Recently, different substances designated for local anesthesia or as substances harmful to health have had a boom in their illegal use to perpetrate crimes associated with adulterated beverages. These substances are colorless and odorless liquids, almost imperceptible to the taste. A sensing system based on a double-aperture common-path interferometer for rapid detection of different types of adulteration (methanol and ethanol) added in different types of alcoholic beverages (brandy and rum) is proposed. The method for determining the adulteration degree is based on measurement of variations on the interference free spectral range from a one-shot interferogram.
We demonstrate generation of passive Q-switched laser pulses of a linear cavity Er-Yb double-clad fiber laser based on the use of a fiber ball lens coated with a thin film of titanium oxynitride (TiOxNy). The fiber ball lens is inserted within the laser cavity in a reflection configuration, alongside a reflecting mirror. Dual-wavelength and tunable single operations of the laser is obtained with the ball lens acting as an interference filter. At the same time, the ball lens coated with TiOxNy, deposited by DC reactive magnetron sputtering, allows saturable absorption suitable for generation of passive Q-switched laser pulses. Single wavelength laser generation tuned in a range of ~4.5 nm and simultaneous dual wavelength generation with separation of 5.1 nm are obtained at the 1.55 µm wavelength region. Pasive Q-switched pulses with maximum repetition rate of 124 kHz, minimum duration of 3.6 µs and peak power of 360 mW are achieved. The maximum pulse energy estimated is of 1.3 µJ.
We present an optical sensor for solute concentration in solutions by using aluminum-doped zinc oxide (AZO) coatings on silica single-mode/coreless/single-mode and single-mode/multimode/single-mode fiber structures. The fiber sensor is based on the detection of the second lossy-mode resonance (LMR) order of the AZO coated fiber structures which covers the near-infrared C and L wavelength bands. AZO thin films with Zn:Al atomic concentration proportions of 92%:8% were deposited on the fiber structures by radio frequency magnetron sputtering technique. Wavelength displacement of the second order LMR notch as a function of concentration variation on isopropyl-alcohol/glycerin liquid mixtures where measured by a simple optical transmission setup, detected in the 1.55 μm wavelength range. In glycerin concentration percentages (c%) variations from 5% to 30%, maximum sensitivity of 1.42 nm/c% was obtained for coreless-fiber-based structures.
KEYWORDS: Solar energy, Solar radiation, Thermoelectric materials, Sun, Semiconductors, Microcontrollers, Digital signal processing, Digital electronics, Computing systems, Renewable energy
In recent years, automotive companies have tried to implement in their vehicles devices that supply renewable energy to the electromechanical systems that make them up, giving rise to well know hybrid and electric cars. The main idea to produce this kind of energy is focused on taking advantage of resources that in the past were useless due to the lack of technology. This work presents a preliminary system of electrical charge from the use of sun heat that is stored in the front panel of the car while it is parked in such a way that the solar radiation falls directly on it. The system uses inversely a Peltier cell, an electronic element that is composed of plates of semiconductor material that has the property of generating heat or cold depending on the polarity that is applied to the plates, for this case one of the cell faces is used to capture the heat energy through the vehicle front windshield. This work presents a system of heat conversion in electrical energy using a Peltier cell, preliminary experimental results obtained are discussed.
Passively mode-locked fiber lasers are capable of generating a variety of optical pulses, depending of the pump power and cavity adjustments, which makes them attractive for research in multidisciplinary fields. In this paper, we analyze the experimental results of a fiber laser operating in passively mode-locked regime. The figure-eight laser cavity configuration uses 4 m of a co-doped Er/Yb double clad fiber, as a gain medium, pumped by a 976 nm diode laser. The cavity is completed by an isolator for ensure unidirectional propagation, two quarter-wave retarders (QWR), and a nonlinear optical loop mirror (NOLM) with 120 m of twisted standard single-mode fiber in the loop acting as saturable absorber. We used a couple of quarter-wave retarders (QWR) QWR1 at the NOLM input and QWR2 into the NOLM loop. By carefully adjusting of the QWRs the laser generates noise-like square pulses at the 1.54 μm range. With the increase of the pump power, the laser generates harmonics of the mode-locking fundamental mode with repetition frequency of 1.38 MHz, from which we can obtain the second, third and fourth harmonic in a controlled mode.
We report an experimental study erbium-doped fiber laser for gas pressure detection in the L-band wavelength region by laser intracavity absorption spectroscopy. By using a high-birefringence fiber optical loop mirror as spectral filter within the ring cavity laser, the wavelength of the generated laser line is finely selected and tuned in a range of ~10 nm in order to select the wavelength where the gas absorption line is exhibited. Experimental results for detection of CO2 pressure with absorption at 1573.2 nm are shown and discussed. The proposed fiber laser sensor exhibits reliability and stability for gas detection with absorption in the L-band such as CO2, CO, and H2S.
We report an in-fiber structure based on the use of a multimode fiber segment and a double cladding fiber segment, and its application as spectral filter in an erbium-doped fiber laser for selection and tuning of the laser line wavelength. The output transmission of the proposed device exhibit spectrum modulation of the input signal with free spectral range of ~21 nm and maximum visibility enhanced to more than ~20 dB. The output spectrum of the in-fiber filter is wavelength displaced by bending application which allows a wavelength tuning of the generated laser line in a range of ~12 nm. The use of the proposed in-fiber structure is demonstrated as a reliable, simple, and low-cost wavelength filter for tunable fiber lasers design and optical instrumentation applications.
We report a linear cavity all-fiber passive Q-switched thulium-doped fiber laser operating at the 2 μm wavelength range. The laser configuration is based on a thulium-doped fiber used as a gain medium and an unpumped segment of holmium-doped fiber which acts as a fiber saturable absorber. The cavity is formed by a fiber optical loop mirror and the flat end facet of the holmium-doped fiber. The fiber segments as saturable absorber is a 1-m long single mode doubleclad holmium-doped fiber. Q-switched pulses are obtained at the wavelength of 2024.5 nm with a pulse width of 1.1 μs. The pulse repetition rate increases as a linear function of the applied pump power. The maximum pulse repetition rate of 100 kHz was obtained with a pump power of 2.4 W.
The design and implementation of an electronic system to real-time capture and processing speckle interference patterns is presented. Because of the random and instability speckle patterns nature, is very useful a system wich allows obtaining and visualizing interference speckle patterns in the shortest time possible. Proposed system captures the first speckle pattern as steady image while captures subsequent patterns from the same source. Images are electronically transformed separately into value arrays and subtracted to obtain real-time interference speckle patterns, these patterns are automatically archived for later analysis. System consist of a CCD camera, a computer interface that makes capturing, a transparent object and a 4f interferometric system whose source is a laser that passes through diffuser glass in order to obtain speckle effect. Experimental results and analytic explanation is showed bellow.
KEYWORDS: Sensors, Data conversion, Gas sensors, Bioalcohols, Microcontrollers, Detection and tracking algorithms, Electromechanical design, Data acquisition, Sensing systems, Resistors, Calibration, Signal processing, Sensor calibration
It have been proposed different solutions to the problem of gas leak detection one being the use of mobile systems. An autonomous system equipped with a gas sensor (ethanol) and controlled by a microcontroller and an algorithm designed to follow the trace of smell in terms of concentration that existed in the place of taking the reading by the sensor built without considering brownouts only taken the arrangement proposed by the sensor, thus the location of the source is made and direct the system directly. In this paper the results of location system made in different workspaces, focusing primarily on the acquisition of sensor data with an analog-digital conversion 10 bits are presented whose resolution would be 4.8 mV per bit against the standard 19 mV commercial resolution. Experimental results and analytic explanation is showed below.
The generation of clean solitons is important for a number of applications such as optical analog-to-digital conversion (ADC) based on soliton self-frequency shift. In real sources the quality of the pulses is deteriorated by dispersive waves, continuous wave (CW), amplified spontaneous emission (ASE). The dispersive waves appear in the spectral profile as side-lobe components that would limit the resolution of ADC. Spectral compression techniques cause the appearance of a pedestal on the spectrum. All of these imperfections of pulses have to be eliminated to improve the performance of alloptical systems. The nonlinear optical loop mirror (NOLM) is a good candidate for these tasks. In the present work we report the implementation of a polarization-imbalanced NOLM for soliton cleaning. The NOLM consists of a nearly symmetrical coupler with a 51/49 coupling ratio, 100 m of twisted OFS Truewave fiber whose dispersion value is 9 ps/nm/km at 1550 nm, and a tunable in-line fiber polarization controller (PC) asymmetrically inserted inside the loop. The use of the nearly symmetrical coupler allows very low transmission for low power components of radiation. At the same time adjustment of the PC allows the adjustment of the nonlinear characteristic to have a maximum transmission for solitons with different durations. We used two sources of pulses, SESAM based and a ring fiber laser. At the appropriate adjustment of PC, we obtained a rejection of ASE by 220 times, rejection of the dispersion waves and the pedestal by more than 200 times. The maximum transmission reached 70%.
We report a linear cavity all-fiber Thulium-doped fiber (TDF) laser with tunable narrow linewidth operating near to 2 μm of wavelength. The TDF is pumped with a laser source at 1567 nm. The cavity is delimited by two fiber optical loop mirrors (FOLM) with high birefringence fiber in the loop (Hi-Bi FOLM) with different periodical wavelength-dependent reflection periods. The wavelength tuning range for the generated laser line of ~44.3 nm depends on the Hi-Bi FOLM with long wavelength period of 54.4 nm. The generated laser spectral width, less than 0.05 nm, is determined by the Hi- Bi FOLM with narrow-band wavelength period of 1 nm. Discrete wavelength tuning is achieved by wavelength reflection displacement of the narrow-band Hi-Bi FOLM by temperature variation on the high birefringence fiber loop. The temperature changes are performed with a temperature electronic controller/meter with resolution of 0.06°C in a temperature range from 22.87 to 49.12°C. Dual-wavelength generation with a wavelengths separation of ~47 nm is also obtained at the single wavelength tuning limits.
Numerical results are presented to show the characterization of an electromechanical actuator capable to achieve equally spaced phase shifts and fraction linear wavelength displacements aided by an interface and a computational system. Measurements were performed by extracting the phase with consecutive interference patterns obtained in a Michelson arrangement setup. This paper is based in the use of inexpensive resources on stability adverse conditions to achieve similar results to those obtained with high-grade systems.
We present experimental results of a proposed dual wavelength fiber laser with Er/Yb double clad fiber. The linear cavity laser is based in the use of two fiber Bragg gratings for wavelength selection and a Sagnac interferometer for cavity losses adjustment to obtain dual-wavelength operation. With pump power variations from the lasing threshold to 890 mW. Self-Q-switched pulses are obtained. With a pump power range from 1.1 W to 1.7 W, self-pulsing operation is observed. With pump power above 2 W CW operation is achieved.
An alternative method for phase-shifting interferometry of two steps by using a speckle interferometer is proposed. It is shown that the introduced phase-step could be unknown because the use of an appropriate fringe-pattern processing. The acquired fringe patterns are processed by well established phase-shifting algorithms in order to compare these results with our proposal. Numerical phase difference between two states of phase object is compared with theoretical method using electronic speckle pattern interferometry (ESPI) . Simulated and experimental results are provided.
We report an all-fiber dual-wavelength actively Q-switched pulsed laser. The linear cavity is limited by two fiber Bragg gratings with central wavelengths of 1538.3 nm and 1548 nm respectively in one side and Sagnac interferometer (SI) in the other side. The pump power is coupled into the doped fiber through a beam combiner. The SI used to equalize generated laser lines competition by cavity losses adjustment is formed by high birefringence (Hi-Bi) fiber in the loop. The SI spectrum wavelength displacement adjustment is performed by temperature variations applied on the Hi-Bi fiber loop with a temperature controller. The Q-switch operation is achieved at pulse repetition rate of 120 kHz with average pulsed output power of 404 mW and pulse duration of 470 ns.
We present an experimental method for straight forward dual wavelength Erbium doped fiber linear cavity laser characterization based in laser line spectrum behavior due to the Hi-Bi FOLM transmission spectrum wavelength displacement by temperature variations in the fiber loop. The laser operation is for a single and dual mode, obtained through the adjustment of the cavity losses by the Sagnac interferometer spectrum wavelength displacement due to the temperature variation of the fiber loop. The method allow determine the laser operation from a single emission line and a two emission lines simultaneously through the Sagnac transmittance spectrum optical power variations measurement due to wavelength spectrum shifting for each laser wavelength generated separately and overlapping these obtained spectrums.
In this paper a linear cavity Erbium doped fiber (EDF) laser based in a fiber Bragg grating (FBG) and a fiber optical loop mirror with a high birefringence fiber in the loop (Hi-Bi FOLM) is used as a strain sensor. The Fabry-Perot cavity is formed by the FBG and the Hi-Bi FOLM, used as a measurement system of strain variations produced on the FBG, used as a strain sensor device. Usually, fiber laser sensor experimental setups determine the measured variable magnitude by using of an optical spectrum analyzer (OSA). Hi-Bi FOLM transmission spectrum wavelength displacement by fiber loop temperature variations measurement can be an attractive application exploiting the characteristics of FOLM transmission spectrum behavior due to Hi-Bi fiber loop temperature variations to determine the FBG strain applied through the maximal optical power monitoring by simple use of a photodetector and a temperature meter.
We show that the cavity quality for generated wavelengths in dual-wavelength laser must be substantially different for
stable dual wavelength operation. In experiments the linear cavity included two FBGs and a fiber optical loop mirror
(FOLM) with a high-birefringence fiber in the loop. The reflection spectrum of the FOLM shifts through temperature
control of the hi-bi fiber loop that allows an adjustment of the ratio between FOLM reflections at generated wavelengths.
The dual wavelength operation required an appropriate adjustment of this ratio. We measured the ratio necessary for
dual wavelength operation at different wavelength separation. Wavelength separation is tuned by axial tension applied to
one of FBG in the range 0.6 - 3 nm. Shorter wavelength always required higher reflection, and ratio between short
wavelength reflection and long wavelength reflection increased strongly with wavelength separation. The tolerance of
dual wavelength generation to reflection adjustment was measured to be about 1%.
We experimentally demonstrate tunable dual wavelength operation of a fiber laser through adjustment of
cavity loss using a Fiber Optical Loop Mirror (FOLM) with a high-birefringence fiber in the loop. The
reflection adjustment of the FOLM was achieved by temperature control of the Hi-Bi fiber. The spectral
spacing has been tuned from 0.98 to 5.6 nm with a tubable fiber Bragg grating. A temperature change of the
Hi-Bi fiber by 0.1 °C causes a change in the reflectances for the wavelengths.
A simple tunable and switchable dual-wavelength fiber laser at room temperature based on a polarization-maintaining
fiber Bragg grating (PM-FBG) is demonstrated experimentally. Experimental results show stable dual-wavelength mode
or wavelength switching modes with a dual-wavelength lines spacing of 0.23 nm to 0.43 nm adjusted by a polarization
controller (PC). Tuning of the lasing lines around 4.3 nm is performed by applying axial strain to the PM-FBG using a
simple structured linear laser cavity.
We report numerically and experimentally analysis of optic fiber Sagnac interferometer and fine adjustment of cavity
loss by the use of the FOLM with a hi-bi fiber in the loop. Changes in transmittance profile amplitude and wavelength
shift are caused by the whirl effect in the connectors of a coupler with ports output connected to a birefringent fiber.
Also the experimental demonstration of dual wavelength operation of a fiber laser through fine adjustment of cavity loss,
using a Fiber Optical Loop Mirror (FOLM) with a high-birefringence fiber in the loop. The reflection and transmission
of the FOLM presents a sinusoidal wavelength dependence which can be shifted by controlling the temperature of the hibi
fiber. A temperature change of the hi-bi fiber by 0.1°C causes a measurable change in the ratio between the
reflectance for the wavelengths R(λ1)/R(λ2). Using this adjustment be able to change the generation mode from single
wavelength to stable dual wavelength generation with equal powers for λ1 and λ2 or to stable dual wavelength generation
with unequal powers at λ1 and λ2. The change of the ratio between the FOLM reflection R(λ1)/R(λ2) allows the
investigation of tolerance of dual wavelength generation on the ratio between cavity loss. Was found that for the switch
from a single wavelength emission at λ1 to single wavelength emission at λ2 the ratio R(λ1)/R(λ2) has to be changed by
the order of magnitude of 10-2. This value shows the tolerance of the dual wavelength laser to the cavity loss adjustment.
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