A critical component of optical communications is the availability of a suitable waveguide technology for the transport of electromagnetic waves with low loss over a broad spectral range. In the past four decades, despite extensive research, the attenuation and spectral bandwidth of silica-based optical fibres have remained relatively unchanged, with state-of-the-art fibres offering values of 0.14 dB km ⁻¹ and 26 THz below 0.2 dB km ⁻¹ , respectively. Here we report a microstructured optical waveguide with unprecedented transmission bandwidth and attenuation, with a measured loss of 0.091 dB km ⁻¹ at 1,550 nm that remains below 0.2 dB km ⁻¹ over a window of 66 THz. Instead of a traditional solid glass core, this innovative optical fibre features a core of air surrounded by a meticulously engineered glass microstructure to guide light. This approach not only reduces attenuation and other signal degradation phenomena, but it also increases transmission speeds by 45%. Furthermore, the approach theoretically supports further loss reductions and operation at wavelengths where broader bandwidth amplifiers exist, potentially heralding a new era in long-distance communications as well as remote delivery of laser beams.

In this paper, we present the development and testing of an optical-based sensor for monitoring the corrosion of reinforcement rebar. The testing was carried out using an 80% etched-cladding Fibre Bragg grating sensor to monitor the production of corrosion waste in a localized region of the rebar. Progression of corrosion can be sensed by observing the reflected wavelength shift of the FBG sensor. With the presence of corrosion, the etched-FBG reflected spectrum was shifted by 1.0 nm. In addition, with an increase in fringe pattern and continuously, step-like drop in power of the Bragg reflected spectrum was also displayed.

We present the selective excitation of the fundamental mode in an anti-resonant hollow-core fiber (ARHCF) fusion-spliced with a commercial large mode area (LMA) fiber. By designing and fabricating a single-ring ARHCF that is mode-matched to a LMA fiber and by splicing the two using a C O 2 laser-based splicer, we achieve a coupling efficiency of 91.2% into the fundamental mode. We also demonstrate an all-fiber integration of an ARHCF with a commercial ytterbium-doped fiber in a laser cavity for beam delivery application. Coupling of the single-mode laser output beam into the fundamental mode of the ARHCF is demonstrated with 90.4% efficiency ( < 0.45 d B loss) for up to 50 W continuous wave beam in a stable and alignment-free all-fiber laser setup.

This paper reports the design, characterization and implementation of a Fiber Bragg Grating (FBG)-based temperature sensor for an Insulted-Gate Bipolar Transistor (IGBT) in a solar panel inverter. The FBG is bonded to the higher Coefficient of Thermal Expansion (CTE) side of a bimetallic strip to increase its sensitivity. Characterization results show a linear relationship between increasing temperature and the wavelength shift. It is found that the sensitivity of the sensor can be categorized into three characterization temperature regions between 26 °C and 90 °C. The region from 41 °C to 90 °C shows the highest sensitivity, with a value of 14 pm/°C. A new empirical model that considers both temperature and strain effects has been developed for the sensor. Finally, the FBG-bimetal temperature sensor is placed in a solar panel inverter and results confirm that it can be used for real-time monitoring of the IGBT temperature.

Efficient continuous-wave laser emission of acetylene molecules at 3.1 μm wavelength has been demonstrated in low-loss hollow-core fiber by optically pumping using a fiber-amplified diode laser around 1.53 μm. In this paper, we report and compare the continuous-wave laser performance of acetylene molecules in the cavity and single-pass configurations. The use of low-loss antiresonant hollow-core fiber makes the single-pass configuration ideal for high-power laser generation and enables over 1.1 W continuous-wave mid-infrared laser output with over 33% slope efficiency relative to the absorbed pump power. The systematic characterization of power-scaling and pump power absorption properties demonstrates that the molecular kinetics inside hollow-core fiber determines the laser performance, and that low fiber attenuation is key to high-efficiency continuous-wave output.