We have performed numerical analysis of the electro- and photo luminescence (PL) of a wafer which would have been used in the manufacture of a multiquantum-well 1.5-mu m InGaAsP-InP-based semiconductor laser diode, It is shown that the deviation of the carrier distribution from a quasi-Boltzmann distribution plays a very important role in the interpretation of PL data. This is dramatically illustrated in the analysis of PL under short circuit conditions. Under this condition, the usual analytical theory predicts no FL, while our calculations agree with our experimental results in which FL is observed. For a wafer with electrical contacts, our calculations show that an increase in the positive applied voltage decreases the PL threshold and that the PL intensity saturates at large pump powers. Both these observations are consistent with the PL experiments. Moreover, our analysis shows that, in addition to the PL spreading effect, a nonBoltzmann carrier distribution is another important factor in determining the threshold of PL intensity.