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A novel media access control protocol is proposed based on EPON considering of the character of orthogonal frequency-division multiplexing passive optical network.Multi-point control protocol,control message format and the priority of services are designed and a dynamic bandwidth allocation algorithms is proposed,which supports multi-service access and ensures quality of service distinguishing user level in specified case.The proposed algorithm uses two-level mechanisms and the allocating progress can be divided into two steps-schedule for different priority of services and schedule for different level optical network unit.The proposed protocol is simulated and the results of delay,packet loss ratio and throughput performance show that the proposed protocol guarantees the quality of service requirements for different services excellently,and meets quality of service requirements of multi-service access.

An architecture of next generation access network namely orthogonal frequency division multiplexing passive optical network was presented,which has high spectrum efficiency,fine bandwidth granularity and low cost.A novel efficient dynamic bandwidth allocation algorithm based on orthogonal frequency division multiplexing passive optical network namely fixed cyclic polling in pipeline dynamic bandwidth allocation algorithm was investigated.To meet the quality of service requirements under multi-services access scenario,two level bandwidth allocation mechanisms,bandwidth pre-request for expedited forward service and the smallest bandwidth request allocated the first principle for assured forwarding and the best effort services were applied in this algorithm.A simulation was conducted to study the performance of fixed cyclic polling in pipeline dynamic bandwidth allocation algorithm in orthogonal frequency division multiplexing passive optical network.The results show that the proposed algorithm supports expedited forwarding services with low packet average delay and low jitter,balances priority and fairness between assured forwarding services and best effort services,and achieves bandwidth allocation fairness among different optical network units in the same priority.Compared with the traditional dynamic bandwidth allocation algorithms,fixed cyclic polling in pipeline algorithm meets the quality of service requirements excellently,and adapts orthogonal frequency division multiplexing passive optical network better with higher bandwidth efficiency and lower algorithm complexity.

The impact of positional and radial disorders on the transmission spectrum of photonic crystal waveguides with different shapes of air-holes,including circular,square and elliptic were numerically investigated.It was found that the disorder affects the anti-crossing point greatest.The flat transmission spectrum becomes narrower as disorder increasing.The transmission property performs more sensitive on the air-holes positions than radii.The square air-holes are more robust against the positional disorder.The circular air-holes are more robust alainst the radial disorder.These results provide important theoretical instructions on the imperfection during the manufacture possess in the PCWs experiment.

In order to generate a high quality multi-carrier,the phenomenon caused by different phase deviation of radio frequency was analysed.In this paper,the theoretical analysis revealed that the quality of multi-carrier would deteriorate gradually when the phase deviation decreases from 90°to 0°.But when phase deviation is slightly different from 90°,the quality of multi-carrier is good enough for the application of optical communication.In the experiment,the qualities of multi-carriers with phase deviation of 90°,45°and 0°were compared.The best performance is obtained at 90°.Under the 45°phase deviation,fifty carriers can also be otainted,but the quality decreases slightly that is good enough to apply to optical communication.And a multi-carrier under 0°phase deviation cannot be obtained.