Laser Feedback OFDR With High Sensitivity

Optical frequency domain reflectometry (OFDR) has been widely used in many fields. Nevertheless, the echo signal in OFDR measurements is usually weak. To enhance echo wave for high signal-to-noise ratio (SNR), the emission power of the laser is typically high. To improve the sensitivity to the echo wave and spatial resolution of OFDR, a laser feedback OFDR(LF-OFDR) system is proposed in this paper. Employing the spontaneous enhancement in laser cavity, LF-OFDR provides an improved SNR of about 27 dB without extra amplifiers compared with the conventional OFDR. Consequently, targets at 1.5 km are detected utilizing only a 0.7 nW probe beam. Employing an auxiliary interferometer to suppress the spectral broadening caused by the nonlinearity of frequency modulation, the signal peaks can be effectively calculated at 1.5 km. The spatial resolution in the range of 1.5 km is 1.53 mm. Advanced in photon consumption and resolution, the proposed method promises more economical and precise development of OFDR.