Also the companies operating the networks can also manually re-route traffic around a broken link.
So as new fibre networks are developed and commissioned, the reliability of our worldwide wide area network (WAN) will continue to get better and better.