Bending and Orientational Characteristics of Long Period Gratings Written in D-Shaped Optical Fiber

Abstract

Abstract-Long period gratings (LPGs) were written into a D-shaped single-mode fiber. These LPGs were subjected to a range of curvatures, and it was found that as curvature increased, there was increasingly strong coupling to certain higher order cladding modes without the usual splitting of the LPGs stopbands. A bend-induced stopband yielded a spectral sensitivity of 12.55 nm m for curvature and 2 2 10 2 nm C 1 for temperature. It was also found that the wavelength separation between adjacent bend-induced stopbands varied linearly as a function of curvature. Blue and red wavelength shifts of the stopbands were observed as the sensor was rotated around a fixed axis for a given curvature; thus, in principle, this sensor could be used to obtain bending and orientational information. The behavior of the stopbands was successfully modeled using a finite element approach.Index Terms-Curvature measurement, D-shaped optical fiber, long-period fiber gratings, optical fiber devices, temperature measurement.

Long Period Gratings in New Generation Optical Fibers

“…The index modulation produces a set of attenuation bands seen in the transmission spectrum of the optical fiber. The first paper presenting a LPG written in Dshaped SMF was dated 2004 (Allsop et al, 2004). Few data were given about the fiber structure: the D-fiber was originally designed for coupler fabrication.…”

“…Post-fabrication spectral evolution of an attenuation band from a D-fiber based LPG (period of 400 m). Reproduced with permission from (Allsop et al, 2004).…”

“…In this section, the applications of such devices are briefly resumed: according to the previous sections, first intra-core and then evanescent-wave LPGs will be considered. The bending and orientational characteristics were the main aim of the first study about Dfiber based LPGs (Allsop et al, 2004). Typically increasing curvature causes splitting of LPG attenuation bands in standard SMF.…”

Micro-fabrication of advanced photonic devices by means of direct point-by-point femtosecond inscription in silica

“…Some limited success in making orientation sensors has been achieved with LPGs written into asymmetric fibers such as D-shaped cladding fiber 15 or eccentric core fiber. 16 Although the resulting devices can determine the orientation of the bend, they still present some practical problems; for example, these fibers are generally not easy to connect to standard optical fiber, thus adding complexity and cost to the fabrication procedure for sensor arrays.…”

Stable dual-wavelength erbium-doped fiber laser using novel fabricated side-polished arc-shaped fiber with deposited ZnO nanoparticles

“…Interestingly enough, there has been very little work done on the generation of a dual-wavelength output using D-shaped fibers. This is due to a number of limitations inherent to D-shaped fibers, including asymmetrical geometries that show a reasonable directional bend sensitivity [22] . Thus, a new approach that can overcome these limitations is necessary.…”