69.1-Tbit/s Optical Transmission Technology Using Digital Coherent Multilevel QAM Format

Technological fields
Telecommunications Network Technologies
  • Post 100 G transmission
  • Digital coherent
  • Fusion of light and wireless
Laboratory organization
NTT Network Innovation Laboratories

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NTT has successfully demonstrated ultra-high-capacity (69.1 Tbit/s) optical transmission to meet the expected rapid increase in data traffic. This capacity is the highest reported in the optical communication field. A 69.1-Tbit/s signal generated by wavelength division multiplexing (WDM) of 432 wavelengths each with a capacity of 171 Gbit/s was transmitted over a single fiber over 240 km. The 16 QAM* format used led to an increase in spectral efficiency and demodulation was achieved by a newly developed digital coherent signal processing technique. This technology is useful for future optical core networks. (Tbit/s: terabits per second, tera = 1012.)


  • Ultra-high-capacity optical signal transmission of 69.1 Tbit/s (world record)
  • Sufficient capacity to handle future increases in data traffic
  • Increased spectral efficiency by using 16 QAM format
  • Demodulation algorithm using novel digital coherent signal processing
  • Ultra-wide band and low-noise optical amplifier

Application scenarios

  • Backbone optical core network of NTT Communications
  • Metro optical network of NTT East Corporation and NTT West Corporation
  • * QAM: Quadrature Amplitude Modulation