All-fiber coherent combining of Er-doped amplifiers through refractive index control in Yb-doped fibers

摘要

We propose a simple all-fiber solution for coherent beam combining of Er-doped fiber amplifiers. Thisnmethod, which we believe to be a new method, employs the effect of refractive index changes in Yb-dopednfibers induced at u00011.55 u0001m by optical pumping at u0001980 nm, which is performed for an active phase controlnin the fiber configuration. An algorithm based on population inversion in a two-level system supports thenstraightforward implementation of the effect into a feedback loop. Combining two 500 mW Er-doped amplifiersnin a single-mode fiber is successfully demonstrated with control by u0001120 mW laser diode. The methodnis shown to operate against the acoustic phase noise within the range of u0001u0002 rad and with a rate ofnu00012.6u0002 rad/ms that potentially serves combining of at least 50 amplifiers similar to those used in practicalnwork. © 2009 Optical Society of America