Yojiro Mori

We demonstrate unrepeated 200-km transmission of 40-Gbit/s 16-QAM signals using a digital coherent receiver, where the decision-directed carrier-phase estimation is employed. The phase fluctuation is effectively eliminated in the 16-QAM system with such a phase-estimation method, when the linewidth of semiconductor lasers for the transmitter and the local oscillator is 150 kHz. Finite-impulse-response (FIR) filters at the receiver compensate for 4,000-ps/nm group-velocity dispersion (GVD) of the

We propose a novel configuration of the finite-impulse-response (FIR) filter adapted by the phase-dependent decision-directed least-mean-square (DD-LMS) algorithm in digital coherent optical receivers. Since fast carrier-phase fluctuations are removed from the error signal which updates tap coefficients of the FIR filter, we can achieve stable adaptation of filter-tap coefficients for higher-order quadrature-amplitude modulation (QAM) signals. Computer simulations show that our proposed scheme i

With the rapid spread of cloud-based services, intra-datacenter traffic is growing exponentially. In typical present datacenters, top-of-rack switches, which act as gateways to computer systems, are interconnected via multi-tier electrical-switching networks. The electrical switch necessitates costly optical-to-electrical and electrical-to-optical conversion. Furthermore, its power consumption will explode due to the ever-increasing intra-datacenter traffic. To handle the large volumes of traffi

Abstract High pressure powder X‐ray diffraction studies are reported for the chalcopyrite phases of AgGaX 2 (X = S, Se, and Te). Structural parameters have been determined by the Ftietveld method. While the c/a ratio decreases with increasing pressure, the anion displacement parameter u is constant within experimental error for all samples investigated.

A 1.28-Tbit/s signal on a single carrier is generated by the combination of 16 time-division multiplexing, 16-QAM, and polarization multiplexing. Such a signal is demodulated with a digital coherent receiver having the time-division demultiplexing function.

With the recent growth of network traffic demands, a high-capacity optical-path network based on reconfigurable optical add-drop multiplexers (ROADMs) is highly desirable. Among the various technologies available, extending the useable frequency band is one of the most promising solutions since it can enlarge the network capacity with relatively small signal-quality degradation. However, increasing the number of wavelength signals detracts flexible signal-drop capabilities of the ROADM because t

With the rapid growth in intra-datacenter traffic, the high power consumption stemming from the huge number of electrical switches is becoming a critical issue. Hence, high-port-count optical circuit switches are urgently needed. In this paper, we overview recently developed optical circuit switch architecture based on two-dimensional switches, i.e., space switches and wavelength-routing switches. The attainable maximum switch port counts and hardware requirements are quantitatively evaluated th

We propose a novel configuration of FIR filters adapted by the decision-directed LMS algorithm in the digital coherent receiver. Simulations and experiments show its high tolerance to phase noise and frequency offset for 16-QAM signals.

High pressure X-ray diffraction measurements were performed on AgGaTe2 chalcopyrite semiconductor up to 30 GPa; the space group and atomic positions under high pressure were refined by the Rietveld method. The first phase transition occurred at 3.1 GPa from the chalcopyrite phase to the coexisting phase of the P-4 which is disordered zinc blende (d-B3) and a second phase which is not inconsistent with a Cmcm structure but this is by no means proven. Between 3.1 and 5.4 GPa, all three phases were

We demonstrate unrepeated 200-km transmission of 40-Gbit/s 16-QAM signals. In spite of the launched power limitation due to SPM, the acceptable BER performance is obtained owing to high sensitivity of a digital coherent optical receiver.

We demonstrate transmission of a 100-Gbit/s 32-QAM dual-polarization signal over a 200-km dispersion-managed fiber link using a digital coherent receiver. The receiver sensitivity of −20 dBm at BER = 10−3 is obtained after 200-km transmission.

Abstract A high‐pressure X‐ray diffraction study was carried out for CuGaTe 2 and CuInTe 2 chalcopyrite semiconductors up to 18.0 and 13.0 GPa, respectively. The high‐pressure phase was conclusively assigned to the d‐Cmcm phase (cation site disordered Cmcm). In the case of CuGaTe 2 , the chalcopyrite phase transformed to the d‐Cmcm phase at 12.7 GPa through the tentative d‐SC phase. The bulk moduli for the three phases were determined to be 64, 81, and 103 GPa, respectively. In the case of CuInT