Yasuji Fukasawa

Fusion spliceable and highly efficient Bi/sub 2/O/sub 3/-based EDF for short-length and broadband application pumped at 1480 nm

A conventional fusion splicing to SiO/sub 2/ fiber was achieved in W/sub 2/O/sub 3/-based Er doped fibers (EDF). High slope efficiency of 43 % and broadband gain spectrum were achieved at 1490 nm pumping amplification for only 26 cm-length.

Extra-Broadband and Highly Efficient Short length Bi2O3-based EDF

We demonstrated the 3-dB down bandwidth of 75 nm with average output power over 20 dBm for single-stage operation with Bi2O3-based EDF. Its max power conversion efficiency was 39 % at 1560 nm.

Bi2O3-based glass for S-band amplification

Bi2O3-based thulium (Tm3+) doped glass fiber (Bi-TDF) for S-band amplification was investigated. Tm3+ was doped in Bi2O3-SiO2 based glass and melted using a conventional method. Emission spectra of the 3H4 - 3F4 were measured with pumping at a wavelength of 792 nm using laser diode (LD). Full width of half maximum (FWHM) of the emission is 1.4 times and 1.1 times broader than that of fluoride glass and tellurite glass, respectively. Moreover, the emission peak shifted towards longer wavelength as compared with fluoride and tellurite glasses. Single mode Bi-TDFs with Tm3+ concentrations of 2000 ppm, 3900 ppm and 6000 ppm were fabricated and evaluated with fusion splicing to SiO2 fibers. Gain profiles were measured with bi-directional pumping using 1047 nm Yb fiber lasers. The gain-peaks observed around 1470 nm shifted towards longer wavelength with increasing Tm3+ concentration. Gain properties of Bi-TDF were improved by additional pumping at the wavelength of 1560 nm with Tm3+ concentrations of 2000 ppm and 3900 ppm. A maximum gain over 10 dB of Bi-TDF was obtained using a fusion spliceable Bi-TDF with a length of only 100 cm.

Ultracompact Gain Block with Bi2O3-Based Erbium-Doped Fiber

An ultracompact gain block with Bi2O3-based erbium-doped fiber (Bi-EDF) is presented. The ultracompact gain block includes two pump LDs, two isolators, a photodiode, dichromatic mirrors and a Bi-EDF 23 cm long in the amplifier package with a size of only 45×43×10 mm. We can obtain a net gain of 25 dB and output power of 10 dBm at 1560 nm in the C-band region.

Highly efficient and short length Lanthanum co-doped Bi2O3-based EDF for extended L-band amplification

A 3 dB gain bandwidth of 60 nm was achieved for single-stage operation in the wavelength range from 1560 to 1620 nm using Lanthanum co-doped bismuth based Er doped fiber with only 200 -250 cm length, which exhibited power conversion efficiency of 30%. In addition, no increase in noise figure was observed at the wavelength region beyond 1610 nm.

Extra-broadband and highly efficient short length Bi/sub 2/O/sub 3/-based EDF

We demonstrated the 3-dB down bandwidth of 75 nm with average output power over 20 dBm for single-stage operation with Bi/sub 2/O/sub 3/-based EDF. Its max power conversion efficiency was 39 % at 1560 nm.

A Study on Relation between Brightness Uniformity of LCD and Cell Gap Deviation

The purposes of this study are to understand the relation between brightness uniformity of LCDs and its cell gap deviation caused by flatness of their substrates and to propose a flatness criterion of substrates considering human sensibility to the uniformity. Examinations are performed using periodic linear deviations in brightness uniformity on LCD cell samples. Result of psychophysical test shows that human sensibility to the linear defects depends on a cross gradient for the brightness signal projection to a linear direction. Therefore linear defects in uniformity can be evaluated by the gradient value. To demonstrate correlation between the deviation to brightness uniformity of LCDs and the cell gap deviation caused by flatness deviations of their substrates, some cross sections on LCD cell samples are tested. Brightness deviations are measured by image processing technique and cell gap deviations are calculated from measured surface profiles of their front and rear substrates that were pieces of the cells. Strong similarity between both deviations is observed. From this result it becomes clear that periodic linear deviations to the brightness uniformity on LCDs can come from surface corrugation of substrates caused by glass surface or coated layers. Then flatness of substrates can be evaluated according to the human sensibility to the brightness uniformity of LCDs by using gradient value of surface profiles and allowable limits of substrate corrugation can be determined by this experimental process in the same cell production condition.