High power fiber lasers are now mature products and have numerous applications as medical, military, industrial processing and telecommunication. Usually single mode fiber lasers are pumped with single mode pump diode featuring low output power. Double-clad fiber lasers (DCFL) overcome the issue related to low power single mode pump diodes to take fully advantage of large low cost multimode diodes. Improvement in high power multimode diode combined with double-clad fiber technology permit to DCFLs to be very efficient and promising. They are mainly operating in CW regime however Q-switch or mode lock regimes are also achievable. DCFLs in CW regime can feature several watt output power. Up to 30W CW Ytterbium DCFL has been demonstrated indicating that fiber laser is able to handle very high optical power without any optical damage. Also fiber lasers included tens of meters long fiber, improving heat dissipation and leading to a less critical thermal management compare to bulk lasers. For terrestrial telecommunication applications, DCFLs are mainly operating in CW regime and in particular, Ytterbium DCFL is largely used as a pump for Raman Fiber Laser (RFL). The RFLs are used for components testing, pumping EDFAs and Raman amplifiers.