Error probability upper bound for perfect sequences implemented with super-structured fibre Bragg gratings

The success of coherent optical code-division multiple-access (OCDMA) systems is strongly dependent on the optical encoder/decoder technology and on the selection of the correct OCDMA codes/sequences. For this reason, in this study, the authors present a method to implement perfect sequences with Super-Structured Fibre Bragg Gratings (SSFBGs). A new SSFBG power reflection model has been found. They have also derived a property that explains why the SSFBGs should use codes derived from m-sequences. Usually, OCDMA researchers try many different codes into SSFBGs in order to select the SSFBG encoders that result in lower error probability. In the authors work, they show that a SSFBG can be considered to be a perfect sequence encoder. For this reason, the codes written into the SSFBGs should be selected based on their new property. This property permits to design and select quickly the correct codes with low power contrast ratios. In addition, a new error probability upper bound, which is a function of the code family and of its power contrast ratio is also presented. With this new bound, it is not necessary to use an optical simulator to estimate the maximum bit error rate of an OCDMA system, if some power contrast ratios of the selected SSFBG code set are known.