Embodiments of the present disclosure provide a method and device of signal processing in optical fiber communication systems. The method includes dividing electrical signals for a plurality of receivers in the optical fiber communication system into a plurality of groups, the plurality of groups each being associated with at least one of the plurality of receivers. The method also includes obtaining time-domain multiplexed signals by multiplexing the electrical signals in the plurality of groups in time domain. The method also includes multiplexing the time-domain multiplexed signals in the plurality of groups in frequency domain such that the time-domain multiplexed signals occupy respective sub-bands of a transmission bandwidth for the optical fiber communication system. The method also includes converting the frequency-domain multiplexed signals into analog optical signals for transmission.