The modulation response characteristics of a Fabry-Perot semiconductor laser(slave FP-LD) subjected to light injection from another Fabry-Perot semiconductor laser(master FP-LD) have been investigated theoretically.The results show that the modulation response performances of the slave FP-LD depend on the light injection strength,the central mode frequency detuning Δf and the mode spacing difference Δλ between the slave FP-LD and the master FP-LD.With the increase of the light injection strength from the master FP-LD,the 3 dB modulation bandwidth of the slave FP-LD will be enhanced;however,if the injection strength is increased to certain degree,the front side of the relaxation oscillation peak will be reduced to below 3 dB,which results in the rapid decrease of the 3 dB modulation bandwidth.With the increase of Δf,for a relatively small injection strength level,the 3 dB modulation bandwidth will behave a monotonous enlargement until the slave FP-LD operates in a period-one state(P1).For a relatively strong optical injection level,the slave FP-LD has a broad injection-locked frequency detuning area.Within the injection-locked area,with the increase of frequency detuning Δf,the 3dB modulation bandwidth increases at first and then decreases after experiencing a maximum value.For given light injection strength and frequency detuning,the 3 dB modulation bandwidth of the slave FP-LD has two maximums and behaves a symmetrical distribution with the change of Δλ.By choosing reasonable parameters,the 3 dB modulation bandwidth can be significantly improved.For the parameter values selected in this paper,the 3 dB modulation bandwidth can increase 5.5 times compared with the case of free running. The modulation response characteristics of a Fabry-Perot semiconductor laser (slave FP-LD) subjected to light injection from another Fabry-Perot semiconductor laser (master FP-LD) have been been theoretically. The results show that the modulation response performances of the slave FP-LD depend on the light injection strength, the central mode frequency detuning Δf and the mode spacing difference Δλ between the slave FP-LD and the master FP-LD. With the increase of the light injection strength from the master FP-LD, the 3 dB modulation bandwidth of the slave FP-LD will be enhanced; however, if the injection strength is increased to certain degree, the front side of the relaxation oscillation peak will be reduced to 3 dB, which results in the rapid decrease of the 3 dB modulation bandwidth. The increase of Δf, for a more small injection strength level, the 3 dB modulation bandwidth will behave a mononony enlargement until the slave FP-LD operates in a period-one state (P 1). For a relatively strong optical injection level, the slave FP-LD has a broad injection-locked frequency detuning area. With the injection-locked area, with the increase of frequency detuning Δf, the 3dB modulation bandwidth increases at first and then decreases after experiencing a maximum value. For given light injection strength and frequency detuning, the 3 dB modulation bandwidth of the slave FP-LD has two maximums and behaves a symmetrical distribution with the change of Δλ.By choosing reasonable parameters, the 3 dB modulation The bandwidth can be significantly improved. For the parameter values ​​selected in this paper, the 3 dB modulation bandwidth can increase 5.5 times compared with the case of free running.