Double‐RSOA colorless WDM‐PON for 5G fronthaul applications

The introduction of 5G mobile systems poses significant challenges to the design of the fronthaul structure. The dense coverage, comprising several small cells operating in the millimeter‐wave range, with an enormous number of antennas, makes conventional digital‐radio‐over‐fiber unfeasible. On the other hand, the centralized architecture of the optical fronthaul is well‐suited for the passive optical network (PON) topology, with WDM‐PON as a strong contender due to its capability to establish logical point‐to‐point optical links to each cell site. However, the large‐scale deployment of WDM‐PON requires the availability of colorless transmitters, where the same hardware is able to generate any wavelength needed by the network. In this context, this paper investigates an analog fronthaul configuration over a colorless WDM‐PON for 5G and beyond, employing the techniques of self‐seeding in the downlink and carrier reuse in the uplink. We numerically evaluated the EVM when transmitting 1.25 Gbps at 3.5 GHz and 10 Gbps at 26 GHz in a 20 km optical link. The results are within the 3GPP requirements, demonstrating the feasibility of the proposed fronthaul. The introduction of 5G mobile systems poses significant challenges to the design of the wireless fronthaul. The dense coverage, comprising several small cells operating in the millimeter‐wave range, with a very large number of antennas, makes conventional digital‐radio‐over‐fiber unfeasible. On the other hand, the centralized architecture of the optical fronthaul is well‐suited for the passive optical network (PON) topology, placing wavelength division multiplexing PON (WDM‐PON) as a strong contender, due to its capability to establish logical point‐to‐point optical links to each cell site. However, the large‐scale deployment of WDM‐PON fronthauls requires the availability of colorless transmitters, where the same hardware can generate any wavelength demanded by the network. To solve this problem, this paper proposes an analog‐radio‐over‐fiber fronthaul topology operating on a colorless WDM‐PON for 5G and Beyond applications. We use the self‐seeding technique on the provider side and the carrier reuse scheme on the antenna side to ensure a fully colorless network. We also combine two cascaded reflective semiconductor optical amplifiers (RSOAs) to improve transmission efficiency. The proposed setup was evaluated utilizing computational simulations calibrated to experimental data. The results show that our fronth