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Shigeru Nakamura

Bio: Shigeru Nakamura is an academic researcher from NEC. The author has contributed to research in topics: Optical switch & Silicon photonics. The author has an hindex of 13, co-authored 48 publications receiving 780 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a symmetric-Mach-Zehnder (SMZ)-type switch was used to achieve error-free all-optical wavelength conversion at 168 Gb/s, which is the highest repetition rate ever reported.
Abstract: Error-free all-optical wavelength conversion at 168 Gb/s, which is the highest repetition rate ever reported, has been achieved by using a symmetric-Mach-Zehnder (SMZ)-type switch. Low-power-penalty 84-Gb/s operation is also demonstrated. The push-pull switching mechanism of the SMZ switch enables such ultrafast operation based on cross-phase modulation associated with the carrier depletion in a semiconductor optical amplifier. The configuration of the delayed-interference signal-wavelength converter, which is a simplified variant of the SMZ switch, is used in this experiment.

190 citations

Journal ArticleDOI
TL;DR: In this paper, a delayed-interference signal-wavelength converter (DISC) is proposed, whose speed is not restricted by the carrier lifetime and its structure consists of only two essential components, namely, a semiconductor optical amplifier and a passive split delay.
Abstract: A new all-optical semiconductor-band-filling-based wavelength converter, named delayed-interference signal-wavelength converter (DISC), is proposed. Its speed is not restricted by the carrier lifetime and its structure is very simple: it consists of only two essential components, namely, a semiconductor optical amplifier and a passive split-delay. Using this converter, 3.8-THz-shifted (from 1530 to 1560-nm) 14-ps-long pulses are generated from 1530-nm 140-fJ 0.7-ps pulses with high-conversion efficiency.

134 citations

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate 200-fs switching and 1.5-Tb/s demultiplexing with a polarization-discriminating symmetric Mach-Zehnder (PD-SMZ) all-optical switch.
Abstract: We demonstrate 200-fs switching and 1.5-Tb/s demultiplexing with a polarization-discriminating, symmetric Mach-Zehnder (PD-SMZ) all-optical switch. This switch is based on a highly efficient but slowly relaxing band-filling effect resonantly excited in a passive InGaAsP bulk waveguide. By using a mechanism that cancels out the effect of the slow relaxation, ultrafast switching is realized. The applicability of this mechanism to optical demultiplexing of well over 1 Tb/s is experimentally demonstrated for the first time. High-repetition operation at 10 GHz with the same nonlinearity used for the present ultrafast switching is also verified.

75 citations

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate compact and low-loss $8 \times 8$ silicon photonic switch modules, which are applicable to transponder aggregators (TPAs) in colorless, directionless, and contentionless reconfigurable optical add-drop multiplexers.
Abstract: We demonstrate compact and low-loss $8 \times 8$ silicon photonic switch modules, which are applicable to transponder aggregators (TPAs) in colorless, directionless, and contentionless reconfigurable optical add-drop multiplexers. Newly designed silicon optical switch chips incorporating spot size converters with polarization insensitive and wavelength insensitive properties over C/L bands are packaged. The developed module shows about 6-dB average excess optical loss, including optical coupling loss, on all 64 optical paths with low-polarization-dependent loss and low crosstalk. Using these compact optical switch modules, we construct a TPA prototype featuring over 100-port optical switch subsystem densely mounted on one board and confirm its feasibility.

60 citations

Proceedings ArticleDOI
06 Mar 2011
TL;DR: Polarization-independent wavelength path switching with one-chip silicon photonic circuit including 64 thermo-optical switch elements within 12mm × 3mm was demonstrated in this article, where any path can be constructed by simply turning on one switch element.
Abstract: Polarization-independent wavelength path switching is demonstrated with one-chip silicon photonic circuit including 64 thermo-optical switch elements within 12mm × 3mm. Owing to uniformity, any path can be constructed by simply turning on one switch element.

47 citations


Cited by
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Journal ArticleDOI
26 Mar 2007
TL;DR: In this paper, the authors demonstrate error-free wavelength conversion at 320 Gb/s by employing a semiconductor optical amplifier that fully recovers in 56 ps. Error-free operation is achieved without using forward error correction technology.
Abstract: We demonstrate error-free wavelength conversion at 320 Gb/s by employing a semiconductor optical amplifier that fully recovers in 56 ps. Error-free operation is achieved without using forward error correction technology. We employ optical filtering to select the blue sideband of the spectrum of the probe light, to utilize fast chirp dynamics introduced by the amplifier, and to overcome the slow gain recovery. This leads to an effective recovery time of less than 1.8 ps for the wavelength converter. The wavelength converter has a simple configuration and is implemented by using fiber-pigtailed components. The concept allows photonic integration

234 citations

Journal ArticleDOI
TL;DR: In this paper, an error-free and pattern-independent wavelength conversion at 160 Gb/s was demonstrated using an optical bandpass filter (OBF) placed at the amplifier output.
Abstract: Error-free and pattern-independent wavelength conversion at 160 Gb/s is demonstrated. The wavelength converter utilizes a semiconductor optical amplifier (SOA) with a recovery time greater than 90 ps and an optical bandpass filter (OBF) placed at the amplifier output. This paper shows that an OBF with a central wavelength that is blue shifted compared to the central wavelength of the converted signal shortens the recovery time of the wavelength converter to 3 ps. The wavelength converter is constructed by using commercially available fiber-pigtailed components. It has a simple configuration and allows photonic integration.

214 citations

Journal ArticleDOI
20 Sep 2021
TL;DR: In this paper, the main classifications and features of novel SDM fibers such as multicore fibers (MCFs), multimode fibers, few-mode MCFs, and coupled-core MCFs are discussed.
Abstract: Research on space-division multiplexing (SDM) came to prominence in early 2010 being primarily proposed as a means of multiplying the information-carrying capacity of optical fibers at the same time as increasing efficiency through resource sharing. Proposed SDM transmission systems range from parallel single-mode fibers with shared amplifier pump lasers to the full spatial integration of transceiver hardware, signal processing, and amplification around a fiber with over 100 spatial channels comprising multiple cores each carrying multiple modes. In this paper, we review progress in SDM research. We first outline the main classifications and features of novel SDM fibers such as multicore fibers (MCFs), multimode fibers, few-mode MCFs, and coupled-core MCFs. We review research achievements of each fiber type before discussing digital-signal processing, amplifier technology, and milestones of transmission and networking demonstrations. Finally, we draw comparisons between fiber types before discussing the current trends and speculate on future developments and applications beyond optical data transmission.

200 citations

Journal ArticleDOI
Long Chen1, Young-Kai Chen1
TL;DR: A 8×8 broadband optical switch on silicon for transverse-electrical polarization using a switch-and-selector architecture is demonstrated and the upper bound of total power consumption is estimated to be less than 70 mW even without optimization of the default state of the individual switch elements.
Abstract: We demonstrated a 8×8 broadband optical switch on silicon for transverse-electrical polarization using a switch-and-selector architecture. The switch has a footprint of only 8 mm × 8 mm, minimum on-chip loss of about 4 dB, and a port-to-port insertion loss variation of only 0.8 dB near some spectral regions. The port-to-port isolation is above 30 dB over the entire 80-nm-wide spectral range or above 45 dB near the central 30 nm. We also demonstrated a switching power of less than 1.5 mW per element and a speed of 2 kHz, and estimated the upper bound of total power consumption to be less than 70 mW even without optimization of the default state of the individual switch elements.

197 citations

Journal ArticleDOI
TL;DR: In this paper, a symmetric-Mach-Zehnder (SMZ)-type switch was used to achieve error-free all-optical wavelength conversion at 168 Gb/s, which is the highest repetition rate ever reported.
Abstract: Error-free all-optical wavelength conversion at 168 Gb/s, which is the highest repetition rate ever reported, has been achieved by using a symmetric-Mach-Zehnder (SMZ)-type switch. Low-power-penalty 84-Gb/s operation is also demonstrated. The push-pull switching mechanism of the SMZ switch enables such ultrafast operation based on cross-phase modulation associated with the carrier depletion in a semiconductor optical amplifier. The configuration of the delayed-interference signal-wavelength converter, which is a simplified variant of the SMZ switch, is used in this experiment.

190 citations