Distributed temperature sensor system based on Raman scattering using correlation-codes

Soto, Marcelo A.; Sahu, P. K.; Faralli, S.; Bolognini, G.; Pasquale, F. Di; Nebendahl, B.; Rueck, C.

doi:10.1049/el:20070990

Cited by 45 publications

(25 citation statements)

References 4 publications

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“…After drilling the boreholes, fiber optic cables were attached along the pipe loops and the double-U pipes were lowered into the boreholes. Temperature is measured along the fiber optics, by applying the DTS technique (Soto et al, 2007). This technique is based on Raman optical time domain reflectometry (Dakin and Pratt, 1985).…”

Section: Distributed Temperature Sensing (Dts) Technique and Dtrt Promentioning

confidence: 99%

Heterogeneous bedrock investigation for a closed-loop geothermal system: A case study

et al. 2016

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a b s t r a c tThis paper investigates bedrock heterogeneity by applying three different geophysical approaches, in order to study the long-term behaviour and the interaction between closed-loop geothermal systems. The investigated site consists of four boreholes equipped with geothermal pipes on the campus of University of Liege, Belgium. The first approach includes acoustic borehole imaging, gamma-ray logging and cuttings observation and results to a detailed fracture characterisation, rock identification and layer dip angle determination. The second approach consists of measuring the thermal conductivity of cuttings at the laboratory. Study of cuttings thermal conductivity measurements can contribute to bedrock heterogeneity knowledge concerning the transition of one formation to another and the layer dipping. The third approach is based on high-resolution temperature profiles, measured during the hardening of the grouting material and the recovery phase of a Distributed Thermal Response Test. Through this approach a correlation of the temperature profiles to the geological characteristics of the surrounding bedrock is identified. The analysis of this correlation can provide information on fractured zones, alternation of different rock types and layering dipping. This latter approach can be easily applied on closed-loop geothermal systems to characterise the bedrock and investigate its heterogeneity as well as contribute to the their long-term behaviour prediction and to the optimisation of their efficiency.

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Section: Distributed Temperature Sensing (Dts) Technique and Dtrt Promentioning

confidence: 99%

Heterogeneous bedrock investigation for a closed-loop geothermal system: A case study

et al. 2016

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“…Application example: A mathematical model derived from a real RDTS [6] (refer again to Fig. 2 for its scheme) has been used to simulate and compare the performance of both multi-pulse and conventional singlepulse techniques.…”

Section: Shadowed Blocks Refer To Multi-pulse Technique Implementationmentioning

confidence: 99%

“…The simulations have been performed considering a 30 km fibre length (T R ≃ 300 ms) and f max ¼ 300 kHz. Using cyclic Simplex [6]. The sensing fibre is maintained at the room temperature of 300 K, apart from a short track between 14.5 and 15 km where the temperature is equal to 323 K. Figs.…”

Section: Shadowed Blocks Refer To Multi-pulse Technique Implementationmentioning

confidence: 99%

SNR enhancement of Raman-based long-range distributed temperature sensors using cyclic Simplex codes

Baronti¹,

Lazzeri²,

Roncella³

et al. 2010

Electron. Lett.

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Presented is a novel approach for enhancing the signal-to-noise ratio (SNR) of optical fibre distributed temperature sensors. The proposed method is based on cyclic codes and it can be implemented by highpower lasers, which are required for long-range applications but are unsuitable for conventional coding techniques. The expected performance improvement, in terms of temperature resolution, sensing range and measurement time, is confirmed by simulations.Introduction: Optical fibre distributed temperature sensors based on spontaneous Raman scattering (RDTS) have potential application in several industrial and scientific fields for reliable temperature monitoring over long distances (up to a few tens of kilometres) [1]. They are based on optical time-domain reflectometry (OTDR): an optical pulse is sent along a sensing fibre and the temperature-dependent backscattered Stokes (S) and anti-Stokes (AS) photons are acquired as a function of time. The collected samples are then processed to extract the temperature profile.The main issue to face in long-range RDTS design is the low signalto-noise ratio (SNR) due to the weakness of the backscattered S and AS traces, which generally exhibit optical power levels lower than a few nW. The energy of the launched pulse is indeed bounded by the targeted spatial resolution, which implies a small pulse width, and by the threshold for the onset of the fibre nonlinearities, which upper bounds the pulse peak level. To reduce the noise power introduced by the optical/electrical receiver, and reach a temperature resolution of a few degrees at the fibre-end, trace averaging is typically employed. However, the greater the number of averages, the longer the measurement time, which might become unsuitable for several applications requiring short response times.Coding techniques based on Simplex or Golay codes exploit a set of different sequences (i.e. codes) of short (about 10 ns) NRZ laser pulses to increase the launched energy without impairing the spatial resolution [2]. However, the required high repetition rate of the laser pulses -a hundred of MHz for a meter-scale spatial resolution -is not achievable by high peak power lasers, such as rare-earth doped fibre or passive Q-switched ones, which feature a maximum repetition rate of some hundreds of kHz [3].Here, a new coding technique tailored to high-power pulsed lasers is proposed [4]. The basic idea is to periodically sense the probing fibre with a multi-pulse pattern the repetition period of which is equal to the fibre round-trip time. This way, the pattern results as a code spread along the whole fibre, with a bit time inversely proportional to the code length. The pulse width can be kept in the order of 10 ns to guarantee a meter-scale spatial resolution and the peak power can be set close to the nonlinear effect threshold.

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“…The combined benefits of cyclic coding and high peak power levels allow for temperature sensing over 26 km standard SMF, attaining a temperature resolution better than 3°C and a spatial resolution of 1 m along the whole fiber length, within 30 s acquisition time. However, much longer sensing distances can be achieved relaxing the spatial resolution and measurement times.In RDTS systems an optical pulse is launched into an optical fiber and the spontaneous Raman scattering (SpRS) is measured by optical time-domain reflectometry techniques [1][2][3]. In particular, the intensity trace of the temperature-dependent anti-Stokes component has to be normalized by a temperature-independent trace, such as the Stokes SpRS or Rayleigh component [2,3], so that the intensity variations due to the local fiber losses are cancelled out.…”

mentioning

confidence: 99%

“…In RDTS systems an optical pulse is launched into an optical fiber and the spontaneous Raman scattering (SpRS) is measured by optical time-domain reflectometry techniques [1][2][3]. In particular, the intensity trace of the temperature-dependent anti-Stokes component has to be normalized by a temperature-independent trace, such as the Stokes SpRS or Rayleigh component [2,3], so that the intensity variations due to the local fiber losses are cancelled out.…”

mentioning

confidence: 99%

Raman-based distributed temperature sensor with 1 m spatial resolution over 26 km SMF using low-repetition-rate cyclic pulse coding

et al. 2011

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We experimentally investigate the benefits of a new optical pulse coding technique for long-range, meter and submeter scale Raman-based distributed temperature sensing on standard single-mode optical fibers. The proposed scheme combines a low-repetition-rate quasi-periodic pulse coding technique with the use of standard high-power fiber lasers operating at 1550 nm, allowing for what we believe is the first long-range distributed temperature measurement over single-mode fibers (SMFs). We have achieved 1 m spatial resolution over 26 km of SMF, attaining 3°C temperature resolution within 30 s measurement time. © 2011 Optical Society of America OCIS codes: 060.2370, 280.1350 Distributed fiber-optic sensors based on Raman scattering are becoming a widely adopted technology [1], with a range of industrial applications spanning from oil and gas pipelines (for fire and leakage detection), to firealarm systems, reservoir and power cables monitoring. Raman-based distributed temperature sensor (RDTS) systems exploit the strong temperature sensitivity of the anti-Stokes Raman backscattered light, which is, however, characterized by extremely low power values, resulting in challenging measurements and requiring the use of high-sensitivity photodiodes, as well as the acquisition of many traces to decrease the noise impact through averaging. To partially overcome the trade-off among temperature resolution, sensing range and acquisition times, RDTS systems commonly employ multimode fibers (MMFs) [2,3], which are characterized by higher backscattering coefficients and also allow for higher input peak power levels before the onset of nonlinearities [3]. Unfortunately, modal dispersion ultimately limits the RDTS spatial resolution when using MMFs. Although this issue can be partially overcome by using graded-index MMFs, the best achievable spatial resolution is still limited to several meters when operating over long sensing ranges (tens of kilometers). In spite of these limitations, for many applications a better spatial resolution would be highly desired over long distances, together with fast acquisition times and high temperature resolution. In order to enhance the sensing performance of RDTS systems, optical pulse coding techniques have been proposed based on either directly or externally modulated semiconductor lasers in MMFs [2] and SMFs [4]. In both cases the strong potential in terms of signal-to-noise ratio (SNR) enhancement provided by optical coding has been somehow limited by the available power in semiconductor lasers. In particular, for RDTS systems operating on standard SMFs with pulse coding, the maximum peak power level from a semiconductor laser that can be reasonably coupled into the sensing fiber is of the order of few hundred milliwatts; however, in principle, up to ∼3-4 W could be used before exciting detrimental nonlinear effects, such as stimulated Raman scattering.Hence, the use of new coding schemes, which could be used with high-power pulsed lasers [such as Q-switched and rare-earth-doped fiber lasers ...

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Distributed temperature sensor system based on Raman scattering using correlation-codes

Cited by 45 publications

References 4 publications

Heterogeneous bedrock investigation for a closed-loop geothermal system: A case study

Heterogeneous bedrock investigation for a closed-loop geothermal system: A case study

SNR enhancement of Raman-based long-range distributed temperature sensors using cyclic Simplex codes

Raman-based distributed temperature sensor with 1 m spatial resolution over 26 km SMF using low-repetition-rate cyclic pulse coding

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