Phase-Noise-Compensated Optical Frequency-Domain Reflectometry

The theory of phase-noise-compensated optical frequency-domain reflectometry (PNC-OFDR), a novel type of optical frequency-domain reflectometry (OFDR) with a measurement range much longer than the laser coherence length, is described, and the signal and noise spectral densities are deduced for a discussion of signal-to-noise ratio (SNR). The analysis of PNC-OFDR shows the possibility of obtaining a high SNR by using many reference signals for phase-noise compensation. By using a ldquoconcatenately generated phaserdquo (CGP), only a single auxiliary interferometer is needed for phase-noise compensation, and other reference signals can be easily generated by performing a calculation based on signal use obtained from the single auxiliary interferometer. An experimental investigation shows the feasibility of using CGPs for PNC-OFDR by dividing the fiber under test into several sections for phase-noise compensation. Moreover, the influence of strong reflection events on Rayleigh backscattering is discussed by considering the dead zone caused by a fiber/air Fresnel reflection. It is shown theoretically that a dead zone that has no influence on the neighboring section can be achieved by using suitable parameters in an actual system.