PERFORMANCE ANALYSIS OF ADAPTIVE BIT LOADING SIPM-OOFDM IN INTENSITY MODULATION AND DIRECT DETECTION TDM- AND TWDM-PON SYSTEMS

Technological advancements over recent decades prompted the development of bandwidth-intensive services, necessitating the deployment of optical fibers in access networks up to the subscriber. To address these increasing demands, innovative transmission techniques, including advanced modulations and architectures, are expected. This study aimed to enhance transmission distance and user capacity in Passive Optical Networks (PON). The Subcarrier Index Power Modulated Optical Orthogonal Frequency Division Multiplexing (SIPM-OOFDM) technique, which conveyed additional information per subcarrier compared to conventional OOFDM, was implemented using MATLAB R2019a. To further improve the capacity performance, an Adaptive Bit Loading SIPM-OOFDM (ABL-SIPM-OOFDM) was implemented. We have modeled an IM/DD link in Optisystem7 and simulated the performance of conventional SIPM-OOFDM and ABL-SIPM-OOFDM in Time Division Multiplexing-PON (TDM-PON) and Time and Wavelength Division Multiplexing-PON (TWDM-PON) systems. The ABL-SIPM-OOFDM is shown to achieve an effective data rate of 18 Gb/s in TDM-PON, compared to 13 Gb/s with conventional SIPM-OOFDM, for a Bit Error Rate (BER) target of 10^-3 at 20 km of fiber length with power budget supporting 64 users. This represents a 5 Gb/s increase in transmission capacity over the conventional approach.Additionally, in a TWDM-PON setup, the ABL-SIPM-OOFDM achieved an effective data rate of approximately 41 Gb/s over a distance of 40 km, supporting 64 Optical Network Units (ONU with 4 wavelengths each). In conclusion, the proposed ABL-SIPM-OOFDM demonstrated significant potential as a candidate for NG-PON systems, meeting the requirement of a 40 Gb/s downlink data rate for at least 256 users over a fiber distance of 40 km.