Performance Investigation of Bidirectional Optical IM/DD OFDM WDM-PON using RSOA as a Colorless Transmitter Mahmoud Alhalabi Institute of Natural and Applied Science, Erciyes University, Kayseri, Turkey eng.halabi@hotmail.com Necmi Taşpınar Department of Electrical and Electronics Engineering, Erciyes University, Kayseri, Turkey taspinar@erciyes.edu.tr Fady El-Nahal Electrical Engineering Department Islamic University of Gaza Gaza, Palestine fnahal@iugaza.edu.ps Abstract— In this paper, we have designed and simulated bidirectional hybrid Intensity Modulated and Direct Detected Optical Orthogonal Frequency Division Multiplexing Wavelength Division Multiplexing Passive Optical Network (IM/DD-OFDM-WDM-PON) with 40 Gbps 16-QAM downstream and 2.5 Gbps On-Off keying (OOK) upstream signal by using Optisystem software. The simulated system is considered as a simple, low cost and colorless network as a Reflective Semiconductor Optical Amplifier (RSOA) transmitter was used at the Optical Network Unit (ONU) and no Dispersion Compensating Fiber (DCF) is needed. Obtained results show that the simulated IM/DD-OFDM-WDM-PON can achieve good Bit Error Rate (BER) performance over propagation length of 20 km. For comparison and analysis, BER performance of the simulated network is analyzed and studied as well as the effect of the propagation length on the constellation diagram, and the relation of BER and bit energy and noise density ratio (Eb/No). Keywords—component; Intensity Modulated and Direct Detected (IM/DD), Orthogonal Frequency Division Multiplexing (OFDM), Wavelength Division Multiplexing (WDM), Passive Optical Network (PON), Quadrature Amplitude Modulation (QAM), Bit Error Rate (BER), Reflective Semiconductor Optical Amplifier (RSOA). I. INTRODUCTION Wavelength Division Multiplexing Passive Optical Network (WDM-PON) is considered as a cost-effective solution in broadband optical communication since it satisfies several advantages such as higher capacity, better performance and long reach of optical fiber [1-2]. As well as, an Orthogonal Frequency Division Multiplexing (OFDM) technique adds more advantages to WDM-PONs as it provides more flexible bandwidth allocation and a higher data rate for Optical Network Units (ONUs) [3]. OFDM is a preferred solution for WDM-PON because it can provide high spectral efficiency, high tolerance to chromatic dispersion and extend the transmission distance. For reducing implementation cost of PONs, colorless optical sources at ONU are used to re- modulate downstream signal with lower upstream bit rate such as Reflective Semiconductor Optical Amplifier (RSOA) and injection-locked Fabry–Perot laser diode (FP-LD) [4]. RSOA is considered as reflector, modulator, amplifier and colorless transmitter simultaneously, and it is used to re-modulate downstream signal for generating upstream signal without adding any additional system cost. Recent years, RSOA is preferred for using with PONs due to cost effective [5]. Intensity modulated direct detected OFDM system is considered as cost effective optical OFDM system compared to Coherent detection OFDM system because local laser is not be used at ONU in IM/DD system [6]. Our simulated system combines all mentioned techniques to achieve high data rate and cost-effective optical OFDM system. M-Quadrature Amplitude Modulation (QAM) is used to increase both the capacity and efficiency of optical systems to support low Bit Error Rate (BER) and high data rate. IM/DD optical OFDM system is considered as a cost-effective optical communication system which can be found in a lot of optical applications [7-12]. According to [13], a bidirectional WDM- PON system based on modulated OFDM signal for 40 Gbps downstream signal and RSOA reused scheme with OFDM signal for 10 Gbps upstream signal was demonstrated. In [14], Bidirectional long reach WDM-PON system provided 20 Gbps downstream data and 10 Gbps upstream data and RSOA was presented and implemented over 45 km optical fiber. In [15], a novel cost-effective RSOA based bidirectional WDM-Ro-FSO- PON was established for next-generation free space optics (FSO) network. 10 Gbps downstream, 1.25 Gbps upstream signal and 1.49 Gbps video signal were sent over 500 m FSO channel. In [16], a 10 Gbps bidirectional RSOA based WDM- PON was analyzed by using Differential Phase Shift Keying (DPSK) downstream signal and OFDM modulated upstream signals over 25 km fiber transmission. In [17], an article wavelength reuse WDM-PON architecture based on incoherent unpolarized light was demonstrated. RSOA was used as a simple, low-cost and colorless reused optical source. In [18], a bidirectional RSOA based WDM-PON using 10 Gbps DPSK downstream signal and 5 Gbps OOK signal re-modulated for with high extinction-ratio in both directions was demonstrated over 20 km optical range. In [19], an EDFA-based 40 Gbps downstream and 10 Gbps upstream signals long-haul WDM- PON scheme was achieved by using QPSK downstream and FBG optical equalizer-based RSOA IM-DD for upstream signal over 40 km fiber transmission. In [20], a novel architecture of WDM OFDM-PON was demonstrated for sending 10 Gbps data both in downstream and upstream transmissions up to 50 km. Direct detection OFDM was used ETAI 2021 Conference Proceedings, ISSN 2545-4889, Vol. 2, Issue 1, Paper ID: ETAI 9-3 307