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Fibre lasers are lasers made from thin strands of a light-guiding glass. Atomic or molecular impurities introduced into the fibre when it is formed provide the optically active component, and the optical feedback required for stimulated emission can be created by patterning part of the fibre so it acts as a mirror.
Pulses of adjustable duration are generated by a mode-locked random fibre laser that can drive advances in sensing. Rayleigh backscattering from cm-long sections of telecom fibre provides laser feedback and spectral selectivity to the Fourier limit.
Nonlinear optical effects are by default weak but they can be enhanced by sculpting the resulting spectrally periodic pulses from a fibre laser into an optimal shape.