In this work, it is demonstrated numerically that an asymmetric Moiré fiber grating operated in reflection can provide the required spectral response to implement an all-optical fractional ...differentiator. In our case, the accumulated phase shift is not associated with a point phase shift, as when working with fiber Bragg gratings and long-period gratings with punctual defects, but is distributed all over the grating. The proposed device is supported by numerical simulations, and a dimensionless deviation factor is calculated to make quantitative analysis feasible. The performance of the proposed device is analyzed using numerical simulations by computing the fractional time derivatives of the complex field of an arbitrary transform-limited Gaussian pulse. A comparison with the performance given by theoretical differentiation is also presented.
In this book the reader will find a collection of chapters written by different research teams, describing different applications of optical fibers for sensing. This work is mainly addressed to ...researchers already working in this area, but it is also accessible to anyone with a scientific background who desires to have an updated overview of the recent progress in this domain. It will also be valuable to scientists and engineers who have become newly involved in this field. Each chapter is self-contained and can be read independently of the others. This book intends to provide highlights of the current research in this area, showing the recent advances in the field of optical fiber sensing.
A general technique for obtaining the soliton number, and hence the nonlinear coefficient, in wave-guides with high dispersion and loss is derived and demonstrated numerically and experimentally in a ...kilometer-long standard silica fiber pumped close to 2 µm.
Here we present a self-started passively mode-locked thulium-doped fiber laser with in-band pumping at 1561 nm that fully retains polarization and emits beyond 2 μ m. We obtained a sequence of light ...pulses at 13.084 MHz, where the pulse and spectral widths were 94 ps and 70 pm, respectively, at 2069.5 nm. The measured instantaneous angular frequency shows that these light pulses are chirp-free.
In this work, we compare the operation of a passively modelocked polarization-maintaining emission in two thulium-doped fiber lasers pumped at 1561 nm, with emission at wavelengths of 1.951 μm in one ...case and 2.07 μm in the other. We obtained a sequence of light pulses at 15.6 MHz, whose temporal width was 81 ps at 1.95 μm, and a sequence of light pulses at 13.1 MHz, whose temporal width was 94 ps at 2.07 μm. Finally, we also measured the long-term stability of this setup during a 24-h operation, as well as the short-term stability in a simulated harsh environment. The results confirm the superior performance of fiber laser systems with a fully polarization-maintaining design.
We report the generation of short pulses at 1 μm using an all-polarization-maintaining (PM) fiber configuration. The pulses are provided by an all normal-dispersion Fabry-Perot Yb-doped cavity and ...are compressed with an anomalous polarization-maintaining photonic crystal fiber (PM PCF). Opposed to standard configurations; here the filtering action is solely performed by the finite bandwidth of the gain medium. The laser generates 8 ps width sech 2 profile pulses at 1046.8 nm with a -10 dB bandwidth of 5.9 nm. After compression using the PM PCF, pulses with an FWHM of 3 ps were obtained, limited by the actual value of the available anomalous dispersion. We also report the changes in the output light pulses when both the net-normal dispersion of the cavity and the medium gain length were varied. We found that the lack of a specific filter within the cavity does not deteriorate the performance as compared with previous works.
In this book the reader will find a collection of chapters written by different experts around the world, describing the current research trends in both short- and long-period fiber grating ...technology. This work is mainly addressed to researchers already working in this area, but it is also accessible to anyone with a scientific background who desires to have an updated overview of the recent progress in this domain. It will also be valuable to scientist and engineers who have become newly involved in this field. Each chapter is self-contained and can be read independently of the others. This book intends to provide highlights of the current research in this area, showing the recent advances in the field of fiber gratings.
Resonant couplings in U-shaped fibers for biosensing Londero, Carolina; Delgado-Pinar, Martina; Cuadrado-Laborde, Christian ...
Journal of lightwave technology,
07/2023, Letnik:
41, Številka:
13
Journal Article
Recenzirano
Odprti dostop
U-shaped tight curvatures in optical fibers lead to resonant couplings between the fundamental and higher order modes that are sensible to different parameters, such as strain or temperature, for ...example. The optical response of the sensor consists on the shift of the resonant wavelength of the coupling. In the case of singlemode fibers, the coupling involves a so-called "cladding mode" and, due to its evanescent field, the curved region will be sensible to changes in the external medium, as well. In this paper, we present the fabrication and characterization of a robust, easy-to-make, U-shaped fiber sensor based on singlemode telecom fiber and its application for biosensing. The resonant nature of the sensing mechanism presents the advantage of large dynamic ranges for RI variations without the ambiguity of other techniques such as interferometry. We studied the performance of the U-shaped fiber sensor for different bending radii, to optimize its sensitivity and detection limit at 1550 nm operation wavelength, as well as the effect of temperature on its response. The shift of the resonant wavelength was measured in detail as a function of the external RI within the range 1.33-1,37; the detection limit was established in (3.71±0.03)×10 -5 RIU. Furthermore, the device was successfully tested as a proof of concept biosensor, using a system model antigen-antibody (BSA-aBSA.)
PDF
