Coded optical time domain reflectometer system based on orthogonal frequency division multiplexing technology

In this paper an Optical Time Domain Reflectometer (OTDR) sensing method based on Orthogonal Frequency Division Multiplexing (OFDM) technology is proposed. In this system, the probe signal consist of multiple Simplex coded sequences which modulated onto different orthogonal sub-carriers. The signal-to-noise ratio (SNR) of the system can be improved by the coding gain of the Simplex codes. Meanwhile, different pulsed sequences can be sent into the fiber simultaneously, which solves the time-consuming problem of the traditional coded OTDR. In the Simplex coding OTDR distributed sensing system based on OFDM technology built by this method, compared with a 50 ns single pulse, the SNR of the fiber end of the 31-bit coding curve is improved by 4.42 dB, and the measurement time is reduced by 96.77% compared to traditional Simplex coding OTDR system.