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Research paper on Optical CDMA System Based on Spectral Encoding of LED

I. INTRODUCTION
11. PRINCIPLE OF OPERATION
111. TRANSMITIERA ND RECEIVER DESCRIPTION
Iv. PERFORMANCE CALCULATION
V. CONCLUSION
REFERENCES

I. INTRODUCTION-
                               0PTICAL code-division multiple access (CDMA) net- works based on frequency-domain encoding of coherent  and noncoherent  broad-band sources have been proposed recently. In the former case, high-cost mode-locked lasers providing ultrashort pulses are necessary, as well as complicated receivers including optical threshold elements and optical correlators. In the latter case, encoding/decoding is done with guided-wave ladder networks, and to achieve coherence correlation, the delays at the receiver need to match those at the transmitter to within the coherence time of the noncoherent source. This is typically less than 1 ps and therefore requires complex electronics, such as feedback control loops in order to compensate the change in optical path lengths induced by temperature variations [21. In this letter we propose an optical CDMA system based on amplitude spectral encoding of low-cost broadband sources such as LED’s. Our system requires only standard optical elements and simple direct-detection receivers. We show that tens to hundreds of users can transmit asynchronously with negligible probability of error, giving an aggregate network throughput in the range of 50-100 Gb/s. Furthermore, since the spectral width of an LED is independent of the modulating signal, the so-called spreading gain is independent of the data rate, a major advantage in CDMA systems.
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