To recover the decoded signals based on the existing commercial receiver modules is an important practical developing direction of optical code division multiple access (OCDMA) systems. The en/decoders with high power-contrast-ratio (PCR) can help to form the electrical decision signals with high signal-noise-ratio (SNR) under the narrow-band receiver condition. Based on the commercial narrow-band receiver, i.e., 10 G PIN+TIA and 10 G clock data recorery (CDR), two-user 10 Gb/s 60 km error-free transmission experiment is implemented with the self-designed fiber-Bragg-grating (FBG)-based en/decoders with high PCR. The three-user 10 Gb/s back-to-back (BTB) error-free experiment is also achieved. In the experiment, different bit-error-rate (BER) curves are tested with different users and w/o transmission. Both the impairing factors which cause the power punishment and the approaches to improve sytem performance are analyzed.