A cost-effective hybrid wavelength division multiplexing (WDM), optical code division multiple access (OCDMA) scheme by sharing a single multiport encoder in a central office and using tunable decoders in an optical network unit has been proposed and demonstrated in a field trial. A Ill-km error-free field transmission of asynchronous 3-WDM x 10-OCDMA x 10.71 Gb/s/user has been achieved with differential phase-shift keying for data modulation and balanced detection. Forward-error-correction and opticapl-thresholding techniques were not used in the experiment.