Most artisans visually characterize Chiapas amber, mainly in appreciating the blue-green color emitted by fluorescence when incident ultraviolet light illuminates it. However, false amber pieces generate this coloration, misleading local and international buyers. Thus, we propose an optomechatronic device (OD) to determine whether amber from Chiapas is authentic. This device measures the fluorescence intensity and, through a database, determines whether amber is authentic. The infrared and ultraviolet spectroscopy techniques validated the results obtained with the OD.
We designed a cubic-phase gallium nitride (c-GaN) homojunction for ultraviolet-C (UVC) detection. A physical model approach was employed to design the dimensions of the detector and the doping concentrations of each layer. The calculated electrical and optoelectronic properties were employed to perform a simulation program with integrated circuit emphasis (SPICE) equivalent circuit model to integrate c-GaN photodetection capabilities into a CAD electronic simulator. The model allows estimating the transport properties in the darkness and under ultraviolet (UV) illumination conditions. Furthermore, the effect of depletion capacitance was taken into account thinking in the circuitry amplification stage. When a transient UVC flash occurs, the SPICE simulation revealed that the output signal is in the order of 300 μV, which is suitable to be amplified by a transimpedance amplifier.
A fiber-optic temperature sensor configuration is presented. This configuration consists of a fiber structure made from a no-core optical fiber coated with a thermochromic material as a transducer element between two multimode fibers. The excitation wavelength selected was in the absorption spectrum of the thermochromic material. The proposed sensor had a sensitivity of −0.08895 dB / ° C with a linear adjusted R-square of 0.9964 in a temperature range of 27°C to 63°C. The sensor response was characterized and validated with a commercial electronic temperature sensor.
We propose new instrumentation to measure the refractive index (RI) of transparent liquids as a function of temperature. The physical phenomenon used to carry out the measurement is the light refraction that occurs in transparent liquids. A width change in a reference object is produced by light refraction, which is related to the RI. Image processing was used to measure the object width using an image from a digital microscope. The instrument measures the RI from a range of 15°C to 100°C with an accuracy of 10 − 4 % . The measurement procedure was calibrated with distilled water and acetonitrile samples, and the Sellmeier and Cauchy equation was used to compare our results. Finally, as an appropriate application, the RI of lophine in a solution was measured.
The fiber Raman amplifier employs the intrinsic properties of silica fiber to obtain the amplification, thus they use the transmission fiber as the amplification medium, where the gain is created along the transmission line. The amplification is realized by Stmulated Raman Scattering (SRS). This nonlinear process occurs when a sufficiently powerful pump is within the same fiber as the signal. In this paper, we showed experimental and numerical analysis of SRS in optical fibers. We obtain a continuous spectral when we plot the energy content in each Stokes sublines with the wavelength, which are self-pump between them. The numerical results are in agreement with the experimental results, just as the waveform in the time of optical fiber end and the energy is transferred from the signal pump to the Stokes sublines. With the simulations, we can obtain several parameters of this optical amplifier like the optical fiber effective length to obtain the amplification.
A multipoint fiber laser sensor, which consists of two cavities coupled based in three Bragg gratings of fiber optics and interrogated by the longitudinal mode beating frequency is presented. We used one Bragg grating (reference) and two Bragg gratings (sensors), which have the lowest reflection wavelength. The reference grating with the two sensors grating make two cavities: first one is the internal cavity which has 4230 m of length and the next one is the external cavity which has 4277 m of length. Measuring the laser beating frequency with a radio frequency (rf) analyzer for a resonance cavity and moving the frequency peaks when the another cavity are put in resonance, we prove that the arrangement can be used as a two points sensor for determining the difference of temperature or stress between these two points. On the other hand, one principal peak and three harmonics with bandwidths of 52 Hz were obtained with the rf analyzer. Their bandwidth was controlled by an intra-caivty fiber Optical Delay Line (ODL) and was measured with the rf analyzer.
We present a design of an Er-doped fiber amplifier (EDFA) with high amplification. The purpose of the device is amplification of low power pulses from laser diodes to powers sufficiently high for investigations of optical fiber nonlinear processes. The optical amplifier consists of two stages. As the first stage we use the reflecting configuration where a signal is amplified twice in the same Er-doped fiber. The second stage works as a high power amplifier. The input pulses have pulse duration of 1 ns - 100 ns, and wavelength 1549.1 nm. The maximum amplification of this design is 50 dB. We obtained the output pulses with maximum power of 50 W. These pulses were used successfully to investigate the NOLM and SRS.
We develop a simple method to measure the set of parameters of an erbium-doped fiber which is needed to elaborate the numeric model of an amplifier when a 980-nm pump is used. We start from the Rate Equations and field propagation equations for signal and pump and shows the necessity of the attenuation coefficients at low powers for pump and signal and the knowledge of four parameters (defined as A, B,C, D) which include cross sections and overlap factors for signal and pump, erbium-doped concentrations, lifetime, and effective area. Our experimental procedure allows measuring the ABCD parameters without the knowledge of all parameters of a fiber. The ABCD parameters obtained experimentally were applied to a computer program to calculate the characteristics of amplifiers and then the calculation results were compared with the experimental characteristics of amplifiers. The comparison showed reasonably good agreement of the calculated and measured characteristics.
In this work we decided to show the behavior about the bend loss caused by soft and swellable materials. The principal measurements of fiber bend loss caused by soft and swellable materials were done with perturbation periods of 1 mm to 20 mm, because we needed to be close in the range of small curture. We used soft materials that have different moduli of Young. To accomplish this measure, we used single mode and multimode fibers. We had to watch the behavior over range of wavelength 1400nm to 1600nm with different radii of curvature. We would like to point out that the material that has the highest modulus of Young causes the highest loss. Ours results show that the highest attenuation and fastest sensor operation can be achieved at respectively long periods of perturbation, more than 10 mm in our experiments.
We show simulated results about changes of the polarization states from a beam of light in an optical fiber, when we introduce a magnetic field in one section of the fiber. The model includes controllable parameters such as, the current applied to a reel (magnetic field), the birefringence, the incident angle of the light and the magnetic field into the fiber. The theory, simulations and experimental verification of this problem are discussed.
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