Amplified telecommunication system for wavelength-division multiplexing transmission having an equalized reception power

A method for determining the optimum length of an active fiber in an optical amplifier for operation in a multiple wavelength system, wherein said amplifier comprises an input and an output, a rare earth-doped active fiber and pumping means for supplying a pumping light signal of a predetermined pumping power to said active fiber, said method comprising the steps of:

• optically connecting the input of the optical amplifier to the output of the optical amplifier;
• supplying said active fiber with the pumping signal from said pumping means for causing light emission from said active fiber at a predetermined emission power;
• controlling the spectral range and optical power of said emission;
• and
• selecting a length for said active fiber such that the emission exhibits two stable emission peaks at two different wavelengths within a band of wavelengths and at a predetermined power of the optical signal at said output.

A multi-wavelength optical telecommunication system comprising:

• an optical signal transmitting station comprising optical signal generating means for simultaneously generating at least two optical transmission signals at two different wavelengths in a band of predetermined width;
• a receiving station for receiving said optical transmission signals;
• an optical fiber line connecting said transmitting and receiving stations for simultaneously transmitting both of said optical transmission signals from said transmitting station to said receiving station, said optical fiber line comprising at least two optical line amplifiers connected in series and to said transmitting station and said receiving station by optical fibers, each of said line amplifiers comprising a length of active fiber doped with dopants including a rare earth material and a pumping means coupled to the active fiber for amplifying both said optical transmission signals;
• and
• wherein the length of active fiber of at least one of said line amplifiers, the power of the pumping means of said at least one of said line amplifiers and said dopants are selected so that the optical signal/noise ratios for said optical transmission signals having different wavelengths and received at said receiving station are substantially equal when said optical transmission signals are simultaneously transmitted from said transmitter station to said receiving station.