Study On Simultaneous Transmission Of Millimeter-Wave And UWB Signals In RoF System

Radio-over-fiber (RoF), millimeter-wave and Ultra Wide Band (UWB) are fast developing wireless access technologies. With the advancement of access network technology, services are becoming complex, and bandwidth is increasing. Merging of different access networks makes use of advantages of each access method, and makes access more flexible and more efficient. For these reasons, this paper studies on simultaneous transmission of millimeter-wave and UWB signal in RoF system.Two novel schemes are proposed for millimeter-wave generation and up conversion in optical domain. Both principle analyzing and experimental validation are performed. The first scheme uses only one dual parallel Mach-Zehnder modulator (DPMZM) to generate optical single-sideband millimeter-wave signal employing frequency quadrupling. 40 GHz optical millimeter-wave with 1 Gb/s pseudorandom bit sequence data is generated, whose power penalty is only 0.8 dB after transmission through 20 km single-mode fiber (SMF). The second scheme uses two cascaded MZ modulators to generate optical single-sideband millimeter-wave signal employing frequency quadrupling. 40 GHz optical millimeter-wave with 1 Gb/s pseudorandom bit sequence data is generated, whose power penalty is only 0.7 dB after transmission through 20 km single-mode fiber.Two novel schemes are proposed for UWB generation in optical domain. Both principle analyzing and experimental validation are performed. The first scheme uses two parallel MZ modulators to generate UWB monocycle pulses without using electrical pulse source. UWB signal with 1 Gb/s pseudorandom bit sequence data is generated, whose 10 dB bandwidth is about 6 GHz. The second scheme uses only one MZ modulator to generate UWB doublet pulses. UWB signal with 1 Gb/s pseudorandom bit sequence data is generated, whose 10 dB bandwidth is about 7 GHz. A RoF experimental system is designed and built, in which millimeter-wave and UWB signal transmit simultaneously on the same optical wavelength. Millimeter-wave and UWB signal both carry 1 Gb/s pseudorandom bit sequence data. The center frequency of the millimeter-wave is 40 GHz, and the 10 dB bandwidth of UWB signal is 7 GHz. Crosstalk between the millimeter-wave and UWB signal is within tolerance. The power penalty of millimeter-wave is 0.7 dB after transmission through 20 km single-mode fiber and is 2.3 dB for the crosstalk of UWB signal.The RoF system above has a low requirement for microwave components, a high tolerance for chromatic dispersion of fiber, and a high efficiency of optical spectrum utilizing. This system is therefore practicable and potential.