A distributed antenna system, comprising: a first access unit and a remote unit, wherein the first access unit and the remote unit are coupled to each other via an analog optical fiber, and the first access unit comprises: a first port configured to receive a first downlink analog radio frequency signal from a first base station; a first analog-to-digital conversion unit coupled to the first port and configured to perform analog-to-digital conversion on the first downlink analog radio frequency signal to generate a first downlink digital signal; a first digital processing unit coupled to the first analog-to-digital conversion unit and configured to perform digital signal processing on the first downlink digital signal to generate a second downlink digital signal; a first digital-to-analog conversion unit coupled to the first digital processing unit and configured to perform digital-to-analog conversion on the second downlink digital signal to generate a second downlink analog radio frequency signal; an analog optical module coupled to the first digital-to-analog conversion unit and configured to perform electro-optical conversion on the second downlink analog radio frequency signal to generate a first downlink analog optical signal which is transmitted to the remote unit via the analog optical fiber and further configured to receive an uplink analog optical signal from the remote unit, and convert the uplink analog optical signal into a first uplink analog radio frequency signal; a second analog-to-digital conversion unit coupled to the analog optical module and configured to perform analog-to-digital conversion on the first uplink analog radio frequency signal to generate a first uplink digital signal; the first digital processing unit further coupled to the second analog-to-digital conversion unit and further configured to perform digital signal processing on the first uplink digital signal to generate a second uplink digital signal; and a second digital-to-analog conversion unit coupled to the first digital processing unit and the first port and further configured to perform digital-to-analog conversion on the second uplink digital signal to generate a second uplink analog radio frequency signal which is transmitted to the first base station via the first port. a first port configured to receive a first downlink analog radio frequency signal from a first base station; a first analog-to-digital conversion unit coupled to the first port and configured to perform analog-to-digital conversion on the first downlink analog radio frequency signal to generate a first downlink digital signal; a first digital processing unit coupled to the first analog-to-digital conversion unit and configured to perform digital signal processing on the first downlink digital signal to generate a second downlink digital signal; a first digital-to-analog conversion unit coupled to the first digital processing unit and configured to perform digital-to-analog conversion on the second downlink digital signal to generate a second downlink analog radio frequency signal; an analog optical module coupled to the first digital-to-analog conversion unit and configured to perform electro-optical conversion on the second downlink analog radio frequency signal to generate a first downlink analog optical signal which is transmitted to the remote unit via the analog optical fiber and further configured to receive an uplink analog optical signal from the remote unit, and convert the uplink analog optical signal into a first uplink analog radio frequency signal; a second analog-to-digital conversion unit coupled to the analog optical module and configured to perform analog-to-digital conversion on the first uplink analog radio frequency signal to generate a first uplink digital signal; the first digital processing unit further coupled to the second analog-to-digital conversion unit and further configured to perform digital signal processing on the first uplink digital signal to generate a second uplink digital signal; and a second digital-to-analog conversion unit coupled to the first digital processing unit and the first port and further configured to perform digital-to-analog conversion on the second uplink digital signal to generate a second uplink analog radio frequency signal which is transmitted to the first base station via the first port.