## 1 Introduction
The concept of evolving optical transport networks in order to support multiple traffic streams that are addressed for varying radio terminals has been explored in [9]. More specifically, the use of optical networking segments to setup and orchestrate the BBU-DU-RU interconnection has been recently discussed through the literature as a practical solution for the support of active functionalities across the optical edge of mobile networks [10; 11; 12; 13]. At the same time, the exploitation of optical switching-enabled hybrid transport layouts that are handling standardized legacy traffic has been showcased in [3; 13; 14; 15], including, for example, the concurrent transmission of multiple CPRI lanes in [13] or the co-existence of 5G, passive optical network (PON) and datacenter (DC) traffic in [3]. Inspired by these works, similar architectures could accommodate reconfigurable fiber and fiber-wireless (FiWi) transport architectures, relying on the flexible point-to-multipoint (PtMP) connectivity of both analog and digital centralized transceivers with variable radio units, located anywhere in the field. During the past years, the adoption of new fiber transmission schemes along the standardDigital-Radio over Fiber (D-RoF) solution has been explored in lab-scale experiments targeting the demonstration of mixed analog and digital formats' propagation over shared fiber infrastructure [9] aiming to show the benefits of hybrid A/D-RoF fronthauling. In this direction, [12] discusses the employment of an Arrayed Waveguide Grating Router (AWGR)-enabled PtMP transport topology, aggregating and steering A-RoF traffic to the radio units. Although these experiments highlight the potential adoption of beyond-CPRI schemes in multi-tenant transport networks, the actual integration of these solutions, employing both standard and analog optical transceivers, in a mobile core network as well their seamless operation in true mobile services is far beyond their scope. At the same time, the employment of traffic-transparent optical networking units to host such hybrid transport architectures has scarcely been reported in the literature. In this paper, we present a hybrid transport system architecture comprising both standardized and beyond-CPRI mobile transport segments via a reconfigurable wavelength aggregation optical node. The demonstrated architecture focuses on the accommodation of heterogeneous mobile traffic streams stemming not only from standard digital optical transceivers but also from a custom Fully Programmable Gateway Array (FPGA)-based A-IFoF transceiver within a transparent optical layout. The mixing of legacy and currently evolving transport technologies was achieved via a software defined networking (SDN)-enabled node supporting spatial-spectral flexible switching functionalities. The employed hybrid optical node enabled the co-integration of four individual network segments, some of them carrying real-world application services, after the integration of the demonstrated setup into the mobile network operator (MNO)'s infrastructure. The MNO's equipment was interconnected through the CPRI interface and it enabled the delivery of services over mobile phones, including 4K video streaming and Internet Protocol (IP) calls over both fiber and converged fiber-wireless paths. Finally, the successful operation of the presented topology was verified via physical layer performance evaluation metrics including the acceptable EVM values for complex radio waveforms and error-free operation of the binary optical streams. The remainder of the present manuscript is structured as follows: Section 2 introduces the concept of the Wavelength Selective Switch (WSS)-enabled hybrid node and the architecture of the proposed dynamically reconfigurable transport network segment, while Section 3 presents the implementation of a converged Fiber-Wireless (FiWi) fronthaul layout, based on the development of a real-time A-IFoF transceiver.