Simplified Brillouin optical time-domain analysis with extended measurement range by frequency dithering

We demonstrate a simplified Brillouin optical-time domain analysis system based on direct current modulation of a laser diode with an extended measurement range and an enhanced spatial resolution. Slow and periodic frequency dithering is additionally applied to the laser diode to suppress the noise originated from coherent Rayleigh scattering. The distribution of Brillouin gain spectra along a 25 km fiber is successfully measured with a 1 m spatial resolution and an accuracy of sigma = 0.78 MHz, confirming its high practicality as a cost-effective solution.