Author details

Figure 12 illustrates the variation of the BER as a function of the fiber length for three codes with various Fs and Ds. It can be noted that the dispersion effect increases as the fiber length increases. However, for this particular chip duration, the dispersion has no impact on the BER for optical fibers shorter than 5 km. On the other hand, when the fiber's length is greater than 5 km, system performance is deteriorated. In order to complete our study, the BER versus data rate D, for a code length F = 181, has been simulated (Figure 13). For example, on the one hand, we can observe that the performances of an OOC (F = 181, W = 4) are not affected by the fiber dispersion up to D = 600 Mbits/s for a 1-km-long optical link. On the other hand, for a 20-km-long optical link, the performances are degraded from a data rate

BER versus data rate D for an OCDMA link with OOC (F = 181, W = 4) and N = 5 active users.

The curves indicate that for making the effect of dispersion negligible, without using in the OCDMA link, a dispersion compensated component, we should have a

In this chapter, we studied the DS-OCDMA multiple access technique envisaged for optical communications, in particular in PON access networks. To maintain high rates, the code spreading length should be as low as possible. In this case and for an incoherent system, it has been shown that the IAM multiple access interference, linked to the use of quasi-orthogonal unipolar codes, is very important and does not make it possible to maintain the quality of the link. It is, therefore, necessary to reduce the MAI in order to be closer to the specifications. For this purpose, two structures were studied: the serial interference cancelation (SIC) and the parallel interference cancelation (PIC). We first developed the approximate theoretical expression of the SIC error probability for unipolar codes whose intercorrelation is

The parametric study has shown that the OCDMA link performances in the access network context are significantly overestimated when the fiber chromatic

trade-off between OOC code length F and data rate D.

D = 100 Mbits/s.

Figure 13.

Multiplexing

dispersion is neglected.

6. Conclusion

86

Younes Zouine and Zhour Madini\* Department of Electrical and Telecommunication, ISET Laboratory ENSA, Kenitra, Morocco

\*Address all correspondence to: zmadini@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
