Broadband radio-over-fiber link based on high-speed optical modulator for multi-band millimeter-wave radio

We demonstrated a broadband millimeter-wave signal delivery system over an optical fiber using a high-speed optical modulator. The high spurious-free dynamic range of the system is capable of high-capacity radio signal transport.

The development of high-speed wireless link technology to enhance the availability of broadband access services is an emerging topic. Currently, only the wireline communication technology such as the optical fiber link is capable of signal delivery with a capacity greater than 10 Gb/s. Moreover, a recently developed optical fiber link technology has achieved a 100-Gb/s capacity using a single carrier and a single fiber. On the other hand, in an advanced radio communication in the microwave band, the capacity has been limited to much lower than 10 Gb/s because of its narrow range of available bandwidths. The millimeter-wave (MMW) radio communication is a promising candidate for high-speed wireless access because of its broad bandwidth. In particular, in the 60-GHz band, the IEEE 802.11ad standard has been set as the MMW wireless local access network with its available bandwidth of 7 GHz in the Industry-Science-Medical band [1]. In addition, multi-band MMW radio prescribed by the IEEE 802.11aj standard, which simultaneously uses the 45- and 60-GHz frequency band, requires broad-bandwidth signal transmission [2]. However, the atmospheric attenuation coefficient at 60 GHz is much greater than 10 dB/km, and thus, these MMW radios are capable of short-or middle-range transmission. Therefore, an optical extension link using a radio-over-fiber (RoF) technology is indispensable for simultaneous distribution of the radio signals at these bands [3]. In this study, we propose and demonstrate a broad-bandwidth RoF link with a high-speed optical modulator and an optical bandpass filter (OBPF) to form a single-sideband (SSB) signal [4]. Fig. 1. Schematic of the broad-bandwidth RoF link configuration. (b) Obtained optical spectra at 40.5, 47, 57, and 66 GHz.