| RoF (Radio over Fiber) technique belongs to microwave photonics and uses analogue fiber links to transmit and distribute microwave/millimeter wave signals. It integrates the techniques of optical communications and wireless communications, and act as important role in fields of wireless communication, intelligent road vehicle communication, broadband wireless access networks and military, etc. RoF has been a hot research field in the world. In this thesis, several critical problems in RoF systems, such as microwave/ millimeter-wave all-optical generation, microwave frequency up/down conversion with signal transmission, design of RoF architecture, and application of wire and wireless signals transmission are researched. The main contents of the dissertation are as follows:(1) All-optical frequency up-conversion in RoF system based on cross-phase modulation in a high nonlinear dispersion-shifted fiber is proposed. The numerical calculated results show that 40 GHz pulse pump beam at wavelength 1.54μm can makeweak signal with wavelength of 1.56μm split and generate two adjacent one-ordersidebands because of the modulation instability induced by cross-phase modulation. The carrier and sidebands are 40 GHz spacing and the phase differences are invariable. The pulse width, power of the pump beam and fiber length has great impact on the power difference of the carrier and sideband. The simulation results verify the above principle and 2.5 Gb/s data signal is up-converted into 40 GHz millimeter-wave. The optimized fiber length and pump power are 600m and 17 dBm respectively.(2) Simultaneous all-optical frequency down-conversion technique based on cross-phase modulation in a high nonlinearity dispersion-shifted fiber (HNL-DSF) is proposed and verified by simulation, and its application to a wavelength-division-multiplexing (WDM) radio over fiber is also proposed. Error-free simultaneous all-optical frequency down-conversion of the 16 WDM RoF upstream channels is achieved. We propose the idea of down-conversion and give the up-link schematic diagram of CS and BS. The converted characteristic and transmission performance are studied. We have verified by simulation that sixteen WDM optical RF signals that carry 2.5Gb/s ASK data at 44 GHz are well simultaneously down-converted to 4GHz based on XPM in a HNL-DSF. All 16 wavelengths show almost identical performance. A proper LO power is between 21 dBm and 26 dBm and too large LO power will results in extra nonlinear effects. The simulated results show the performance of WDM signals is in good accordance with a single signal without any interference, and the power difference of two beat frequencies of the down-conversion signal is independent of the optical local oscillator power. The optimum length of the HNL-DSF is between 200m and 300m. The wavelength span of larger than 20 nm for down-conversion signal can be obtained. Results indicate that the scheme has very good conversion performance at a very high data rate and can provide a very useful solution for more wavelength channel applications at all bands without any interference and saturation limitation in RoF systems.(3) We propose a novel RoF architecture to reduce the system cost at both central office (CO) and base station (BS). In this architecture, the concept of multi-channel full-duplex is proposed first time. Multi-channel which share a single light source in CO can reduce the system cost. By incorporating frequency conversion based on cross-phase modulation in HNL-DSF and optical filtering techniques in CO, 60 GHz DWDM optical millimeter wave carriers are generated with four times frequency of the local oscillator signal. The BS is simplified by using the separated optical carrier along with downlink mm-wave signals to carry the upstream data. The bidirectional full-duplex 2.5 Gb/s data is successfully transmitted over 40 km standard single-mode fiber (SMF). The power penalty for the down-link data after transmission over 40 km SMF is smaller than 0.6 dB, while for the up-link data, the power penalty after transmission over 40 km SMF is neglected. The system has the capacity to generate much high frequency mm-wave.(4) A novel full-duplex RoF system using a single light source at central station (CS) is proposed and demonstrated. The scheme is employed to generate 40 GHz optical millimeter-wave at CS for downlink transmission by using a semiconductor optical amplifier based on cross-gain modulation and optical filtering technique. Baseband signal of the down-link data is only modulated on one of the optical carrier sidebands while the up-link data will be modulated on optical carrier in the base station and sent back to the CS. Additionally, in course of frequency up-conversion, base-data are not converted between the different wavelengths, so degradation of extinction ratio is avoided and the merits of this way are fully made use of. The bidirectional full-duplex 2.5 Gb/s data is successfully transmitted over 40km standard single-mode fiber (SMF). The upstream channel is less than 0.5 dB power penalty and the downstream channel is 3.5 dB power penalties. This system shows good performance over long-distance delivery and has important applicable value in high radio frequency sector and multi-channel full-duplex system.(5) Simultaneous generation of wired and wireless signals RoF system is proposed and demonstrated. The scheme generates double-side band signal by using a phase modulation. After separating the spectra of the upper sideband, the lower sideband and the carrier, baseband data at 2.5 Gb/s of the wireless signal is only modulated on one of the optical sidebands while the wired data at 10 Gb/s is modulated on the optical carrier by common intensity modulator, respectively. The transmission performance of the two signals is analyzed. Fiber dispersion only leads to the time shift of the baseband data carried by millimeter-wave, while there is not code interference between the upper and lower sidebands. The two signals are successfully transmitted over 50km SMF. Power penalty is less than 1 dBm. The results show that this system is suitable for long-distance delivery and can deliver super-broadband services serving both stationary and mobile users.
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