Fukutaro Hamaoka

Super high density multi-carrier transmission system by MIMO processing

We propose a super high density multi-carrier transmission system with MIMO processing by estimating the precise subcarrier spacing. We experimentally and numerically demonstrate that the proposed system enables the sub-carrier spacing to be reduced to half the baud rate.

Field trial of simultaneous 100-Gbps and 400-Gbps transmission using advanced digital coherent technologies

We achieve double the performance in 400-Gbps optical transmission employing advanced digital coherent technologies based on field trials. Additionally, we show stable transmission of 400-Gbps channels that does not affect the existing 100-Gbps channels.

Coded Eight-Dimensional QAM Technique Using Iterative Soft-Output Decoding and Its Demonstration in High Baud-Rate Transmission

We proposed coded eight-dimensional (8-D) quadrature amplitude modulation (QAM) and experimentally demonstrated in high baud-rate transmission. Both high baud rate and multilevel modulation techniques are necessary for large capacity long haul transmission without increasing the number of transponders. However, optical signal-to-noise ratio (OSNR) tolerance of higher order modulation is low due to the short minimum Euclidean distance. Therefore, to relax OSNR tolerance by enlarging minimum Euclidean distance, we proposed 8-D modulation formats. The spectral efficiency of the proposed coded 8-D-16QAM, 8-D-32QAM, and 8-D-64QAM is equivalent to polarization division multiplexed (PDM)-8QAM, PDM-16QAM, and PDM-32QAM, respectively. To confirm the applicability of the proposed 8-D modulation to high baud rate transmission, we experimentally demonstrated 96-GBaud 8-D-16QAM wavelength division multiplexed transmission over 5,-252 km using iterative soft output decoding. The line data rate is 576-Gbps and a net rate 478-Gbps. At the same spectral efficiency, 8-D-16QAM using iterative soft output decoding can expand the transmission reach by 1212 km compared to conventional PDM-8QAM.

Characteristics Investigation of High-Speed Multi-Carrier Transmission Using MIMO-Based Crosstalk Compensation in Homodyne Detection Scheme

We experimentally investigate the characteristics of a multi-carrier optical transmission system with neighboring-crosstalk compensation using multiple-input multiple-output processing as an integrated part of a polarization-demultiplexing stage in a homodyne detection scheme for high-speed optical signals. We show that the crosstalk compensation yields adequate performance in the presence of high polarization mode dispersion and high-speed changes in the state of polarization. We also clarify the performance required of local oscillators in the receivers for adequate crosstalk compensation in this scheme. Furthermore, we show the applicability of the system equipped with delay compensation to long-haul transmission through 480-km WDM transmission experiments employing 256-Gb/s optical multi-carrier signals with the subcarrier spacing of 25 GHz, which corresponds to 78% of the signal baud rate.

Optical 8-Dimensional Time-Polarization Modulation Using Square- QAM-Constellation and a Simple Decoding Algorithm

We propose optical 8D time-polarization modulation using square-QAM-constellation and a simple decoding algorithm. Experiments show that the proposed modulation format can achieve significant gain and the decoding algorithm has the same performance as conventional maximum-likelihood-detection.

Field trial of distance-adaptive optical transmission with digital in-band OSNR estimation.

We present a feasible distance-adaptive optical transmission system that selects the optimum modulation format by referencing the estimated optical signal to noise ratio (OSNR) information transmitted from an opposing transceiver via a feedback channel. A modulation format free time-domain-multiplexed pilot sequence enables OSNR estimation and feedback channel transmission. Thanks to a feedback channel transmission, this system does not need to pass through a control plane in optimizing scheme. Using this system, we demonstrated 106.6 Gb/s QPSK and 213.3 Gb/s 16 QAM distance-adaptive optical transmission in a fully automatic manner in a field-installed fiber of 70.4 to 211.2 km.

An adaptive-equalizer-less low-complexity DSP using differential code shift keying

We propose the use of differential code shift keying (DCSK) for a symbol rate adaptive low-complexity DSP algorithm by eliminating adaptive-equalizer (AEQ) with limited influence on circuit size. As a proof of concept, a 300km transmission using DCSK format was demonstrated without using AEQ.

Evaluation of maximum ratio combining in route diversity transmission and application to hitless optical path switching in field installed fibre

Hitless optical path switching using maximum ratio combining in route diversity transmission is successfully achieved under the condition of a field environment even if there are large polarization mode dispersion and fibre nonlinearities.