Analysis of transmission characteristics of long period gratings in tapered optical fibers

Abstract

We report an analysis of the transmission characteristics of long period gratings written in a linearly tapered optical fiber. Such gratings are best analyzed by a coupled mode theory that includes several cladding modes simultaneously. However, the numerical solution needs to be modified to take into account the changing propagation constants along the length of the fiber. The transmission spectra show certain distinctive features that depend on the grating period and choice of the phase-matched coupled cladding modes. For low-order modes, the resonances broaden and tend to vanish as the taper of the angle increases. For higher-order modes, the resonances remain well defined but shift toward higher or lower wavelengths and broaden. The transmission spectrum is also highly sensitive to a change in the ambient atmosphere.

Arc-induced long-period fiber gratings inscribed in asymmetric adiabatic tapers

“…On the other hand, there have been several published works on the use of one or two LPFGs and a fiber tapers to create novel optical devices [15], or the LPFG is directly written on the taper [16,17]. In both cases, the objective is to improve the transfer function characteristics of the resultant device.…”

“…In this case the broadened bands are attributed to overlapping of attenuation bands due to the variation of the phase matching condition along the taper. In [17] a theoretical analysis of the transmission characteristics of LPFGs in tapered fibers was realized, showing that tapering induce a wavelength dependent chirp and apodization. Here, we present the characteristics of LPFGs inscribed on the longer transition of adiabatic asymmetric tapers.…”

Fabrication of corrugated Ge-doped silica fibers

“…In fiber laser applications tapered fibers with distributed Bragg reflectors (DBRs) are used for dispersion compensation [7]. Fiber tapers with long-period DBRs are used for sensing different physical properties such as temperature, stress or refractive index [8][9][10]. Tapered and corrugated waveguides have many potential uses in fiber output couplers and beam steerers [11] and tailoring the properties of photonic crystal fibers [12].…”