Simplified Coherent Receiver for Analogue Radio Transmission Over High Optical Budgets

The bandwidth and latency demands driven by 5G wireless networks are putting a focus on analog radio-over-fiber techniques as a promising candidate for broadband optical fronthauling. In contrast to intensity modulation / direct detection systems, as they are commonly adopted for mobile fronthaul links due to their simplicity, we are exploring a migration option towards coherent radio-over-fiber transmission. A simplified coherent homodyne receiver based on an electro-absorption modulated laser is co-integrated at the die-level with a transimpedance amplifier and evaluated for analogue coherent radio-over-fiber transmission. This low-complexity homodyne receiver can unlock channel selectivity and high receiver sensitivity inherent to coherent detection, but without the need for digital signal processing. We will demonstrate a sensitivity that allows for an optical budget of 42 dB, and thus eases the fixed-mobile convergence in power-splitting fiber plants. We further show filterless radio signal reception in presence of modulated adjacent channels. Signal integrity is confirmed through transmission of orthogonally frequency multiplexed radio signals with 16-point quadrature amplitude modulated formats, with an error vector magnitude below the corresponding antenna limit.