Partially coherent interaction of the feedback light with the field in the laser cavity is affirmed with the fiber Bragg grating (FBG) stabilized 980-nm pump lasers, on the contrast of normally accepted totally incoherent state of operation in the “coherence collapse” regime. Coherence parameter y was defined in this paper to identify the fraction of feedback light working coherently. It is shown that y can be determined by fitting the measured power-difference versus pumping-rate curve to the simulation results. Experiments confirm that coherence parameter y decreases while the distance between the FBG and the laser facet increases, and vice versa. While, if the device is kept operating in the “coherence-collapse” regime, y would not change with the amount of feedback. This work will be help to improve the performance of the high power FBG stabilized 980-nm pump laser. / Thesis / Master of Applied Science (MASc)