Open Access
Second-order non-local effects mitigation in BOTDA sensors by tracking the BFS profile
(SPIE, 2017) Mompó Roselló, Juan José; Iribas Pardo, Haritz; Urricelqui Polvorinos, Javier; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
We demonstrate a technique to mitigate the residual second-order non-local effects in Brillouin optical time-domain analysis (BOTDA) sensors in which the Brillouin frequency shift (BFS) profile is not uniform along the fiber. It is based on adding a wavelength modulation to the probe wave that makes it track the average BFS found along its way. Using this method we are able to inject a total probe wave power of 15 dBm in a 120-km sensing fiber link, which, to the best of our knowledge, is the highest probe power ever demonstrated in a long-range BOTDA sensing fiber link. The enhancement in the detected signal-to-noise ratio brought by the use of such power provides 2-MHz BFS measurement precision at the end of the 120-km sensing link with 3-m spatial resolution, all without the need to resort to additional means such as the use of coding or Raman gain.
Open Access
Phasorial differential pulse-width pair technique for long-range Brillouin optical time-domain analysis sensors
(Optical Society of America, 2014) Urricelqui Polvorinos, Javier; Sagüés García, Mikel; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We introduce a novel phasorial differential pulse width pair (PDPP) method for Brillouin optical time domain analysis (BOTDA) sensors that combines spatial resolution enhancement with increased tolerance to non local effects. It is based on the subtraction of the complex time domain traces supplied by a sensor configuration that uses a phase modulated probe wave and RF demodulation. The fundamentals of the technique are first described theoretically and using numerical simulation of the propagating waves. Then, proof of concept experiments demonstrate the measurement of the Brillouin frequency shift distribution over 50 km. The system is shown to withstand large variations of the pump power generated by its interaction with a powerful probe wave along the fiber; hence, highlighting the potential of the PDPP technique to increase the detected signal to noise ratio in long range BOTDA. Moreover, the PDPP is also shown to increase the measurement contrast by allowing the use of relatively long duration pulses while retaining 1 m spatial resolution.
Open Access
Dynamic BOTDA measurements based on Brillouin phase-shift and RF demodulation
(Optical Society of America, 2012) Urricelqui Polvorinos, Javier; Zornoza Indart, Ander; Sagüés García, Mikel; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We demonstrate a novel dynamic BOTDA sensor based, for the first time to our knowledge, on the use of the Brillouin phase shift in addition to the conventional Brillouin gain. This provides the advantage of measurements that are largely immune to variations in fiber attenuation or changes in pump pulse power. Furthermore, the optical detection deployed leads to an enhanced precision or measurement time and to the broadening of the measurement range. Proof of concept experiments demonstrate 1.66 kHz measurement rate with 1 m resolution over a 160 m sensing fiber length. Moreover, a measurement range of 2560 µε with a precision of 20 µε is successfully proved.
Open Access
Synthesis of Brillouin frequency shift profiles to compensate non-local effects and Brillouin induced noise in BOTDA sensors
(Optical Society of America, 2014) Urricelqui Polvorinos, Javier; Sagüés García, Mikel; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We present a novel technique for Brillouin optical time domain analysis (BOTDA) sensors that simultaneously compensates non local effects and reduces Brillouin noise. The technique relies on the wavelength modulation of the optical source to modify the Brillouin interaction between probe and pump waves during their propagation. The resulting Brillouin distribution mimics the wavelength modulation, creating a virtual Brillouin frequency shift profile along the sensing fiber. The fundamentals of the technique are first described theoretically and using numerical simulations. Then, proof of concept experiments demonstrate the capabilities of the system to reduce large variations of the pump power resulting from the interaction with high probe powers and to decrease the Brillouin induced noise enhancing the signal to noise ratio (SNR) of the system. Furthermore, we show, for the first time to our knowledge, measurements of the Brillouin distribution using an injected optical power higher than the Brillouin threshold of the fiber.
Open Access
Brillouin optical time-domain analysis sensor with pump pulse amplification
(Optical Society of America, 2016) Mompó Roselló, Juan José; Urricelqui Polvorinos, Javier; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We demonstrate a simple technique to provide conventional Brillouin optical time-domain analysis sensors with mitigation for pump pulse attenuation. The technique is based on operating the sensor in loss configuration so that energy is transferred from the probe wave to the pump pulse that becomes amplified as it counter-propagates with the probe wave. Furthermore, the optical frequency of the probe wave is modulated along the fiber so that the pump pulse experiences a flat total gain spectrum that equally amplifies all the spectral components of the pulse, hence, preventing distortion. This frequency modulation of the probe brings additional advantages because it provides increased tolerance to non-local effects and to spontaneous Brillouin scattering noise, so that a probe power above the Brillouin threshold of the fiber can be safely deployed, hence, increasing the signal-to-noise ratio of the measurement. The method is experimentally demonstrated in a 100-km fiber link, obtaining a measurement uncertainty of 1 MHz at the worst-contrast position.
Open Access
Brillouin optical time-domain analysis sensor assisted by Brillouin distributed amplification of pump pulses
(Optical Society of America, 2015) Urricelqui Polvorinos, Javier; Sagüés García, Mikel; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We demonstrate the extension of the measurement range of Brillouin optical time-domain analysis (BOTDA) sensors using a distributed Brillouin amplifier (DBA). The technique is based on injecting a DBA pump wave in the fiber to generate an additional Brillouin interaction that amplifies the BOTDA pump pulses and compensates optical fiber attenuation. This amplification does not introduce any significant noise to the BOTDA’s probe wave due to the inherent directionality of the Brillouin gain. Additionally, we deploy a differential pulse-width pair measurement method to avoid measurement errors due to the interplay between the self-phase modulation effect and the changes in the temporal shape of the pulses induced by the transient behavior of Brillouin gain. Experimental proof-of-concept results in a 50-km fiber link demonstrate full compensa- tion of the fiber’s attenuation with no penalty on the signal-to-noise ratio of the detected signal.
Open Access
Latest research on long-range Brillouin distributed sensing
(SPIE, 2019) Loayssa Lara, Alayn; Urricelqui Polvorinos, Javier; Iribas Pardo, Haritz; Mariñelarena Ollacarizqueta, Jon; Mompó Roselló, Juan José; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería Eléctrica, Electrónica y de Comunicación; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernua projecto 0011-1365-2017-000122
We review the latest developments in long-range Brillouin optical time-domain analysis sensors. The factors that impair the performance of these sensors, particularly in terms of their distance range, are discussed together with the latest methods to overcome them. We focus on our recent contributions based on the application of the probe dithering method, which is based on introducing a wavelength modulation to the probe wave. This technique is shown to effectively compensate nonlocal effects originated in the depletion of the pump pulse as well as of its pedestal. In addition, it can provide amplification to the pump wave with a slight modification of the setup. Furthermore, this method can be combined with pump pulse coding and a new technique for coding linearization that we have devised to further extend the sensing length into the hundreds of kilometers range.
Open Access
BOTDA measurements tolerant to non-local effects by using a phase-modulated probe wave and RF demodulation
(Optical Society of America, 2013) Urricelqui Polvorinos, Javier; Sagüés García, Mikel; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We demonstrate a Brillouin optical time domain analysis sensor based on a phase modulated probe wave and RF demodulation that provides measurements tolerant to frequency dependent variations of the pump pulse power induced by non local effects. The tolerance to non local effects is based on the special characteristics of the detection process, which provides an RF phase shift signal that is largely independent of the Brillouin gain magnitude. Proof of concept experiments performed over a 20 km long fiber demonstrate that the measured RF phase shift spectrum remains unaltered for large frequency dependent deformations of the pump pulse power. Therefore, it allows the use of a higher optical power of the probe wave, which leads to an enhancement of the detected signal to noise ratio. This can be used to extend the sensing distance, to improve the accuracy of the Brillouin frequency shift measurements, and to reduce the measurement time.
Open Access
Compensation of nonlocal effects induced by the extinction ratio of pump pulses in Brillouin optical time-domain analysis sensors
(Optical Society of America, 2019) Mariñelarena Ollacarizqueta, Jon; Iribas Pardo, Haritz; Urricelqui Polvorinos, Javier; Loayssa Lara, Alayn; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We demonstrate a technique to compensate the nonlocal effects that appear in Brillouin optical time-domain analysis sensors when pump pulses with limited extinction ratio are deployed. These recently discovered nonlocal effects are originated in the interaction between the probe wave and the pulse pedestal. Hence, their compensation method is based on deploying a modulation (dithering) of the optical frequency of the probe and pulse pedestal waves that provides a reduction of the effective interaction length between them. This is implemented by taking advantage of the chirp associated to the direct current modulation of a semiconductor laser used as common source for both waves. The net effect of this procedure is that the probe and pulse pedestal waves display efficient Brillouin interaction just at correlation peaks along the fiber where the frequency difference between both waves remains constant. Proof-of-concept experiments in a 25-km sensing link demonstrate the performance of the technique, where large errors of more than 10 MHz in the measurement of the Brillouin frequency shift are completely compensated by introducing a sinusoidal dithering to the laser source.
Open Access
Second-order nonlocal effects mitigation in Brillouin optical time-domain analysis sensors by tracking the Brillouin frequency shift profile of the fiber
(IEEE, 2017) Mompó Roselló, Juan José; Iribas Pardo, Haritz; Urricelqui Polvorinos, Javier; Loayssa Lara, Alayn; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
We report on an additional limitation that has been found in Brillouin optical time-domain analysis (BOTDA) sensors due to the so-called second-order nonlocal effects (NLE). Second-order NLE appear in BOTDA setups that deploy a double probe waves to compensate the transfer of energy between the pump pulse and the probe wave, and are related to a spectral distortion of the pump pulse that leads to measurement errors and an effective limit on the maximum probe power that can be deployed in the sensor. We theoretically and experimentally demonstrate that the techniques that have been presented so far in the literature to compensate second-order NLE are only effective in the case that the Brillouin frequency shift (BFS) along the sensing fiber is uniform. However, this requirement for uniformity is not realistic in real world scenarios in which a variety of fibers with different BFS and subjected to different environmental conditions are typically deployed. Therefore, we demonstrate a new method to mitigate the effects of BFS variation in the BOTDA setups that compensate second-order NLE. This method is based on introducing an additional wavelength modulation to the probe wave so as to track the mean BFS changes along the sensing fiber link. With this method, we demonstrate a BOTDA setup that, without coding, distributed amplification, or any other form of performance enhancement, achieves a sensing length of 120 km with 3-m spatial resolution and 2-MHz measurement precision. Moreover, the setup demonstrates, to our knowledge, the largest probe power ever injected in a BOTDA sensing link.