Detection of 2-mm-long strained section in silica fiber using slope-assisted Brillouin optical correlation-domain reflectometry

Abstract

Slope-assisted Brillouin optical correlation-domain reflectometry is a single-end-access distributed Brillouin sensing technique with high spatial resolution and high-speed operation. We have recently discovered its unique feature, that is, strained or heated sections even shorter than nominal resolution can be detected, but its detailed characterization has not been carried out. Here, after experimentally characterizing this "beyondnominal-resolution" effect, we show its usefulness by demonstrating the detection of a 2-mm-long strained section along a silica fiber. We also demonstrate the detection of a 5-mm-long heated section along a polymer optical fiber. The lengths of these detected sections are smaller than those of the other demonstrations reported so far.

Recent Advances in Brillouin Optical Correlation-Domain Reflectometry

“…In this section, we describe the fundamentals, unique features, and recent advances of the high-speed configuration of BOCDR, named slope-assisted BOCDR [59][60][61], with an emphasis on the so-called beyond-nominal-resolution effect.…”

Prevention of false peak detection of Brillouin gain spectrum by using peak tracking and trend analysis

“…These are Brillouin Optical Correlation Domain Analysis (BOCDA) 10 and Brillouin Optical Correlation Domain Reflectometry (BOCDR) 11 . The correlation domain methods are reported to achieve spatial resolution better than 1 cm 12 …”

“…11 The correlation domain methods are reported to achieve spatial resolution better than 1 cm. 12 A problem common for optical fiber sensors using Brillouin scattering light is that when two peaks exist in Brillouin gain spectrum (BGS), the peak pertaining to BFS due to temperature and/or strain at observation point may be misrecognized. 13,14 Such false detection occurs when an optical fiber spans two areas with different temperature, or when two different strains are applied to an optical fiber.…”

Bending-loss-independent operation of slope-assisted Brillouin optical correlation-domain reflectometry

“…In SA-BOCDR, the Brillouin frequency shift (BFS), which corresponds to the information on the applied strain and temperature, is converted into the spectral power on the slope of the Brillouin gain spectrum (BGS). In addition to the high-speed operation 30 , SA-BOCDR has some unique features, such as the detection capability of the shortest-ever strain (<2 mm) below the nominal spatial resolution 34 , 35 and the sensitivity on not only strain and temperature but also locally applied loss 30 . The latter feature is sometimes beneficial 36 , but from the viewpoint of stable measurement of strain and temperature, the final output of SA-BOCDR should not be influenced by unintended loss applied to the sensing fiber.…”