This paper deals with the sensitivity to polarization of multiple quantum wells (MQW) semiconductor InGaAs/InP saturable absorbers in Fabry-Perot (F-P) micro-cavity used as nonlinear mirrors (NLM) under normal incidence. This sensitivity to polarization is due to an anisotropy of MQW materials. In this experimental study, we localize the singular axis of the crystal and we determine the conditions where the sensitivity to polarization is the most evident. Then, we examine the reflectivity of the NLM as a function of the wavelength and the polarization of the input optical signal and the temperature of the chip. Finally, we try to assess the consequences for a 2R regenerator (for re-amplification and re-shaping) based on those NLM by evaluating the polarization dependent losses according to the wavelength of the input signal and the temperature of the chip.