Method, device, and system for locking wavelength of optical signal

A method, device, and system for locking the wavelength of optical signal is disclosed, wherein the method includes the steps of: obtaining the output power of a second laser; obtaining the temperature difference between a first laser and the second laser according to the corresponding relationship between the output power of the second laser and the temperature difference between the first laser and the second laser; adjusting the temperature of the first laser according to the corresponding relationship between the wavelength of the second laser and the temperature difference. The method, device, and system can enable the wavelength of the optical signal outputting from a slave laser to be stable, and the entire control process to be simple and not to require external intervention.