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We propose a single laser source-based free space optical link for transmission of bidirectional data of three different channels between modular data centers, where each channel has a data rate of 20 Gbps. The downlink channels are transmitted using a combination of differential quadrature phase shift keying (DQPSK) and pulse amplitude modulation (PAM). The uplink channels are transmitted using On-Off keying (OOK). The optical signals are transmitted over a 500-m free space optical (FSO) link based on Gamma–Gamma channel model. A regenerative wavelength converter is used to generate multiple optical pulsed carriers from the received downlink optical signals. The performance of the proposed architecture is evaluated under medium turbulence condition, which represents the FSO channel in a data center scenario. Our simulation results show that the proposed architecture gives acceptable bit-error-rate (BER) results. The architecture can be used as a potential substitute to fiber-based interconnects in a data center or a general point link in a passive optical network (PON), enabling high data-rate and cost-efficient transmission. [ABSTRACT FROM AUTHOR]