Full list of publication from our group can be found here.

Selected publications

  • T. Hirooka, M. Okazaki, T. Hirano, P. Guan, M. Nakazawa, and S. Nakamura, “All-optical demultiplexing of 640-Gb/s OTDM-DPSK signal using a semiconductor SMZ switch,” IEEE Photon. Technol. Lett., vol. 21, no. 20, pp. 1574-1576, October (2009).

    The all-optical demultiplexing of a 640-Gb/s single- polarization optical time-division-multiplexing signal is successfully demonstrated by using a symmetric Mach-Zehnder switch incorporating semiconductor optical amplifiers. An ultrafast switching gate as narrow as 1.4 ps is realized by using a low-jitter, subpicosecond pulse train as a control pulse, which facilitates low-penalty demultiplexing.

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  • K. Kasai, T. Omiya, P. Guan, M. Yoshida, T. Hirooka, and M. Nakazawa, “Single-channel 400-Gb/s OTDM-32 RZ/QAM coherent transmission over 225 km using an optical phase-locked loop technique,” IEEE Photon. Technol. Lett., vol. 22, no. 8, pp. 562-564, April (2010).

    A single-channel 400-Gb/s transmission with a polarization-multiplexed , 10-Gsymbol/s, four-optical time-division multiplexed (OTDM) 32 return-to-zero/quadrature amplitude modulation (RZ/QAM) scheme is demonstrated for the first time. By using an optical phase-locked loop technique and a clock recovery circuit, we have successfully obtained a very stable pulsed-local oscillator whose phase was locked to the transmitter, and achieved precise demultiplexing and demodulation simultaneously. As a result, 400-Gb/s data were transmitted over 225 km with a bit-error-rate performance below the forward-error correction limit. Furthermore, we also realized a 320-Gb/s to 450-km transmission with an OTDM 16 RZ/QAM scheme.

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  • T. Hirano, P. Guan, T. Hirooka, and M. Nakazawa, “640-Gb/s/channel single-polarization DPSK transmission over 525 km with ultrafast time-domain optical Fourier transformation,” IEEE Photon. Technol. Lett., vol. 22, no. 14, pp. 1042-1044, July (2010).

    A single-channel 640-Gb/s differential phase-shift-keying transmission over 525 km was successfully demonstrated in a single polarization. A new ultrafast time-domain optical Fourier transformation (OFT) circuit was developed, in which the strong chirp required for the OFT of a subpicosecond optical pulse was realized with a phase modulator operated in a round-trip configuration. By applying this technique to a 640-Gb/s transmission, the tolerance to higher order polarization-mode dispersion was greatly improved and error-free transmission was achieved.

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  • P. Guan, H. C. H. Mulvad, Y. Tomiyama, T. Hirano, T. Hirooka, and M. Nakazawa, “1.28 Tbit/s/channel Single-polarization DQPSK Transmission over 525 km Using Ultrahigh-speed Time-domain Optical Fourier Transformation,” ECOC2010, We.6.C.3.

    A single-channel 1.28 Tbit/s transmission over 525 km is demonstrated for the first time with a single-polarization DQPSK signal. Ultrafast time-domain optical Fourier transformation is successfully applied to DQPSK signals and results in improved performance and increased system margin.

  • H. C. H. Mulvad, P. Guan, K. Kasai, T. Hirooka, and M. Nakazawa, “High-Resolution 640 Gbit/s Clock Recovery using Time-Domain Optical Fourier Transformation and Narrowband Optical Filter,” ECOC2010, Mo.1.A.6

    We demonstrate pre-scaled 40 GHz clock recovery from 640 Gbit/s optical time-division-multiplexed data using LiNbO3 modulators, based on time-domain optical Fourier transformation and optical filtering. The clock recovery is used in a 640 Gbit/s error-free transmission over 300 km.