Abstract

We describe the first on-line 256 QAM digital coherent optical transmission system with an ECLD light source and DFB LD-based injection-locking, and an FPGA-based transceiver. In this system, precise optical phase control was achieved with an optical injection-locking circuit and a phase-locked loop circuit at the receiver, which helped to reduce the complexity of digital signal processing in the FPGA-based receiver. The precise polarization-demultiplexing of a 256 QAM signal was realized by using a training symbol in the FPGA. With these techniques, we successfully demonstrated the on-line detection of a QAM signal with a multiplicity as high as 256. We then present a 10 channel WDM 80 Gbit/s/ch, 256 QAM bi-directional coherent transmission as a high capacity next-generation mobile fronthaul by using the FPGA-based transmission system. We achieved error-free operations with a 14% overhead FEC for 10 km down-link (on-line) and up-link (off-line) transmissions for all channels.

80 Gbit/s, 256 QAM coherent transmission over 150 km with an injection-locked homodyne receiver

Keisuke Kasai, Yixin Wang, Shohei Beppu, Masato Yoshida, and Masataka Nakazawa
Opt. Express 23(22) 29174-29183 (2015)

320 Gbit/s, 20 Gsymbol/s 256 QAM coherent transmission over 160 km by using injection-locked local oscillator

Yixin Wang, Keisuke Kasai, Masato Yoshida, and Masataka Nakazawa
Opt. Express 24(19) 22088-22096 (2016)

10.51-Tbit/s multi-channel IF-over-fiber transmission with SDM/WDM/SCM for beyond-5G mobile fronthaul accommodating ultra-high-density antennas

Shinji Nimura, Kazuki Tanaka, Shota Ishimura, Kosuke Nishimura, Ryo Inohara, Takehiro Tsuritani, and Masatoshi Suzuki
J. Opt. Commun. Netw. 15(8) C263-C270 (2023)

Injection-locked 256 QAM WDM coherent transmissions in the C- and L-bands

Takashi Kan, Keisuke Kasai, Masato Yoshida, Toshihiko Hirooka, and Masataka Nakazawa
Opt. Express 28(23) 34665-34676 (2020)

Fronthaul Based on Pulse-Width Modulation in RSOA WDM PONs With Broadband and Coherent Seeds

A. Gatto, P. Parolari, L. Combi, U. Spagnolini, R. Brenot, and M. Martinelli
J. Opt. Commun. Netw. 8(11) B55-B60 (2016)