Optical Engineering (OPT ENG)

Publications in this journal

• Article: Study on hydrofluoric acid-based clad etching and chemical sensing characteristics of fiber Bragg gratings of different reflectivity fabricated under different UV exposure times

  J. Kumar, R. Mahakud, O. Prakash, S. K. Dixit
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  ABSTRACT: An experimental study on hydrofluoric acid (HF)-based clad etching and chemical sensing characteristics of fiber Bragg gratings (FBG) of different reflectivity fabricated under different UV (255 nm) exposure times is presented. Two FBGs of reflectivity 11% and 93% were inscribed by phase mask–based exposition of the photosensitive fibers by a 5.5 kHz repetition rate of 255 nm UV pulses for 15 s and 10 min, respectively. These two FBGs, employed in an HF-based clad etching experiment, revealed a much higher etching rate of 2.03 μm∕ min for the grating of reflectivity 11% as compared to 1.69 μm∕ min for the grating of reflectivity 93%. The performance of these etched FBGs were also studied for refractive index sensing of the chemicals ethanol and ethylene glycol under different fiber etching times, hence of different residual cladding diameter. It was observed that the same refractive index sensitivity for both the chemicals could be achieved under smaller etching time, i.e., larger residual cladding diameter, for the FBG with lower reflectivity. This differentiating behavior of FBGs under etching and sensing may be linked to the different degree of densification in fused silica fiber cladding under different UV fluence exposures.
  Optical Engineering 05/2013; 52(5):054402.
• Article: Exponentiated Weibull fading model for free-space optical links with partially coherent beams under aperture averaging

  Ricardo Barrios, Federico Dios
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  ABSTRACT: The recently proposed exponentiated Weibull (EW) fading channel model is assessed with partially coherent beams (PCBs) using the Gaussian Schell-model (GSM) theory. The use of a PCB in freespace optical links has been suggested as an atmospheric turbulence mitigation technique, called transmitter aperture averaging. A wave optics code based on the GSM theory is used to generate a PCB propagating in atmospheric turbulence, and the probability distribution function (PDF) is obtained from the simulated irradiance data. This study on the PDF includes the new proposed EW model in the presence of aperture averaging, in weak-to-strong turbulence regime. Point receiver conditions are also analyzed. For completeness of the study, the Lognormal and the Gamma-Gamma models have also been included in the analysis, allowing for a direct comparison to the EW distribution. Using a least-squares curve fitting algorithm, the EW model always has the best fit to simulated PDF data. Thus, the EW fading channel model proves to be valid for PCBs.
  Optical Engineering 04/2013; 52(4):046003.
• Article: Target Recognitions in Multiple Camera CCTV Using Colour Constancy

  Soori U, Yuen PWT, Han JW, Ibrahim I, Chen WT, Hong K, Merfort C, James D, Richardson M
  Optical Engineering 04/2013; 52(4):047202.
• Article: Remote sensing and characterization of oil on water using coherent fringe projection and holographic in-line interferometry

  Arcadi Chirita, Nikolai Kukhtarev, Tatiana Kukhtareva, Sonia Gallegos
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  ABSTRACT: Abstract. We suggest combining several optical methods for remote sensing and characterization of crude oil films and emulsions. These are coherent fringe projection illumination (CFP), holographic in-line inter-ferometry (HILI), and laser-induced fluorescence. The combined methods of CFP and HILI are described in the frame of coherent superposition of partial interference patterns. It is shown that in addition to detection and identification of oil, laser illumination in the green-blue region can also degrade oil. This finding indicates that properly structured laser clean-up can be an alternative method of decontamination.
  Optical Engineering 03/2013;
• Article: Fringe projection by perfilometry

  L. Salas, E.Luna, J. Salinas, V. García, M. Servín
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  ABSTRACT: We present a method to obtain profilometry of a suitable object by fringe projection. The method is appropriate to the case of large objects as compared to the distance from the illuminating source, that is, a nonconstant equivalent wavelength. We develop an experiment to laterally displace a set of fringes on a sphere and obtain quantitative results. There are several orientation parameters involved in the method, and a minimization algorithm is developed to adjust the values of some of them. A series of numerical experiments are performed on this method to test its accuracy under various circumstances. We show that the method can currently attain precisions of 'leq/80 (leq stands for equivalent wavelength) and identify possible sources of error.
  Optical Engineering 02/2013; 42(11):3307.
• Article: Fringe projection by perfilometry

  L. Salas
  Optical Engineering 02/2013;
• Article: Investigation in acousto-optic laser stabilization for crystal resonator-based optoelectronic oscillators

  Patrice Salzenstein, Vitaly B. Voloshinov, Arseniy S. Trushin
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  ABSTRACT: Potentialities are investigated for using acousto-optic cells based on a TeO2 crystal to stabilize a microwave signal generated by an optoelectronic oscillator. Bulk acoustic waves at two radio frequencies (RF) near 60 MHz are launched in the two identical cells providing a required locking on of a microwave signal. Differences between RF signals are up to 400 kHz to follow quality factor of the optic resonator typically in the range of 5 × 10^8. Critical alignment of the two cells is performed thanks to an extraordinary polarized laser beam launched at a very low Bragg angle of light incidence. Moreover, the system is operating for any resonator to be inserted into the optoelectronic oscillator with a Q factor in the range of 2 × 10^7 − 10^11.
  Optical Engineering 02/2013; 52(2):024603.
• Article: Salient point region covariance descriptor for target tracking

  S. Cakir, T. Aytaç, A. Yildirim, S. Beheshti, Ö. N. Gerek, A. E. Cetin
  Optical Engineering 02/2013; 52(2).
• Article: Generation of an amplitude modulated optical wave up to 275 GHz by laser wave mixing for optical component bandwidth measurement

  P Dherbecourt, O Latry, E Joubert, M Ketata
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  ABSTRACT: This paper presents a method to achieve an amplitude-modulated optical wave in the range of telecommunication frequencies for optical components bandwidth tests. The principle is based on the optical heterodyning of two free distributed feedback lasers. The frequency tunability of the modulated wave reaches 275 GHz with high stability. These characteristics constitute the originality of our work. Our laboratory has developed an experimental fusion setup that enables the realization of numerous optical fiber components. Component bandwidth measurement enables their validation for high-rate data transmissions. We present in this paper results obtained for a 57-GHz beat signal in a fast photodiode and we describe bandwidth optical components tests in the 0 to 40 GHz range. ©2002 Society of Photo-Optical Instrumentation Engineers.
  Optical Engineering 01/2013; 41(7):1469-1470.