Effect of the linewidth enhancement factor on the operation of InGaAs/InP pumping lasers emitting a wavelength of 980 nm under strong optical feedback is investigated. The investigations are performed based on a new external optical feedback model for semiconductor lasers, which is applicable under any arbitrary strength of optical feedback. The results show that the semiconductor laser operates under strong optical feedback in CW, pulsation and chaos and pulsation operation at lower and higher values of the linewidth enhancement factor respectively. We predict that semiconductor laser subjected to strong optical feedback exhibits much more stable pulsing operation under higher values of the linewidth enhancement factor which, means that the laser is locked at the external cavity frequency.