Harmonic components and dispersion of mobile network signals due to fiber-optical transmission

Several system applications require optical transmission of very high bit-rate digital as well as microwave and millimeter-wave carrier signals. Without completeness, a few recent applications are mentioned such as: 5G and Radio-over-Fiber (RoF) systems, Gigabit Passive Optical Networks (GPON), optical interconnection within Cloud for telecommunication Network Elements (NE), upgrade of mobile access, backhaul and core networks (NW) or phased array and antenna beamforming applications. Both chromatic dispersion and harmonic distortion result in unwanted limitations in the maximum distance and bandwidth. Dispersion penalty has been widely investigated in fiber-optical links transmitting microwave or millimeter-wave signals. However, less attention is addressed to the effect of the harmonics of the modulating fundamental electrical signal. This paper presents some theoretical and experimental results estimating the level of harmonics during the optical transmission.