Control link switching method and device and RRU in double fiber transmission system

The invention discloses a control link switching method and device and an RRU in a double fiber transmission system so as to detect control link abnormities in the double fiber transmission system and trigger control link to switch, and guarantee normal operation of a communication system. The method comprises the following steps: a link state judgment module determines a current control link, wherein the current control link is a first communication link or a second communication link; the link state judgment module judges whether a warning signal output by a first warning acquisition module or a second warning acquisition module is received, wherein the first warning acquisition module outputs the warning signal when the first communication link is judged to be abnormal, and the second warning acquisition module outputs the warning signal when the second communication link is judged to be abnormal; and if the link state judgment module receives the warning signal of current control link abnormity, the link state judgment module triggers a link switching control module to carry out control link switching.