Abstract: In order to study relationship between output power and device temperature of a vertical cavity surface emitting laser (VCSEL)and determine the temperature range at which the user can use the network normally, the relationshipmodel between output power and working current (P-I) was used to do theoretical analysis and experimental verification. Then the model was optimized by simplifying the parameters and introducing voltage-current (U-I) relationship curve. The model parameters were obtained by means of Levenberg-Marquardt (LM) algorithm. The P-I characteristic curve data at different temperatures were predicted by comparing the similarity between measured data and fitting data at 20℃.The results show that, at a fixed temperature, optical output power increasesat first and then decreaseswith the increaseof driving current. At the fixed driving current, optical output power decreaseswith the increaseof temperature. To ensure the normal Internet using, room temperature of VCSEL laserscan notbe higher than 31℃.