Cesar Elosua

Long-range hybrid network with point and distributed Brillouin sensors using Raman amplification.

We propose a novel concept for hybrid networks that combine point and distributed Brillouin sensors in a cost-effective architecture that also deploys remote distributed Raman amplification to extend the sensing range. A 46-km proof-of-concept network is experimentally demonstrated integrating point vibration sensors based on fiber Bragg gratings and tapers with distributed temperature sensing along the network bus. In this network the use of Raman amplification to compensate branching and fiber losses provides a temperature resolution of 0.7 degrees C and 13 m. Moreover, it was possible to obtain good optical signal to noise ratio in the measurements from the four point vibration sensors that were remotely multiplexed in the network. These low-cost intensity sensors are able to measure vibrations in the 0.1 to 50 Hz frequency range, which are important in the monitoring of large infrastructures such as pipelines.

Resilient Amplified Double-Ring Optical Networks to Multiplex Optical Fiber Sensors

In this paper, we report the experimental demonstration of an amplified optical fiber double-ring network for the multiplexing of sensors. The network is designed to be inherently resilient to fiber failures because it enables simultaneous interrogation of all the optical fiber sensors using both rings. We demonstrate the feasibility of so-called ldquodedicated protectionrdquo for fiber optic intensity sensors. Raman amplification is used to overcome the losses of the couplers used in the rings, providing power transparency. In this novel configuration, Raman pumping is activated only when a fiber failure occurs. We demonstrate how the topology allows the received powers from the sensors to be equalized.

Application of gold complexes in the development of sensors for volatile organic compounds

Two different kinds of sensors have been developed by using the same kind of vapochromic complexes. The vapochromic materials [Au2Ag2(C6F5)4L2]n have different colours depending on the ligand L. These materials change, reversibly, their optical properties, colour and fluorescence, in the presence of the vapours of volatile organic compounds (VOCs). For practical applications, two different ways of fixing the vapochromic material to the optical fibre have been used: the sol-gel technique and the electrostatic self-assembly method (ESA). With the first technique the sensors can even be used to detect VOCs in aqueous solutions, and using the second method it has been possible to develop nanosensors.

PET optimization for improved assessment and accurate quantification of 90Y-microsphere biodistribution after radioembolization

PURPOSE 90Y-microspheres are widely used for the radioembolization of metastatic liver cancer or hepatocellular carcinoma and there is a growing interest for imaging 90Y-microspheres with PET. The aim of this study is to evaluate the performance of a current generation PET/CT scanner for 90Y imaging and to optimize the PET protocol to improve the assessment and the quantification of 90Y-microsphere biodistribution after radioembolization. METHODS Data were acquired on a Biograph mCT-TrueV scanner with time of flight (TOF) and point spread function (PSF) modeling. Spatial resolution was measured with a 90Y point source. Sensitivity was evaluated using the NEMA 70 cm line source filled with 90Y. To evaluate the count rate performance, 90Y vials with activity ranging from 3.64 to 0.035 GBq were measured in the center of the field of view (CFOV). The energy spectrum was evaluated. Image quality with different reconstructions was studied using the Jaszczak phantom containing six hollow spheres (diameters: 31.3, 28.1, 21.8, 16.1, 13.3, and 10.5 mm), filled with a 207 kBq/ml 90Y concentration and a 5:1 sphere-to-background ratio. Acquisition time was adjusted to simulate the quality of a realistic clinical PET acquisition of a patient treated with SIR-Spheres®. The developed methodology was applied to ten patients after SIR-Spheres® treatment acquiring a 10 min per bed PET. RESULTS The energy spectrum showed the 90Y bremsstrahlung radiation. The 90Y transverse resolution, with filtered backprojection reconstruction, was 4.5 mm in the CFOV and degraded to 5.0 mm at 10 cm off-axis. 90Y absolute sensitivity was 0.40 kcps/MBq in the center of the field of view. Tendency of true and random rates as a function of the 90Y activity could be accurately described using linear and quadratic models, respectively. Phantom studies demonstrated that, due to low count statistics in 90Y PET acquisition, the optimal parameters for the standard OSEM+PSF reconstruction were only one iteration and a postreconstruction filter of 6 mm FWHM, for both TOF and non-TOF reconstructions. Moreover, when TOF is included, the signal to noise ratio increased and visibility achieved 100% by the experienced observers and 93.3% according to the Rose model of statistical detection. In 50% of patients, TOF allowed the visualization of 90Y radioembolized lesions not seen without TOF, confirming phantom results. Liver activity was accurately quantified, with no significant differences between reconstructed and actual delivered activity to the whole-liver [mean relative difference (10.2±14.7)%]. CONCLUSIONS Qualitative and quantitative 90Y PET imaging improved with the introduction of TOF in a PET/CT scanner, thereby allowing the visualization of microsphere deposition in lesions not visible in non-TOF images. This technique accurately quantifies the total activity delivered to the liver during radioembolization with (90)Y-microspheres and allows dose estimation.

Optical Fiber Sensors Array to Identify Beverages by Their Odor

Four optical fiber sensors have been grouped in an array which is able to distinguish odors of different drinks. The sensing materials employed have been deposited onto optical fibers following the electrostatic self assembly method. The responses have been characterized in terms of reflected optical power; more specifically, the dynamic range and the recovery of each device have been used to discriminate between the samples. Data mining techniques based on the combination of principal component analysis and artificial neural networks are performed. The final system is trained to distinguish between grape juice, wine, and vinegar by using a set of one hundred samples of each one. Furthermore, the array can be located at up to 6 km away from the optical header, offering the possibility of in situ measurements.

Micro and Nanostructured Materials for the Development of Optical Fibre Sensors

The measurement of chemical and biomedical parameters can take advantage of the features exclusively offered by optical fibre: passive nature, electromagnetic immunity and chemical stability are some of the most relevant ones. The small dimensions of the fibre generally require that the sensing material be loaded into a supporting matrix whose morphology is adjusted at a nanometric scale. Thanks to the advances in nanotechnology new deposition methods have been developed: they allow reagents from different chemical nature to be embedded into films with a thickness always below a few microns that also show a relevant aspect ratio to ensure a high transduction interface. This review reveals some of the main techniques that are currently been employed to develop this kind of sensors, describing in detail both the resulting supporting matrices as well as the sensing materials used. The main objective is to offer a general view of the state of the art to expose the main challenges and chances that this technology is facing currently.

Improved Multifrequency Phase-Modulation Method That Uses Rectangular-Wave Signals to Increase Accuracy in Luminescence Spectroscopy

We propose a novel multifrequency phase-modulation method for luminescence spectroscopy that uses a rectangular-wave modulated excitation source with a short duty cycle. It is used for obtaining more detailed information about the luminescence system: the information provided by different harmonics allows estimating a model for describing the global frequency response of the luminescent system for a wide range of analyte concentration and frequencies. Additionally, the proposed method improves the accuracy in determination of the analyte concentration. This improvement is based on a simple algorithm that combines multifrequency information provided by the different harmonics of the rectangular-wave signal, which can be easily implemented in existing photoluminescence instruments by replacing the excitation light source (short duty cycle rectangular signal instead of sinusoidal signal) and performing appropriate digital signal processing after the transducer (implemented in software). These claims have been demonstrated by using a well-known oxygen-sensing film coated at the end of an optical fiber [a Pt(II) porphyrin immobilized in polystyrene]. These experimental results show that use of the proposed multifrequency phase-modulation method (1) provides adequate modeling of the global response of the luminescent system (R(2) > 0.9996) and (2) decreases the root-mean-square error in analytical determination (from 0.1627 to 0.0128 kPa at 0.5 kPa O2 and from 0.9393 to 0.1532 kPa at 20 kPa O2) in comparison with a conventional phase-modulation method based on a sinusoidally modulated excitation source (under equal luminous power conditions).

An amplified coarse wavelength division multiplexing self-referencing sensor network based on phase-shifted FBGs in transmissive configuration

A new amplified CWDM (coarse wavelength division multiplexing) self-referencing sensor network using phase-shifted fibre Bragg gratings (PS-FBGs) is experimentally demonstrated in this work. The network uses the PS-FBGs to address intensity sensors in a transmissive configuration, obtaining simultaneously in reflection a wavelength encoded reference signal. In order to enable the remote operation of the sensors, we have introduced optical amplification at the interrogation header of the network, using highly doped erbium fibre.

46-km-Long Raman Amplified Hybrid Double-Bus Network With Point and Distributed Brillouin Sensors

We experimentally demonstrate a 46-km hybrid network that combine point and distributed Brillouin sensors. The proposed sensor network multiplexes low-cost intensity point sensors based on fiber-optic tapers, which are able to measure vibrations in the 0.01 to 50 Hz frequency range. The sensor network with a double-bus is a low noise configuration, which offers a higher optical signal to noise ratio and dynamic range than a single-bus. Thus, the number of sensors to be multiplexed could increase or we could reach further distances. The system also deploys remote distributed Raman amplification to extend the sensing range.

Optical Fiber Sensors to Detect Volatile Organic Compound in Sick Building Syndrome Applications

Health issues, such as Sick Building Syndrome (SBS), are being taken into account in new constructions, houses and several non industrial environments. SBS produces several manifestations, for example, respiratory irritative symptoms, headache and fatigue. It is caused by several factors. Most of them are related with the air quality, and the presence of Volatile Organic Compounds (VOCs), among other parameters. It is obvious that is very important to keep these parameters under control, and so, the development of new devices to achieve this is more and more interesting dur- ing last few years. Some important features using sensors for this application are robustness, easy installation, on line and real time use. Although there are electronic devices already available, optical fiber sensors offer all the performances men- tioned before, as well as other ones exclusive of this technology: sensors networking and electromagnetic immunity mainly. In this work, we will show a review about the SBS aim, the sensing architectures of optical fiber technology, and the opportunities that it has in this increasing market niche.