Study On Radio-over-Fiber System Based On Optically Injected Semiconductor Laser Technology

With the development of high-speed large capacity fiber-optics transmission andtechnology breakthroughs in all-optical network, next generation mobile communication hasgradually developed into an combined system with wireline and wireless communications, aswell as an connected system with fixed and mobility links. As a newly developed widebandaccess network candidate, radio-over-fiber (RoF) has attracted much attention nowadays,which integrated the broadband of (?)ptical fiber transmission and the mobility of wirelesscommunication. Based on the Period one (P1) nonlinear dynamics of optically injected lasersystem, power penalties and signal distortions induced by fiber dispersion and nonlinearities,and the optimization techniques from both of the modulation schemes, coding famats of theRoF signal and optical fiber transmission link are studied in this dissertation. It is oberservedthat the power fluctuation of the radio frequency (RF) at the basestation, due to dispersion fordouble-side-band (DSB), and induced by fiber nonlinearities for single-side-band (SSB) andoptical-carrier-suppression (OCS) RF modulation schemes, are drastically decreased. Aencoding format for data frequency modulation (FM) is proposed to further improvetransmission properties. "One-for-many" scaled translational symmetric compensationsystem is presented and posterior Wiener filtering is applied in high-speed and large capacityfiber-optic transmissions to compensate for the comibined effects of fiber dispersion, intraandinter-channel nonlinearities, and the parametric amplified noise effectively.By introducing Runge-Kutta solutions to numerically solve the coupled rate equations ofoptically injected laser system, the nonlinear dynamic properties with one-beam injection aredemonstrated. Based on which, the output optical spectrums with dual-beam injection areinvestigated. Weak low frequency and strong high frequency injection can generate subcarrierwaves periodically on the P1 state obtained by single high frequency injection. Thus providesmulti-channel optical carried RF to obtain division multiplexing (WDM) RoF signals. Stronglow frequency and weak high frequency injection will increase the RF frequency and broaden the range of its P1 state, which supplies wide data bandwidth for the fixed injection frequency.Meanwhile, it also gives a novel idea for generating optical carried high-speed data signals.Frequency response method is appled to derive the photodiode current analyticalexpressions of RF obtained at the basestation with fiber dispersion effect, where single cosinedata input; DSB, SSB and OCS RF modulations, Amplitude modulation (AM) and FM datamodulations are considered under subcarrier modulation. The numerical simulations of thetransmission properties of each modulation schemes mentioned above are conducted based onsolving nonlinear Schr(o丨¨)dinger equation (NLSE) by using of split-step Fourier method. It isshown that AM signals with each RF modulation schemes have serious optical spectrumbroadening than the corresponding FM signals due to fiber nonlinearities. The amplitudefluctuation of the sending power at the basestaion can be changed by data modulation depths,and the fluctuation periods of each modulation signals can be controlled by fiber dispersioncoefficient and the RF frequency.The transmission properties of data coding formats of return to zero RZ, non-return to zeroNRZ and the differcial phase shift keying RZ-DPSK in RoF system are demonstratednumerically for AM, FM modulation with DSB, SSB and OCS RF modulation schemes. Thecomparisons of optical spectrums between the input and output fiber transmission signals andpower penalty curves show us that RZ-DPSK is more tolerant to fiber nonliearities with thesmallest spectum broadening, while RZ has the best immunity to fiber dispersion with thesmallest fluctuation amplitude. In addition, FM has better system performance than AM foreach coding format with the same system parametrers. However, for FM, different datasymbols have different RF subcarrier frequencies, which introduce different fluctuationperiods for the recovery data at the end users. In order to avoid such discord, FM withnegative voltage encoding format is applied in RoF system to optimize eye opening penalitiesof the recovery data.Based on the transfer function of fiber dispersion and the first-order perturbation solutionof NLSE, the principle requirements for dispersion and nonlinearities compensation inOptical phase donjugation (OPC) transmission line are obtained, respectively. The RoFsystem using the OPC compensation fiber transmission line is numerically simulated. It isnoticed that the power penalties and eye opening penalies in the first half fiber can bereversed by the second half fiber transmission symmetrically, which is tansparent to themodulation formats of the input signal. Besides, the scaled mirror symmetric and translational symmetric compensation systems by using of OPC are proposed for high-speed, largecapacity fiber transmission lines. Mirror symmetric power distribution about OPC is neededto set up a scaled mirror symmetric compensation line to reach exact compensation, whichcan be realized by distributed amplifying fibers, and the two portions of fiber has the samesign dispersion coefficients. By using of two transmission fibers with opposite signdispersions, scaled translational symmetric compensation system can realize the first-ordernonlinearity compensation. By taking advantage of the additivity of first-order nonlinearperturbations, "one-for-many" compensating fiber spans transmission lines with scaledtranslational symmetry is presented. One span of a highly-nonlinear type can compensateseveral fiber spans of another type with weaker nonlinearity up to the first-order perturbationsPosterior Wiener filtering is applied to decrease the parametric amplified noise inducd byinline amplifier noises and fiber nonlinearities. The nonlinear phase noise can be eliminatedto a large extent by the adaptive filters.The overall results of this dissertation illustrate that the proposed signal modulationencoding formats and fiber transmission optimization methods can improve RoF transmissionperformance and reshape signals. This related study has significantly theorical and practicalvalue for exploring wider transmission bandwidth and increasing the system capacity.