Yoshikuni Miyata

Fast optical channel recovery in field demonstration of 100-Gbit/s Ethernet over OTN using real-time DSP

A field trial of 100-Gbit/s Ethernet over an optical transport network (OTN) is conducted using a real-time digital coherent signal processor. Error free operation with the Q-margin of 3.2 dB is confirmed at a 100 Gbit/s Ethernet analyzer by concatenating a low-density parity-check code with a OTN framer forward error correction, after 80-ch WDM transmission through 6 spans x 70 km of dispersion shifted fiber without inline-dispersion compensation. Also, the recovery time of 12 msec is observed in an optical route switching experiment, which is achieved through fast chromatic dispersion estimation functionality.

Progress in soft-decision FEC

We discuss the practical implementation of LDPC codes in soft-decision FEC for 100 Gb/s digital coherent systems. The question of the definition of net coding gain for differential QPSK used to avoid cycle slip is raised.

Iteration-Aware LDPC Code Design for Low-Power Optical Communications

Recent low-density parity-check (LDPC) codes have shown capacity-approaching performance for various communications systems. However, their promising performance cannot always be obtained due to practical constraints, such as finite codeword length, finite iteration, finite memory, and finite precision. In this paper, we focus on a practical design method of high-performance LDPC codes under a constraint of finite-iteration decoding for low-power optical communications. We introduce an iteration-aware LDPC code design approach, which is based on decoding trajectory in extrinsic information transfer chart analysis. It is demonstrated that an LDPC code designed by the conventional curve-fitting method exhibits nearly 2 dB of penalty, when the maximum number of iterations is limited. The results suggest that the LDPC code should be adaptively changed, e.g., when the number of decoding iterations is decreased to save power consumption. We also extend our design method to a multi-objective optimization concept by taking average degrees into account, so that the threshold and the computational complexity are minimized at the same time. The proposed Pareto-optimal codes can achieve additional 2-dB gain or 50% complexity reduction at maximum, in low-power decoding scenarios.

Turbo demodulation for LDPC-coded high-order QAM in presence of transmitter angular skew

We analyze demodulation methods for high-order QAM formats in the presence of quadrature angular skew caused by imperfect biasing of the transmitter. Proposed turbo demodulation improves skew tolerance of up to 33-degree angle for an SNR penalty of 1dB for 1024QAM.

Han–Kobayashi and Dirty-Paper Coding for Superchannel Optical Communications

Superchannel transmission is a candidate to realize Tb/s-class high-speed optical communications. In order to achieve higher spectrum efficiency, the channel spacing shall be as narrow as possible. However, densely allocated channels can cause non-negligible inter-channel interference (ICI) especially when the channel spacing is close to or below the Nyquist bandwidth. In this paper, we consider joint decoding to cancel the ICI in dense superchannel transmission. To further improve the spectrum efficiency, we propose the use of Han-Kobayashi superposition coding. In addition, for the case when neighboring subchannel transmitters can share data, we introduce dirty-paper coding for pre-cancelation of the ICI. We analytically evaluate the potential gains of these methods when ICI is present for sub-Nyquist channel spacing.

A study on power-scaling of triple-concatenated FEC for optical transport networks

We studied the power scaling using the measured power consumption and error correction performance of a triple-concatenated FEC. It was confirmed that the triple-concatenated FEC enabled 98% power reduction by controlling the NCG to suit the OSNR of the link.

Interference management with Han-Kobayashi coding: Dual-carrier coherent optical communications

We propose to use Han-Kobayashi (HK) coding and dirty-paper coding (DPC) to cope with inter-carrier interference (ICI) in dual-carrier transmissions. We show the considerable benefit of those methods to increase throughput in presence of strong ICI for dense carrier spacing.

100/150/200 Gb/s real-time demonstration of SD-FEC employing MSSC-LDPC codes for flexible coherent transport

To support forthcoming flexible coherent transport, we demonstrate a multiple-structured spatially-coupled LDPC with BCH codes which offers modulation flexibility, rate-adaptability and pilot-aided cycle-slip mitigation.