Evaluation of direct modulation and external modulation in temporal phase encoding system

This paper aims to evaluate the system performance in term of bit error rate (BER) in an optical code division multiple access (OCDMA) metropolitan area network using direct modulation and external modulation technique. A four-user system is developed and tested up to 100 km at 10 Gbps. A set of twenty and twenty-five chips unique optical code sequences is applied to encrypt the data via appropriate grating writing profile. Temporal phase encoding technique is adopted using compact Fiber Bragg Grating. The encoding technique used is based on short-period grating via coupled mode theory. The BER of the system over received power and the required input power is examined. The maximum allowable distance in order to support error free transmission, BER<;10^-9 is identified. The performance enhancement with and without the dispersion compensating device is presented.