US Patent 7095554 Pumping method and unit for optical amplifiers

Optical pumping unit comprising a first pump source adapted to emit a first pump radiation at wavelength λp1; a second pump source adapted to emit a second pump radiation at wavelength λp2, with wavelength λp2 different from wavelength λp1; and a common coupling section comprising a first and a second port connected to the first and second pump source for respectively receiving the first and the second pump radiation; a third port for a signal radiation at wavelength λs; a fourth port, wherein the coupling section is adapted to combine, in the fourth port, the signal radiation and the first and second pump radiation through a reversal of the direction of propagation of the first pump radiation from the first port to the fourth port.