The present disclosure provides example data transmission methods and apparatuses. One example method includes obtaining a radio signal by using an input port. Based on a correspondence between an input port and a bearer channel, a bearer channel corresponding to the radio signal is determined. Code Division Multiple Access (CDMA) modulation and carrier modulation on the radio signal are performed according to a codeword and a frequency sub-band corresponding to the bearer channel, to obtain a modulated electrical signal. The modulated electrical signal is then modulated to an optical wavelength corresponding to the bearer channel to obtain a modulated optical signal, and the modulated optical signal is sent to an optical network.