Kishi NAOTO (來住 直人)

Offer Organization: Japan Society for the Promotion of Science, System Name: Grants-in-Aid for Scientific Research, Category: Scientific research (C), general, Fund Type: -, Overall Grant Amount: - (direct: 3300000, indirect: 990000)
本研究計画においては、径の微小な複数のコアが、通常の光ファイバのコア径程度の小さな領域に密集して存在する光ファイバ構造を対象とする。この光ファイバ構造においては、それらの複数コア全体が光伝送のための一本のコアの役割を果たしている。このような波長程度の大きさの微細構造を持つ光ファイバは、通常の単一コア光ファイバでは得られない光波伝搬特性を持つ可能性がある。そこで本研究計画では、微細径密集コア光ファイバの光波伝搬特性を、精密な電磁界解析と、それに基づいた試作光ファイバの特性評価により解明する。特性の中でも、主として光ファイバの波長分散特性の光ファイバの構造に対する依存性を明らかにすることに重点を置き、微細密集コア光ファイバの持つ、通常の光ファイバでは実現困難で有用な特性の可能性を追求する。

Offer Organization: Japan Society for the Promotion of Science, System Name: Grants-in-Aid for Scientific Research, Category: Scientific research (C), general, Fund Type: -, Overall Grant Amount: - (direct: 3600000, indirect: 1080000)
There are different signal formats in optical fiber communication networks. In such networks, processing function in network node should work independently from the signal formats, such as intensity- and phase-modulations.
In this project, regenerative optical signal processing functions, such as pulsewidth tunable regenerative pulsewidth conversion, optical multicasting function to distribute a single-channel signal to multiple-wavelength channels, conversion of a wavelength-division multiplexing signal to a optical time-division multiplexing signal, and distortion-compensating variable optical delay line to change the timing of the signal, are studied. These processing functions are investigated for phase-modulated signal as well as conventional intensity-modulated signals. The results of the study suggest that most of these functions are applicable independent from the signal formats.

Offer Organization: Japan Society for the Promotion of Science, System Name: Grants-in-Aid for Scientific Research, Category: Scientific research (B), general, Fund Type: -, Overall Grant Amount: - (direct: 9800000, indirect: 2940000)
In optical communication networks, optical node functions are very important which convert the signal wavelength and waveform and/or compensate signal distortions. So far, such optical node functions have assumed the same signal format. On the other hand, there are many signal formats according to the properties of the signal sources and destinations. In this study, optical node functions which allow multiple signal formats were investigated.
The research results include realization of (1) wavelength/waveform conversion and waveform reshaping function applicable to various signal modulation formats, (2) polarization- and signal format-independent waveform conversion function, and (3) OTDM(optical time-division multiplexing) to WDM(wavelength-division multiplexing) conversion function.

Offer Organization: Japan Society for the Promotion of Science, System Name: Grants-in-Aid for Scientific Research, Category: Scientific research (C), general, Fund Type: -, Overall Grant Amount: - (direct: 3500000, indirect: 1050000)
Variable optical delay-line is very important for optical signal timing adjustment in optical communication networks. In this study, optical Fourier transformation(OFT) is appliedto such variable optical delay-line to realize distortion-free operation. The characteristics of the OFTincorporatedoptical delay-line, which is realized with a phase modulator, a suitable length of opticalfiber, and a wavelength converter is evaluated. Distortion-free as well as variable time-delay operation of the delay-line is successfully demonstrated.

Offer Organization: Japan Society for the Promotion of Science, System Name: Grants-in-Aid for Scientific Research, Category: Scientific research (C), general, Fund Type: -, Overall Grant Amount: - (direct: 3200000, indirect: 300000)
The purpose of the project is to develop optical interfaces to convert the wavelength/waveform of optical signal between different optical networks. The achievements of this project are as follows.
With the use of a multi-stage semiconductor optical-amplifier based wavelength converter, large wavelength hopping over 300 nm was achieved for optical signals with bit-rates of 2.5 Gb/s and Gb/s. Waveform regeneration with inverting wavelength conversion was achieved. Multi-casting of optical signal at 1550 nm wavelength band was also demonstrated with the multi-stage wavelength converter, by which signal degradation due to nonlinear-mixing in semiconductor optical amplifier was successfully suppressed.
Pulse-width tunable waveform conversion by combination of fiber- and semiconductor-based switches was success-fully applied for NRZ(non return-to-zero) to RZ(return-to-zero) conversion. The output pulsewidth was tunable between 20 ps and 80 ps. Due to the pulsewidth conversion, transmission performance over 20 km was largely improved.
As an alternative way for pulsewith-shrinking, Raman amplifier based pulsewidth compressor was also examined. Output pulsewidth tunability for modulated signal between 13 ps and 3 ps was achieved.
As an application of waveform conversion technique with a semiconductor optical-amplifier, widely wavelength-tunable optical clock pulse generator was developed. Higher-quality optical clock pulses were obtained in comparison with conventional wavelength-tunable lightsources. Waveform optimization method with this optical clock was also found.

Offer Organization: Japan Society for the Promotion of Science, System Name: Grants-in-Aid for Scientific Research, Category: Scientific research (C), general, Fund Type: -, Overall Grant Amount: - (direct: 3700000, indirect: -)
The purpose of the project is to develop lightsources with controllabilities of their frequencies, waveforms, and number of channels. The achievements of this project are as follows.
With the use of semiconductor-amplifier based waveform/wavelength converter, a 16-channel multi-wavelength light-source with variable pulsewidth between 10ps and 90ps were demonstrated. The generated optical signals were successfully applied to transmission over fibers with various dispersion values between - 100ps/nm and 460ps/nm so that the power penalties of received signals were minimized by adjusting the pulsewidths. Pulsewidth optimized signal was also found to be superior to conventionally used optical signal formats.
A multi-wavelength fiber laser with an intra-cavity phase modulation was demonstrated. Multi-wavelength output with a good spectral flatness within 5nm was successfully demonstrated.
Wavelength conversion with a semiconductor optical amplifier was applied to realize a variable wavelength optical clock in the wavelength range between 1460nm and 1610nm. 10GHz clock signal was successfully obtained with a very high optical signal to noise ratio.
Narrow-linewidth single-polarization single-frequency fiber laser controlled by an external light injection was demonstrated. With a proper adjustment of lasing and external light powers, low-drift wavelength tunable operation between 1545nm and 1560nm was achieved.
Improvement of multi-wavelength lightsource based on supercontinuum spectrum generation through Raman soliton effect in optical fiber was investigated with the use of seed pulses with shorter pulsewidth. With the use of 1.3ps pulsewidth seed light source, larger bandwidth and better flatness of the generated spectrum was obtained. Detailed characterization of the generated spectrum is still in progress.