Signal transmission method and apparatus

An apparatus, comprising:

• a signal combiner, configured to:
• superimpose a first electrical signal onto a first radio frequency electrical signal to obtain a unipolar-envelope modulated signal, and output the unipolar-envelope modulated signal to an optical modulator, wherein the first radio frequency electrical signal is determined based on a baseband signal, an upper envelope of the first radio frequency electrical signal and a lower envelope of the first radio frequency electrical signal are symmetric with respect to a direct current component, and a carrier wave in the unipolar-envelope modulated signal is a sine wave;
• and
• the optical modulator, configured to perform optical modulation on the unipolar-envelope modulated signal to obtain a first radio frequency optical signal, wherein the first radio frequency optical signal is a unipolar-envelope radio frequency optical signal, a lower envelope of the first radio frequency optical signal is flat, and a lower envelope amplitude of the first radio frequency optical signal is less than or equal to a first value, wherein:
• the optical modulator is further configured to send the first radio frequency optical signal;
• the first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting a baseband amplitude signal corresponding to the baseband signal;
• and
• the unipolar-envelope modulated signal is a radio frequency electrical signal with a flat lower envelope, and an upper envelope of the unipolar-envelope modulated signal corresponds to the upper envelope of the first radio frequency electrical signal;
• or the unipolar-envelope modulated signal is a radio frequency electrical signal with a flat upper envelope, and a lower envelope of the unipolar-envelope modulated signal corresponds to the lower envelope of the first radio frequency electrical signal.

A non-transitory computer-readable storage medium storing computer program or instructions, wherein the computer program or the instructions, when executed by at least one processor of a communication apparatus, cause the communication apparatus to perform operations comprising:

• superimposing a first electrical signal onto a first radio frequency electrical signal to obtain a unipolar-envelope modulated signal, and output the unipolar-envelope modulated signal to an optical modulator, wherein the first radio frequency electrical signal is determined based on a baseband signal, an upper envelope of the first radio frequency electrical signal and a lower envelope of the first radio frequency electrical signal are symmetric with respect to a direct current component, and a carrier wave in the unipolar-envelope modulated signal is a sine wave;
• and
• performing optical modulation on the unipolar-envelope modulated signal to obtain a first radio frequency optical signal, wherein the first radio frequency optical signal is a unipolar-envelope radio frequency optical signal, a lower envelope of the first radio frequency optical signal is flat, and a lower envelope amplitude of the first radio frequency optical signal is less than or equal to a first value;
• and
• sending the first radio frequency optical signal, wherein:
• the first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting a baseband amplitude signal corresponding to the baseband signal;
• and
• the unipolar-envelope modulated signal is a radio frequency electrical signal with a flat lower envelope, and an upper envelope of the unipolar-envelope modulated signal corresponds to the upper envelope of the first radio frequency electrical signal;
• or the unipolar-envelope modulated signal is a radio frequency electrical signal with a flat upper envelope, and a lower envelope of the unipolar-envelope modulated signal corresponds to the lower envelope of the first radio frequency electrical signal.