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Dual-resonance long-period grating in fiber loop mirror structure for liquid refractive index measurement

Zawisza R., Eftimov T., Mikulic P., Chinifooroshan Y., Celebańska A., Bock W. J., Jaroszewicz L. R.

Opto-Electronics Review

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2018

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Vol. 26, No. 1

24--28

EN

An interferometric structure based on a Dual-Resonance Long-Period Grating (DRLPG) within a Fiber Loop Mirror (FLM) is presented in this paper. Its purpose is to measure the refractive index (RI) of liquid analytes. The grating is the RI sensing probe, while the FLM serves as a band-pass filter. Due to the high extinction ratio of the FLM, amplitude measurements can be obtained, allowing implementation of the differential interrogation method to establish the sensitivity of the device. The use of a polarization controller makes it possible to fine-tune the interferometric peaks with respect to the two notches of the DRLPG. Precisely aligned configuration produces a maximum sensitivity of 3871.5 dB/RIU within the RI range of 1.3333 up to 1.3419 with linear sensor response.

2

An interferometric structure with a dual-resonance long period grating for strain sensing

Zawisza R., Jaroszewicz L. R., Mikulic P., Bock W. J.

Opto-Electronics Review

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2018

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Vol. 26, No. 4

325--328

EN

Spectral characteristics and amplitude tunability of a long period grating with a dual- resonance inside fiber loop mirror are studied in terms of applied stress caused by elongation. Inserting the polariza-tion controller between grating and part of polarization maintaining fiber in the loop structure enables tuning of resonance and interferometric peaks. The maximum sensitivity of demonstrated sensor is of 1.943 dB/mε for the range of 1.1–4.4 mε. Combination of these two optical components allows to measure strain in a wider range comparing with sensors based on standard long period grating.

3

Electrically tunable long-period fiber gratings with low-birefringence liquid crystal near the turn-around point

Czapla A., Bock W. J., Woliński T. R., Mikulic P., Dąbrowski R., Nowinowski-Kruszelnicki E.

Opto-Electronics Review

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2017

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Vol. 25, No. 4

290--295

EN

In this work, an electrically tunable long-period fiber grating (LPFG) coated with liquid crystal layer (LC) is presented. As a LC layer, a prototype low-birefringence 1550A LC mixture was chosen. As a LPFG host, two types of gratings were studied: the LPFGs based on a standard telecommunication fiber, produced by an electric arc technique with a period of 222 µm, and the LPFGs based on a boron co-doped fiber written by a UV technique with a period of 226.8 µm. The relatively short period of these gratings allowed exploiting unique sensing properties of the attenuation bands associated with modes close to the turn-around point. Experiments carried out showed that for the UV-induced LPFG with a LC layer, on the powered state the attenuation band could be offset from the attenuation band measured in the unpowered state by almost130 nm. When the arc-induced LPFG was coated with the LC, the depth of the attenuation band could be efficiently controlled by applying an external E-field. Additionally, all experimental results obtained in this work were supported by the theoretical analysis based on a model developed with Optigrating v.4.2 software.

4

Sterowanie odpowiedzią czujników opartych na światłowodowych siatkach długookresowych (LPG) poprzez zastosowanie cienkich pokryć

Śmietana M., Bock W. J., Mikulic P.

Elektronika : konstrukcje, technologie, zastosowania

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2012

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Vol. 53, nr 11

23-25

PL

Przedstawiono wyniki badań nad zastosowaniem cienkich warstw pokryciowych do sterowania czułością światłowodowych siatek długookresowych (ang. Long-period Grating, LPG) na zmiany współczynnika załamania otoczenia. Do pokrycia struktur LPG wykorzystano metodę chemicznego osadzania z fazy gazowej wspomaganą plazmą wysokiej częstotliwości (ang. Radio Frequency Plasma Enhanced Chemical Vapor Deposition, RF PECVD), której użycie umożliwia uzyskania cienkich i jednorodnych pokryć na powierzchni światłowodu. Właściwości pokryć mogą być determinowane poprzez odpowiedni dobór parametrów procesu osadzania. Przedstawiono możliwości wykorzystania warstw diamentopodobnych (DLC) i azotku krzemu (SiNx) do sterowania odpowiedzią struktur na zmiany współczynnika załamania otoczenia, co umożliwia ich późniejsze zastosowania, choćby jako wysokoczułych biosensorów, czujników wilgotności, ciśnienia hydrostatycznego lub temperatury.

EN

The work presents results on application of thin overlays for tuning sensitivity of Long-period Gratings (LPGs) to variations in external refractive index. For deposition of thin films there has been applied Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF PECVD) method, which allows for obtaining thin and uniform overlays on the surface of the fiber. Properties of the films can be determined in wide range by selection of certain set of deposition process parameters. There has been shown application of diamond-like carbon (DLC) and silicon nitride (SiNx) thin films for spectral response tuning of the gratings to variations in external refractive index. The effect can be applied for developing highly sensitive biosensors, as well as humidity, hydrostatic pressure, and temperature sensors.

5

Towards tuning of thermal sensitivity of the long period fiber gratings using a liquid crystal layer

Czapla A., Bock W., Mikulic P., Woliński T.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2010

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Vol. 58, nr 4

503-508

EN

A high-efficiency thermal tuning filter based on a long-period fiber grating (LPFG) combined with a low-birefringence liquid crystal (LB LC) cladding layer is presented. Two types of LPFGs were studied and compared: the LPFGs based on a standard telecommunication fiber produced by an electric arc technique, and the LPFGs based on a boron co-doped fiber written by a UV technique. Both types of LPFGs when enhanced with an external LB LC layer exhibit two different temperature sensitivities, which depend on the temperature range of operation. For the LPFGs based on standard telecommunication fiber we can conclude that the presence of the LB LC cladding increases the thermal tuning efficiency by more than one order of magnitude over the value for the LPFGs in air. In the case of the LPFGs based on the boron co-doped fiber we discovered it is possible to obtain either a temperature-independent attenuation band or the attenuation bands with high temperature sensitivities, just by careful choice of the order of the cladding mode and the operating wavelength.