Time Phase Shifting Based Demodulation Method for Fast Optical Fiber Transfer Delay Measurement

A fast optical fiber transfer delay (OFTD) measurement system based on time phase shifting is proposed to meet the requirement of dynamic measurement scenarios, such as distributed MIMO communication systems and free space laser positioning. The probe optical signal is modulated by a single-frequency electrical signal within a pulse envelope. The pulse envelope provides a time reference for unambiguous measurement, while the single-frequency modulation simplifies the signal processing requirements. With the demodulation in the time and phase domain, the OFTD demodulation computation complexity is reduced by N times, where N is determined by the collected data length. Therefore, the OFTD measurement speed is enhanced while ensuring measurement accuracy and range. Additionally, the proposed method avoids the need for broadband signal generation or frequency sweeping, thereby simplifying the system structure.