132.2-Gb/s PDM-8QAM-OFDM Transmission at 4-b/s/Hz Spectral Efficiency

In this letter, we investigate 132.2-Gb/s polarization-division-multiplexed orthogonal frequency-division-multiplexing (PDM-OFDM) transmission at 25-GHz channel spacing. We show that the nonlinear tolerance is dependent on the OFDM symbol length. By using 14.4-ns-long OFDM symbols, 7 times 132.2-Gb/s transmission of PDM-OFDM at 4-b/s/Hz spectral efficiency is reported over 1300-km standard single-mode fiber.