Multipoint Vibration Sensing Using Fiber Bragg Gratings and Current-Modulated Laser Diodes

Multipoint vibration sensing is demonstrated using fiber Bragg gratings and optical-frequency-domain reflectometry (OFDR). Using OFDR, a few thousand arrayed sensors can be monitored with a measurement time limited by the wavelength-scanning rate of the light source. Here, a laser diode serves as the source. Its wavelength can be modulated by varying the injection current at high frequency using a laser-diode controller, so that high-speed scanning can be achieved. It is experimentally demonstrated that the proposed sensor achieves vibration measurement with a noise density of 7 fm/ $\sqrt{\rm Hz}$ , measurement time of 10 $\mu$ s.