The OTDR With High Dynamic Range Based on LFM Signal and FDM

In this paper, we proposed a kind of novel optical time-domain reflectometer (OTDR) which employed the linear frequency modulation (LFM), the fractional Fourier transform (FrFT), and electrical domain frequency division multiplexing (FDM) technologies. In our proposed OTDR, the intensity of the probe pulse was modulated by the LFM signal. At the receiver of the OTDR, the LFM signal was recovered through FrFT after the direct detection. The LFM and FrFT were helpful to overcome the deterioration induced by the multipath interference of Rayleigh backscattering and improve the signal-to-noise ratio (SNR) of the backscattered probe signal to realize a higher dynamic range (DR). With the FDM technology, the DR could be expanded furthermore. Experiments showed that about 11dB DR improvement was realized by our method with the same spatial resolution (SR) compared with a single pulse OTDR.