Radio over fiber in multimedia access networks

Dominant broadband access technologies today are Digital Subscriber Line (DSL) and hybrid fiber coaxial (HFC) networks. DSL leads, with global subscribers exceeding 100 million, while cable-modem subscribers worldwide total 55 million in 2005 [1]. Recently, fiber-to-the-home (FTTH) and fiber-to-the-curb (FTTC) scenarios are also on the rise. In all these access networks, optical fiber plays an imperative role. Fiber carries multimedia signals such as video, audio and Internet data with a combination of subcarrier multiplexed radio over fiber (SCM-ROF) and digital baseband formats. Despite the IPTV hype, the most bandwidth hungry video (especially HDTV) is predominantly transmitted in SCM-ROF format. In addition, wireless broadband multimedia access using the ROF technique is also on the rise. Newly released 71-76 GHz, 81-86 GHz, and 92-95 GHz bands for wireless multimedia delivery will trigger wide deployment of ROF technology. Therefore, ROF plays key role in both wired and wireless broadband multimedia access networks [2]. However, there are number of issues in the design and deployment of ROF links for multimedia access. Nonlinearity of the optical modulator (either direct or external); loss due to electrical-optical-electrical conversion and increasing intensity noise are key concerns. Some of our recent work involves with adaptive digital nonlinearity and noise cancelation [3], optical domain reduction in unmodulated carrier [4] and all optical de-multiplexing of closely spaced RF signals by Bragg grating filters [5] and multi system signals over fiber.