Investigation of the power coupling of novel wavelength-selective couplers incorporating axially symmetric long-period fibre gratings

Evanescent-field coupling was studied experimentally in novel optical-fibre-based wavelength-selective couplers, using axially symmetric long-period fibre grating (LPFG) structures. The coupling characteristics of a wavelength-selective coupler at the resonant wavelength were investigated for different LPFG offset distances. It was shown that the wavelength-selective couplers effectively transferred light power at the LPFG resonant wavelength from one fibre to another. The performance of the couplers was consistent with simulations performed in MATLAB using coupled-mode theory.