OPTICAL FIBER TELECOMMUNICATION SYSTEM

The present invention relates to an optical fiber telecommunication system and more in particular to an optical telecommunication system having a high loss transmission line. It relates also to an optical fiber amplifier doped with a rare earth, such as erbium, for use in said system. The optical fiber telecommunication system comprising: - a transmission station producing at least one transmission optical signal in a predetermined wavelength band carrying the information; - a receiving station for receiving said transmission optical signal; - an optical fiber line connecting said transmission station and said receiving station, and - at least one optical fiber amplifier connected along said line for amplifying said transmission optical signal, said amplifier having a total optical output power greater than 20 dBm. The optical fiber amplifier for amplifying a transmission optical signal compris ing: - a first stage and a second stage; - an isolator placed between the first stage and the second stage; in which the second stage comprises: - an erbium doped fiber; - pump means comprising two pump sources at different wavelengths in a second stage pump wavelengths band; - a WDM coupling means coupling said different wavelengths as a composite second stage pump signal; - a coupler coupling said composite second stage pump signal and said transmission optical signal to said erbium doped fiber.