Fiber laser is becoming an enabling technology for coherent Lidar applications and free space communications due to its
high efficiency, compact size and reliable operation. In these applications, high extinction rate and high OSNR are
musts for a fiber laser. However, current Q-switched fiber lasers and solid state lasers cannot meet these criteria.
Innovative approach has to be conceived to meet the requirements.
In this paper, we will discuss our researches on high energy/power ns pulsed fiber lasers. Modulation schemes for seed
laser in getting various optical waveforms to accommodate pulse narrowing in high power amplification and reduce SBS,
high power operation of fiber amplifiers, nonlinearity mitigation in high power fiber lasers, and trade-offs among the
parameters such as OSNR, power/energy scaling, extinction ratio, interpulses background noise (contrast ratio), and
efficiency will be discussed.