High sensitivity of dual resonant peaks of long-period fibre grating to surrounding refractive index changes

Shu, Xuewen; Zhu, Xuemei; Jiang, Shan; Shi, Wei; Huang, Dexiu

doi:10.1049/el:19991040

Cited by 63 publications

(23 citation statements)

References 5 publications

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“…It can be noticed that the band_3 is a superposition of two neighboring attenuation bands. This effect can occur if the period of the LPFG is sufficiently short [17,18]. When a bare LPFG is mainly surrounded by the 5CB, a significant reduction in the depth of attenuation bands is observed and is compared in Table I.…”

Section: Resultsmentioning

confidence: 99%

A Novel Electrically Tunable Long-Period Fiber Grating Using a Liquid Crystal Cladding Layer

Czapla

Woliński

Nowinowski-Kruszelnicki

et al. 2010

Acta Phys. Pol. A

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The main aim of the presented work is the integration of a long-period fiber grating and a liquid crystal into a hybrid structure, in order to develop an innovative fiber optic device controlled by an external electric field. The studied long-period fiber grating was fabricated using UV irradiation in a boron co-doped fiber (PS1250/ 1500, manufactured by Fibercore). As a liquid crystal we used a typical 5CB nematic liquid crystal. The sensing mechanism of the proposed loss filter relies on long-period fiber grating attenuation bands sensitivity to optical properties of the liquid crystal layer. The results obtained show that the long-period fiber grating with a nanosized liquid crystal layer exhibits one order of magnitude higher electrical sensitivity and a lower level of the voltage control than the long-period fiber grating with a micro-sized liquid crystal layer.PACS IntroductionIn order to achieve light coupling between two co--propagating modes, a grating formed in an optical fiber usually requires a pitch of several hundred micrometers. This type of grating is called a long-period fiber grating (LPFG). Compared to other optical devices, LPFGs have a number of unique advantages such as low-level back reflection, low insertion losses and compact construction (the grating is an intrinsic fiber device). The LPFGs have found a variety of applications in optical communications [1,2]. Tuning of the LPFGs is very attractive since it can offer a form of dynamic spectral control [3,4]. The central attenuation wavelength of the LPFGs is highly sensitive to temperature, strain, bend or surrounding refractive index (SRI) changes. For these reasons filters based on the LPFGs have generated a significant interest for applications in the sensing field as well.Liquid crystals (LCs) are attractive candidates as a coating material since their properties can be controlled through temperature, optical, electrical and magnetic fields [5][6][7]. There are three key points for a good design in order to combine a LPFG and a LC into one component: selection of the LC refractive indices, inherent SRI sensitivity of the LPFG and the LC layer thickness. Majority of LCs have refractive indices that are higher than the refractive index of the silica glass. Thus, the LPFG sensitive to SRI is limited to the range where SRI is higher than the refractive index of the fiber cladding. In this case, the core modes couple to leaky modes [8] and the dependence on the resonance wavelength on the SRI is not so straightforward. So far, most of the studies have focused on the analysis of the SRI sensitivity when the

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Section: Resultsmentioning

confidence: 99%

A Novel Electrically Tunable Long-Period Fiber Grating Using a Liquid Crystal Cladding Layer

Czapla

Woliński

Nowinowski-Kruszelnicki

et al. 2010

Acta Phys. Pol. A

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“…Some modes of the grating spectrum exhibit a double resonance within the measurement range, with the core mode coupling energy to a cladding mode at two different wavelengths [11], [19], double resonances appear because of the specific dispersion curves of the core and cladding modes which make the resonance wavelength curve to have a turning point as function of the grating period for a specific set of modes in a range of periods. Since the resonance wavelength have opposite slopes as function of the grating period at both sides of the turning point, these resonances shift in opposite spectral directions when the properties of the waveguide are modified.…”

Section: Uv Inscriptionmentioning

confidence: 99%

Water Diffusion Into UV Inscripted Long Period Grating in Microstructured Polymer Fiber

et al. 2010

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Abstract-A long period grating was photoinscribed step-bystep in microstructured poly(methyl methacrylate) fiber for the first time using a continuous wave HeCd laser at 325 nm, irradiating the fiber with a power of 1 mW. The grating had a length of 2 cm and a period of 1 mm. A series of cladding mode coupling resonances were observed throughout the spectral region studied of 600 to 1100 nm. The resonance wavelengths were shown to be sensitive to the diffusion of water into the fiber.Index Terms-Humidity, long period grating, microstructured polymer optical fiber (mPOF), optical fiber sensor, photonic crystal fiber (PCF).

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“…Wavelength shift of a particular resonance (747nm in figure 3) due to the diffusion of water into the fibre. Some modes of the grating spectrum exhibit a double resonance within the measurement range, with the core mode coupling energy to a cladding mode at two different wavelengths [5,6]. These resonances shift in opposite spectral directions when the properties of the waveguide are modified.…”

Section: Spectral Response When Exposed To Watermentioning

confidence: 99%

Long period fibre gratings photoinscribed in a microstructured polymer optical fibre by UV radiation

et al. 2009

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Long period gratings were written step-by-step in microstructured poly(methyl methacrylate) (PMMA) fibre using a continuous wave HeCd laser at 325nm irradiating the fibre with a power of 1mW. The grating had a length of 2 cm and a period of 1mm. A series of cladding mode coupling resonances were observed throughout the spectral region studied of 600 to 1100nm. The resonance wavelengths were shown to be sensitive to both surrounding refractive index and the water content of the polymer fibre.

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High sensitivity of dual resonant peaks of long-period fibre grating to surrounding refractive index changes

Cited by 63 publications

References 5 publications

A Novel Electrically Tunable Long-Period Fiber Grating Using a Liquid Crystal Cladding Layer

A Novel Electrically Tunable Long-Period Fiber Grating Using a Liquid Crystal Cladding Layer

Water Diffusion Into UV Inscripted Long Period Grating in Microstructured Polymer Fiber

Long period fibre gratings photoinscribed in a microstructured polymer optical fibre by UV radiation

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