-The performance of optical carrier suppression (OCS) radio over fiber (RoF) system is evaluated through tuning the modulation index of Mach-Zehnder modulator, and two different data modulation schemes are considered. The quantitative simulation results validate that there exist an optimum modulation index, and the system performance could be improved if the data signal is modulated on only one of two sidebands.

The spectral efficiency and bit-error-rate (BER) of phase encoding optical code division multiple access (OCDMA) systems is evaluated, coherent time-spreading (TS) and spectral phase encoding (SPE) OCDMA systems are considered. The results indicate that SPE-OCDMA has better tolerance to performance degradation due to receivers bandwidth limitation than TS-OCDMA system, while for the practical en/decoders with implementable longest code length, TS-OCDMA can yield a spectral efficiency advantage over SPE-OCDMA systems.

The quantum-confined Stark effect on the optical absorption of intersubband transitions in an asymmetric AlxGa1-xN/In0.3Ga0.7N/GaN quantum wells is investigated by means of the density matrix formulism. The built-in electric field generated by the piezoelectric and spontaneous polarizations competing against to the external electric fields is considered. As the result, the influences of the built-in and external electric fields on the energy potentials and the eigen stares are discussed in detail. When the positive external electric field is applied, the peak values of the absorption coefficients from 3-2, 2-1 and 3-1 transitions are reduced and moved to the lower photon energy levels. With the negative field, the exactly opposite results can be obtained. Moreover, it is indicated that the results of the wavelengths from the 3-2, 2-1 and 3-1 transitions are reduced by the positive external electric field and increased by the negative field.

The effect of the modulation index of Mach-Zehnder modulator on single sideband (SSB) radio over fiber (RoF) system is investigated, and two different data modulation schemes are considered. The quantitative results suggest that there exist an optimum modulation index, and the system performance could be improved if the data signal is modulated on only optical carrier or sideband.