Evaluation of radio-over-fiber link for 45-GHz- and 60-GHz-band simultaneous transmissions

The demand for a high-capacity radio link is an emerging issue to enhance the availability of broadband access not only on wireline (optical) but also on wireless (radio) links. In fact, a recently developed optical technology achieves 100-Gb/s capacity with a single carrier; however, advanced radio communication in the microwave region limits its capacity to 1 Gb/s. Therefore, a high-capacity radio link with a high-frequency carrier is highly demanded and is being developed rapidly. A millimeter-wave radio communication technology developed on the basis of the IEEE802.11ad standard at the 60-GHz band is one of the possible solutions to increase the radio link capacity; however, its high atmospheric attenuation limits the transmission distance to several tens of meters [1]. Therefore, a high-capacity interconnection between the service areas is necessary to expand the service areas. A radio-over-fiber (RoF) technology is a promising method to connect the radio access units (RAUs) via an optical fiber with a low loss feature, and the demonstration of the principle of RoF signal transmission at the 60-GHz band has already been reported [2, 3]. The recent progress in the IEEE802.11aj standard, which focuses on the radio standards in China, has achieved a high-capacity link at the 60-GHz band as well as at the 45-GHz band [4]. Thus, simultaneous transmissions at the millimeter-wave band are required; however, the evaluation results of the IEEE802.11aj RoF transmission could not be obtained owing to its broadband feature. In this study, we have evaluated 45-GHz- and 60-GHz-band simultaneous transmissions with an extremely high-bandwidth RoF transceiver.