Ultrahigh Capacity Fiber-Optic Transmission Systems

Doktorsavhandling, 2001

The subject of this thesis is ultrahigh capacity optical communication systems. Such systems will use a combination of techniques for dense wavelength-division multiplexing (D-WDM) and ultrahigh speed all-optical time-division multiplexing (O-TDM). The work may be separated into two parts; the first part aims at ultrahigh bit-rate applications involving clock-recovery and high speed O-TDM field transmission experiments. Two single channel field experiments with line rates of 40 and 80 Gbit/s over 400 and 172 km respectively are demonstrated using soliton pulses environment. The reported line rate of 80 Gbit/s was the first single channel transmission experiment above 40 Gbit/s over installed fiber. Furthermore, nonlinear crosstalk due to four-wave mixing in D-WDM systems are studied under the influence of PMD. The second part deals with a novel type of amplifiers based on fiber optical parametric amplification. One important feature of these amplifiers is that they may be tailored to operate at a specific wavelength and they may thus open up new, previously unused, transmission bands. A cw pumped fiber based parametric amplifier is demonstrated with 39 dB black box gain. This is the first demonstration of a cw pumped fiber based parametric amplifier showing a net black box gain. The very fast relaxation time (~fs) may be used for all-optical signal processing. Three signal processing applications based on a fiber optical parametric amplifier are proposed and demonstrated; a 40-10 Gbit/s O-TDM demultiplexer with more than 40 dB gain, a 40 GHz pulse source providing wavelength tunable pulses below 4 ps and an all-optical sampling system with a temporal resolution of 1.6 ps demonstrating visualization of 300 Gbit/s data. Finally, a simple technique for increasing the maximum launched power into an optical fiber by increasing the stimulated Brillouin scattering threshold is proposed and evaluated.