Two-dimensional wavelength-hopping/time-spreading synchronous optical code-division multiplexing systems using a heterodyne detection receiver and pulse-position modulation (PPM) signaling are investigated. Prime sequences are used as signature code for both wavelength hopping and time spreading. Performance of the proposed systems is theoretically analyzed taking into account various kinds of noise and interference, including multiple access interference, optical beating interference, crosstalk, and receiver noise. We also compare the performance of the proposed systems with the conventional ones using ON-OFF keying signaling. Numerical results show the improvement in both number of users and optical power gain with a proper selection of PPM word length M.

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