We report numerical simulation and hyperspectral Raman imaging of three index-guiding solid-core photonic crystal fibers (PCFs) of different air-cladding microstructures to assess their respective potential for evanescent-field Raman spectroscopy, with an emphasis on achieving surface-enhanced Raman scattering (SERS) over the entire fiber length. Suspended-core PCF consisting of a silica core surrounded by three large air channels conjoined by a thin silica web is the most robust of the three SERS-active PCFs, with a demonstrated detection sensitivity of $1\times {10}^{-10}\mathrm{M}$ R6G in an aqueous solution of only $\sim 7.3\mu \mathrm{L}$ sampling volume.

A $30\mathrm{cm}$ long solid-core photonic crystal fiber (PCF) with immobilized and discrete Ag nanoparticles was used to obtain forward-propagating surface-enhanced Raman scattering (SERS) of $2\mu \mathrm{M}$ Rhodamine 6G (R6G) aqueous solution filled in the cladding air channels. The intensity distributions of characteristic Raman vibrational bands of silica and R6G in PCF were mapped for the first time to our knowledge by hyperspectral Raman imaging. We show that the measured SERS intensity arises exclusively from the forward-propagating core mode as a result of evanescent-field interaction with R6G in the innermost ring of the cladding air channels.