Transmission and reflection SPR disposable fibre probes for bio-chemical sensing

A comparison between the characteristics of transmission and of reflection based surface plasmon resonance (SPR) fiber sensors is presented. Both sensors are built using a multimode fiber with 400 μm silica core diameter, un-cladded on a length of 2 cm and then coated with a 50 nm gold layer. The reflection based setup uses a bifurcated fiber bundle to avoid complex and expensive circulators or couplers. The effect of misalignments and mating tolerances are investigated. The comparison between transmission and reflection based setups shows that the same fiber sensor exhibits a higher sensitivity when used in the reflection based configuration. The latter is also advantageous since it allows the use of the fiber sensor as a disposable probe.