Brillouin-Based Distributed Temperature Sensor Employing Pulse Coding

Soto, Marcelo A.; Sahu, P. K.; Bolognini, G.; Pasquale, F. Di

doi:10.1109/jsen.2007.913143

Cited by 51 publications

(23 citation statements)

References 4 publications

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“…Traditionally the method is based on the intensity modulation of a pump wave, enabling a natural incorporation of unipolar code sequences (containing 0's and 1's) into conventional distributed fiber sensors. This is the case of conventional optical time-domain reflectometers (OTDR) [21,22], Raman-based distributed sensors [23,24], Brillouin-OTDR sensors [25,26], hybrid schemes [27], and laser range finder [28], in which pulse coding has shown important improvement with respect to conventional schemes. In addition, unipolar coding has also been used in BOTDA sensing [9][10][11]; however, the Brillouin gain and loss processes can offer the unique possibility to implement another kind of coding scheme: the so-called bipolar coding [12] (i.e.…”

Section: Principle Of Bipolar Golay Coding and Impact Of Pump Depletimentioning

confidence: 99%

Increasing robustness of bipolar pulse coding in Brillouin distributed fiber sensors

2015

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Abstract:The robustness of bipolar pulse coding against pump depletion issues in Brillouin distributed fiber sensors is theoretically and experimentally investigated. The presented analysis points out that the effectiveness of bipolar coding in Brillouin sensing can be highly affected by the power unbalance between -1's and + 1's elements resulting from depletion and amplification of coded pump pulses. In order to increase robustness against those detrimental effects and to alleviate the probe power limitation imposed by pump depletion, a technique using a three-tone probe is proposed. Experimental results demonstrate that this method allows increasing the probe power by more than 12.5 dB when compared to the existing single-probe tone implementation. This huge power increment, together with the 13.5 dB signal-to-noise enhancement provided by 512-bit bipolar Golay codes, has led to low-uncertainty measurements (< 0.9 MHz) of the local Brillouin peak gain frequency over a real remoteness of 100 km, using a 200 km-long fiber-loop and 2 m spatial resolution. The method is evaluated with a record figure-of-merit of 380'000. Gonzalez-Herraez, and L. Thévenaz, "Extending the real remoteness of long-range Brillouin optical time-domain fiber analyzers," J. Lightwave Technol. 32(1), 152-162 (2014). 18. Y. Dong, L. Chen, and X. Bao, "Extending the sensing range of Brillouin optical time-domain analysis combining frequency-division multiplexing and in-line EDFAs," J.

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Section: Principle Of Bipolar Golay Coding and Impact Of Pump Depletimentioning

confidence: 99%

Increasing robustness of bipolar pulse coding in Brillouin distributed fiber sensors

2015

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“…Optical pulse coding in Brillouin optical time-domain reflectometry (BOTDR) [8] or analysis (BOTDA) [9] was firstly implemented using non-return-to-zero (NRZ) intensity-modulated pulses. However, it was quickly proved that the pre-excitation of the acoustic wave resulting from sequences of NRZ pulses leads to a nonlinear Brillouin interaction that breaks the linearity required by pulse coding techniques [10], resulting in distortions of the measured Brillouin gain spectrum due to bit patterning effects.…”

Section: Implementation Of Pulse Coding In Brillouin Distributed Fibementioning

confidence: 99%

Advanced Pulse Coding Techniques for Distributed Optical Fiber Sensors

Soto

Thévenaz

2013

Frontiers in Optics 2013

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Advanced optical pulse coding methods to enhance the performance of distributed optical fiber sensors are reviewed. In particular, the latest implementations dedicated to highperformance long-range Raman and Brillouin based distributed sensing are described.OCIS codes: (060.2370) Fiber optics sensors; (290.5830) Scattering, Brillouin; (290.5860) Scattering, Raman. IntroductionIncreasing the number of resolved points in distributed optical fiber sensors, by either improving the spatial resolution or extending the fiber length, is one of the main challenges that new techniques have been facing during the last years [1]. Considering that the sensor response is proportional to the optical energy contained in the pulse propagating along the fiber, the signal-to-noise ratio (SNR) of the measurements results to be reduced whenever the spatial resolution is improved (i.e. shorter pulses are used) or the sensing distance is extended, leading to poorer sensing performance. In order to increase the dynamic range of acquired temporal traces, longer pulses and/or higher peak power could be used. However, the pulse peak power launched into the fiber cannot be increased indefinitely as a consequence of the onset of nonlinear effects, while on the other hand longer pulses lead to an unavoidable degradation of the spatial resolution. The onset of the nonlinear effects is essentially determined by the peak power launched into the fiber, and hence, an alternative to increase the optical energy propagating in the fiber without increasing the peak pump power is to spread the energy in the time domain by using suitable coded pulse sequences [2,3], thus avoiding nonlinearities and maintaining the spatial resolution given by the single-pulse duration.In this paper, a review of the theory of optical pulse coding is first addressed. The specific constraints to real implementations of pulse coding are then described for high-performance sensing schemes based on Raman and Brillouin scattering. Recent novel methods, including bipolar and time-frequency domain coding, are also discussed.

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“…We recently demonstrated that optical coding, namely Simplex coding [6], can be effectively employed in direct-detection LPR-based Brillouin distributed temperature sensors (BDTS), providing significant temperature resolution improvement due to electrical signal-to-noise ratio (SNR) enhancement with respect to conventional single-pulse schemes. This enhancement is expressed by the coding gain G COD = (L+1)/(2√L), which depends on code length L. On the other hand, in coherent-detection schemes, the SpBS signal is mixed with an optical local oscillator (OLO) before photodetection, allowing for higher sensitivity and dynamic range in comparison to direct-detection schemes.…”

Section: Theorymentioning

confidence: 99%