Figure Presented A full-length accumulative photonic crystal fiber (PCF) that is surface-enhanced Raman scattering (SERS)-active is achieved by immobilizing Ag nanoparticles inside the air channels of solid-core and hollowcore PCFs using a polyelectrolytemediated process. Raman gain in PCFs prevails with coverage density below 0.5 nanoparticle m-2. Light attenuation dominates, however, at a higher density. Controlled coverage density and uniformity of nanoparticles is the key to the exploitation of the length benefit of the PCF platform. 2010 WILEY-VCH Verlag GmbH &. Co. KGaA, Weinheim.