Recently, the number of pixels of an image sensor has reached more than one Mega in the field of video
endoscopes, while analog signal transmission bands that use existing electric wires will face physical limitations from
the perspective of signal bandwidth and EMC (Electro Magnetic Compatibility) noise. In order to solve these problems,
we have developed a bi-directional digital optical communication endoscope system that employs both an image sensor
and a single line optical fiber. In addition, due to the fiber's high-speed image signal transmission, we have incorporated
a digital circuit for serial modulation and deserial demodulation. Consequently, we confirmed that transmission speeds
of a 1Gbps downlink image signal and a 110Kbps uplink control signal were achieved as a result of simultaneous
communication. We also designed and tested a compact, co-axial
bi-directional optical transmitter and receiver module
that can be built into the distal side of a scope. The optical communication module size is less than φ4×10mm. It was
confirmed that this module could be installed in the distal side of a current endoscope.
In dye-sensitized solar cells, electron transport in nano-porous thin TiO<sub>2</sub> film electrodes plays an important role in energy conversion efficiency. Previous studies have revealed that the electron transport property is largely influenced by electron density in the electrodes and the preparation methods of the TiO<sub>2</sub> electrodes. In this paper, we study the electron diffusion in nano-porous TiO<sub>2</sub> electrodes with and without dye adsorption. The electron diffusion coefficient is derived from pulsed laser induced current transients in the presence and absence of bias light. Measurements are repeated with various light intensities to examine electron density dependence. The experiments are performed for the electrodes prepared from two different TiO<sub>2</sub> particles and for two different electrolytes. For all cases, dye adsorption is found to increase electron diffusion coefficients under the same electron density in the electrodes. The increase of diffusion coefficients is confirmed by open-circuit voltage transient measurements. The charge trap on the electrode surface is studied from the relationship between open-circuit voltage and charge density in the dyed TiO<sub>2</sub>electrodes. The reduction of surface charge trap density due to the dye adsorption is discussed.