Fiber-optic localized surface plasmon resonance sensor excited with ambient light through a fluorescent fiber

• A fiber optic sensor based on localized surface plasmon resonance that may operate with ambient light is demonstrated • A fluorescent optical fiber was used as an intermediate waveguide • The sensors with a simple interrogation can achieve a refractive index resolution of 1 × 10 -4 Optical fiber sensors based on localized surface plasmon resonance (LSPR) have attracted considerable interest in the past years. These sensors are compact, versatile, and ideal for monitoring chemical and biological parameters in remote sites. LSPR-based fiber sensors need a broadband excitation light source and high-quality opto-mechanical components to inject light into the microscopic fiber core. In this work, it is demonstrated, for the first time to the best of our knowledge, that LSPR fiber sensing is possible with ambient light through an intermediate fluorescent cylindrical waveguide. The latter was a double-doped polymer optical fiber that had an emission band that matched the resonance wavelength of gold nanoparticles, which were immobilized on a D-shaped multimode optical fiber. As proof of concept, we report on refractive index sensing with detection limits of 1 × 10 -4 . We believe that the results reported here can pave the way to the use of inexpensive, long-lasting, eco-friendly, sustainable light sources that are important for cost-effective LSPR fiber sensing.