Ultrahigh-speed DAC for Optical Communications Systems

Technological fields
Cutting-edge Technologies
  • Optical communications systems
  • DAC
  • InP HBT
Laboratory organization
NTT Photonics Laboratories

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Digital coherent optical transmission schemes with advanced modulation formats, such as M-QAM*1 and OFDM*2, are promising techniques for constructing future beyond-100-Gbit/s/ch optical communications systems. In the transmitter for such systems, ultrahigh-speed DACs*3 are key components for generating complex modulated signals. NTT Laboratories have sophisticated ultrahigh-speed transistor, InP HBT*4, technology and circuit design techniques, and have succeeded in developing ultrahigh-speed 6-bit DACs for such systems of the future.


  • The first 6-bit DAC that can operate at a sampling rate above 30 GS/s
  • Provides various modulated signals, such as M-QAM and OFDM
  • Uses our in-house ultrahigh-speed transistor, InP HBT, technology
  • Novel circuit design techniques for ultrahigh-speed and low-power operation
  • Uses broadband packaging technique

Application scenarios

  • Future ultrahigh-speed and large-capacity optical communications systems
    (e.g. beyond-100-Gbit/s/ch optical communications systems)
  • Future ultrahigh-speed optical access systems
  • Measurement tools
    (e.g. ultrahigh-speed arbitrary waveform generator)
  • *1 M-QAM: M-ary Quadrature Amplitude Modulation
  • *2 OFDM: Orthogonal Frequency Division Multiplexing
  • *3 DAC: Digital-to-Analog Converter
  • *4 InP HBT: Indium Phosphide Heterojunction Bipolar Transistor