An Optical CDMA System Based on Spectral Encoding of LED

In this letter we propose an optical code-division multiple access (CDMA) system based on amplitude spectral encoding of low-cost broadband sources such as light-emitting-diodes. The proposed system uses a standard nondispersive lens-grating apparatus, and simple direct-detection receivers. We show that by assigning to N subscribers the N cycles shifts of a single unipolar m-sequence of period N, complete orthogonality between the users can be achieved, provided that the spectrum is properly equalized. We show that without any equalization, and for N = 511, up to 200 users can transmit asynchronously with an average error probability equal to 10⁻⁹, depending on the received power level. An aggregate network throughput of 100 Gb/s can therefore be obtained.