Simultaneous measurements of temperature and strain were demonstrated by measuring the stimulated Brillouin scattering frequency shift and gain in two separate types of optical fibers: dispersion shifted and special GeO2-doped optical fiber. This novel approach allows for a hybrid frequency division and time division multiplexing scheme for developing advanced distributed strain sensing. The preliminary measurements show a temperature resolution of approximately 1.6 and a strain resolution of 32 µε.

We performed 10 Gbit/s optical soliton transmission experiment over 2,000 km with bit error rate of < 10-9 in a comb-like dispersion profiled fiber (CDPF) loop of 80 km amplifier spacing which corresponds to 1.8 times of dispersion distance. By reducing the average dispersion of the CDPF, error free distance of 3,000 km was obtained.

We propose novel all-optical functional devices using waveguide X-junctions with localized third order optical nonlinearity, where one branch is made from a Kerr-like nonlinear material and the rest are made from linear ones. All-optical switching operations can be obtained because of bistable like nonlinear dispersion characteristics in linear and nonlinear coupled guided-wave systems. The performances of the devices are analyzed by the Beam Propagation Method (BPM) modified for nonlinear waveguides combined with the nonlinear normal mode analysis. The methods to construct the waveguides with localized nonlinearity are also discussed by utilizing the technologies for the selective control of a band-gap energy of semiconductor Multi Quantum Well (MQW) structures and the performances of the designed devices are presented.

We propose novel all-optical functional devices using waveguide X-junctions with localized third order optical nonlinearity, where one branch is made from a Kerr-like nonlinear material and the rest are made from linear ones. All-optical switching operations can be obtained because of bistable like nonlinear dispersion characteristics in linear and nonlinear coupled guided-wave systems. The performances of the devices are analyzed by the Beam Propagation Method (BPM) modified for nonlinear waveguides combined with the nonlinear normal mode analysis. The methods to construct the waveguides with localized nonlinearity are also discussed by utilizing the technologies for the selective control of a band-gap energy of semiconductor Multi Quantum Well (MQW) structures and the performances of the designed devices are presented.

By sacrificing approximately ten percent of the transmission speed, ultra-high speed optical time division multiplexed network can be fully operatable by the use of currently available electrical switches. The network utilizes dispersion managed quasi-solitons and transmits TDM packet which comprises of ATM cells that are introduced from a gateway through bit compression to match to the ultra-high speed traffics. The network can provide flexible bandwidth and bit on demand at burst rate of the maximum LAN speed.

We present an experimental and theoretical study of multiple diffraction rings of a cw Ar+ laser beam from a nitrobenzene solution of BDN (bis-(4-dimethylaminodithiobenzil)-nickel) caused by the spatial self-phase modulation. We examine in detail the effect of the intensity and phase shift profiles of the beam in the nonlinear medium by comparing the measured ring patterns with the theoretical results based on the Fraunhofer diffraction. Although the thickness of the sample is only 180 µm in our experiment, it is found that the intensity and phase shift profiles are broadened owing to the self-defocusing effect. It is also found that the phase shift profile is further broadened by the thermal diffusion. These two effects become remarkable when the focused beam is used.

Widely tunable coherent terahertz (THz)-wave generation was successfully demonstrated based on the laser light scattering from the lowest A1-symmetry polariton mode by using a Q-switched Nd:YAG laser pumping. This method exhibits multiple advantages like wide tunability (frequency: 0. 9-2. 2 THz), coherency and compactness of its system. In this paper, the general performances of this THz-wave generator, as well as the recent development of the system and its application are reported. Measurements of tunability, coherency, power, polarization, radiation angle, and divergence are shown. The cryogenic cooling of the crystal was performed in addition, and a more than one hundred times higher THz-wave output was observed. A spectroscopic application of our wave source is demonstrated by measuring the water vapor absorption.