Fiber-optic 40-GHz mm-wave link with 2.5-Gb/s data transmission

A broad-band millimeter-wave (mm-wave) transmission link for downstream transmission is investigated. The mm-wave carrier is created by a dual-frequency optical source based on suppressed-carrier double-sideband modulation of a narrow linewidth laser. The optical sidebands generated in the modulation are divided into two separate fibers by filtering with fiber Bragg gratings. One of the waves is modulated with baseband data up to 2.5 Gb/s. The fibers are combined and connected with the base station (BS) via a single-mode fiber. At the BS, the mm-wave modulated signal with data is created with a wide bandwidth photodetector through heterodyne mixing of the two optical waves. This mm-wave signal is amplified and transmitted to the mobile unit, where the reception is performed using self-homodyne mixing, in order to ensure carrier frequency independence. Error-free data transmission was demonstrated for the downlink after 44 km of single-mode optical fiber.