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 hollow-core PCFs using a polyelectrolyte-mediated process. Raman gain in PCFs prevails with coverage density below 0.5 nanoparticle mu 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.