Effect of macro-bending on resonant wavelength and intensity of long-period gratings in photonic crystal fiber

Department of Chemical Engineering & Materials Science, Stevens Institute of Technology, Hoboken, New Jersey, United States
Optics Express (Impact Factor: 3.49). 03/2007; 15(4):1804-10. DOI: 10.1364/OE.15.001804
Source: PubMed


We report the spectral characteristics of CO(2)-laser inscribed long-period gratings (LPGs) in endlessly single mode photonic crystal fiber (PCF) subject to macro-bending. The coupling modes as a result of bending were studied by examining the shifts of resonant wavelengths, the splits of attenuation bands, and the variation in coupling strength of the transmission spectra. A bending coefficient of ~ 27.9 nm.m was determined in the PCF at 180 degrees rotational orientation relative to the point of laser inscription in the curvature range from 2.6 m(-1) to 3.5 m(-1). Compared with conventional fiber LPGs fabricated using the same method, the PCF-based LPGs possess higher sensitivity both to bending and orientation, making them promising for sensor applications.

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Available from: Henry Du, Apr 14, 2015
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    • "For example, in ship hull shape sensing applications, it is necessary to determine both the amplitude and orientation of applied bend at the same time (so-called directional or vector sensing) [4]–[8]. Long period gratings (LPGs) have been with some success for these purposes because bending causes shifts in the resonance wavelength or a separation of the resonances when mode splitting occurs, and these changes can be vectorial in nature because of the relative orientation of the bend plane with that of the field profiles of the cladding modes involved [4]–[6]. Manuscript received June 07, 2010; revised July 28, 2010; accepted July 28, 2010. "
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    • "In order to measure exact bending radius that requires precise estimation in bending sensitivity, a metal plate was inserted between fiber holders, as shown in Fig. 2 [2], [8]. The sample fiber containing HLPG was attached to the plate with an adhesive . "
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    • "The emergence of PCFs opens the door for new possibilities in ultra-broadband transmission, high-power optical fiber amplifiers and lasers, optical fiber sensors, and so forth. PCF sensors in various forms have been demonstrated for the measurement of strain [7], temperature [8], refractive index [9], bending [10], and gas concentration [11]. "
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