**4. Summary**

This chapter describes some of the basic concepts regarding optical fibers and dynamics of Q-switched and modelocked fiber lasers with the help of the existing literature. It includes the description of double clad fiber structure and cladding pump technique. Later, it presents some details about Q-switching and its types. It also includes a detailed description of modelocked lasers, especially, passive modelocked lasers along with a brief introduction of solitons, which are an integral part of the most modelocked fiber lasers. Moreover, examples of Q-switched and modelocked fiber lasers are presented by using double clad Thulium-Ytterbium co-doped fiber. A cladding pump technique is employed with a 980-nm multi-mode laser diode. The Q-switched pulses are produced by using a saturable absorber fabricated with MWCNT-PVA film, while modelocked pulses are generated with the help of graphene-PVA film. The Q-switched laser is produced with a repetition rate in the range 18.8– 50.6 kHz, whereas the modelocked laser generates pulses with a repetition rate of 11.76 MHz.
