Distance and bandwidth enhancement of fiber optic transmission

The optical wavelength required to obtain gain from Erbium Doped Fiber Amplifiers is in the 1550 nm range. The vast majority of fiber links in place today have a chromatic dispersion minimum for a wavelength around 1300 nm. High bit rate transmission at 1550 nm through long sections of this fiber results in pulse broadening which ultimately corrupts the signal and therefore imposes a transmission distance limitation. Techniques that reduce the impact of chromatic dispersion are required to achieve further distances.;Duobinary coding to reduce transmission bandwidth, chirped transmission using a Mach-Zehnder external modulator, and optical multiplexing and demultiplexing based on signal polarization orientation are three techniques that are shown to significantly increase chromatic dispersion-limited transmission distance. Both electrical multiplexed and Optical Time Division Multipiexed (OTDM) externally modulated transmitters are experimentally studied to determine the impact of dispersion on eye closure and receiver sensitivity. The degradation of receiver sensitivity with distance is reported as a chromatic dispersion penalty. Simulations are also performed to compare the obtained waveform plots.;Electrically multiplexed transmitter studies focus on duobinary coding and chirped transmission. Compared to binary signaling over increasing distance, binary transmission with duobinary reception is shown to reduce dispersion penalties above 2.8 dB for zero chirp transmission, and above 0.6 dB for chirped transmission. For zero chirp transmission, duobinary reception increases transmission distance by 44% (108 km versus 75 km) for a 5 dB penalty. For chirped transmission, it increases transmission distance by 13% (156 km versus 138 km) for a 3 dB penalty.;OTDM transmitter studies focus on duobinary coding and polarization multiplexing and demultiplexing. A novel parallel duobinary encoder is presented. Receiver sensitivity data is not reported for duobinary coding because of performance limitations of components. Polarization multiplexing and demultiplexing are shown to at least double the maximum transmission distance of a 10 Gb/s OTDM transmitter (50 km with 4.5 dB penalty versus 100 km with maximum of 2.2 dB penalty). The maximum operation speed of any component in this polarization-based system is one half the speed required for electrical multiplexing and demultiplexing.