Fiber Chromatic Dispersion Effects of Broadband mm-Wave Subcarrier Optical Signals and Its Elimination

The millimeter-wave (mm-wave) frequency band offers the free-space bandwidth necessary for future broadband wireless communications services. A high-capacity broadband wireless network can be the quickest and most cost-effective method of delivering services to a large number of customers in a dense environment. Millimeter-wave optical fiber links can effectively distribute mm-wave signals from a central office to remote antennas located at suitable vantage points for line-of-sight interconnection to other nodes of the network. As described in [112], these fiber links offer simplification of base stations and centralized control and stabilization of mm-wave carrier signals for conformity to FCC standards. Even though it is expected that this type of fiber systems will take advantage of legacy metropolitan fiber cable plant infrastructure at the dispersion minimum of 1,300 nm. The low fiber loss and availability of optical amplifiers at 1,550 nm can extend the central office coverage over a much larger service area than 1,300 nm links. Therefore it is still important to understand how dispersion in a fiber link can affect the transmitted information on mm-wave subcarriers. The effects of fiber chromatic dispersion on a single carrier have been examined in [113, 114]. A two-tone analysis was done in [115]. Because future broadband high-capacity services will have many digital channels, a multiple-channel analysis is needed. A CATV band simulation was reported in [116]. This chapter explores the effects of fiber chromatic dispersion on broadband 18 channel mm-wave sub-carrier multiplexed (SCM) transmission. Instead of studying a particular digital QAM format, the study here concentrates on the fundamental limits due to chromatic dispersion-induced carrier degradation and intermodulation distortion at mm-wave frequencies. Transmission of multichannel mm-wave signals over single-mode fiber will also be limited by the optical link noise contributions from the receiver, laser RIN, and fiber amplifiers.