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Timeline of Roberto Rojas-Laguna

2018
Nov
13
Published new article






Design of a Fabry-Perot interferometer based on silicon wafer for dielectric gas sensing applications

Published: 13 November 2018 by SPIE-Intl Soc Optical Eng in Infrared Sensors, Devices, and Applications VIII

doi: 10.1117/12.2320598

In this work a design and analysis of a Fabry-Perot interferometer (FPI) based on a silicon wafer for possible application in a SF6 gas sensor used in electric power systems is presented. The sensor design is based on cross correlation spectroscopy principle with an FPI, which acts an optical modulator. Hence, due to characteristics of the FPI transmission spectrum, it can be used detect molecules with very well defined ro-vibrational lines such as those produced by diatomic and linear molecules. The design of the FPI depends mainly of the SF6 absorption wavelength peaks and of the optimum thickness of the silicon wafer. For this reason, in order to measure this absorption peaks a HITRAN database was used. The optimum thickness of the silicon wafer was calculated and simulated transmission spectrum. Finally, we demonstrated by using analytical simulations that a silicon wafer can be implemented as a FPI and used in a SF6 gas sensor.

0 Reads | 0 Citations
2018
Sep
19
Published new article






Reconfigurable passband filter using a controllable variable inductance

Published: 19 September 2018 by SPIE-Intl Soc Optical Eng in Metamaterials, Metadevices, and Metasystems 2018

doi: 10.1117/12.2321697

A filter which its bandpass frequency can be reconfigured is presented. Its central frequency ranges from 316 MHz to 392 MHz (22% tuning). The filter is based on a miniaturized compose right/left-handed ring resonator. The reconfiguration of its resonant frequency is implemented by shifting a short location, thus changing its effective lefthanded inductance. This is opposed to the conventional capacitance change of other reconfigurable filters. The relation short location versus central frequency is quasi-linear. The short location could be controlled by a servomotor configuration.

0 Reads | 0 Citations
2018
Sep
14
Published new article






The polarization effects of the pumping source of a ring tunable wavelength laser Er-doped fiber

Published: 14 September 2018 by SPIE-Intl Soc Optical Eng in Optical Manufacturing and Testing XII

doi: 10.1117/12.2321239

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.

4 Reads | 0 Citations
2018
Aug
10
Published new article




Article

Erbium Ring Fiber Laser Cavity Based on Tip Modal Interferometer and Its Tunable Multi-Wavelength Response for Refractiv...

Published: 10 August 2018 by MDPI in Applied Sciences

doi: 10.3390/app8081337

A tunable multi-wavelength fiber laser is proposed and demonstrated based on two main elements: an erbium-doped fiber ring cavity and compact intermodal fiber structure. The modal fiber interferometer is fabricated using the cost-effective arc splice technique between conventional single-mode fiber and microfiber. This optical fiber structure acts as a wavelength filter, operated in reflection mode. When the refractive index and temperature variations are applied over the fiber filter, the ring laser cavity provides several quad-wavelength laser spectra. The multi-wavelength spectra are tuned into the C-band with a resolution of 0.05 nm. In addition, the spectra are symmetric with minimal power difference between the lasing modes involved, and the average of the side mode suppression ratio is close to 37 dB. This laser offers low-cost implementation, low wavelength drift, and high power stability, as well as an effect of easy controllability regarding tuned multi-wavelength.

2 Reads | 0 Citations
2018
Jan
01
Published new article




Article

Tip Fiber-Optic Intermodal Interferometer for Refractive Index Sensing

Published: 01 January 2018 by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Photonics Technology Letters

doi: 10.1109/lpt.2017.2771409

We propose an all-fiber-optic multimode interferometer for measuring liquid refractive index. The interferometer was manufactured by using arc splice technique between standard single mode fiber and optical microfiber. A maximum refractive index sensitivity of 112dB/RIU is experimentally demonstrated. In addition, thermal effects exhibit low phase modulation (12pm/°C) with minimal intensity variations (-10.7*10-3dB/°C), as a result, cross-sensitivity around 0.05*10-6 RIU/ °C and 0.9 *10-6 RIU/ °C are obtained for intensity and phase modulation. The stability analysis shows minimal wavelength and power variations, 0.01nm and 0.27dB respectively, for constant temperature and refractive index. Spatial frequency analysis was explored as an alternative method to measure liquid refractive index avoiding thermal effects.

5 Reads | 1 Citations
2017
Oct
31
Published new article




Article

A dual modality optical fiber sensor

Published: 31 October 2017 by Informa UK Limited in Journal of Modern Optics

doi: 10.1080/09500340.2017.1397220

We propose and demonstrate a fibre optic system based on bi-tapered silica fibre that can simultaneously measure strain and fibre curvature. Both modalities on the signal can be extracted with no measurable crosstalk between them. The experimental signal has a pure phase modulation when strain is applied to the tapered fibre optic section of the sensor and the signal shows only intensity modulation when an un-tapered fibre section is bent. High sensitivity is achieved from the experimental results for strain and bending losses and the estimation of measurement errors is 0.2 and 0.1%, respectively. This system offers low-cost, compactness and it can be adapted for structural health monitoring.

6 Reads | 0 Citations
2017
Oct
20
Published new article




Article

Magnetic Field Sensing Based on Bi-Tapered Optical Fibers Using Spectral Phase Analysis

Published: 20 October 2017 by MDPI in Sensors

doi: 10.3390/s17102393

A compact, magnetic field sensor system based on a short, bi-tapered optical fiber (BTOF) span lying on a magnetic tape was designed, fabricated, and characterized. We monitored the transmission spectrum from a broadband light source, which displayed a strong interference signal. After data collection, we applied a phase analysis of the interference optical spectrum. We here report the results on two fabricated, BTOFs with different interference spectrum characteristics; we analyzed the signal based on the interference between a high-order modal component and the core fiber mode. The sensor exhibited a linear response for magnetic field increments, and we achieved a phase sensitivity of around 0.28 rad/mT. The sensing setup presented remote sensing operation and low-cost transducer magnetic material.

0 Reads | 1 Citations
2017
Aug
23
Published new article






A dual tapered Mach-Zehnder interferometer for magnetic field sensing

Published: 23 August 2017 by SPIE-Intl Soc Optical Eng in Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications XI

doi: 10.1117/12.2273956

0 Reads | 0 Citations
2017
May
16
Published new article






Temperature sensing setup based on an aluminum coated Mach-Zehnder Interferometer

Published: 16 May 2017 by SPIE-Intl Soc Optical Eng in Optical Sensors 2017

doi: 10.1117/12.2265735

In this paper a temperature sensing setup based on a Photonic Crystal Fiber (PCF) Mach-Zehnder Interferometer (MZI), coated with aluminum is proposed. Here, this interferometer is fabricated through the concatenation of two sections of Single Mode Fiber (SMF) with a segment of PCF between them. The SMF-PCF joint acts as beam splitter causing the excitement of PCF’s, both cladding and fundamental core modes. In the PCF-SMF union, the cladding modes couple again to the core of the SMF, and interfere with the fundamental core mode, this interaction results in an interference pattern spectrum. Moreover, the MZI was coated with aluminum, using the evaporation technique. By adding a thin metal layer to the PCF section, the general thermal coefficient of the structure changes, enhancing the sensitivity of the device. Experimental results show that a visibility of 13 dBm can be obtained and a sensitivity of 250 pm/°C. Finally, the proposed structure is simple, cost effective and easy to fabricate. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

0 Reads | 0 Citations
2017
Feb
21
Published new article




Article

Fast Parabola Detection Using Estimation of Distribution Algorithms

Published: 21 February 2017 by Hindawi Limited in Computational and Mathematical Methods in Medicine

doi: 10.1155/2017/6494390

This paper presents a new method based on Estimation of Distribution Algorithms (EDAs) to detect parabolic shapes in synthetic and medical images. The method computes a virtual parabola using three random boundary pixels to calculate the constant values of the generic parabola equation. The resulting parabola is evaluated by matching it with the parabolic shape in the input image by using the Hadamard product as fitness function. This proposed method is evaluated in terms of computational time and compared with two implementations of the generalized Hough transform and RANSAC method for parabola detection. Experimental results show that the proposed method outperforms the comparative methods in terms of execution time about 93.61% on synthetic images and 89% on retinal fundus and human plantar arch images. In addition, experimental results have also shown that the proposed method can be highly suitable for different medical applications.

0 Reads | 2 Citations
2017
Feb
20
Published new article






Torsion sensing setup based on a Mach-Zehnder interferometer with photonics crystal fiber

Published: 20 February 2017 by SPIE-Intl Soc Optical Eng in Photonic Instrumentation Engineering IV

doi: 10.1117/12.2251495

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. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

0 Reads | 0 Citations
2017
Jan
01
Published new article




Article

Symmetric and Asymmetric Core-Offset Mach-Zehnder Interferometer Torsion Sensors

Published: 01 January 2017 by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Photonics Technology Letters

doi: 10.1109/LPT.2017.2735298

In this letter, symmetric and asymmetric core-offset Mach-Zehnder interferometer (MZI) torsion sensors based on a single mode fiber (SMF) are presented. Here, three different MZIs were implemented and their interference patterns and torsion characteristics have been experimentally investigated. In our devices, the maximum torsion sensitivities are 6x10-3, 12x10-3, and 23x10-3 nm/°, with the possibility to discriminate between clockwise and anticlockwise rotation. Finally, these interferometers only employ SMF and can be fabricated at low cost.

1 Reads | 0 Citations
2016
Dec
09
Published new article




Article

Determination of Magnetic Field using a Fabry-Perot Cavity Containing Novel Nanoparticles

Published: 09 December 2016 by Informa UK Limited in Instrumentation Science & Technology

doi: 10.1080/10739149.2016.1269017

Mn0.75Zn0.25Fe2O4 nanoparticles were used to characterize magnetic fields using an all-fiber Fabry–Perot interferometer. The 20-nm nanoparticles were fabricated with citrate and displayed a coercive field of approximately 10 mT. The nanoparticles were dispersed in oleic acid to prepare a magnetic fluid to fill a Fabry–Perot structure fabricated by arc splicing with conventional single-mode and hollow core photonic crystal fibers. This device provided sensitivity and resolution of 0.11 dB/mT and 0.09 mT, respectively. Thermal analysis indicated that the magnetic measurements are weakly depending on temperature (0.7 pm/°C and 7 × 10−3 dB/°C). This device offers low-cost fabrication, simple implementation and may be used in several industrial applications.

4 Reads | 1 Citations
2016
Jun
10
Published new article




Article

A Core-Offset Mach Zehnder Interferometer Based on A Non-Zero Dispersion-Shifted Fiber and Its Torsion Sensing Applicati...

Published: 10 June 2016 by MDPI in Sensors

doi: 10.3390/s16060856

In this paper, an all-fiber Mach-Zehnder interferometer (MZI) based on a non-zero dispersion-shifted fiber (NZ-DSF) is presented. The MZI was implemented by core-offset fusion splicing one section of a NZ-DSF fiber between two pieces of single mode fibers (SMFs). Here, the NZ-DSF core and cladding were used as the arms of the MZI, while the core-offset sections acted as optical fiber couplers. Thus, a MZI interference spectrum with a fringe contrast (FC) of about 20 dB was observed. Moreover, its response spectrum was experimentally characterized to the torsion parameter and a sensitivity of 0.070 nm/° was achieved. Finally, these MZIs can be implemented in a compact size and low cost.

4 Reads | 8 Citations
2016
Jan
01
Published new article




Article

Ytterbium Fiber Laser Based on a Three Beam Optical Path Mach-Zehnder Interferometer

Published: 01 January 2016 by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Photonics Technology Letters

doi: 10.1109/LPT.2016.2616466

In this letter, a switchable ytterbium doped double cladding photonic crystal fiber (Yb-doped-DCPCF) laser based on a three optical path Mach-Zehnder interferometer (MZI) is presented. Here, the MZI with three-beam path was achieved by fusion splicing a segment of an Yb-doped-DCPCF between two pieces of single mode fibers. Moreover, in the proposed laser arrangement, the Yb-doped-DCPCF segment is acting simultaneously as the MZI and also as the gain medium. This laser can be switched to emit a single or double line by controlling the polarization state and it operates within the range from 1028 to 1033 nm. In addition, the laser emission has a linewidth of 0.07 nm and a single-mode suppression ratio of 40 dB. Finally, it is shown that the fiber laser arrangement is compact and robust and that requires a relativity simple fabrication procedure.

0 Reads | 0 Citations
2016
Jan
01
Published new article






L-Band Switchable Multiwavelength Fiber Laser Using a Novel Photonic Crystal Fiber

Published: 01 January 2016 by The Optical Society in Integrated Photonics Research, Silicon and Nanophotonics

doi: 10.1364/sensors.2016.setu2e.5

An all in-fiber Mach-Zehnder interferometer using a photonic crystal fiber is presented for a switchable multiwavelength laser, which emits in the L-band for communications. Three laser emissions are achieved by controlling the polarization state.

0 Reads | 0 Citations
2016
Jan
01
Published new article






Analysis of Polarization of a broadband visible light source by inducing of twist in photonic crystal fiber

Published: 01 January 2016 by The Optical Society in Latin America Optics and Photonics Conference

doi: 10.1364/laop.2016.ltu4a.40

In this work supercontinuum generation by twisting solid core photonic crystal fiber and pulsed source at 532nm is presented. Besides, ellipticity study for different filters and its relation with the supercontinuum results is discussed.

0 Reads | 0 Citations
2015
Oct
15
Published new article




Article

Analytical Modelling of a Refractive Index Sensor Based on an Intrinsic Micro Fabry-Perot Interferometer

Published: 15 October 2015 by MDPI in Sensors

doi: 10.3390/s151026128

In this work a refractive index sensor based on a combination of the non-dispersive sensing (NDS) and the Tunable Laser Spectroscopy (TLS) principles is presented. Here, in order to have one reference and one measurement channel a single-beam dual-path configuration is used for implementing the NDS principle. These channels are monitored with a couple of identical optical detectors which are correlated to calculate the overall sensor response, called here the depth of modulation. It is shown that this is useful to minimize drifting errors due to source power variations. Furthermore, a comprehensive analysis of a refractive index sensing setup, based on an intrinsic micro Fabry-Perot Interferometer (FPI) is described. Here, the changes over the FPI pattern as the exit refractive index is varied are analytically modelled by using the characteristic matrix method. Additionally, our simulated results are supported by experimental measurements which are also provided. Finally it is shown that by using this principle a simple refractive index sensor with a resolution in the order of 2.15 × 10−4 RIU can be implemented by using a couple of standard and low cost photodetectors.

0 Reads | 1 Citations
2015
Jun
01
Published new article




Article

Laser Temperature Sensor Based on a Fiber Bragg Grating

Published: 01 June 2015 by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Photonics Technology Letters

doi: 10.1109/lpt.2015.2406572

In this letter, a temperature sensor based on a fiber ring laser is presented. A fiber Bragg grating was used as a sensor head, and a Mach-Zehnder interferometer (MZI) was utilized as a wavelength selective filter to enhance the temperature sensing capability. The MZI was achieved by splicing a piece of photonic crystal fiber between two segments of single-mode fiber. Moreover, it is shown that when the laser emission wavelength is shifted as the temperature is varied, achieving a temperature sensitivity of 18.8 pm/°C at 1550 nm, within the temperature range from 20 °C to 90 °C.

0 Reads | 11 Citations
2015
May
28
Published new article




Article

Torsion sensing setup based on a three beam path Mach-Zehnder interferometer

Published: 28 May 2015 by Wiley in Microwave and Optical Technology Letters

doi: 10.1002/mop.29208

In this letter, a torsion sensing arrangement based on a three beam path Mach–Zehnder interferometer (MZI) is presented. The MZI with three beam paths was fabricated by fusion splicing a piece of double ytterbium‐doped double‐cladding photonic crystal fiber (Yb‐d‐DPCF) between two segments of single mode fiber (SMF). Moreover, in our sensing arrangement the Yb‐d‐DPCF segment is acting both as the MZI as the gain medium. Here, a spectral MZI fringe shifting is induced by applying torsion over the Yb‐d‐DPCF. By this setup, a torsion sensitivity of 0.001 nm/° was achieved. Finally, it is shown that the sensing arrangement is compact and robust. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1857–1860, 2015

0 Reads | 6 Citations
2015
Apr
29
Published new article






Sub- and Nanosecond Pulsed Lasers Applied to the Generation of Broad Spectrum in Standard and Microstructured Optical Fi...

Published: 29 April 2015 by Springer Nature in Springer Series in Optical Sciences

doi: 10.1007/978-94-017-9481-7_10

This chapter provides an experimental and theoretical overview of pulsed lasers applications focused on obtaining supercontinuum light source. Particular attention is paid to the supercontinuum generation with short piece of conventional and microstructured fiber. An investigation in the regime of long pulses is performed through pumping sources with pulse duration of 700 ps and 6 ns, showing that it is possible to obtain this kind of source in an economical way by using a microchip laser and a few meters of standard fiber, and achieve spectral broadening comparable with that one using a femtosecond laser. In this chapter the nonlinear effects in short lengths of optical fibers are analyzed, starting with modulation instability, stimulated Raman scattering, and stimulated Brillouin scattering. The interaction of these effects for obtaining supercontinuum light source is shown. It also shown that using a Nd:YAG laser with pulse duration of 6 ns and a repetition rate of 50 Hz to pump two joined photonic crystal fibers with different microstructure and dispersion is possible to obtain a spectral broadening with a greater flatness. Finally the spectral evolution of pumping pulses is presented for different input intensities and different lengths of standard and microstructured fibers.

5 Reads | 0 Citations
2014
Nov
15
Published new article




Article

All-Fiber Curvature Sensor Based on an Abrupt Tapered Fiber and a Fabry–Pérot Interferometer

Published: 15 November 2014 by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Photonics Technology Letters

doi: 10.1109/lpt.2014.2349979

In this letter, a highly sensitive curvature sensor arrangement based on an abrupt tapered fiber (ATF) concatenated with an all-fiber micro Fabry-Pérot interferometer (MFPI) is presented. Here, as the ATF is bent, the MFPI spectral fringes contrast decreases. In addition, the curvature sensitivity is considerably enhanced due to the use of the ATF. Finally, it is shown that with this arrangement, at 1530-nm wavelength, it is possible to detect curvature changes with a sensitivity of 11.27 dB/m -1 and a curvature resolution of 8.87 × 10 -3 m -1 within the measurement range of 0 - 3.5 m -1 .

0 Reads | 4 Citations
2014
Jan
01
Published new article






Tunable Dual-Wavelength Ytterbium Doped Photonic Crystal Fiber Laser Based On A Mach-Zehnder Interferometer

Published: 01 January 2014 by The Optical Society in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference

doi: 10.1364/cleo_at.2014.jth2a.130

A tunable dual-wavelength ytterbium doped photonic crystal fiber laser based on a Mach-Zehnder interferometer is presented. The laser tunes from 1026nm to 1034nm by controlling the birefringence with a linewidth of 0.007nm and a contrast of 40dB.

0 Reads | 0 Citations
2014
Jan
01
Published new article






Tunable Broadband in Supercontinuum Spectrum Based on Polarization Effects

Published: 01 January 2014 by The Optical Society in Laser Science

doi: 10.1364/fio.2014.jtu3a.38

We demonstrated that the bandwidth control in supercontinuum source is possible through polarization effects induced on a PCF. The spectral width obtained can be selected from 740 nm-1430 nm while it maintains a good flatness.

1 Reads | 0 Citations
2013
May
14
Published new article




Article

An All Fiber Intrinsic Fabry-Perot Interferometer Based on an Air-Microcavity

Published: 14 May 2013 by MDPI in Sensors

doi: 10.3390/s130506355

In this work an Intrinsic Fabry-Perot Interferometer (IFPI) based on an air-microcavity is presented. Here the air microcavity, with silica walls, is formed at a segment of a hollow core photonic crystal fiber (HCPCF), which is fusion spliced with a single mode fiber (SMF). Moreover, the spectral response of the IFPI is experimentally characterized and some results are provided. Finally, the viability to use the IFPI to implement a simple, compact size, and low cost refractive index sensor is briefly analyzed.

5 Reads | 11 Citations
2013
Mar
04
Published new article




Article

High Temperature Optical Fiber Sensor Based on Compact Fattened Long-Period Fiber Gratings

Published: 04 March 2013 by MDPI in Sensors

doi: 10.3390/s130303028

A compact high temperature fiber sensor where the sensor head consists of a short fattened long period fiber grating (F-LPFG) of at least 2 mm in length and background loss of −5 dBm is reported. On purpose two different F-LPFGs were used to measure temperature variations, taking advantage of their broad spectrum and the slope characteristics of the erbium light source. This approach affected the spectrum gain as the linear band shifting took place. The measured sensitivity of the long period fiber gratings were about 72 pm/°C in a range from 25 to 500 °C. Here, the temperature rate of the experiment was 0.17 °C/s and the temperature response time was within 3 s. Moreover, temperature changes were detected with an InGaAs photodetector, where a sensitivity of 0.05 mV/°C was achieved.

1 Reads | 4 Citations
2009
Sep
26
Published new article






Modes in a long period grating fabricated on dispersion shifted fiber

Published: 26 September 2009 by SPIE-Intl Soc Optical Eng in Seventh Symposium on Optics in Industry

doi: 10.1117/12.847115

In this work we present the modal study of a dispersion shifted fiber (4 layers) and also in a fabricated long period grating in the same fiber type using the RSoft Software ®. For the grating analysis, the refraction index and the diameters were varied to simulate the changes due to the diameter increment provided by the electrical arc discharges effect. The structural optical fiber change, due to the periodic fattening induced by the electric arc, is added to the grating analysis as a sinusoidal type variation in each optical fiber layer. Several wavelengths are considered for the analysis and some of them are the ones commonly used by operational lasers and diodes launched in optical fibers. Results depicted the existence of many excited light modes when working with a wide spectrum white light source. When these modes satisfy the phase matching condition, they will couple in the LPFG providing it of particular filtering characteristics because of the fiber type and technique (fattening) of fabrication.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

0 Reads | 0 Citations
2008
Jan
01
Published new article






Noise Suppression ASE of Erbium Doper Fiber Laser by Means of a Filter Optical Fiber Fattening

Published: 01 January 2008 by The Optical Society in Advanced Solid-State Photonics

doi: 10.1364/fio.2008.jsua28

In this work we present the results obtained to couple a filter Optical fiber to Erbium doper fiber laser, with this setup we eliminate noise ASE.

0 Reads | 0 Citations
2008
Jan
01
Published new article






Gas Sensor Design Using a Fabry-Perot Interferometer and a Pyroelectric Detector

Published: 01 January 2008 by AIP Publishing in AIP Conference Proceedings

doi: 10.1063/1.2926937

A gas sensor design based on cross correlation spectroscopy using a FPI with long cavity length (>500 μ m ) as a modulator and with a pyroelectric detector is presented. This technique can be suitable to detect molecules with very well defined ro‐vibrational lines such as CO, CO 2 and CH 4 . To induce modulation one mirror of the FPI is scan over λ/2, this will shift the spectral FPI transmission fringe pattern producing the cross correlation principle. In this design the FPI is illuminated with a converging beam and it is placed just in front of the pyroelectric detector, this configuration can be useful if the FPI and the detector are integrated within a MEMS. Furthermore here the FPI scan is driven using a triangular waveform. Therefore in this work we will analyze the effects of illuminate the FPI with a converging beam and their consequences in the overall sensor response. Moreover we will review some possible effects in the sensor response for driving the FPI mirror scan with a triangular waveform. This issue can be very important since it can change the harmonic composition of the modulated signal and consequently the overall sensor response since the pyroelectric detector responsivity is frequency dependant. Finally, simulation results and experimental measurements are provided.

0 Reads | 0 Citations
2007
Feb
08
Published new article






Experimental investigation of a figure-eight fiber laser with a symmetrical NOLM and highly twisted fiber-in-the-loop

Published: 08 February 2007 by SPIE-Intl Soc Optical Eng in Lasers and Applications in Science and Engineering

doi: 10.1117/12.700704

We report experimental results that demonstrate the mode-locking operation of a figure eight fiber laser based on a symmetrical nonlinear optical loop mirror (NOLM) with a twisted low-birefringence fiber in the loop. The mode-locking operation is achieved by nonlinear polarization rotation in the NOLM, where the counterpropagating beams accumulate a differential nonlinear phase shift when they have different polarizations. By adjusting a single quarter wave (QW) retarder in the NOLM it was possible to change the NOLM transmission behavior from a maximum to a minimum at low input power. Self-starting mode-locking operation was found for only specific settings of the QW retarder. The pulse repetition frequency was around 0.8 MHz. The mode-locked laser operated stably for hours and the adjustment procedure was straightforward. We achieved stable generation of picosecond pulses with milliwatts of average output power.

3 Reads | 0 Citations
2006
Nov
01
Published new article




Article

Pulse breakup and Raman-shifted solitons in a standard fiber with subnanosecond pumping in the presence of noise

Published: 01 November 2006 by The Optical Society in Journal of the Optical Society of America B

doi: 10.1364/josab.23.002336

We present a numerical study of the wave breakup and soliton formation in a standard single-mode fiber pumped by variable pulse lengths in the range from 20 to 400 ps in the presence of noise. The average power and the standard deviation of the trailing soliton were calculated. We calculated also the average distance at which the soliton time delay reaches 1.5 times the pulse width. We found that for pulses longer than 100 ps the breakup starts from the amplification of the noisy modulation of the amplitude by the modulation instability mechanism even for very low noise power, while for pulses shorter than 20 ps the breakup starts from the pulse collapse. For intermediate durations, wave breakup starts from the pulse collapse at low noise power, while for higher noise power, modulation instability prevails.

0 Reads | 1 Citations
2006
Feb
09
Published new article






Polarization properties of nonlinear optical loop mirror with twisted fiber and birefringence bias in the loop

Published: 09 February 2006 by SPIE-Intl Soc Optical Eng in Lasers and Applications in Science and Engineering

doi: 10.1117/12.644182

The nonlinear optical loop mirror (NOLM) is used in application like optical switching and demultiplexing, all-optical active mode locking, passive mode locking, pedestal suppression, pulse shaping, etc. This device offers a versatile way to obtain a nonlinear transmission behavior through the nonlinear differential phase shift between the two interfering beams due to the self-phase modulation. Recently we discussed a NOLM device using a symmetrical coupler, highly twisted fiber, and a quarter-wave (QW) retarder introducing the polarization asymmetry in the loop. We have shown high contrast operation, flexibility of characteristics, and stability in time. In this report we analyze theoretically and study experimentally the transmission behavior for different input polarization considering as well different output polarizations. We propose a simple description of the NOLM transmission for right- and left-hand circular output polarization at different output polarization states. The nonlinear characteristics depend on the QW retarder plate angle, but also on the polarization state at the NOLM input. Experiments were carry out with the NOLM consisted of a 500-m length SMF-28 fiber with twist rate of 7 turns/meter. Experiments show a good agreement with our theoretical approach. Appropriate choice of the input and output polarizations allows very high contrast, at least higher than 5000. Our measurements were restricted by sensitivity of our detection system to measure low power pulses at conditions when theoretically transmission must be equal zero. Experiments show flexibility and stability of characteristics. Adjustment of the QW retarder and input polarization allows tuning the critical power over a wide range.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

0 Reads | 0 Citations
2006
Feb
09
Published new article






Stimulated Raman scattering and broadband spectrum generation of nanosecond pulses from a directly modulated DFB laser

Published: 09 February 2006 by SPIE-Intl Soc Optical Eng in Lasers and Applications in Science and Engineering

doi: 10.1117/12.645269

We report the investigation of stimulated Raman Scattering (SRS) in a standard fiber using a directly modulated DFB laser with wavelength equal to 1549 nm, amplified by a two stage Erbium-doped fiber amplifier. The amplifier provides amplification of 2-mW peak power input pulses to 100-W peak power output pulses. This setup provides a simple source of high power pulses for nonlinear investigation. However, the directly modulation of DFB lasers causes transient oscillations at the beginning of pulses. In our case pulses consisted of a 2-ns transient part followed by a steady-state plateau. We used a monochromator to measure the spectrum at the fiber output. A fast photodetector was placed at the monochromator output and pulse shapes were measured for different wavelengths. This technique allows the separate measurement of the spectrum of different parts of output pulses. We used the SMF-28 fiber with the standard dispersion of 20 ps/nm-km for our wavelength. We made measurements of the output spectra for four fiber lengths: 210 m, 600 m, 4.5 km, and 10 km. For short fiber lengths (210 m and 600 m) the spectra of the transient part and the plateau part were similar and manifest modulation instability (MI) and four-wave mixing (FWM). For 4.5-km long and 10-km long fibers we found that the transient part generates a continuous broadband spectrum while the plateau causes the Stokes wave with the spectrum maximum centered at 1656 nm.

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2006
Jan
01
Published new article






Figure-Eight Fiber Laser with a Symmetrical NOLM and a Fiber Bragg Grating

Published: 01 January 2006 by The Optical Society in Laser Science

doi: 10.1364/fio.2006.fthd5

We experimentally demonstrate the operation of a figure-eight fiber laser based on a symmetrical NOLM with twisted low-birefringence fiber and a fiber Bragg grating. We investigate how the NOLM transmission affects the laser mode-locked operation.

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2006
Jan
01
Published new article






Evolution of Broadband Spectrum Generation and Stimulated Raman Scattering from Nanosecond Pump Pulses in Single-Mode Op...

Published: 01 January 2006 by The Optical Society in Laser Science

doi: 10.1364/fio.2006.jsua70

At pumping of a standard fiber by an amplified directly modulated DFB laser the leading part of the pulse generates a broadband spectrum while the plateau causes the Raman amplification resulting in flat spectrum.

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2005
May
02
Published new article




Article

Intra-pulse Raman frequency shift versus conventional Stokes generation of diode laser pulses in optical fibers.

Published: 02 May 2005 in Optics Express

doi:

We report experimental observations of stimulated Raman scattering in a standard fiber using a directly modulated DFB semiconductor laser amplified by two erbium-doped fibers. The laser pulse width was variably controlled on a nanosecond-scale; the laser emission was separated into two distinct regimes: an initial transient peak regime, followed by a quasi steady-state plateau regime. The transient leading part of the pump pulse containing fast amplitude modulation generated a broadband Raman-induced spectral shift through the modulation instability and subsequent intra-pulse Raman frequency shift. The plateau regime amplified the conventional Stokes shifted emission expected from the peaks of the gain distribution. The output signal spectrum at the end of a 9.13 km length of fiber for the transient part extends from 1550 nm to 1700 nm for a pump pulse peak power of 65 W. We found that the Raman-induced spectral shift is measurable about 8 W for every fiber length examined, 0.6 km, 4.46 km, and 9.13 km. All spectral components of the broadband scattering appear to be generated in the initial kilometer of the fiber span. The Stokes shifted light generation threshold was higher than the threshold for the intra-pulse Raman-induced broadened spectra. This fact enables the nonlinear spectral filtering of pulses from directly modulated semiconductor lasers.

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2005
Feb
14
Published new article






Optical fiber current sensor based on a magnetic structure

Published: 14 February 2005 by SPIE-Intl Soc Optical Eng in Merida - DL Tentative

doi: 10.1117/12.611601

In this work the implementation of a sensor of optical fiber current is reported by means of a magnetic structure. The sensing element (magnetic structure) consists of a magnet placed in the center of a plastic membrane. The variation in the intensity of the light caused by a mirror adapted to the membrane allowed to detect the changes in the presence of a magnetic field produced by an alternating current. Its changes were detected optically. We design a circuit to convert the light to equivalent in data to be process by a PC. The data are read and by means of a program in software Labview, is the equivalent of current according to the intensity of detected magnetic field.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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2005
Jan
01
Published new article




Article

Intra-pulse Raman frequency shift versus conventional Stokes generation of diode laser pulses in optical fibers

Published: 01 January 2005 by The Optical Society in Optics Express

doi: 10.1364/opex.13.003388

We report experimental observations of stimulated Raman scattering in a standard fiber using a directly modulated DFB semiconductor laser amplified by two erbium-doped fibers. The laser pulse width was variably controlled on a nanosecond-scale; the laser emission was separated into two distinct regimes: an initial transient peak regime, followed by a quasi steady-state plateau regime. The transient leading part of the pump pulse containing fast amplitude modulation generated a broadband Raman-induced spectral shift through the modulation instability and subsequent intra-pulse Raman frequency shift. The plateau regime amplified the conventional Stokes shifted emission expected from the peaks of the gain distribution. The output signal spectrum at the end of a 9.13 km length of fiber for the transient part extends from 1550 nm to 1700 nm for a pump pulse peak power of 65 W. We found that the Raman-induced spectral shift is measurable about 8 W for every fiber length examined, 0.6 km, 4.46 km, and 9.13 km. All spectral components of the broadband scattering appear to be generated in the initial kilometer of the fiber span. The Stokes shifted light generation threshold was higher than the threshold for the intra-pulse Raman-induced broadened spectra. This fact enables the nonlinear spectral filtering of pulses from directly modulated semiconductor lasers.

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2004
Oct
21
Published new article






Control in LabView of the monochromator DK240 and measurement of absorption and emission of erbium-doped Fiber

Published: 21 October 2004 by SPIE-Intl Soc Optical Eng in SPIE Proceedings

doi: 10.1117/12.591172

We present the control of the monochromator DK240 developed by a program in LabVIEW, this program adjusts the entrance/exit slits, the scan of the measurement of the wavelength in a range from 100 nm to 3000 nm as well as the scan speed, we also show experimental setup to measure the absorption of Erbium-Doped Fiber and its experimental graph.

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2004
Oct
21
Published new article






Dependence of the polarization of multiple dark waveguides in nonlinear liquids

Published: 21 October 2004 by SPIE-Intl Soc Optical Eng in SPIE Proceedings

doi: 10.1117/12.590697

We present the polarization dependence in the formation of dark spatial waveguides in nonlinear liquids like CS2. Our experimental and numerical results about the formation of dark waveguides show the dependence between the polarization and the formation of multiple waveguides. With a polarization angle between 100° - 120° for the incident beam we show that the wide of the waveguide is minimum and even dark spatial waveguides are formed. A discussion about waveguides formation is presented for others polarization angles. In this work we show an improvement in the method to measure low birefringence in optical fibers.

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2004
Oct
21
Published new article






Non-optical loop mirror inducing birefringence bias macro bendings in the loop

Published: 21 October 2004 by SPIE-Intl Soc Optical Eng in SPIE Proceedings

doi: 10.1117/12.592184

This paper is about a numerical investigation of the NOLM (non optical loop mirror) with low birefringence fiber and a 0.5/0.5 coupler. We induce birefringence to the loop fiber bias macro bendings considering self-rotation polarization of the input beam. This is done in order to find its possible advantages as an optical switch.

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2004
Oct
21
Published new article






Twist in the center of the loop of Sagnac interferometer of optical fiber to determine the beat length

Published: 21 October 2004 by SPIE-Intl Soc Optical Eng in SPIE Proceedings

doi: 10.1117/12.591672

In this work we showed an improvement in the method to measure low birefringence in optical fibers with the Sagnac interferometer published in paper previous in which the fiber twists in an end of the loop of the interferometer and the entrance of the light every time it is adjusted that twists the fiber. In this work we twist the fiber in the center of the loop of the Sagnac interferometer it is very simple and we don't need light polarization neither to adjust the axes in the entrance of the fiber. It can use for the mensuration a section of shorter fiber that a beat length. Some theoretical and experimental results are presented.

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