In this work, we present the design and analysis of fiber optic interferometric devices for its application in vibration detection, allowing to create an optical system based on interferometric interactions that can vary the sensitivity through external signals e.g., NLPs (noise-like pulses). The simulation of numerical schemes of the fiber optic interferometer using the MATLAB software is presented, which will allow the development of a first prototype of experimental model. Numerical implementations will be performed in MATLAB using Jones matrices to model the behavior of the fiber optic interferometer. This numerical analysis allows to develop a compact experimental model, capable of varying its transmission, sensitivity and FSR (free spectral range), being able to study the interferometric response to external vibrations and modifying the input parameters, such as power, polarization, and operation range. The input characteristics for the interferometric system can be generated by a fiber optic pulsed laser e.g., F8L (figure eight laser), which can vary its output temporarily, spectrally and in polarization. The complete analysis will allow to propose an all-fiber experimental scheme that is compact and portable compared to conventional interferometric arrays, as are works where arrays of hundreds of meters are implemented, based on the study of fiber optic resonators that improves vibration detection system sensitivity. Subsequently, the first tests were performed using MATLAB functions based on pattern recognition, filtering, and amplification of repetitive signals, which will be experimentally tested in the interferometer in a future work. Finally, potential future applications of this work include detection of vibration anomalies in structures and motors, as well as the detection of sound for integration in specialized medical devices to treat hearing problems.
In this work, we present a temporal and spectral study of properties of a pulsed fiber laser in a figure-eight configuration (F8L) through the automatic adjustment of polarization controller plates. The experimental scheme consists of telecom fiber, a double-clad fiber doped with Er/Yb that allows higher power at the laser output, an optical isolator, a saturable absorber, and retarder plates. Automated polarization control system was developed using computer-aided design and additive manufacturing applied to each polarization stage within the fiber laser. The laser operation is automatically adjusted by means of an optical control system, composed of a quarter-wave retarder (QWR) to allow the self-starting operation, while the angles of the QWR, half-wave retarder (HWR), and QWR plates in the polarization controller allows to adjust the temporal duration of the pulses, as well as the spectral width at the laser output. The laser through automated adjustments on retarder plates generates an emission centered at ~1550 nm, with pulse durations between 189.5 ps to 350 ps (spectral widths between 13.4 nm and 53.4 nm), with repetition frequencies of 904 kHz, and it is possible to generate a supercontinuous spectrum of more than 250 nm. The emission obtained corresponds to noise-like pulse operation, which is very useful for the development of applications such as generation of harmonic mode locking pulses, supercontinuum with high flatness, and optical rogue waves, among others. Finally, the proposed study allows showing the advantages of self-adjusting the laser using automated control, with the aim of finding more precisely modes of operation of interest in multivariable systems.
In this work, we show an optoelectronic system based on a plastic optical fiber (POF), which can detect changes in the RGB composition in liquid solutions. This system consists of a white light (LED) with 3 W of power, and 20 centimeters of POF with cladding in the U-configuration,where 0.5 cm is without cladding that allows having contact with the rest of the solution. Also, the arrangement of photodiodes allows us to capture the intensity of light that comes from the fiber. Furthermore, we tested different solutions where we observed changes in the RGB color composition, using different concentrations of water with alcohol. These results shall allow us to design in the future a prototype for measuring the refractive index in different liquid solutions.
In this numerical work, we present some cases of transmission behavior in a power-symmetric, polarization-imbalanced nonlinear optical loop mirror (NOLM) through a three-dimensional (3D) analysis. The study has been implemented using the Jones matrices for inputs at linear and circular polarization and varying the length in the loop. The results show control over the switching power and the maximal transmission, which let us see more easily the graph visualization at the output of a scheme. However, we can determine the characteristics of the experimental operation (fiber loop, input power, angles of the retarder plates, critical power, and input polarization). These results can be used to establish regions for potential applications in optical communications such as ultrafast optical signals processing, optical switching, demultiplexing, filtering, logic gates, and pulse compression.
For remote data acquisition, the integration of optical and electronic instrumentation systems (OSA, oscilloscope, polarimeter) is proposed, reaching automation through control protocols (TCP/IP). A graphical interface was developed through the LabVIEW virtual environment, using MATLAB to present the results of accumulated spectra and temporal evolutions. Using our automated data acquisition system, we analyze in detail the operating characteristics and stability at the output of a passively mode-locked fiber laser (figure-eight laser, F8L), looking to expand the study on the evolution of the polarization and the behavior of the pulses according to the adjustment of the polarization control plates included in the laser cavity.
This work reports the experimental demonstration of supercontinuum (SC) generation with broad spectral output of 950 nm maximum or a 3.7 dB variation within the range from 1300 to 1600 nm and demonstrate how some fiber properties enhance nonlinearities and shows different SC output spectrum. Broad spectrum was achieved throughout a subnanosecond microchip pulsed laser operating at 1064 nm. Three different conventional fibers were employed: highnumerical aperture fiber (HNAF), dispersion shifted fiber (DSF) and single mode fiber (SMF). SMF was wrapped in different diameters to induce fiber losses. Several combinations of these three fibers and diameters resulted in high spectral width as well as high flatness in the telecom band.
This paper presents several broad-spectrum sources generated by pumping a 532nm laser microchip, with 600ps pulses and various combinations of conventional thin-core optical fibers. Fibers with a core of 2.1μm, 2.5μm and 3.5μm were used; with lengths of 38m, 23.3m and 19.7m respectively. We present the results derived from experimenting with each type of fiber separately, as well as making combinations among them, obtaining broad spectrum light sources (supercontinuous light) with a spectral width of approximately 300nm and powers greater than -20dBm.
The analysis of polarization evolution in a tunable fiber laser in a ring configuration is presented, an interferometer was used to tune the laser and was manufactured with thin-core fiber (Thin-Core Fiber, TCF). The interferometer was achieved by splicing a segment of thin-core fiber (Thin-Core Fiber, TCF) between two segments of single-mode fiber SMF-28 (Single-Mode Fiber). Single and double and triple line emissions were obtained by means of the angular micrometric deflection in the TCFMI (Thin-Core Fiber Modal Interferometer) interferometer section, as well as depending on the position of the polarization controller plates (PC1 and PC2). Also, a uniform tuning was achieved, depending on the polarization state of the pumping source and the position of the plates of the second polarization controller (PC2), which started at 1534.70265 nm and moved to the left side to 1531.65142 nm and the evolution of the polarization state in this tuning range was observed. A tuning range of 1527.01738 to 1553.66363 nm was also achieved by means of the angular micrometric deflection in the TCFMI interferometer section.
In this work, we present an analytical methodology to evaluate the response of a three-beam path Mach-Zehnder interferometer (MZI) based on a multiresolution signal analysis using a discrete Wavelet transform (DWT). Here, the MZI was implemented by fusion splicing of a segment of ytterbium-doped double cladding photonic crystal fiber (Yb-d-DCPCF) between two pieces of single mode fibers. Moreover, Yb-d-DCPCF core and claddings were used as the arms of the MZI, while the hole collapsed regions acted as optical fiber couplers. So, the MZI interference pattern occurs of two main modal interferences, between the core and cladding. Hence, as a result, an interference spectrum with aperiodic sinusoidal waveform was observed. In this way, in our proposed methodology we decompose the interference spectrum into eight bands of spatial frequency (SF) using the DWT with a wavelet mother Daubechies order twenty (db20) for detecting the two main modal interferences. The spectral analysis of the decomposed signal reveals that the level 7 and 8 contain the two main modal interference between the core and the cladding 1 and cladding 2, respectively. Additionally, the fundamental mode is obtained in the level 8. In the same way, the decomposed signal provides information about the wavelength and spatial frequency simultaneously that can be used for knowing the energy spectral density. Finally, we claim that the proposed methodology provides the best accuracy in SF of MZI intermodal and DWT indicates the wavelength region in which the propagation modes occur, improving the description of the refractive index difference.
We present an experimental study of liquid refractive index effects into Ytterbium ring fiber laser cavity configuration. The laser is operated using a bi-tapered optical fiber immersed in water-alcohol concentrations. When the tapered fiber is dipped into a distilled water, a single lasing line with a peak power centered at 1025 nm is achieved. Afterward, by changing the polarization state into the cavity the lasing line can be switched. Moreover, by modifying the refractive index liquid surrounding media the lasing lines can be controlled and special liquid provide nonlinear response. The laser offers compactness, low effective cost and good stability.
A magnetic field sensor based on a Mach-Zehnder interferometer with standard single mode fiber (SMF-28) is proposed. Here, the MZI was developed by using tapered optical fiber technique. Moreover, the Mach-Zehnder interferometer is manufactured with two tapers, with a core diameter of 25~40 μm and a length of 5 mm, and a separation between the tapers about of 4~6.5 cm. The MZI was covered by a fluid with magnetic proprieties. Performing experiments with magnets, coils and transformers, hoping that the proposed sensor offers a good option to measure the magnetic field in electrical devices.
In this experimental manuscript, a switchable Erbium-doped fiber ring laser based on an all-fiber Fabry-Perot filter was demonstrated. The filter is composed by several air micro-cavities formed into a section of a single-mode fiber splice joints with special hollow-core photonic crystal fiber. These micro-cavities are formed by air and silica, which produces several reflections generated at each silica-air-silica interfaces. Using this experimental setup we obtain a very high stable triple-laser emission at 1529.450nm, 1549.100nm and 1555.350nm with a linewidth of 0.2nm and a side-mode suppression ratio of 32dB, 37dB and 29dB respectively. These laser emission show a maximal peak power fluctuation around 0.4dB, 1.5dB and 2.6dB, with 0.025nm of wavelength oscillations. These results were observed after monitoring the laser cavity during an hour by recording the data each three minutes. By appropriately adjusting of transversal load applied over the Fabry-Perot filter between 0g and 550g, the ring laser cavity can be operated in double- wavelength, triple- wavelength, or quadruple- wavelength states. For this analysis, the all-fiber Fabry-Perot filter was set between a metal layer (below) and a thin glass layer (above) where transversal load was applied, here uniform load distribution over all the Fabry-Perot filter structure is achieved, as a result, the air intra-cavities that conform the filter are affected and the gain-losses profile is modified into the laser arrangement. The lasing emissions obtained in this work have a side-mode suppression ratio greater than 30dB. This ring laser cavity design offers a compact, simple and low-cost implementation and can be used in different applications where a very stable double, triple or quadruple laser lines are required.
In this work, multi-parameter fiber optic sensing setup is demonstrated by the simultaneous analyses of curvature and transversal load. The experimental arrangement operates by using two compact all fiber Fabry-Perot interferometers. Using a 2x1 optical fiber coupler the reflected interference patterns provided by each interferometer are combined, consequently new interference spectrum is obtained. Overlapping interference spectra is generated, and when curvature and load are simultaneously applied, intensity and phase variations are independently observed. The load information is obtained through a wavelength shifting generated by one interferometer, meanwhile the curvature data were analyzed using the intensity modulation provided by the other interferometer. The load analysis presents sensitivity around 0.1nm/N and moreover the experimented curvature shows a resolution of 0.4*10-3cm-1.
A torsion experimental sensing setup based on a Mach-Zehnder interferometer (MZI) with photonics crystal fiber is presented. The MZI was fabricated by fusion splicing a piece of photonic crystal fiber (PCF) between two segments of a single-mode fiber (SMF). Here, a spectral MZI fringe shifting is induced by applying torsion over the SMF-PCF-SMF. As a result a torsion sensitivity of 35.79 pm/ and a high visibility of 10 dB were achieved. Finally, it is shown that the sensing arrangement is compact and robust.
In this work, we study the changes of polarization at different wavelengths in a supercontinuum source generated
through a microchip laser in the IR spectrum. We use a microchip laser pulsed as pumped source, 1064 nm of
wavelength, and a photonic crystal fiber by generated a supercontinuum spectrum. We twist the fiber to the purpose to
induce birefringence and study the changes of the state of polarization, and through bandpass filters we observe a single
wavelength of the broad spectrum obtained. Besides, ellipticity study for different filters and its relation with the
supercontinuum results is discussed.
Tunable wavelength erbium doped fiber linear cavity laser, based on mechanically induced long-period fiber gratings (MLPFG) is presented. The laser was tuned applying pressure over the MLPFG, in order to monitor this, pressure is applied over a plate with periodic grooves that has a short length, this pressure is controlled by a digital torque tester as a result tunable effect is observed. The grooves have a period of 620µm and the maximal pressure without breakpoint fiber is around 0.80lb-in2. Furthermore, the MLPFG used can be erased, reconfigured and exhibit a transmission spectra with termal stability, similar to high cost photoinduced long period gratings. In this work, by pressure increment distributed over the MLPFG from 0.40 lb-in2 to 0. 70 lb-in 2, tuned operation range of 14nm was observed and single line emission was tuned in the C telecommunication band. According to the stability analysis the signal to noise ratio was 29 dB and minimal wavelength oscillations of 0.29nm.
In this work, we performed a numerical analysis of the supercontinuum spectrum generation in a couple of photonic crystal fibers with different structure. The proposed configuration initially has an input pulse with hyperbolic secant profile to generate noise-like pulses as output signal, by the Runge-Kutta method (RK4IP). By using the same configuration, now these noise-like pulses are used as pump for supercontinuum generation obtaining a broad and good flatness spectrum. The numerical analysis presented here demonstrates the potential of noise-like pulses from a passively mode-locked fiber laser for broadband spectrum generation combining two different photonic crystal fibers. Besides this paper helps to understand the phenomena of supercontinuum generation which is mainly related to Raman self-frequency shift.
In this work we show the changes of polarization at different wavelengths in the end of a photonic crystal fiber (PCF) by means bandpass filters in a supercontinuum light source. A linear and circular polarization was introduced in a piece of PCF, showing the changes of the polarization for each wavelength of each one of the filters from 450 to 700nm. We used a microchip laser as pumping source with wavelength of 532nm and short pulses of 650ps with repetition rate of 5kHz. We obtained a continuous spectrum in the visible spectral region, showing a comparison of the polarization state at the fiber input with respect to polarization state in the fiber output for different wavelengths by rotating the axes of the PCF.
This paper presents the design and implementation of an optical sensor to detect color changes in fruit by means of white light reflection to measure fruit ripeness in industrial and agricultural applications. The system consists of a LED RGB array including photodetectors, a power source and plastic optic fiber (POF). By means of Labview ® graphic interface we can control the power emission of the diodes digitally mixing the colors at different intensities until we achieve white light to be used as a source for the color sensor. We used an ATmega2560 microcontroller as a data collection device to monitor the colors obtained and to show them as color models using Matlab ®. We show results from tests conducted using two guava samples, observing the evolution of the color change on the fruit skin until they became overripe.
We study a passively mode-locked double-clad Erbium-Ytterbium fiber ring laser producing noise-like pulse through nonlinear polarization evolution and polarization selection. Single noise-like pulsing is only observed at moderate pump power. As pump power is increased, and through polarization controllers adjustments, harmonic mode-locking of growing order were successively appearing. For pump powers close to the damage threshold of the setup, we reach harmonic orders beyond 1200 and repetition frequencies in excess of a quarter of a GHz. Finally, these experimental results could be useful in the quest for higher pulse energies and higher repetition rates in passively mode-locked fiber lasers.
We study the nonlinear processes involved in the generation of broadband spectra with selectable spectral width. The
continuum spectra were generated in short piece of SMF-28 fiber as nonlinear media pumped by a microchip laser at
1064 nm. Bending effects in the spectra were observed through wrapping the fibers on a cylindrical tube. We show that
the spectral characteristics directly depend on the properties of the nonlinear medium, the excited nonlinear effects, and
the location of the wrapped section which can produce a filtering effect on the SC spectrum. Finally, the main
advantages of the proposed scheme are to obtain an adjustable bandwidth for a supercontinuum source through an easy
and flexible control, and to provide a low-cost configuration in which photonic crystal fibers are not used.
We show the sensing of load by means mechanically induced long-period fiber grating (MLPFG) made by applying
pressure by means a screw to a pair of grooved plates over single-mode fiber. We used a torquemeter in order to obtain
precision in the adjustment screw and thus establish an equilibrium pressure applied to a specific region of the optical
fiber to form the long-period grating mechanically induced fiber. The increase the torque to screw, the resonance
wavelength of MLPFG increases its depth over 16 dB. We use a detector to observe the changes amplitude according to
the fiber pressure.
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