Solving the Near-Far Problem in Dynamic Frequency Hopping-Optical Code Division Multiple Access using Power Control

Abstract

In this study, a distributed power controlalgorithm is proposed for Dynamic FrequencyHopping Optical-CDMA (DFH-OCDMA) system. Ingeneral, the DFH-OCDMA can support highernumber of simultaneous users compared to otherOCDMA techniques. However, the performance ofsuch system degrades significantly as the receivedpower does lower than its minimum threshold. Thismay obviously occur in a DFH-OCDMA networkwith near-far problem which consist of differentfiber lengths among the users, that resulting tounequal power attenuation. The powermisdistribution among simultaneous active users atthe star coupler would degrade the Bit Error Rate(BER) performance for users whose transmittingsignals with longer fiber lengths. In order to solvethese problems, we propose an adaptive distributedpower control technique for DFH-OCDMA tosatisfy the target Signal to oise Ratio (SR) for allusers. Taking into account the noise effects ofMultiple Access Interference (MAI), Phase InducedIntensity oise (PII) and shot noise, the system cansupport 100% of users with power control ascompared to 33% without power control when theinitial transmitted power was -1dBm with 30simultaneous users