A fully coherent optical code-division multiple access (OCDMA) scheme that combines spectral phase encoding (SPE) and spectral line pairing to generate signals through heterodyne decoding is proposed. A simple balanced receiver performs sourceless heterodyne detection, canceling speckle noise and multiple-access interference (MAI). A 16 user 100% load system transmitting at 40 Gbits is simulated, and a 4 user 50% load system transmitting at 4.25 Gbit/s is experimentally demonstrated for the first time.