A system for generating pulsed laser beam, comprising: a laser diode pump for generating a raw laser beam; a wavelength-division multiplexer connected to said pump, for multiplexing the raw laser beam; an erbium-doped fibre connected to said multiplexer; an isolator connected to said erbium-doped fibre; a coupler, one end of which is connected to said isolator, and the other end of which is connected to the port through which the pulsed laser beam is output; and a saturable absorber made of erbium-doped fibre, one end of which is connected to said coupler, and the other end of which is connected to said multiplexer.