Patent ID: 6049415
Filing Date: 2000-04-11
Classification: H01S

Abstract:
An optical amplifier comprising:a first stage polarization separator that receives an input optical signal along an input path, the optical signal having a polarization state which results in its being directed along a first path by the first stage polarization separator;a first stage optical gain medium along the first path that amplifies the optical signal, the first stage gain medium having a relatively low noise figure;a first stage reflector that reflects the amplified first path optical signal back through the first gain medium;a first stage polarization shifter that changes the state of polarization of the first path optical signal by a predetermined amount such that upon return of the optical signal to the first stage polarization separator, the optical signal follows a second path out of the first stage polarization separator;a second stage polarization separator that receives the optical signal output along the second path and directs it along a second stage amplifier path;a second stage optical gain medium along the second stage amplifier path that amplifies the optical signal, the second stage gain medium having a relatively power output;a second stage reflector that reflects the optical signal back through the second stage gain medium; anda second stage polarization shifter that changes the state of polarization of the optical signal by a predetermined amount, such that upon return of the optical signal to the second stage polarization separator the optical signal follows an output path from said second stage polarization separator.