Simultaneous Distributed Vibration and Temperature Sensing Using Multicore Fiber

Abstract

Distributed optical fiber sensing that enables simultaneous vibration and temperature monitoring is demonstrated in this work, which is achieved by implementing polarization optical time-domain reflectometry (P-OTDR) and Raman optical time-domain reflectometry (ROTDR) respectively through space-division multiplexed (SDM) configuration in different cores of a multicore fiber (MCF). Optimized system setup is obtained in the proposed hybrid system, where only one laser source is used, and the generated pulse is shared by the two reflectometers. Owing to the reason that separate interrogation fiber cores are used by the two reflectometers, the proposed hybrid system allows for simultaneous measurements of spontaneous Raman and Rayleigh scattering signals, thus it no longer suffers from the incompatible pump power levels issue, which results from different pump power demands, and hinders the implementation of the hybrid system in single mode fiber due to the fiber nonlinear effects imposed restriction. In addition, in order to extend the sensing range, we also explore the employment of wavelet transform denoising technique in the improvement of signal-to-noise ratio of ROTDR measurement. Eventually, simultaneous distributed vibration and temperature sensing in 5.76 km sensing range with 3 m spatial resolution and 0.57 • C temperature uncertainty has been demonstrated. The proposed hybrid sensing system has the outstanding advantage of high reliability, since the cross-sensitivity issue is effectively mitigated, which shows great potential for pipeline monitoring in oil and gas industry.INDEX TERMS Multicore fiber, space-division multiplexing, distributed temperature sensing, distributed vibration sensing.

Temperature Resolution Improvement in Raman-Based Fiber-Optic Distributed Sensor Using Dynamic Difference Attenuation Recognition

“…The Raman-based DTS employs spontaneous Raman-optics effect through detecting the Raman backscattered anti-Stokes and Stokes components [17][18][19][20][21]. There are two types of temperature demodulation principles, dual demodulation principle [22][23][24][25] (DDP), and self-demodulation principle [11,14,26] (SDP). The system based on the DDP scheme uses the intensity ratio of anti-Stokes over Stokes light for detecting the surrounding environmental temperature.…”

Wavelet Decomposition Layer Selection for the φ-OTDR Signal

“…Wavelet transform (WT) stands as a widely employed technique for denoising, filtering, and compressing signals in distributed fiber optic sensing systems, contributing to the enhancement of various sensing technologies, such as Brillouin optical time-domain analyzer (BOTDA), Brillouin optical time-domain reflectometry (BOTDR), Raman optical time-domain reflectometry (ROTDR), phase-sensitive optical time-domain reflection (φ-OTDR), and optical frequency-domain reflectometer (OFDR), among others technologies [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Its synergy with artificial intelligence methods also helps in time-frequency feature analysis and facilitates feature extraction [15][16][17][18][19][20][21][22].…”

Heterogeneously Integrated Multicore Fibers for Smart Oilfield Applications

“…Multicore fibers, a significant component of space-division multiplexing, have been investigated for a few decades and are thought to be a strong candidate to meet the exponential growth of capacity demand [19,20]. On the other hand, in the area of optical sensing, there have been some reports about utilizing multicore fibers to measure multi variables, such as vibration, temperature, and strain [18,[21][22][23]. For smart oilfields, compared with normal single-mode fibers, a unique characteristic of multicore fiber is that bending would generate local tangential strain in off-center cores, and the strain is angularposition-dependent.…”