c of the laser diode at a plurality of specific temperatures e g a low temperature u2212 40 u00b0 c a normal temperature 25 u00b0 c and a high temperature 85 u00b0 c into the following equation 1 and equation 2 equation 1 represents the relationship between the threshold current i th t of the laser diode 3031 and temperature t and equation 2 represents the relationship between the slope efficiency se t and temperature t i th t i 0 k 1 exp t t 1 equation 1 where i 0 k 1 and t i are characteristic constants se t s 0 u2212 k s exp t t s equation 2 where s 0 k s and t s are characteristic constants referring to fig4 the method of the present invention includes the following steps 4 a to begin with as there must exist a linear or substantially linear relationship between the optical power p t and the on current i t of a common laser diode at any given temperature t the aforementioned manufacturer provided characteristic data are used to determine the characteristic constants in equation 1 and equation 2 at the specific temperatures then the threshold currents i th t and the corresponding slope efficiencies se t in an entire temperature range are determined by an applicable approximation method after that the relationship between the optical power p t and the on current i t of the laser diode 3031 over the entire temperature range is determined as given by the following equation p t i t u2212 i th t se t equation 3 in another preferred embodiment of the present invention considering that different fiber optic transceivers 300 or laser.