Jiro Hiroishi

Low-loss and low-dispersion-slope highly nonlinear fibers

In recent technologies, various optical signal processing systems have been reported. In many of these applications, highly nonlinear fibers (HNLFs) are used as key parts. Especially, low loss and low dispersion slope are critical features of the HNLFs. In this paper, their design and characteristics, packaging technology, and applications are introduced.

Nearly exact optical beat-to-soliton train conversion based on comb-like profiled fiber emulating a polynomial dispersion decreasing profile

We show that an optical beat signal is almost exactly converted to a soliton train through the propagation along a fiber with a polynomial dispersion decreasing profile, which is numerically optimized through iterative calculation. In the experiment, we demonstrate the 160-GHz beat-to-soliton conversion with a 40-pair comb-like profiled fiber, which is designed to emulate the optimized dispersion profile. The optical beat is compressed to a 324-fs soliton train with a high peak-to-pedestal ratio of more than 21 dB, and its spectral envelope is almost completely converted into a sech/sup 2/ shape.

Generation of in-phase pulse train from optical beat signal

We propose and demonstrate generation of an in-phase optical pulse train from an optical beat signal. The proposed method is based on four-wave mixing occurring between the two continuous waves of the beat signal and on spectral filtering to shape the spectrum to be symmetric about the carrier frequency. We perform an experiment to verify the proposed method and obtain a 1.5 ps width in-phase pulse train from a 160 GHz beat signal. Furthermore, we employ a pulse compression scheme to reshape and compress the obtained pulse train, and we show that a 160 GHz repeating, 0.7 ps FWHM, nearly transform-limited, in-phase sech pulse train is successfully generated.

Investigation of a Downsized Silica Highly Nonlinear Fiber

Theoretical influences of reducing the cladding diameter for silica highly nonlinear fiber (HNLF) have been investigated by the finite-element method. Downsized HNLF with 56-mum cladding was fabricated, and certain reliability was confirmed through mechanical and environmental tests. A coin-sized module was obtained using over 200 m of 56-mum HNLF.

Improvement of FWM conversion efficiency by SBS-suppressed highly nonlinear dispersion-decreasing fiber with a strain distribution

We demonstrated 8 dB SBS-suppression and a uniform dispersion simultaneously by down-sized dispersion-decreasing HNLF applying distributed strain. FWM wavelength conversion efficiency of -2 dB was achieved with single CW pumping.

FWM wavelength conversion with over 60nm of 0dB conversion bandwidth by SBS-suppressed HNLF

We demonstrated FWM wavelength conversion with maximum conversion efficiency of 1.5 dB using a single CW pump with no phase modulation by SBS-suppressed HNLF. Over 60 nm of conversion bandwidth with over-0 dB conversion efficiency was obtained.

Generation of 160-GHz sub-picosecond in-phase pulse train from optical beat signal

We propose a method to generate in-phase optical pulse train from optical beat signal based on four-wave mixing and asymmetric spectral filtering. A 160-GHz repeating, 0.7-ps-FWHM, nearly transform-limited, in-phase sech pulse train is successfully generated.

Stationary rescaled pulse in dispersion-managed comblike profiled fiber for highly efficient and high-quality optical pulse compression

A stationary rescaled pulse (SRP) exists in a dispersion-managed comblike profiled fiber (DM-CPF) that consists of alternate concatenations of normal-dispersion highly nonlinear fiber and single-mode fiber. Numerical analysis reveals that the newly found SRP exhibits a nearly Gaussian temporal profile with a small amount of pedestal in spite of a relatively large compression ratio. We apply the SRP propagation to optical pulse compression based on DM-CPF and demonstrate highly efficient and high-quality optical pulse compression. Using a three-step DM-CPF, we experimentally show that a 2.6 ps width input pulse is successfully compressed to a nearly Gaussian pulse having the width of 0.39 ps and the peak-to-pedestal ratio of 19.3 dB.

Compact optical pulse compressor based on comb-like profiled fiber comprised of HNLF and hole-assisted fiber

We develop a hole-assisted fiber with large anomalous dispersion and low macro-bending loss to realize compact module of CPF pulse compressor. Using the fabricated module, we demonstrate C-band wavelength-tunable pulse compression for 40 GHz pulse train

Experiment of zero dispersion tuning by stretching down-sized HNLF

Zero dispersion of drawn HNLF was tuned by fiber stretching. Small cladding fiber is attractive for this purpose. 16nm tuning range of ¿0 was realized and performance of this tuning was confirmed by FWM wavelength conversion experiments.