Erbium Doped Fiber Amplifiers (EDFA) are used in fiber optic transmission lines to restore the optical signal level. The advantage of erbium amplifiers is the lack of conversion into an electrical signal, the possibility of simultaneously amplifying signals with different wavelengths (which makes it possible to amplify a spectrally multiplexed signal), the exact range of erbium amplifiers corresponds to the minimum optical loss of optical fibers based on quartz glass, and a relatively low noise level and ease of incorporation into a fiber optic system. The principle of operation of EDFA amplifiers is based on the phenomenon of stimulated emission. The operation of lasers is based on the same phenomenon. In this educational set, students will get acquainted with the principles of operation and the device of fiber amplifiers. The phenomenon of stimulated emission will be studied. The lifetime of the excited state of ⁴I_13/2 Er³⁺ ions will be measured. Students will also get acquainted with the basic principles of a semiconductor laser, study pulsed and continuous radiation modes, learn how to measure the dependence wavelength and power of a laser on the temperature , the total and differential slope efficiency, pulse duration and pulse repetition rate, and modulate radiation.