Laser functioning and generalities
Continuous and impulsionnal lasers
As the first laser has bee created in 1960, the first fiber optic laser was designed in 1961. The first fiber laser was built in 1964. After that, main progresses were about loss reductions in the fiber, and dopping, with different dopping element. But the major progress was sheath pumping, not anymore only core pumping. This allowed to increase considerably the pumping powers allowed into the fiber optics.
To give an idea, signal reducing inside fiber optics was 20 dB/km in 1970. It rapidly dropped to 3 dB/km (at 1060 nm) in 1974, then to 0.5 dB/km (at 1200 nm) in 1976 and to 0.2 dB/km (at 1550 nm) in 1979. Nowadays,and for almost fifteen years, it is close to 0.15 dB/km (around 1570 nm).