Daniel A. May-Arrioja

Surface Plasmon Resonance-Based Optical Fiber Embedded in PDMS for Temperature Sensing

A compact, simple-to-fabricate, low-cost, and highly sensitive optical fiber temperature sensor based on surface plasmon resonance (SPR) is reported. The sensor consists of a core mismatch fiber structure fabricated by splicing a small piece of single-mode fiber (SMF) between two multimode fibers (MMF). SPR is generated when evanescent field interacts with the gold layer deposited over the SMF cladding. Then, the sensor was embedded in polydimethylsiloxane (PDMS), which acts as a temperature to refractive index transducer. Due to PDMS high thermooptic coefficient, the SPR dip underwent a noticeable wavelength shift when a variation of temperature occurred. The device was tested in the 20-60 °C range showing a linear response and a sensitivity of 2.60 nm/°C. This sensor is appealing for temperature monitoring in microfluidic devices made of PDMS due to its high performance and simply fabrication process.

Fiber Optic Pressure Sensor Using a Conformal Polymer on Multimode Interference Device

We report experimental results on an optical fiber pressure sensor based on multimode interference effects (MMIs). The key component is a small multimode fiber (MMF) section without cladding, which is placed on a direct contact with a polydimethilsiloxane polymer layer previously attached to a pressure-sensitive membrane. When the applied pressure is increased, both the polymer contact area and the induced stress on the MMF increase directly proportional with the applied pressure. Both effects contribute to losses of the propagating modes, and since the MMI spectrum is formed by the interference of the propagating modes, the net effect is that the intensity of the spectral response of the MMI is reduced as the pressure is increased. Therefore, by tracking a single wavelength, the intensity changes are correlated to the applied pressure values. The response of the sensor is highly linear within a pressure range of 0-960 kPa with a sensitivity of - 0.145 ×10-3 mW/kPa. The key features of the MMI pressure sensor are its low-cost and high repeatability.

Highly Sensitive Fiber Optic Refractive Index Sensor Using Multicore Coupled Structures

In this paper, we demonstrate highly sensitive refractive index (RI) sensing based on multicore coupled structures. Specifically, we use a seven-core fiber (SCF) as the sensing element. The interaction of the SCF and its surroundings is induced by controllably etching material from the cladding in order to expose its external cores. Thus, the sensor sensitivity can be tuned by simply controlling the etching depth. In our case, the cladding of a 10-mm-long piece of SCF, spliced between two single-mode fibers, was slowly removed until the remaining cladding around the external cores is only 2.5xa0μm. Sensitivity on the order of 1 × 104xa0nm/RIU is experimentally demonstrated. These sensing architectures are compact, all-fiber, simple to fabricate, and highly sensitive. Based on our results RI changes of 10–4–10–5 can be resolved with standard laboratory-graded equipment, which opens the possibility of using this type of sensing architectures in biological applications.

Spectral narrowing due to linear coupling in two-core fibers

We develop for the first time, to the best of our knowledge, a comprehensive theory to describe the nonlinear propagation of picosecond pulses through symmetric two-core fibers (TCFs). Considering the elementary TCF switching process, we derive an exact analytical expression for the nonlinear phase shift of a picosecond pulse of arbitrary shape and chirp. Applying our results to an unchirped Gaussian input pulse, we demonstrate spectral narrowing in the propagation of the pulse through a TCF. Our results show that the linear coupling induces that spectral narrowing. The amount of narrowing of the pulse spectra depends on the peak power of the input pulse.

Fiber optic refractometer based in multimode interference effects (MMI) using Indium Tin Oxide (ITO) coating

In this paper we report the experimental results of a fiber optic refractometer based in multimodal interference effects (MMI) using an Indium Tin Oxide (ITO) coating. The MMI sensor is able to detect different liquid concentrations of glycerin and other substances. In addition, the use of ITO coating, deposited by the sputtering technique, allows a significant increment in the device sensitivity. In specific, we obtained a sensitivity around 297.12 nm/RIU for 18nm ITO coating thickness.

Temperature Sensor Based on an Asymmetric Two-Hole Fiber Using a Sagnac Interferometer

We report in this paper a temperature sensor based on an asymmetric two-hole fiber (ATHF) using a Sagnac interferometer (SI) configuration. The operation principle is based on the birefringence change induced by the temperature difference between the air holes and the silica fiber. As a result, the transmitted spectrum of the SI exhibits a sinusoidal profile which is shifted when the temperature is increased. A linear wavelength shift as a function of temperature is observed, and a sensitivity of 2.22u2009nm/°C was achieved using a 2u2009m long asymmetric THF, which is in the same order as those previously reported using similar microstructured fibers. The advantage of this system is a linear response, the use of a microstructured fiber with a simpler transverse geometry, and the use of bigger holes which can facilitate the insertion of several materials and improve the sensitivity of the sensor for different applications.

Fiber Optic Sensors Based on Multicore Structures

We present a review of the fundamentals and applications of fiber optic sensors based on multicore coupled structures. The fundamentals of these coupled structures are approached in general for arbitrary distributions of N cores on the foundations of coupled mode theory. The principle of operation of fiber optic sensors using this type of architectures is illustrated via numerical simulations of the simplest coupled structure—the two-core fiber. Illustrative experimental results using fiber optic sensors based on two- and seven-core multicore fibers are shown for a number of applications including temperature, curvature, and refractive index sensing. The main aspects of the performance of multicore fiber sensors are highlighted throughout this chapter and their characteristics, especially their sensitivity, are compared to those of other existing fiber sensing architectures such as fiber Bragg gratings, long period gratings, and photonic crystal fibers, among others.

MMI fiber optic refractometer with universal pH indicator coating

In this paper we show the preliminary results about fabrication of an optical fiber refractometer based on multimode interference effects (MMI) provided with Universal pH Indicator coating. The layer, deposited by coating dip-coating technique, allows increase the refractometer sensitivity which is around 344.5054 nm/RIU in a range of 1.333 to 1.4223. Highly repetitive and reversible refractometer have been achieved using a simple fabrication process. The device shown offers the possibility to be used as instrument to identify substances included aggressive liquids as gasoline.

Integrated Microring Resonator as a Perfect Absorber

Coherent perfect absorption is demonstrated in an integrated microring n resonator laterally coupled to two optical waveguides. Two counterpropagating waves n of equal phase and intensity are launched into the microring resonator and n eventually they get absorbed.

Automatic system for phase shift measurement using correlation

We have developed a program for phase shift measurement on fringes pattern. Our program has capability to measure displacement of vertical fringes, tilted, curvy, and circular fringes, because of the use of pattern correlation.