Controlling time-frequency characteristic of optical impulse in the Radio-over-Fiber transmission systems using Mach-Zehnder modulator

The article describes new method of optical signals multiplexing in Radio-over-Fiber networks based on signal’s chirp (frequency-time characteristic). A method for chirp control using Mach-Zehnder Modulator (MZM) is described. Mathematical proof of possibility of chirp control in MZM is given. The dependence of chirp function on control input voltage is found. The experiment procedure is described. The experiment was conducted using optical BER-tester, MZM, DC-voltage source, ramp generator and optical line with a length of 20 km. It was found that BER decreases twice when using ramp generator instead of DC-voltage source on control input of MZM. As a conclusion, the possibility of transmitting a small amount of additional data (for example, network service information, control signals or switching labels) using the chirp of optical signal is described. The use of chirped signals in SDN is suggested for the transmission of service data between network nodes as an example of practical application for described technology.