Simplified Brillouin optical time-domain sensor based on direct modulation of a laser diode

We propose and experimentally demonstrate a novel kind of Brillouin optical time-domain sensor based on direct modulation of a laser diode (LD) which is free from the use of any microwave device. The Brillouin pump and the probe waves are alternately generated by the LD modulation, and an optical time-domain analysis adopted for distributed measurement. Maps of Brillouin frequency shift are obtained with a spatial resolution of 2 m and an accuracy of ±2 MHz in a 2 km optical fiber.