The developments of Internet of Things,Virtual Reality and Artificial Intelligence (AI) technology have increased the demand for bandwidth of optical fiber access passive optical netwo rk,in which the modulators have become a key factor restricting the bandwidth of passive optical network.Chirp -managed lasers,which combine the advantages of direct modulated lasers and external modulators,have attract ed wide attention for their simple structure and easy integration in low speed optical access network.The dynamic characteristics of chirp-managed lasers were studied by using coupled rate equation theory.The generation princi ple and time-frequency characteristics of 40Gbit/s chirp-managed modulation format were analyzed.The performance of the chirp-managed modulation format was compared with that of the 40Gbit/s non-re turn-to-zero (NRZ) signal generated by the external modulator in the high speed access network without dis persion compensation.The results show that the 40Gbit/s chirp-managed modulation format with a bandwidt h of 48.5GHz has a corresponding dispersion tolerance of 215ps/nm at the 1dB sensitivity penalty. Compared with NRZ modulation format,the transmission distance of chirp-managed modulation format without dispersion com pensation is increased by 1.6times,which shows a very strong anti-dispersion capability and embodies high a pplication values in high speed access networks.Relevant results provide a theoretical reference for the actual system design.