The possibility of developing a multichannel optical chemical sensor, based on molecularly imprinted polymers (MIPs) and surface plasmon resonance (SPR) in a D-shapedmultimode plastic optical fiber (POF), is presented by two cascaded SPR-POF-MIP sensorswith different thicknesses of the gold layer. The lowcost, the high selectivity and sensitivity of the SPR-POF-MIP platforms and the simple and modular scheme of the optical interrogation layout make this systema potentially suitable on-linemulti-diagnostic tool. As a proof of principle, the possibility of simultaneous determination of two important analytes, dibenzyl disulfide (DBDS) and furfural (2-FAL), in power transformer oil was investigated. Their presence gives useful indication of underway corrosive or ageing processes in power transformers, respectively. Preliminarily, the dependence of the performance of the D-shaped optical platform on the gold film thickness has been studied, comparing two platforms with 30 nm and 60 nm thick gold layers. It has been found that the resonance wavelengths are different on platforms with gold layer of different thickness, furthermorewhen MIPs are present on the gold as receptors, the performances of the platforms are similar in the two considered sensors.