Subsea Optical Amplifier Fundamentals - Part 1

TAT-8 was the first Atlantic optical cable. It was RFS in 1988 and signified a bandwidth revolution with its capacity 10x that of its coaxial predecessors. By modern day standards it was a pygmy with 280 megabits total throughput. But it heralded the beginning of a long period of rapid throughput growth. Optical repeaters were spaced every 50 kilometers or 30 US miles. Photo diodes received the weak incoming signals, converted them into a digital representation of zeros and ones, and then laser diodes generated fresh light signals. A copper conductor provided power. Lots of redundancy in terms of components were built into this amplifiers to avoid repairs. However, this approach had a severe drawback, namely the throughput could not be increased in a time where Moore's law was rapidly increasing transmission rates. The pace of the optical-electrical-optical conversion was set in stone because an upgrade would require replacing all the hardware on all the amplifiers. TAT-8's ca...