The effect of pulse duration on the Brillouin frequency shift accuracy in the differential cross-spectrum BOTDR (DCS-BOTDR) fiber sensor

• Published in: Optical fiber technology Vol. 72; p. 102977
• Main Authors: Zan, Mohd Saiful Dzulkefly, Almoosa, Ahmed Sabri Kadhim, Ibrahim, Mohd Faisal, Elgaud, Mohamed M., Hamzah, Abdulwahhab Essa, Arsad, Norhana, Mokhtar, Mohd Hadri Hafiz, Bakar, Ahmad Ashrif A.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.09.2022
• Subjects: BFS accuracy; BOTDR; Cross-correlation; Signal differential; Signal differential; BFS accuracy; BOTDR; Cross-correlation
• ISSN: 1068-5200; 1095-9912
• DOI: 10.1016/j.yofte.2022.102977

•The cross-correlation between short and long pulses in BOTDR results in a narrow Brillouin spectrum width.•The subtraction between two optical pulses with slightly different duration offers sub-meter spatial resolution measurement.•The DCS-BOTDR technique offers a potential application for long distance fiber measurement with high measurement accuracy. In this paper, we report the effect of pulse duration on the Brillouin frequency shift (BFS) accuracy measurement in our previously proposed differential cross-spectrum Brillouin optical time domain reflectometry (DCS-BOTDR) fiber sensing technique. The DCS-BOTDR uses a pair of optical pulsed probes generated via intensity modulation scheme, in which the first probe consists of a long- and short duration of pulses separated by a short interval, while the second probe only has the long pulse with the same duration as the first one. From the experimental analysis, by varying the duration of the long pulse between 6 and 60 ns, we found that an optimum range of the long pulse duration between 14 and 22 ns provided good measurement of BFS accuracy around 5.3 MHz. Furthermore, by heating up a 2 m fiber section at the end of a 4 km test fiber, by using long- and short pulse durations of 18 ns and 4 ns respectively, we have successfully demonstrated 40 cm spatial resolution and 4 °C of temperature resolution measurement.