FIELD: communications engineering. SUBSTANCE: fiber-optic communication line has amplifiers 6-9 built around optical fibers with active core for signals transmitted. Two optical-pump emitting laser diodes 19,20 are connected to each active optical fiber incorporated in line amplifiers 6-9, one on each end of optical fiber. First diode 19 of the two runs continuously and diode 20 is held in reserve and starts functioning as soon as first one fails. Laser diodes 19,20 are coupled with microprocessor unit 29 capable of forcing them to send alarm signals to line stations 10, 11 and to receive control signals from the latter which change application of these diodes 19, 20. EFFECT: improved reliability. 5 cl, 7 dwg
