Manufacturing and Spectral Features of Different Types of Long Period Fiber Gratings: Phase-Shifted, Turn-Around Point, Internally Tilted, and Pseudo-Random

Chiavaioli, Francesco; Baldini, Francesco; Trono, C.

doi:10.3390/fib5030029

Cited by 13 publications

(3 citation statements)

References 43 publications

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“…The spectral response of LPFGs can be controlled by adding a phase shift in the middle of the grating [19,28,29], while the phase shift is formed by a section of fiber without grating, mechanically, or by the changes in its refractive index [30,31]. In contrast to homogeneous LPFGs, a pass band is created in the resonance notches of the phase-shifted LPFGs as a result of interference between two parts of the grating.…”

Section: Introductionmentioning

confidence: 99%

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

Иванов

Caldas

Rego

2021

Sensors

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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.

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Section: Introductionmentioning

confidence: 99%

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

Иванов

Caldas

Rego

2021

Sensors

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“…Over the past few years, random fiber gratings (RFGs) have drawn a great deal of interest in the field of random fiber lasers and optical fiber sensing [1][2][3][4][5]. By introducing refractive index modulations with random periods in the fiber core, RFGs can mimic Rayleigh scattering in the fiber with a broadband reflection spectrum.…”

Section: Introductionmentioning

confidence: 99%

Random Fiber Grating Characterization Based on OFDR and Transfer Matrix Method

Zhou

Chen

et al. 2020

Sensors

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Random fiber gratings (RFGs) have shown great potential applications in fiber sensing and random fiber lasers. However, a quantitative relationship between the degree of randomness of the RFG and its spectral response has never been analyzed. In this paper, two RFGs with different degrees of randomness are first characterized experimentally by optical frequency domain reflectometry (OFDR). Experimental results show that the high degree of randomness leads to low backscattering strength of the grating and strong strength fluctuations in the spatial domain. The local spectral response of the grating exhibits multiple peaks and a large peak wavelength variation range when its degree of randomness is high. The linewidth of its fine spectrum structures shows scaling behavior with the grating length. In order to find a quantitative relationship between the degree of randomness and spectrum property of RFG, entropy was introduced to describe the degree of randomness induced by period variation of the sub-grating. Simulation results showed that the average reflectivity of the RFG in dB scale decreased linearly with increased sub-grating entropy, when the measured wavelength range was smaller than the peak wavelength variation range of the sub-grating. The peak reflectivity of the RFG was determined by κ2LΔP (where κ is the coupling coefficient, L is the grating length, ΔP is period variation range of the sub-grating) rather than κL when ΔP is larger than 8 nm in the spatial domain. The experimental results agree well with the simulation results, which helps to optimize the RFG manufacturing processes for future applications in random fiber lasers and sensors.

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“…For several decades, significant research efforts have been focused on the considerable potential of long-period fiber gratings (LPFGs) [1][2][3][4][5][6][7][8][9][10][11]. The cladding modes enable a wide field of applications, including band rejection and tunable filters, and are also applied as optical fiber sensors for temperature, refractive index (RI) and strain detection [12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Graphene-assisted high-precision temperature sensing by long-period fiber gratings

Wang

Ren

Kong

et al. 2019

J. Phys. D: Appl. Phys.

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The tapered long-period fiber grating (TLPFG) and rotated chiral long-period fiber gratings (CLPFG) heated by a CO2 laser were fabricated by periodically tapering and rotating standard single-mode fibers (SMF). The temperature sensing characteristics of the TLPFG and CLPFG between 30 °C and 60 °C were experimentally investigated, and the slopes of the wavelength shift corresponded to 0.115 nm °C−1 and 0.04 nm °C−1, respectively. The graphene films were coated on gratings to fabricate graphene-coated TLPFG (GTLPFG) and graphene-coated CLPFG (GCLPFG). Given the thermal effects of graphene, the slopes of the resonance dip shift of the GTLPFG and GCLPFG between 30 °C and 60 °C increased to 0.196 nm °C−1 and 0.113 nm °C−1, respectively. Additionally, the high temperature sensing properties of TLPFG and CLPFG between 100 °C and 1000 °C were investigated. The slopes of the higher-order resonance dips of the TLPFG and CLPFG corresponded to 0.119 nm °C−1 and 0.09 nm °C−1, respectively, during the heating process, and to 0.116 °C−1 and 0.09 nm °C−1, respectively, during the cooling process. In the low and high temperature zones, the TLPFG exhibited higher sensitivity when compared to that of the CLPFG, while the CLPFG exhibited higher sensing precision with linearity approaching 1. Given the simple and unsophisticated fabrication process and the high quality and sensitivity of the fabricated gratings, the proposed sensors can play an important role in high-precision temperature-sensing applications.

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Manufacturing and Spectral Features of Different Types of Long Period Fiber Gratings: Phase-Shifted, Turn-Around Point, Internally Tilted, and Pseudo-Random

Cited by 13 publications

References 43 publications

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

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

Random Fiber Grating Characterization Based on OFDR and Transfer Matrix Method

Graphene-assisted high-precision temperature sensing by long-period fiber gratings

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