A simplified coherent-detected radio-over-fiber link with intensity and phase modulation and simple digital phase noise cancellation

Abstract

Reducing the complexity and the cost is the key to introducing high-performance coherent technologies into practical radio-over-fiber (RoF) links. In this paper, we propose a coherent-detected RoF link with low-complexity optical configuration and a light digital signal processing (DSP) unit. Based on a dual-parallel Mach–Zehnder modulator (DP-MZM) at the transmitter, the amplitude and phase of a light wave are modulated to achieve spectral-efficient use of the optical source. After transmission over a single optical fiber, the modulated signals are coherent-detected at the receiver by being interfered with an independent local oscillator laser and then are demodulated digitally. Compared with other two-optical-source coherent-detected RoF links, our proposed scheme can accomplish dual-channel RF signal transmission albeit with halved optical configuration. Additionally, the DSP algorithm to get rid of the laser phase fluctuation between two lasers is simple and efficient. An experimental demonstration is done. Two 16-QAM microwave vector signals at the same symbol rate of 50 Msymbol/s are transmitted over 25-km single mode fiber (SMF) and the error vector magnitudes (EVMs) of 3.15% and 3.53% are obtained respectively. To explore its potential, two 64-QAM microwave vector signals are transported with similar conditions and the measured EVMs are 4.05% and 5.88%, respectively.