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We report the results of two field trials aimed at achieving high fiber capacity over regional and long-haul distances. In the first trial, 41 superchannels with digital Nyquist pulse-shaping were generated and tightly packed to fill up both C-band and L-band. Each subcarrier was modulated with 24.8-Gbaud dual-polarization 16 quadrature amplitude modulation (DP-16QAM) data. The signal carrying net 54.2 Tb/s data was transmitted over 634 km of dispersion uncompensated field-installed standard single mode fiber with the aid of hybrid EDFA and Raman amplification and digital coherent detection. In the second trial for long-haul distances, we extended the transmission distance over 1,822 km. This increase in reach was achieved by reducing the net total capacity to 40.5 Tb/s and modulating the signals with dual-polarization 8 quadrature amplitude modulation (DP-8QAM) Nyquist carrier modulation. A novel rate-adaptive low-density parity-check coding was employed, so that the transmitted channels can exhibit different code rates, adapted by the concatenation of hard-decision and soft-decision forward error correcting codes for enhancing error-correction capability. To the best of our knowledge, we achieved the highest field trial capacity to date at 54.2 Tb/s in regional distances. Furthermore, in long-haul applications, the reported capacity × distance product of 73.79 Pb/s·km is the highest to date.