Study of ultrashort-pulse code-division multiple-access scheme for fiber-optic communications and its hybrid spectral overlay with wavelength-division-multiplexing technique.

摘要

This dissertation demonstrates and extends the technical feasibility of spectral phase encoding/decoding based ultrashort-pulse optical code-division multiple-access (CDMA) scheme for local-area and metropolitan-area fiber-optic communications. The ultrashort pulse CDMA technique not only provides a unique multiplexing possibility on its own, but also complements other multiplexing approaches, in particular optical wavelength-division-multiplexing (WDM) technique. This thesis work includes both device and system level studies. At the device level, a femtosecond fiber laser was constructed as a broadband source for CDMA experiments. The complete dispersion compensation for distortion-less transmission of 400-fs pulses over a 10-km fiber link was achieved through the use of a dispersion compensating fiber and a femtosecond pulse shaper. The accumulated fiber nonlinearity during ultrashort-pulse propagation was investigated to facilitate power budget analysis in CDMA data transmission. At the system level, the bit-error-rate performance of a CDMA channel under multi-access interference was evaluated. The possibility of error-free CDMA operation in a multi-user environment was demonstrated. The feasibility of spectrally overlaying CDMA on WDM for the hybrid WDM/CDMA operation was also investigated through back-to-back system measurements.