BUSCADOR RECOLECTA

In this study, a new method for increasing simultaneously the sensitivity and interrogation stability of fiber-optic intensity sensors is presented. The configuration is based on a double-coupler ring resonator. On one side, the attenuation sensitivity of the sensor is enhanced by placing it inside a ring resonator. On the other side, the stability of the interrogation method is widely improved by creating an external lasing ring resonator with matched spectral response. The combination of the wavelength selective response of the ring resonator and optical amplification from Er-doped fiber amplifier is used to create different fiber lasers. The resulting lasers present an impressive sensitivity enhancement and a dynamic range increment up to 15 dB. Simultaneously, the instability of the system is reduced to ±0.05 dB. In comparison with systems based on tunable laser interrogation, our method is >100 times more stable and also simpler, as no wavelength tunable elements are required., Ministerio de Economía y Competitividad, European Commission

We present theoretical and experimental results on a slow-light assisted all-fiber configuration that can be used for
efficient sensing of a variety of parameters (pressure, displacement...). In particular, we report here a structure that can be
transformed into a slow-light assisted displacement sensor capable of sub-micrometric resolution values with a
potentially simple intensiometric measurement scheme. The basic element in the structure is a lossy ring resonator tuned
close to the critical coupling regime. In this working regime, the resonator transfer function displays extremely high
group delay values close to the resonances, and, accordingly, a large sensitivity to additional losses. A mechanic
transducer transforms displacement into small additional losses in the ring. This leads to strong variations in the log
transmission of the resonances, which are shown to scale with the group index. This scheme shows orders of magnitude
sensitivity enhancements over a conventional bending-loss configuration. We believe that this structure can be further
developed to provide large sensitivity enhancements to conventional intensiometric fiber sensors., European Commission, Ministerio de Economía y Competitividad, Comunidad de Madrid, Ministerio de Ciencia e Innovación

In this work, we present a new method for increasing simultaneously the sensitivity and interrogation stability of fiberoptic intensity sensors. The configuration is based on a double-coupler ring resonator. On one side, the attenuation sensitivity of the sensor is enhanced by placing it inside a ring resonator. On the other side, the stability of the interrogation method is rendered close to perfect by creating an external lasing ring resonator with matched spectral response. The resulting lasers allow the stable interrogation of the sensors with an impressive sensitivity enhancement. In our experiments, the dynamic range of the intensity sensor (and consequently its sensitivity) is increased 15 dB by using this laser-based interrogation system. Simultaneously, the instability of the system is reduced to ±0.05 dB. In comparison with systems based on external interrogation, our method is <100 times more stable and also simpler, as no wavelength tunable elements are required., Ministerio de Ciencia e Innovación, Ministerio de Economía y Competitividad, European Commission

Along the last years, much debate has been done on the efficiency of slow-light phenomena in order to enhance light-matter interactions, especially for sensing purposes. This improvement could be key to develop more compact and sensitive devices. In this work we develop an all-fiber sub-micrometric displacement sensor using slow-light sensitivity enhancement in a lossy ring resonator. In the proposed structure the losses produced by the displacement of a mechanic transducer can be translated into strong variations of group index and therefore strong transmittance variations. We show that this effect is strictly related to slow light, and not related to confinement effects or any other., European Commission, Ministerio de Economía y Competitividad, Comunidad de Madrid, Ministerio de Ciencia e Innovación

High-Q resonators have been widely used for sensing purposes. High Q factors normally lead to sharp spectral peaks which accordingly provide a strong sensitivity in spectral interrogation methods. In this work we employ a low-Q ring resonator to develop a high sensitivity sub-micrometric resolution displacement sensor. We use the slow-light effects occurring close to the critical coupling regime to achieve high sensitivity in the device. By tuning the losses in the cavity close to the critical coupling, extremely high group delay variations can be achieved, which in turn introduce strong enhancements of the absorption of the structure. We first validate the concept using an Optical Vector Analyzer (OVA) and then we propose a simple functional scheme for achieving a low-cost interrogation of this kind of sensors., European Commission, Ministerio de Ciencia e Innovación, Comunidad de Madrid, Ministerio de Economía y Competitividad

22nd International Conference on Optical Fiber Sensors, OFS 2012, Beijing, China, 15-19 Oct. 2012, We demonstrate theoretically and experimentally that a wide-range tuning of group delay values can be achieved in a
lossy fiber ring resonator. The tuning mechanism relies simply on varying the loss/coupling ratio in the resonator. This
simple structure may be used advantageously in different regimes for many sensing configurations, both for achieving
extremely high sensitivity enhancements (by working close to critical coupling, where the group index becomes
extremely large) or suppression of undesired refractive index effects (e.g. Kerr effect), by working in the under-coupled
regime., Ministerio de Ciencia e Innovación, Comunidad de Madrid