Bidirectional radio-over-fiber link employing optical frequency multiplication

We propose a bidirectional radio-over-fiber link consisting of an optical downlink transmission employing the optical frequency multiplication principle, a remote local oscillator (LO) generation, a remote down-conversion of the radio-frequency uplink signals, and an optical uplink transmission employing intensity modulation-direct detection. Experiments demonstrate the optical up-conversion of 64-level quadrature amplitude modulated radio signals to 17.8 GHz after transmission over 4.4 km of multimode fiber, 12.5 and 25 km of single-mode fiber in the downlink; the uplink performance is evaluated in terms of down-conversion loss employing the optically generated LO.

I. Introduction

Radio-Over-Fiber (RoF) distribution antenna systems have been long recognized as a flexible, bandwidth-efficient, and cost-effective option for fiber-based wireless access infrastructure, especially in in-building and corporate environments [1]. Fig. 1. Bidirectional RoF link employing OFM. They enable the consolidation of the radio access control and signal processing at a centralized control station (CS) and the delivery of the radio signals transparently to simplified antenna sites (AS) via optical fiber. When deployed in current cellular access networks, direct modulation of a laser diode with the radio-frequency (RF) signal is the most common method to reduce cost and complexity, rather than external modulation [2]. Also for the popular wireless local area network systems, experiments with transmission over multimode fiber (MMF) have been carried out [3].