High spatial resolution fast Brillouin optical time-domain analysis enabled by frequency-agility digital optical frequency comb

Abstract

A significant spatial resolution enhancement scheme for digital optical frequency comb (DOFC)-based fast Brillouin optical time-domain analysis (BOTDA) is proposed and experimentally demonstrated by using frequency-agility probes, without sacrificing the frequency resolution. The proposed system ensures high spatial resolution by using short frame duration, meanwhile enabling high frequency resolution retrieval of the Brillouin gain spectrum using frequency interleaving of multiple frequency-agility DOFC probes. Additionally, quadratic phase coding is introduced to release the influence of the high peak to average power ratio of the probes. Eventually, the proposed BOTDA sensor achieves a record 5-m spatial resolution over 10-km fiber with less than 2-MHz frequency uncertainty, and a 1-GHz dynamic measurement range. For proof of concept, 10-Hz vibration sensing is also successfully demonstrated at a 40-Hz sampling rate, showing great potential for fast measurement. It is worth mentioning that a higher spatial resolution can be achieved by using more frequency-agility DOFC probes, albeit at the expense of increasing the measurement time.