Embodiments of the present invention disclose an optical transmitter, a 10 G-DML, an MPD 1, an MPD 2, a collimation lens, and a narrowband optical filter are disposed in a TO to achieve monitoring of an optical power, received optical powers are monitored by using the MPD 1 and the MPD 2, the detected optical powers are output to a wavelength locking monitoring circuit by using a TO pin, variations, which are detected by the wavelength locking monitoring circuit, of the optical power and a variation of a wavelength locking factor K0 are separately compared with corresponding thresholds, and a comparison result are sent to a wavelength locking control circuit, to enable the wavelength locking control circuit to adjust, according to the comparison result and by using the TO pin, a temperature of a TEC to perform wavelength alignment.