We present the first experimental demonstration of a practical, fully coherent, optical code division multiple access (OCDMA) scheme that can fully suppress multiple access interference (MAI) and speckle noise without phase locking or thresholding and gating. The scheme is sourced from an optical comb generator and uses spectral phase encoding and a heterodyne receiver with balanced detection. Here we present results for a four-user configuration at 50% load. At 4.5 Gbits/s per user, the system achieves a signal to MAI ratio of 648 at a bit error rate of 10(-7).