Patent ID: 8774237

Claim:
A multi-cascaded all fiber pulsed arrangement for amplifying optical discrete pulses generated by an external source and incident on an external surface, comprising: upstream and downstream fiber amplifiers each operative to amplify the discrete pulses, a stretch of an optical path, including the upstream and downstream fiber amplifiers, being provided with internal impurities defining at least one parasitic resonant cavity therebetween; at least one passive saturable absorber (“SA”) located in the one parasitic cavity and coupled to output and input of respective upstream and downstream fiber amplifiers, the SA being configured with a recovery time τ 1 <Tround_trip, where τ is a recovery time of the SA, and Tround trip is a round-trip time of light within the one resonant cavity, the τ 1 being selected to have Qsat_sa<Qsat_gb and to be sufficient to prevent emergence of self-pulsing effect in the fiber amplifiers, wherein Qsat_sa is a saturation energy of the SA and Qsat_gb is a saturation energy of fiber amplifiers; and an output saturable absorber (“OSA”) located between the downstream amplifier and the external surface and configured with a recovery time τ 2 <Tround_trip_br with Tround_trip_br being a time which is necessary for a pulse to propagate towards and backwards between the OSA and the external surface, wherein the OSA substantially suppresses back-reflection of pulse originated downstream from the OSA.