Fiber optic - surface plasmon resonance (FO-SPR) instruments are powerful optical tools with great applicability in biosensing, mainly because they allow real-time quantification of biochemical interactions. Besides, they bring further advantages such as simplicity, portability and cost-effectiveness. These benefits came however with the price of a lower stability and sensitivity when compared to the bulky prism-based SPR platforms, motivating and fueling the general research framework captured in this book, i.e. to look for novel schemes of improving the innovative FO-SPR biosensing technology. In particular, this work connects technology-related elements with biochemical assays development, aiming the design of FO-SPR devices with improved performance and extended functionality, needed in the context of an increasing demand for low-cost, user-friendly and sensitive biosensors for various applications.