scholarly journals Simulation of the Transmission Spectrum of Long-Period Fiber Gratings Structures with a Propagating Acoustic Shock Front

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7212
Author(s):  
Oleg V. Ivanov ◽  
Paulo Caldas ◽  
Gaspar Rego
Keyword(s):  
Shock Front ◽  
Transmission Spectrum ◽  
Fiber Grating ◽  
Modulation Amplitude ◽  
Fiber Gratings ◽  
Coupled Mode ◽  
Long Period Fiber Grating ◽  
Long Period ◽  
Long Period Fiber Gratings ◽  
Period Fiber Grating

In this paper, we investigate modification of transmission spectra of long-period fiber grating structures with an acoustic shock front propagating along the fiber. We simulate transmission through inhomogeneous long-period fiber gratings, π-shift and reflective π-shift gratings deformed by an acoustic shock front. Coupled mode equations describing interaction of co-propagating modes in a long-period fiber grating structures with inhomogeneous deformation are used for the simulation. Two types of apodization are considered for the grating modulation amplitude, such as uniform and raised-cosine. We demonstrate how the transmission spectrum is produced by interference between the core and cladding modes coupled at several parts of the gratings having different periods. For the π-shift long-period fiber grating having split spectral notch, the gap between the two dips becomes several times wider in the grating with the acoustic wave front than the gap in the unstrained grating. The behavior of reflective long-period fiber gratings depends on the magnitude of the phase shift near the reflective surface: an additional dip is formed in the 0-shift grating and the short-wavelength dip disappears in the π-shift grating.

scholarly journals Sensing Characteristics of Tilted Long Period Fiber Gratings Inscribed by Infrared Femtosecond Laser

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 3003 ◽  
Author(s):  
Jian Tang ◽  
Cailing Fu ◽  
Zhiyong Bai ◽  
Changrui Liao ◽  
Yiping Wang
Keyword(s):  
Refractive Index ◽  
Fiber Grating ◽  
Fiber Gratings ◽  
Long Period Fiber Grating ◽  
Long Period ◽  
Long Period Fiber Gratings ◽  
Fs Laser ◽  
Period Fiber Grating ◽  
Application Fields ◽  
Sensing Characteristics

We propose a novel tilted long period fiber grating (TLPFG) design, inscribed using a line-by-line inscription technique and an infrared femtosecond (Fs) laser. The responses of this TLPFG to external refractive index, temperature, torsion, and strain were systematically investigated to determine its sensing characteristics. The external refractive index (RI) was measured to be −602.86 nm/RIU at an RI of ~1.432. The TLPFG was used to accurately measure temperatures up to 450 °C with a sensitivity of 103.8 pm/°C. The torsion and strain sensitivity of the device were 48.94 nm/(rad/mm) and −0.63 pm/µε, respectively. These results demonstrate that the proposed TLPFG could be used as sensors in a series of application fields including high temperatures and external environments.

scholarly journals Ultrashort Long-Period Fiber Grating Sensors Inscribed on a Single Mode Fiber Using CO2 Laser Radiation

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Marta Nespereira ◽  
João M. P. Coelho ◽  
Manuel Abreu ◽  
José Manuel Rebordão
Keyword(s):  
Laser Radiation ◽  
Single Mode ◽  
Single Mode Fiber ◽  
Fiber Grating ◽  
Fiber Gratings ◽  
Long Period Fiber Grating ◽  
Long Period ◽  
Long Period Fiber Gratings ◽  
Co2 Laser Radiation ◽  
Period Fiber Grating

Sensing performances of ultrashort (as low as 2.4 mm) long-period fiber gratings fabricated with CO2 laser radiation using commercial single mode fibers are presented. These lengths are, to our knowledge, the shortest of those found in the literature for this kind of sensors, approaching those typical in fiber Bragg gratings. Sensitivity to temperature and refractive index are demonstrated, with performances within the range expected for a single LPFG written on a single mode fiber without any enhancing technique. Analysis on results is made based on both theoretical and experimental data.

scholarly journals Transverse Load and Temperature Sensing Using Multiplexed Long-Period Fiber Gratings

Photonics ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 1
Author(s):  
Ismael Torres-Gómez ◽  
Alejandro Martínez-Rios ◽  
Gilberto Anzueto-Sánchez ◽  
Daniel. E. Ceballos-Herrera ◽  
Guillermo Salceda-Delgado
Keyword(s):  
Simultaneous Measurement ◽  
Room Temperature ◽  
Transverse Load ◽  
Fiber Grating ◽  
Fiber Gratings ◽  
Long Period Fiber Grating ◽  
Long Period ◽  
Sensing Applications ◽  
Long Period Fiber Gratings ◽  
Period Fiber Grating

The simultaneous measurement of transverse load and temperature using two long-period fiber gratings multiplexed in the wavelength domain is presented experimentally. For this, a mechanically induced long-period fiber grating (MI-LPFG) and a long-period fiber grating inscribed by a continuous-wave CO2 laser (CO2 LPFG) are connected in cascade. First, the transverse load and the temperature measurements were individually performed by the multiplexed long-period fiber gratings configuration. The MI-LPFG is subject to a transverse load variation from 0–2000 g with steps of 500 g, whereas the CO2 LPFG is unloaded and they are kept at room temperature. Similarly, the CO2 LPFG is subject to a temperature variation from 30 to 110 °C by increments of 20 °C, while the MI-LPFG with a constant transverse load of 2000 g is kept at room temperature. Subsequently, the simultaneous measurement of the transverse load and the temperature is performed by the multiplexed long-period fiber grating following the steps outlined above. According to the experimental results, the transverse load and temperature measurement present high repeatability for the individual and simultaneous process. Moreover, the multiplexed LPFGs exhibit low cladding-mode crosstalk of transverse load and temperature. The coarse wavelength-division multiplexing (CWDM) of long-period fiber gratings is an attractive alternative technique in optical fiber distributed sensing applications.

Dual-Peak Resonance and Transmission Spectrum in Coated Long-Period Fiber Grating

2008 ◽  
Vol 28 (2) ◽  
pp. 219-225 ◽  
Author(s):  
顾铮天 Gu Zhengtian ◽  
徐艳平 Xu Yanping ◽  
邓传鲁 Deng Chuanlu
Keyword(s):  
Transmission Spectrum ◽  
Fiber Grating ◽  
Long Period Fiber Grating ◽  
Long Period ◽  
Period Fiber Grating

scholarly journals Helically twisted long-period fiber gratings of YOFC single-mode fiber with optical fiber welding machine

2021 ◽  
Vol 51 (3) ◽  
Author(s):  
Yunfeng Bai ◽  
Zelong He ◽  
Jiyuan Bai ◽  
Suihu Dang
Keyword(s):  
Single Mode ◽  
Resonance Wavelength ◽  
Single Mode Fiber ◽  
Resonant Peak ◽  
Fiber Grating ◽  
Fiber Gratings ◽  
Long Period ◽  
Welding Machine ◽  
Long Period Fiber Gratings ◽  
Period Fiber Grating

The single-mode fiber provided by YOFC inc is employed for spiral processing by commercial welding machine. It can clearly see the periods structure under the light, but there is no obvious deformation of the fiber core, cladding and surface morphology under a microscope. There is an obvious resonant peak near 1560 nm, half peak width is about 25 nm, the depth of the resonant peak closed to –26 dB, when the period is about 411 μm. It agrees with theoretical calculation results according to the long-period fiber grating coupled-mode theory. The resonance wavelength is caused by coupling between the fundamental mode and the LP14 mode. The responsivities of the helically twisted long-period fiber gratings (H-LPFG) for the temperature is measured, the resonance wavelength is linear with temperature, the slope is 86 pm/℃. Because it is easy to inscribe by commercial welding machine, and has a strong resonance peak, it has potential applications as the temperature sensor.

Intensity dependent spectral properties of long-period fiber grating for applications in lightwave communication

2019 ◽  
Vol 28 (02) ◽  
pp. 1950010
Author(s):  
Vishal Jain ◽  
Santosh Pawar ◽  
Shubhada Kumbhaj ◽  
Pranay Kumar Sen
Keyword(s):  
Spectral Properties ◽  
Resonance Wavelength ◽  
Optical Nonlinearity ◽  
Excitation Intensity ◽  
Fiber Grating ◽  
Coupled Mode ◽  
Long Period Fiber Grating ◽  
Long Period ◽  
Cladding Mode ◽  
Period Fiber Grating

Using nonlinear coupled mode equations, the spectral properties of long-period fiber grating are studied analytically taking into account the Kerr type optical nonlinearity in the medium. The nonlinear coupled-mode equations were solved for co-propagating core and cladding mode amplitudes and expressions for transmittivity and phase factor at high excitation intensity are obtained. It is observed that the resonance wavelength of grating shifts towards higher wavelength side with increasing excitation intensity. Also, the minimum transmittivity of the grating shows oscillating behavior with increasing grating length, whereas the phase of the transmitted wave increases monotonically with length at high input intensities.

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