Orthogonal frequency division multiplexing (OFDM) is a multi-carrier modulation technology, including single sideband modulation and double sideband modulation. In a single sideband modulation OFDM system, at a transmit end, a to-be-sent signal may be carried on an optical carrier transmitted by a laser, then single sideband filtering is performed by using a filter on the optical carrier that carries the to-be-sent signal, and therefore an OFDM signal is transmitted. After the transmitted OFDM signal is transmitted by using an optical fiber link, a transmitted data signal is correspondingly received performed at a receive end according to a pilot in the OFDM signal. In the foregoing OFDM system, a frequency offset phenomenon usually occurs, that is, after performing the single sideband filtering, the filter cannot filter out a carrier frequency at a fading point, which causes deterioration of system performance. Therefore, frequency offset correction needs to be performed on the OFDM system.
In the prior art, a perturbation signal is usually pre-used to implement scrambling on the laser, then a wavelength locker is used to detect the OFDM signal transmitted by the laser, and a center frequency of the laser is determined according to a correspondence that is between the perturbation signal and the center frequency of the laser and that is obtained by means of detection by the wavelength locker, so that the center frequency of the laser is adjusted when offset of the center frequency of the laser occurs, and frequency offset correction of the OFDM system is implemented. As can be seen, the prior art is only applicable to frequency offset caused by the offset of the center frequency of the laser, and efficiency of frequency offset correction is low.