Twisted tilted fiber Bragg gratings: new structures and polarization properties

Abstract

In this Letter, it has been shown that the twisting of TFBGs (tilted fiber Bragg gratings) decreases their sensitivity to the polarization of the input light. It has been proved by a theoretical simulation study that twisting the TFBG by 180° eliminates the sensitivity of the grating to input light polarization changes. We have experimentally proved that our structure produced has an 18 times lower coefficient of variation of transmission for polarization changes than the untwisted TFBG. This Letter also presents a new method for manufacturing the twisted tilted fiber Bragg grating (TTFBG). We have demonstrated the possibility of writing the TTFBG structure twisted by 90° on a fiber with a length of 10 mm. The structure has been further twisted in the other direction by 90°, which is consistent with a structure twisted by 180°. The properties of both structures were determined. Due to the fiber's strength, the TTFBG twisted by 180° has to be 2 cm long. An advantage of the proposed method of producing the TTFBG is that there is a twist of the structure itself after fabrication. This creates new possibilities of using the structure in many applications. This type of grating can be used to reduce the sensitivity to polarization in various sensing applications, in particular, to measure the refractive index. In addition, a 180° twisted TTFBG has properties of direction discrimination in twist sensing applications.

Design and Manufacturing Optoelectronic Sensors for the Measurement of Refractive Index Changes under Unknown Polarization State

“…Mechanism of using FBG as a sensor for the refractive index changes caused by (e.g., pathogens) is shown in Figure 1a. When FBG is immersed in analyte, a response in the form of a Bragg wavelength shift occurs, which is caused by a change in the refractive index [50]. Conventional FBG has very low sensitivity to changes in the surrounding medium RI because the grating structure is inscribed in the core of the fiber and the cladding provides an additional obstacle/barrier to the interaction of light propagating through the FBG perturbated core with the medium surrounding the outside border of the fiber.…”

“…The described system, sensor, and measuring method also have the potent ultaneously measure temperature and refractive index or carry refractometric ments insensitive to temperature changes. This is possible because a temperatu causes a shift in the entire spectral characteristics of the FBG structure [63,64] d the temperature expansion phenomenon and the so-called thermo-optical eff tionally, in the case of TFBG structures, a change in temperature produces the sa and leads to a spectral shift of both the minima of the main Bragg resonance and ima corresponding to the individual cladding modes [50]. Therefore, it is expe in principle, the P-TFBG structure will also be subject to the same phenomena.…”

A Low-Cost Digital Pulsed Coherent Spectrometer for Investigation of NQR in Layered Semiconductor GaSe and InSe Crystals

“…The proposed spectrometer can also be effectively used in practice in combination with optical sensors based on a tilted fiber Bragg grating (TFBG) [24][25][26]. In particular, it can be used for control of mechanical deformation and changes in the crystal structure of semiconductors.…”

Numerical study of polarization evolution governed by linear birefringence, twist-induced circular birefringence and nonlinear birefringence in a single-mode optical fiber

“…In a broad number of optical fiber systems, a uniform twist rate is applied along the fiber, such as fiber Bragg gratings [1][2][3], interferometric schemes [4,5], fiber optic sensors based on induced circular birefringence [6][7][8], optical signal processing devices [9], mode-locked fiber lasers (ML-FL) [10][11][12][13][14] and so on. In most of these physical contexts, the twisted optical fiber is part of a strict polarization control scheme based on birefringence and polarization adjustments, which plays an important role in ensuring predictability and reproducibility of the adjustment process.…”