We report on the development and characterization of single peak fibre Bragg gratings (FBGs) in polymer optical fibre (POF). We use a multimode gradient index cyclic transparent optical polymer (CYTOP) fibre, where the FBGs are inscribed with a femtosecond laser. We adapt the direct-write, plane-by-plane inscription method, where the beam is scanned transversely across the core, to create refractive index changes. In order to reduce the number of fibre modes coupling to the grating, we limit the FBG's spatial extent to the central part of the core, in the region where the gradient index profile peaks. In this way, we are able to excite the strongest lower order modes thereby generating single peak POF-FBG spectra. We support our experimental results with modelling using the bi-directional beam propagation method (Bi-BPM). Furthermore, a FBG array is used as a quasi-distributed sensor, recovering the vibration response of a freely suspended metal beam, using a 6-m sensing strand. The FBGs are multiplexed using a high-speed commercial wavelength demodulator, the output of which provides wavelength- and time-dependent displacement information. The results are compared directly with the performance of a silica fibre-based FBG sensor array, and show a significant sensor sensitivity improvement for the polymer fibre to dynamic strain

We demonstrate a quasi-distributed sensor for cantilever health inspection measurements using a fibre Bragg grating (FBG) array inscribed in a polymer optical fibre. The FBGs were characterised and calibrated for axial strain, temperature and relative humidity prior to their mounting on a carbon cantilever beam; the tail rotor of a helicopter. By using the zero-crossing demodulation algorithm, we recovered the time-dependent, wavelength response from each Bragg grating sensor and the vibration response of the beam was extracted. We used the response of the beam to study how the addition of masses at different positions on the beam influences the vibrational behaviour and mimic the location of ?damage? through the time-dependent results. We show that health inspection measurements are feasible with polymer-based fibre Bragg gratings, offering accurate and rapid detection of damage points on a structural beam.

Laser beams shaped into flattop are widely used in various industrial and medical applications. There are various approaches to produce a flattop beam from a Gaussian beam. In this paper, a novel approach called Method of Projection is used to optimize a single element Radial phase mask to obtain flattop output beam. In this approach, Henkel transform and cross-correlation in iterative loop is used to optimize the parameters. Following this approach, a suitable phase mask pattern is obtained in grayscale. The simulated results are compared with target intensity profile through cross-correlation and further optimized to reach certain goodness value. The designed algorithm is a single element radially symmetric phase mask, which is low cost, alignment-free and robust. Hence, the proposed approach reduces the number of components required to develop a flattop output.

Cold ironing, also known as electrification of onshore power systems, is an important strategy for reducing emissions from vessels while berthed at port. However, effective planning of cold ironing infrastructure requires reliable estimation of the electrical power demand of different vessel categories, especially in ports where measured ship consumption data are limited or unavailable. This paper presents a data-driven approach to synthetic ship power demand modelling for cold ironing decision support, with a case study focused on Cyprus Port of Limassol. Using data collected from various sources, a Random Forest Regression model is developed which creates a relationship between vessel characteristics and power demand. This relationship is expressed as a power density coefficient and is employed to generate a synthetic power consumption profile of each ship visiting the port. The individual ship demand values are then aggregated to determine the total daily power consumption required for cold ironing operation at the port. The results provide insights into vessel-level and port-level electrical demand, supporting cold ironing feasibility studies, shore-side infrastructure sizing, port electrification planning, and energy management decisions.