**Abstract**

Wireless networks applications of 5G and beyond require high throughput and high capacity. To achieve this, a macro cell is split into several small cells. When using Free Space Optics (FSO) some of the small cell base stations (BSs) which are located at the edges of a macro cell may not directly communicate with the base station of that macro cell, resulting in high outage probability (OP) and average bit error rate (ABER). Therefore, there is a need to develop a new system model to improve the OP and ABER performance. For such scenarios, triple-hop (TH) hybrid free space optics/millimeter wave (FSO/mmW) system has been proposed by considering neighboring small cell BSs as intermediate relays to forward the backhaul data. The OP and ABER of the proposed TH hybrid FSO/mmW system are derived for various channel conditions and are further verified by performing Monte-Carlo simulations. In this work, FSO link is modeled by Gamma-Gamma distribution over weak and strong turbulence channel conditions. Further the mmW link is modeled by using Nakagami-m distribution which perfectly models various fading scenarios.

**Keywords:** free space optics, millimeter waves, triple-hop, outage probability, average bit error rate, gamma-gamma, Nakagami-m
