High-precision distributed broadband microwave photonic local oscillator signal transmission system based on frequency tuning

A high-precision distributed broadband microwave photonic local oscillator (LO) signal transmission system based on frequency tuning, comprising:

• a central station unit;
• a remote user unit;
• and
• a plurality of downloading user units;
• wherein the plurality of the downloading user units are connected in series through a first optical fiber link to form a single-fiber bidirectional serial optical link, the first optical fiber link is a single-fiber link;
• a first end of the single-fiber bidirectional serial optical link is connected to the central station unit, a second end of the single-fiber bidirectional serial optical link is connected to the remote user unit;
• the central station unit is configured to convert an LO signal to be transmitted to an optical domain through an optical carrier to form a central station LO optical signal, extract phase/frequency fluctuation information of a first part of the first optical fiber link between the central station unit and the remote user unit according to a remote loopback composite optical signal looped back by the remote user unit, generate a central station frequency shift optical signal according to the phase/frequency fluctuation information of the first part of the first optical fiber link, combine the central station LO optical signal and the central station frequency shift optical signal into a first path to form an output composite optical signal, and output the output composite optical signal to the first optical fiber link;
• the remote user unit is configured to receive the output composite optical signal through the single-fiber bidirectional serial optical link, restore the output composite optical signal to obtain a first output LO signal, perform frequency shifting on each of optical signals in the output composite optical signal, combine the optical signals in the output composite optical signal into a second path to form the remote loopback composite optical signal, and loop back the remote loopback composite optical signal to central station unit;
• and
• the plurality of the downloading user units are configured to couple the output composite optical signal and the remote loopback composite optical signal and restore the output composite optical signal and the remote loopback composite optical signal after being coupled to obtain a second output LO signal, wherein the output composite optical signal is transmitted forward in the first optical fiber link and the remote loopback composite optical signal is transmitted backward in the first optical fiber link.