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Abstract-We demonstrate single laser 32.5 Tbit/s 16QAM Nyquist WDM transmission over a total length of 227 km of SMF-28 without optical dispersion compensation. A number of 325 optical carriers are derived from a single laser and encoded with dualpolarization 16QAM data using sinc-shaped Nyquist pulses. As we use no guard bands, the carriers have a spacing of 12.5 GHz equal to the symbol rate or Nyquist bandwidth of the data. We achieve a net spectral efficiency of 6.4 bit/s/Hz using a softwaredefined transmitter, which generates the electric drive-signals for the electro-optic modulator in realtime.

Abstract:We demonstrate for the first time transmission of 54 Gbit/s and 48 Gbit/s over 44 km and 150 km, respectively, utilizing an optical bandwidth of only 3 GHz. We used polarization division multiplexed 512QAM and 256QAM modulation formats in combination with Nyquist pulse shaping having virtually zero roll-off. The resulting spectral efficiencies range up to 18 bit/s/Hz and 16 bit/s/Hz, respectively. Taking into account the overhead required for forward error correction, the occupied signal bandwidth corresponds to net spectral efficiencies of 14.4 bit/s/Hz and 15 bit/s/Hz, which could be achieved in a wavelength division multiplexed network without spectral guard bands.

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We report on materials and technology development for short-wave infrared photodetectors based on InGaAs p-i-n and avalanche photodiodes (APDs). Using molecular beam epitaxy for the growth of thin layers with abrupt interfaces, which are required for optimized APD structures, excellent crystalline quality has been achieved for detector structures grown on 3-inch InP substrates. For the fabrication of focal plane detector arrays, we employed a mesa etching technology in order to compare the results with the commonly utilized planar technology. Camera detector arrays as well as test structures with various sizes and geometries for materials and process characterization are processed using a dry-etch mesa technology. Aspects of the process development are presented along with measured dark-current and photo-current characteristics of the detector devices