Received: Added at production Revised: Added at production Accepted: Added at production DOI: xxx/xxxx ARTICLE TYPE A Full Duplex Radio over Fiber Architecture Employing 12 Gbps 16 × 16 Optical MIMO for Next Generation Communication Networks Saeed Iqbal 1 | Aadil Raza 2 | Muhammad Fasih Uddin Butt* 1 | Salman Ghafoor 3 | Mohammed El-Hajjar 4 1 Department of Electrical and Computer Engineering, COMSATS University Islamabad, Islamabad, Pakistan 2 Department of Physics, COMSATS University Islamabad, Islamabad, Pakistan 3 School of Electrical Engineering and Computer Science, National University of Sciences and Technology (NUST), Islamabad, Pakistan 4 School of Electronics and Computer Science, University of Southampton, Southampton, United Kingdom Correspondence *Muhammad Fasih Uddin Butt, Department of Electrical and Computer Engineering, COMSATS University Islamabad, Islamabad, Pakistan. Email: fasih@comsats.edu.pk Present Address Department of Electrical and Computer Engineering, COMSATS University Islamabad, Islamabad, Pakistan Summary In this paper, a full duplex Millimeter Wave (mm-wave) enabled Radio-over-Fiber (RoF) architecture is proposed for Distributed Antenna Systems (DAS). This archi- tecture is capable of achieving transmission of 16 × 16 optical Multiple Input Multiple Output (MIMO) spatial streams at 12 Gbps per spatial stream by employ- ing Wavelength Division Multiplexing (WDM) and exploiting its other degrees of freedom such as polarization states and modes of wavelengths. A single laser source based multi-wavelength comb and wavelength reuse techniques along with Plastic Optical Fiber (POF) are employed to make the proposed architecture cost efficient. Optical heterodyne detection is performed at the Radio Access Unit (RAU) to gen- erate mm-wave carrier frequency at 60 GHz. Channel equalization is achieved for Pulse Amplitute Modulation (PAM-4) data signal by employing Least Mean Square (LMS) equalizer to mitigate the optical fiber channel effects. Our proposed system supports 16 × 12 Gbps for Downlink (DL) and Uplink (UL) transmissions. To eval- uate the performance of the proposed system, we compare the receiver sensitivities at FEC limit of 3.8 × 10 -3 of Bit Error Ratio (BER) of Back to Back (B2B) system, employing no fiber effects, with its counterparts. We show that acceptable power penalties for the fiber lengths of 200 meter and 400 meter are achieved for both LP01 and LP11 modes in DL and UL directions. KEYWORDS: Radio-over-Fiber, Distributed Antenna Systems, Wavelength Division Multiplexing, Plastic Optical Fiber, Radio Access Unit, Millimeter Wave 1 INTRODUCTION In recent years, the demand for higher bandwidth and data rate has been increasing exponentially. It has been reported by CISCO that by the end of year 2021, there will be 27.1 billion network devices and 4.6 billion internet users 1 . To meet this unabated demand in future communication networks, several enabling technologies which include, but are not limited to, massive Mul- tiple Input Multiple Output (MIMO) 2 , Millimeter Wave (mm-wave) communications 3 , cell densification such as Distributed 0 Abbreviations: MMG, MultiMode Generator; MF, Mode Filter; PS, Polarization Splitter; PC, Polarization Coupler; MZM, Mach-Zehnder Modulator; OC, Optical Coupler; OS, Optical Splitter.