Error compensation in Brillouin optical correlation-domain reflectometry by combining bidirectionally measured frequency shift distributions

Abstract

In standard single-end-access Brillouin optical correlation-domain reflectometry (BOCDR), the systematic error caused by the phase difference between amplitude modulation (AM) and frequency modulation (FM) in the light source can be up to tens of megahertz, causing considerable errors in strain and temperature measurement. In this letter, we develop a new concept of two-end-access BOCDR, in which light is injected into each end of a sensing fiber in turn and the measured results of the Brillouin frequency shift distributions are combined. We numerically show that this configuration can suppress the systematic error caused by the AM-FM phase difference by approximately 90%.

Systematic-error suppression in low-coherence Brillouin optical correlation-domain reflectometry

“…To clarify the reason for the suppressed systematic errors in low-coherence BOCDR, we conducted a detailed analysis, following a method outlined in Ref. 30 , to calculate both the BGS and BFS distributions. We distinguish between “intrinsic BGS,” which represents the BGS at each position along the FUT, and “measured BGS,” which is the BGS observed using BOCDR.…”

“…While achieving higher spatial resolution is of some technical interest, it comes with the trade-off of a reduced SNR, offering insights into the potential capabilities of the low-coherence BOCDR. Moreover, although certain experimental parameters affecting the spatial resolution were investigated, the effect on the systematic errors caused by direct sinusoidal modulation of the light source, commonly observed in standard BOCDR systems 28 – 30 , was not assessed.…”

Wide-Dynamic-Range Brillouin Optical Correlation-Domain Reflectometry With 20-kHz Sampling Rate

“…By sweeping the modulation frequency, the position of the correlation peak can be scanned along the FUT, enabling distributed measurement of the Brillouin gain spectrum (BGS). In most BOCDR systems [9,[16][17][18][19][20][21][22], the laser driving current is directly modulated to achieve optical frequency modulation because of its system simplicity and cost efficiency, though some exceptions have also been reported [23][24][25].…”

Proposal of compressed sensing-assisted Brillouin optical correlation-domain reflectometry for effective repetition rate enhancement

“…[1][2][3][4][5] To detect fast-varying events and achieve real-time signal processing, numerous state-of-the-art methods have been proposed to accelerate the measurement speed in different sensors. [6][7][8][9][10][11][12] Among the various configurations, [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Brillouin optical correlation-domain reflectometry (BOCDR), which operates by light injection into a single end of a fiber under test (FUT), is one of the ideal options for high-speed operation due to its property of random accessibility. 2,3,5) In other words, the sensing position along the FUT is dependent on the location of the correlation peak (CP), which is uniquely determined by the frequency of the sinusoidal modulation applied to the laser source.…”