1,253 research outputs found
Fabrication and Characterization of Long-Period Gratings in Hollow Core Fibers by Electric Arc Discharge
No full textIn this paper we report on the fabrication and characterization of Long Period Gratings (LPGs) in hollow-core air-silica photonic bandgap fibers (HC-PCFs). The fabrication procedure is based on a pressure assisted Electrode Arc Discharge (EAD) technique. It relies on the combined use of EAD step, to locally heat the HC fiber, and of a static pressure (slightly higher than the external one) inside the fiber holes, to modify the holes. Here, the experimental fabrication of LPG prototypes with different periods and lengths are discussed. And, the sensitivity of LPGs in HC-PCF to environmental parameters such as strain, temperature and static pressure are presented and discussed
Arc-Induced Long Period Gratings from Standard to Polarization-Maintaining and Photonic Crystal Fibers
No full textIn this work, we report about our recent results concerning the fabrication of Long Period Grating (LPG) sensors in several optical fibers, through the Electric Arc Discharge (EAD) technique. In particular, the following silica fibers with both different dopants and geometrical structures are considered: standard Ge-doped, photosensitive B/Ge codoped, P-doped, pure-silica core with F-doped cladding, Panda type Polarization-maintaining, and Hollow core Photonic crystal fiber. An adaptive platform was developed and the appropriate “recipe” was identified for each fiber, in terms of both arc discharge parameters and setup arrangement, for manufacturing LPGs with strong and narrow attenuation bands, low insertion losses, and short length. As the fabricated devices have appealing features from the application point of view, the sensitivity characteristics towards changes in different external perturbations (i.e., surrounding refractive index, temperature, and strain) are investigated and compared, highlighting the effects of different fiber composition and structure
Arc-induced long period gratings: Analysis of the fabrication parameters on the surrounding refractive index sensitivity
No full textThis paper reports on recent numerical and experimental studies about the effects of the fabrication parameters on the Long Period Gratings (LPGs) sensitivity to the surrounding refractive index. The LPGs are fabricated by Electric Arc-Discharge (EAD) technique and the fabrication parameters are optimized by acting on the arc duration, power and electrodes gap. This permits to fabricate several LPGs in standard fiber with period ranging from 400 to 500 Âμm gratings where the coupling is with LP05and LP06cladding modes. Furthermore, we have investigated the surrounding refractive index (SRI) sensitivity of the LPGs as function of the grating period and compared the experimental results with numerical analysis based on coupled mode theory. As we show here, we achieve a good agreement between numerical and experimental results
Sensing Characteristics of Arc-Induced Long Period Gratings in Polarization-Maintaining Panda Fiber
No full textWe present and discuss an investigation of the sensing features of Long Period Gratings (LPGs) fabricated in a polarization-maintaining Panda optical fiber, by means of the Electric Arc Discharge (EAD) technique. In particular, the investigation regards the resonant wavelength shift of first three cladding modes as function of three environmental parameters, such as strain, temperature, and surrounding medium refractive index. We also investigate and discuss the variations of the sensing behavior as a function of the polarization input state. The achieved results show that sensitivity of each resonant wavelength to environmental parameters is modulated by the cladding mode order and by polarization input light, with some appealing characteristics. For instance, the lowest order cladding mode in slow polarization state is practically insensitive to temperature and surrounding refractive index, but sensitive to strain. Temperature and strain sensitivities show opposite signs with the input light polarization. Sensitivity to surrounding refractive index is higher in the case of fast polarization state. These results represent a concrete perspective of the possibility that this device can act as a 3-parameter sensor
Arc-Induced Long Period Gratings in Phosphorus-Doped Fiber
No full textPhosphorus-doped fibers have been reported and discussed in extensive works, as well as the radiation effects on their guiding features in different spectral ranges. However, the assessment of a technique enabling the fabrication of grating devices in this fiber is still an open issue. Here, for the first time to the best of our knowledge, we report on the fabrication of long period gratings (LPGs) in P-doped optical fiber by means of electric arc discharge technique (EAD). LPGs having periods of 500 μm and of 700 μm were presented, achieving the coupling up to LP06 cladding mode, attenuation bands with depth up to 35 dB, power losses lower than 0.5 dB, and devices length less than 20 mm. The results being also compared with numerical simulations. Moreover, the sensitivity characteristics to surrounding refractive index (SRI) and temperature changes of LPGs in P-doped fibers were also investigated. The SRI sensitivity of LP06 for SRI = 1.437 was about −478 nm/RIU, slightly higher than in standard fiber. Whereas, differently from standard Ge-doped fibers, a negative temperature response was found (−116 pm/°C) opening the possibility of new applications, for example for temperature compensation solutions
Arc-Induced Long Period Gratings in Polarization-Maintaining Panda Fiber
No full textIn this letter, we report about the fabrication of long period gratings (LPGs) in a polarization-maintaining Panda optical fiber, by means of the electric arc discharge technique. This is the first time that LPGs are arc-induced in a polarization maintaining fiber. The dependence of the LPG's spectral features on the input light polarization alignment is illustrated, by considering the two principal polarization states, i.e., along the fast and slow axes of the Panda fiber. Moreover, an investigation about the surrounding refractive index sensitivity, as a function of the two principal polarization states, is also reported with interesting results
Experimental Study of the Refractive Index Sensitivity in Arc-induced Long Period Gratings
No full textThis paper presents an experimental study of the sensitivity characteristics to the surrounding refractive index (SRI) in arc-induced long period gratings (LPGs), in order to outline their dependence over the fabrication parameters. Several LPGs were fabricated, with spectral features that are appealing for chemical sensing applications, e.g., negligible power losses, bands depth greater than 20 dB, and total length smaller than 35 mm. In addition, low spatial periods Λ, which are close to the limit of the arc-based fabrication technique, were selected in order to excite high-order cladding modes. In particular, the period was chosen in range 350-500 μm to focus attention on the same cladding modes for the gratings under investigation. Accordingly, a wide experimental analysis was then carried out to investigate the dependence of the sensitivity to SRI changes on the period in order to derive design criteria for LPG fabrication. In the wavelength range 1100-1700 nm and taking into consideration the attenuation bands related to the LP05 and LP06 cladding modes, an SRI sensitivity enhancement up to one order of magnitude can be achieved by proper selection of the grating period
Influence of Period on Surrounding Refractive Index Sensitivity of Arc-induced Long Period Gratings
No full textIn this work, we present the assessment of our electric arc-discharge based technique in order to fabricate optical fiber Long Period Gratings (LPGs) with desired spectral features and period ranging in 410-470 Î1⁄4m, able to excite high order cladding modes useful in chemical sensing applications. Here, a wide experimental investigation was carried out with the aim to study the sensitivity to surrounding refractive index (SRI) changes of several LPGs as function of the grating period, in order to derive a project criterion to improve the SRI sensitivity. Moreover, in order to evaluate the goodness of the experimental results, we compare the experimental results with numerical ones based on coupled-mode theory achieving very good agreement
Fabrication of arc-induced long-period gratings in different silica fibers
No full textIn this work, we report on recent results about the fabrication of Long Period Gratings (LPGs) in different single mode optical fibers, by means of Electric Arc Discharge (EAD) technique. In particular, the results are related to three optical fibers with different doping elements, i.e.: standard telecommunication Ge-doped SMF28, highly photosensitive B/Gecodoped PS1250/1500, and P-doped P-SM-5 fibers. EAD leads to a point-by-point LPG inscription, due to localized tapering of the transversal size of the core and cladding regions along the fiber, and to changes of the silica refractive index due to the stress relaxation induced by local hot spots. Here, we take into consideration both standard and unconventional silica fibers and the aim of the work is to identify an appropriate "recipe" for each fiber, for manufacturing LPGs with strong and narrow attenuation bands (depth higher than 25 dB) and trivial power losses (<0.5 dB). Indeed, a proper combination of arc power and duration, as well as fiber tension, allows for the appropriate core and cladding modulation and thus for the desired LPGs spectral features. The sensitivity characteristics towards surrounding refractive index (SRI) and temperature changes of these LPGs are also investigated, highlighting the effects of different kind of doping
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