both polarizations, confirming that we achieved successful polarization demultiplexing and equalization.
The spectral width of the main lobe of this modulation format was 40 GHz, which was one
sixth of the line rate. Because of this narrow spectral width, an SE of 8 b/s/Hz, which is the highest
so far, can be expected for WDM transmission with a spacing of 25 GHz.
This review described photonics-integrated devices for the high-bit-rate transmission technologies
with advanced modulation formats such as 100G-class PDM-QPSK and 64-QAM. The devices
exhibited sufficiently high levels of performance for practical use. Since they provide the advantages
of mass producibility, dense integration, and high stability, photonics-integrated devices will
contribute to further advances in high-bit-rate transmission.