Ricardo M. Silva

Temperature- and strain-independent torsion sensor using a fiber loop mirror based on suspended twin-core fiber

In this Letter, we present a fiber loop mirror configuration based on a suspended twin-core fiber for sensing applications. Using the suspended twin-core fiber, the fringe pattern is due to the differential optical patch of the light in the two cores associated with a refractive index difference of approximately 10(-3), which indicates an advantage of this approach compared with those based on high-birefringent fibers, namely, the possibility of using a small length of fiber. The sensing configuration was characterized for torsion, temperature, and strain. Using the fast Fourier transform technique, it is possible to obtain measurand-induced amplitude variations of the fringe pattern. The results obtained indicate the viability of a temperature- and strain-independent torsion sensor.

Simultaneous measurement of curvature and strain using a suspended multicore fiber

A suspended multicore fiber sensor for simultaneous measurement of curvature and strain is proposed. The spectral response shows evidences of several interferences arising from the seven cores of the fiber. Once the sensing head presents different sensitivities for curvature and strain measurements, these physical parameters can be discriminated by using the matrix method. The rms deviations are ±19 m(-1) and ±12.90 με for curvature and strain measurements, respectively.

High-Birefringent Fiber Loop Mirror Sensors With an Output Port Probe

Two new configurations of high-birefringent fiber loop mirror with an output port probe are proposed. The two configurations used two couplers spliced between them with unbalanced arms and one output port is used as the probe sensor. The difference between them is that the section length of high-birefringent fiber is located between the two couplers (first new configuration) or spliced in the output port probe (second new configuration). The second new configuration presents great advantage, especially for remote sensing using only one fiber to the sensing head. The two new configurations were compared with the conventional high-birefringent fiber loop mirror when strain is applied and showed similar sensitivities. The first new configuration is studied as an optical refractometer.

Theoretical and Experimental Results of High-Birefringent Fiber Loop Mirror With an Output Port Probe

Theoretical and experimental results of three different high-birefringent fiber loop mirrors with output ports are analyzed. For theoretical model, the Jones matrix analysis is used. The theoretical studies present similar results for all experimental configurations. The last configuration is tested as an interrogation system where the spectral response arises from the combination of the reference signal modulated by the sensor signal. The configuration is characterized in strain with the phase changes recovered from two quadrature phase signals, providing a sensitivity of 16 mrad/με with a resolution of 1.9 με.

Magnetic field sensor with Terfenol-D thin-film coated FBG

In this work a magnetic field sensor based on an FBG coated with a thin film of Terfenol-D is presented. The sensor was tested with two optical interrogation systems: one, a scanning laser system with a 1 pm resolution, and the other a differential white light interferometer (WLI). The results obtained in the magnetic field range of 20 mT to 100 mT, show the possibility of increasing the magnetic field measurement resolution, with temperature fluctuations invariance, by a factor of 4.5 when using the WLI system.

Agent-Based Aircraft Control Strategies in a Simulated Environment

In the recent years, game engines have been increasingly used as a basis for agent-based applications and multi-agent systems, alongside traditional, more dedicated, simulation platforms. In this paper, we test and compare different control strategies for specified high-level maneuvers in aircraft within a gaming simulation environment, each aircraft represented by an independent agent, focusing on communication necessities and maneuver effectiveness. An overview of the simulation environments capabilities, with focus on the structured experiences system, shows the potentials of this platform as a basis for the more comprehensive goals of our project, allowing for the definition and execution of cooperative missions, such as surveillance and search & rescue operations.

High-Birefringent Fiber Loop Mirror Sensors: New Developments

The fiber loop mirror based on a ring configuration is one of the devices in optical fibers most used in communications and sensors (Mortimore, 1988). The device is formed when the two output ports of a directional coupler are spliced. In this configuration, the two waves at the coupler outputs travel in opposite directions but following the same optical paths in an optical fiber ring, which assures constructive interference as the waves re-enter the coupler. Thus, all light is reflected to the input port containing losses essentially in the fiber, the splice region and the coupler. Due to this “mirror” characteristic, the device is frequently used in the formation of resonant cavities in optical fiber lasers (Urquhart, 1989). A structure of this kind, with interesting properties, occurs when the ring contains a section of fiber with high-birefringence. When this happens, an interference pattern is generated. It depends only on the fiber birefringence and length, being independent of the remaining ring extension (Fang & Claus, 1995).

High-birefringent fiber loop mirror with an output port probe for sensing applications

Two new configurations of high-birefringent fiber loop mirror with an output port probe are proposed. The two configurations used two couplers spliced between them with unbalanced arms and one output port is used as the probe sensor. The difference between them is that the section length of high-birefringent fiber is located between the two couplers (first configuration) or spliced in the output port probe (second configuration). The first new configuration is studied as an optical refractometer and the second configuration is analyzed when the strain and temperature are applied.

Temperature and Strain Independent Torsion Sensor using a Sagnac Interferometer based on a Suspended Twin-core Fibre

In this work, it is presented a Sagnac interferometric configuration based on a suspended twin-core fibre for sensing applications. Using the suspended twin-core fibre, the fringe pattern is due to the differential optical path of the light in the two cores associated with a refractive index difference of ~10-3, which indicates an advantage of this approach compared with those based on Hi-Bi fibres, namely the possibility to use a small length of suspended twin-core fibre. The sensing configuration was characterized for torsion, temperature and strain. Using the Fast Fourier Transform technique it is possible to obtain the measurand induced amplitude variations of the fringe pattern. The results obtained indicate the viability of a temperature and strain independent torsion sensor.