The fiber lasers with quasi-distributed gain enable to generate high energy pulses by combining several sections of active fiber . In such lasers the high output energy is achieved as a result of the large cavity length and multiple signal gain inside the laser cavity. In spite of this, the analytical studies of such laser schemes are necessary in order to optimize the output pulse characteristics and order of optical devices. In this work we consider the fiber laser setup as several cells of active fibers with gain, passive fibers, and optical devices with loss. Such scheme can be used to simulate fiber lasers with quasi-distributed gain in case of non-periodical cells and fiber lasers with cavity dumping  with strong periodic cells. Here we consider strong periodic cells.