Mid-infrared methane detection in a photonic bandgap fiber using a broadband optical parametric oscillator.

We demonstrate methane sensing using a photonic bandgap fiber-based gas cell and broadband idler pulses from a periodically-poled lithium niobate femtosecond optical parametric oscillator. The hollow core of the fiber was filled with a methane:nitrogen mixture, and Fourier transform spectroscopy was used to measure transmission spectra in the 3.15-3.35 mum methane absorption region. The method has applications in gas sensing for remote or hazardous environments and potentially at very low concentrations.

Ultrafast-laser inscription of a three dimensional fan-out device for multicore fiber coupling applications.

A fan-out device has been fabricated using ultrafast-laser waveguide-inscription that enables each core of a multicore optical fiber (MCF) to be addressed by a single mode fiber held in a fiber V-groove array (FVA). By utilizing the unique three-dimensional fabrication capability of this technique we demonstrate coupling between an FVA consisting of a one-dimensional array of fibers and an MCF consisting of a two-dimensional array of cores. When coupled to all cores of the MCF simultaneously, the average insertion loss per core was 5.0 dB in the 1.55 mum spectral region. Furthermore, the fan-out exhibited low cross-talk and low polarization dependent loss.

Multiple rare earth emissions in a multicore tellurite fiber with a single pump wavelength.

A three-core tellurite glass fiber having different combinations of rare earth oxide dopants in each core has been fabricated using shaped die-extrusion. Three cores, doped with Ho(3+)-Tm(3+)-Yb(3+), Er(3+)-Ce(3+), and Tm(3+)-Yb(3+) respectively, exhibited visible upconversion (blue, green and red) and infrared emissions at 1.4 microm, 1.5 microm, 1.9 microm and 2.05 microm when pumped at a wavelength of 980 nm. The prospects for multi-band amplifiers and lasers are discussed.

Two-axis bend measurement with Bragg gratings in multicore optical fiber.

We describe what is to our knowledge the first use of fiber Bragg gratings written into three separate cores of a multicore fiber for two-axis curvature measurement. The gratings act as independent, but isothermal, fiber strain gauges for which local curvature determines the difference in strain between cores, permitting temperature-independent bend measurement.

Phase-demodulation error of a fiber-optic Fabry-Perot sensor with complex reflection coefficients.

The influence of reflector losses attracts little discussion in standard treatments of the Fabry-Perot interferometer yet may be an important factor contributing to errors in phase-stepped demodulation of fiber optic Fabry-Perot (FFP) sensors. We describe a general transfer function for FFP sensors with complex reflection coefficients and estimate systematic phase errors that arise when the asymmetry of the reflected fringe system is neglected, as is common in the literature. The measured asymmetric response of higher-finesse metal-dielectric FFP constructions corroborates a model that predicts systematic phase errors of 0.06 rad in three-step demodulation of a low-finesse FFP sensor (R = 0.05) with internal reflector losses of 25%.