Takahide Sakamoto

Tokyo Metropolitan University

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Co-Authors

Tetsuya Kawanishi

Waseda University

299

Masayuki Izutsu

Waseda University

100

Akito Chiba

Gunma University

Isao Morohashi

National Institute of Information and Communications Technology

Guo-Wei Lu

University of Aizu

Iwao Hosako

National Institute of Information and Communications Technology

Naokatsu Yamamoto

National Institute of Information and Communications Technology

Kaoru Higuma

Sumitomo Osaka Cement (Japan)

Atsushi Kanno

Jichi Medical University

Satoshi Shinada

National Institute of Information and Communications Technology

Cooperative Institutions

National Institute of Information and Communications Technology

The University of Tokyo

Osaka University

Japan Science and Technology Agency

National Institute on Consumer Education

Tokyo Metropolitan University

Nokia (United States)

Waseda University

National Center for University Entrance Examinations

Nippon Koei (Japan)

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Advances and challenges in vector modulation technologies

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2008)

Tetsuya Kawanishi Takahide Sakamoto Akito Chiba

This paper describes recent progress of high-speed vector optical modulation technologies based on Mach- Zehnder interferometer devices. Multi-level quadrature amplitude modulation signal can be synthesized by using parallel Mach-Zehnder modulators. We can generate complicated multi-level optical signals from binary data streams, where binary modulated signals are vectorially summed in optical circuits. Modulation speed can be higher than 80 Gbaud by using a dual parallel Mach-Zehnder modulator with thin lithium niobate substrate.

Modulation (music)

Electro-optic modulator

SIGNAL (programming language)

10.1117/12.816361

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Citations (1)

Examination about bias control method of parallel LiNbO3 optical modulators

IEICE Technical Report; IEICE Tech. Rep. (2010)

Yuta Tsuchiya Takahide Sakamoto Tetsuya Kawanishi Hirochika Nakajima

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Citations (0)

Control methods for MZM-based flat comb generator

IEICE Technical Report; IEICE Tech. Rep. (2009)

Takahide Sakamoto Isao Morohashi Kawanishi Tetsuya Izutsu Masayuki

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Broadening of comb bandwidth by multiple modulation using feedback loop in Mach-Zehnder-modulator-based flat comb generator

Isao Morohashi Takahide Sakamoto Naokatsu Yamamoto Tetsuya Kawanishi Iwao Hosako

We demonstrated broadening of the comb bandwidth by constructing a feedback loop in a Mach-Zehnder-modulator-based flat comb generator. By multiple-modulation using the feedback loop, a broadband comb signal was generated.

Comb generator

Feedback loop

Modulation (music)

Electro-optic modulator

Comb filter

10.1109/mwp.2010.5664165

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Citations (3)

Optical 36QAM transmitter based on two tandem IQ modulators with simplified driving electronics

Guo-Wei Lu Takahide Sakamoto Tetsuya Kawanishi

To scale up the capacity and spectrum efficiency in optical transmission systems, high-order quadrature-amplitude modulation (QAM), has raised a lot of research attention. Recently, optical 32 or 36QAM has been deployed to realize high spectrum-efficient Nyquist wavelength-division multiplexing transmission with spectral efficiency of up to 8.37b/s/Hz. Usually optical 32 or 36QAM is synthesized using a single in-phase/quadrature (IQ) modulator driven by 6-level driving electronics, which is referred to as “electrical” approach here. Although the single IQ modulator solution has a simple optical hardware, it requires sophisticated technique for preparing superior-quality 6-level electronics by either combining three binary electrical signals or deploying high-speed digital-to-analog converters (DACs). The operation symbol-rate is restricted by the DACs resolution, linearity of driver amplifiers or bandwidth of electrical components. On the other hand, the tandem-modulator approach, a serial combination of IQ modulators has been utilized for synthesizing various multilevel optical signals such as 8QAM and 16QAM, where only binary electronics are deployed to drive each modulator. If extending this scheme to generate higher-order QAM, we can also benefit from the reduced complexity in driving electronics. Instead of preparing superior-quality 6-level electronics for generating 36QAM, just binary and 3-level electronics are required. In contrast to the “electrical” approach, the proposed scheme provides an alternative approach to synthesize high-order QAM with simplified driving electronics.

QAM

Electro-optic modulator

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Optical trellis-coded modulation with multi-parallel MZM

European Conference on Optical Communication (2009)

Takahide Sakamoto Akito Chiba Isao Morohashi Tetsuya Kawanishi

We demonstrated trellis-coded modulation onto 10-Gbaud 16QAM by electro-optic vector digital-to-analogue converter employing multi-parallel MZM and trellis encoder. The signal was demodulated with a digital homodyne employing Viterbi decoder.

Trellis (graph)

Trellis modulation

Modulation (music)

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Citations (3)

Reconfigurable Optical 8-ary Transmitter based on Arbitrary 2-QAM for Generating 8PSK and 8QAM

Guo-Wei Lu Takahide Sakamoto Tetsuya Kawanishi

Arbitrary 2-QAM is proposed and experimentally demonstrated using an under-driven IQ modulator. By cascading a standard QPSK modulator and a constant-amplitude or non-constant-amplitude 2-QAM, an optical 8PSK or 8QAM could be synthesized, respectively.

QAM

10.1364/nfoec.2012.jth2a.22

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Citations (2)

All-optical modulation format conversion from frequency-shift-keying to phase-shift-keying

Optics Express (2005)

Tetsuya Kawanishi Takahide Sakamoto Masayuki Izutsu

We have realized a novel optical modulation format conversion using double-sideband suppressed-carrier modulation. An optical wideband frequency-shift-keying (FSK) signal, generated by an external FSK modulator, can be directly converted into an optical phase-shift-keying (PSK) signal, where the FSK signal having two spectral components was fed to an optical intensity modulator followed by an optical bandpass filter. Optical frequency of the FSK signal was mapped into optical phase of the bandpass filter output whose phase deviation depends on a chirp of the FSK signal.We demonstrated modulation format conversion from FSK to PSK at 10 Gbps, by using a high-speed optical FSK modulator and a dual electrode Mach-Zehnder intensity modulator.

Frequency-shift keying

Modulation (music)

Minimum-shift keying

SIGNAL (programming language)

10.1364/opex.13.008038

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Citations (8)

Impact of tight optical filtering on orthogonal time-frequency domain multiplexed signals in wavelength-selective switching systems

Takahide Sakamoto

Orthogonal time-frequency domain multiplexing (OTFDM) enables ultra-wideband high-spectral-efficiency multicarrier transmission without relying on optical filters for multiplexing/demultiplexing of subchannels. Impact of tight filtering on OTFDM signal is investigated, assuming bandwidth narrowing in wavelength-selective switching networks.

Wideband

Optical add-drop multiplexer

Frequency-division multiplexing

10.1109/ps.2015.7329009

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Citations (0)

Ultra high extinction-ratio and ultra low chirp optical intensity modulation for pure two-tone lightwave signal generation

Conference on Lasers and Electro-Optics (2008)

Tetsuya Kawanishi Takahide Sakamoto Akito Chiba Masahiro Tsuchiya Hiroyuki Toda

Pure two-tone signal generation with spurious suppression ratio of 47 dB was demonstrated by using an optical Mach-Zehnder modulator with precisely balanced operation, where extinction ratio and chirp parameter were respectively 64 dB and 0.0099.

Extinction ratio

Chirp

Tone (literature)

Modulation (music)

SIGNAL (programming language)

Spurious relationship

Extinction (optical mineralogy)

10.1109/cleo.2008.4550935

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Citations (17)