An optical amplifier (200) comprises an active fiber (201), a first pump source (202) and a second pump source (203). The amplifier further comprises a first and a second coupling device (210, 211) having at least two input ports and at least two output ports. Said first and second coupling devices, said first and second pump sources and said active fiber are connected in such a manner as: the first input ports of said first and seconed coupling devices are connected to said first and second pump sources, respectively; the first output ports of said first and second coupling devices are connected to a first and a second end of said active fiber, respectively; the second output port of said first coupling devices is connected to the second input port os said second coupling device; the second output port of said second coupling device is connected to the second input port of said first coupling device
