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A 1.5-dB gain-flatness over 67 nm is achieved with a novel hybrid amplifier comprised of a distributed Raman amplifier pumped at two wavelengths and an erbium-doped fluoride fiber amplifier. Fourteen 2.5-Gb/s signals spanning 65 nm are successfully transmitted over 900 km using the new amplifiers. Low-noise characteristics compared to the same transmission line with discrete erbium-doped fiber amplifiers are also confirmed.

The effect of Saiko-ka-ryukotsu-borei-to (SRBT) on the stress-induced increase of monoamines in brain regions was investigated in three mouse emotional stress models. Dopamine (DA) and 3,4-dihydroxy-phenyl acetic acid (DOPAC) contents were elevated significantly by electric shock stress, psychological stress and conditioned fear stress in thalamus, hypothalamus and amygdala. The DA and DOPAC levels were decreased by preadministration of SRBT (600 mg/kg, p.o.) in the last two models, but were not altered in electric shock stress. Therefore, this compound seems to be effective in stress involving emotional factors. These results indicate that SRBT affects the brain monoamine neurons leading to psychological change in mice.

A 3 dB gain bandwidth of 75 nm (1531-1606 nm) is realised in a novel configuration of a two-stage erbium-doped fluoride fibre amplifier with a discrete fibre Raman amplifier. Error-free operation in an in-line amplifier configuration is also confirmed through a WDM (2.5 Gbit/s/spl times/9 channel) transmission experiment.

3 dB bandwidths of 52 nm (1556 – 1608 nm) for a silicate erbium-doped fibre amplifier (EDFA) and 50 nm (1554 – 1604 nm) for a fluoride EDFA have been obtained by a novel scheme with two-stage erbium-doped fibres and an intermediate equaliser. Low noise figures and high pump efficiencies of the EDFAs have been confirmed.

The widest, seamless, 76 nm (1531–1607 nm) 3 dB gain-band bidirectional amplifier is realised by combining an erbium-doped fluoride fibre amplifier (1531–1562 nm) and a gain-flattened erbium-doped silicate fibre amplifier (1562–1607 nm) in a novel configuration of gain-band separation between upstream and downstream signals. Bidirectional 10-channel WDM transmission at 2.5 Gbit/s over a 250 km conventional singlemode fibre is successfully demonstrated using our amplifiers as two bidirectional repeaters.

An extremely large 3-dB gain-bandwidth of 75 nm (1531-1606 nm) is achieved with a partially gain-flattened erbium-doped fluoride fiber amplifier and a distributed Raman amplifier. The Raman amplifier consists of a 85-km dispersion-shifted fiber (transmission fiber) and a practical 1505-nm Fabry-Perot laser diode pump. 9/spl times/2.5 Gb/s wavelength-division-multiplexing (WDM) transmission is successfully demonstrated using two 75-nm gain-band amplifiers as in-line and preamplifiers.