This work focuses on practical analysis of the Nonlinear Optical Loop Mirror (NOLM). This all-fiber device serves as a saturable absorbers for passive mode-locking in ultrashort pulse generation. It has a great potential for further development as it’s made in all fiber technology, and can be easily adapted to custom system. <p> </p>We investigate and provide experimental results as well as characteristics of NOLM’s in several different setups. The all-fiber laser system used for testing produced femtosecond pulses with a positive chirp. We present reflection as a function of input power and as a function of the coupler’s coupling. Also, relevant spectral characteristics are shown. These results may be useful in further development of fiber laser systems and other applications.