Subsea Cables & Internet Infrastructure

As noted in my previous post, optical amplification allow light signals to be boosted without being first decoded into a digital representation. Optical-electrical-optical conversions go away. Hence the computer necessary for OEO conversions disappears. This in turn sharply improves the amplifier's reliability and life span. It also eliminates the conversion delay so end-to-end latency is improved. Finally, no computer means less cost. But these benefits are really secondary. More importantly, the advent of optical amplifiers led to a quantum leap in bandwidth that can be attributed to two related developments. The first is that optical amplifiers impose no transmission limits on computer technology. This means that we can lay a cable in the water and then upgrade it at regular intervals as Moore's law improves the ability of computers to process optical signals. Nothing on the wet side changes. Indeed, the introduction of digital processing allowed 10G wave subsea cables like ...

Long haul fibre optic bandwidth ranges from a few terabits per second into the low thirties with the equipment and operating expense sharply rising as transmission rates go up. Repeatered subsea cables generally lie in the 12 to 25 Tbps window with most spatial division multiplexing deployments pushing 12 to 20 Tbps whereas the traditional 6 to 8 pair coherent optics deployments transmit at least 20 Tbps or higher per strand.  The key factor determining the optical transmission rate is attenuation, which refers to the fact that a photon or wavelength's intensity or energy diminishes as it travels through fibre optic glass or any other medium. Light is scattered, reflected backwards or absorbed. Other variables that affect transmission rates include the number of distinct wavelength bands (dense wave division multiplexing) that can serve as distinct optical channels in a given spectrum range (usually the C band). The more channels, the higher the transmission rate. Chromatic dispers...