Masataka Nakazawa

Tohoku University

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A 200 GHz erbium-doped fiber laser using a rational harmonic mode-locking technique

Conference on Lasers and Electro-Optics (1996)

Masataka Nakazawa Eiji Yoshida

An optical short pulse source with a high repetition rate is very important for realizing future ultrahigh speed optical communication [1], Recently, Onodera et al. reported a very interesting technique for generating high repetition rate pulses by the rational detuning of the modulation frequency [2]. This technique was first demonstrated in a 17 GHz actively mode-locked semiconductor laser, and applied optical pulse storage in a cavity [3] and to a 21 GHz fiber laser [4], Rational harmonic mode-locking is a technique where an optical pulse train with a repetition rate of (np±1)△f can be produced when the modulation frequency is set at (p±1/n)△f, where △f is the longitudinal mode spacing, and p and n are integers.

Erbium

Mode-Locking

Modulation (music)

Repetition (rhetorical device)

Q-switching

Harmonic

Source

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Citations (17)

1024 QAM (60 Gbit/s) single-carrier coherent optical transmission over 150 km

Optics Express (2012)

Yuki Koizumi Kazushi Toyoda Masato Yoshida Masataka Nakazawa

We demonstrate a record QAM multiplicity of 1024 levels in a single-carrier coherent transmission. A frequency-domain equalization technique and a back-propagation method are adopted to compensate for distortions caused by hardware imperfections and fiber impairments, respectively. As a result, 60 Gbit/s polarization-multiplexed transmission over 150-km has been achieved at 3 Gsymbol/s within an optical bandwidth of only 4.05 GHz.

Polarization-division multiplexing

QAM

Gigabit

10.1364/oe.20.012508

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Citations (101)

High gain Er3+ -doped fibre amplifier pumped by 820nm GaAlAs laser diodes

Electronics Letters (1990)

Keisuke Suzuki Yoshiharu Kimura Masataka Nakazawa

An optical gain of 22 dB at 1.535 μm is obtained in an Er3+- doped fibre amplifier for a total pump power of 54 mW. The Er3+ doping concentration is 34 ppm, and the pumping source is GaAlAs laser diodes at 820 nm. By using an Er3+ fibre with a doping concentration of 390 ppm, the maximum gain is as high as 29.4 dB for a pump power of 83 mW.

Laser diode

Optical Pumping

10.1049/el:19900618

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Citations (17)

256-QAM (64 Gb/s) Coherent Optical Transmission Over 160 km With an Optical Bandwidth of 5.4 GHz

IEEE Photonics Technology Letters (2009)

Masataka Nakazawa Seiji Okamoto Tatsunori Omiya Keisuke Kasai Masato Yoshida

We report a polarization-multiplexed (Pol-Mux) 4-Gsymbol/s 256 quadrature amplitude modulation (QAM) coherent optical transmission over 160 km. A 64-Gb/s data signal was successfully transmitted with an optical bandwidth of 5.4 GHz. We also describe a Pol-Mux, 10-Gsymbol/s, 128- and 64-QAM (140 and 120 Gb/s) transmission over 150 km.

QAM

10.1109/lpt.2009.2037238

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Citations (70)

Scheme for independently stabilizing the repetition rate and optical frequency of a laser using a regenerative mode-locking technique

Optics Letters (2008)

Masataka Nakazawa Masato Yoshida

We have succeeded in achieving independent control of the repetition rate and optical frequency of a pulse laser by employing a regenerative mode-locking technique. By adopting a voltage-controlled microwave phase shifter or an optical delay line in a regenerative feedback loop we can control the repetition rate of the laser without directly disturbing the optical frequencies. We experimentally show how this independent control can be realized by employing a 40 GHz harmonically and regeneratively mode-locked fiber laser.

Mode-Locking

Repetition (rhetorical device)

10.1364/ol.33.001059

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Citations (17)

Configuration of the optical transmission line using stimulated Raman scattering for signal light amplification

Journal of Lightwave Technology (1986)

Takuya Nakashima Shigeyuki Seikai Masataka Nakazawa

Expansion of a repeater spacing of optical transmission line is investigated using forward stimulated Raman scattering generated by a 1.34-μm Nd:YAG laser to amplify the signal light. Achievable repeater spacing at the 1.42-μm wavelength transmission is numerically estimated on the basis of coupled power equations and experimentally obtained Raman gain for various core-cladding index difference. A transmission distance of more than 200 km is predicted for an input signal light power of 100 μw and a pump power of 200 mW using a fiber with a relative index difference of 1 percent.

Cladding (metalworking)

SIGNAL (programming language)

Repeater (horology)

10.1109/jlt.1986.1074776

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Citations (16)

Chromatic dispersion dependence of GAWBS phase noise compensation with pilot tone

Optics Express (2021)

Kôzô Satô Takashi Kan Masato Yoshida Keisuke Kasai Toshihiko Hirooka

We describe experimental and numerical results regarding the influence of chromatic dispersion in optical fibers on guided acoustic-wave Brillouin scattering (GAWBS) phase noise compensation with a pilot tone (PT). We compared the compensation performance for GAWBS phase noise generated in an ultra-large-area fiber (ULAF) where D ULAF = 21 ps/nm/km with that in a dispersion-shifted fiber (DSF) where D DSF = -1.3 ps/nm/km and found that the performance depends strongly on chromatic dispersion. The numerical analysis shows that the group delay between the signal and PT caused by chromatic dispersion reduces the GAWBS noise correlation between them, which degrades the compensation performance for GAWBS phase noise. It is clarified that a condition for effective GAWBS compensation is that the group delay between the signal and PT should be less than half the period of the GAWBS phase noise component.

SIGNAL (programming language)

10.1364/oe.418891

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Citations (2)

Disaster-resilient networks and optical communication technologies

The Journal of Institute of Electronics, Information and Communication Engineers (2013)

Masataka Nakazawa

Source

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Citations (0)

Study of Optical Pulse Compression with Higher-Order Nonlinearity and Dispersion

Japanese Journal of Applied Physics (1989)

Hirokazu Kubota Masataka Nakazawa

Propagation of ultrashort pulses in single-mode fibers, which involves a third-order dispersion and a self steepening effect (optical shock), have been studied to obtain femtosecond pulses with a grating pair pulse compressor. These effects cause asymmetrically broadened and nonlinearly chirped optical pulses, which degrade the characteristics of the pulse compression. These effects can be partially compensated for and the compressed pulse width can be reduced by using a third-order term of the phase function of the grating pair.

Prism compressor

Pulse compression

Frequency-resolved optical gating

10.1143/jjap.28.609

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Citations (3)

Exa-bit optical communication exploring by 3M scheme

Microoptics Conference (2013)

Masataka Nakazawa

We present recent challenges and efforts toward a hardware paradigm shift to overcome capacity limitation under current optical communication infrastructure. The latest advances in the three “multi” technologies, i. e. multi-level transmission with ultrahigh spectral efficiency, space division multiplexing in multi-core fibers, and mode division multiplexing with MIMO (multiple-input multiple-output), will be overviewed.

Spectral Efficiency

Spatial multiplexing

Multiwavelength optical networking

Time-division multiplexing

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Citations (0)