Analysis of chirp power penalty in 1.55-µm DFB-LD high-speed optical fiber transmission systems

In a 1.55-μm high-speed transmission system using a DFB-LD, the chirp effect in the LD is a factor limiting transmission span length. In order to evaluate the chirp effect, we derive expressions for the chirp power penalty for two cases: the cases of the chirp occurring in both edges of the pulse and in the whole time of the pulse. The calculations based on the results of the LD chirp measurement predict that the chirp effect will be significant above 2 Gbit/s even if the zero dispersion wavelength of fiber is shifted to the 1.55-μm band. Transmission experiments performed at 1.2 Gbit/s and 2.4 Gbit/s verify this prediction.     

Nondestructive Quantitative Evaluation of Porosity Volume Distribution in Aluminum Alloy Die Castings by Fractal Analysis

The nondestructive and three-dimensional quantitative evaluation of porosity in aluminum alloy die castings is proposed to identify whether the predominant cause of pore formation is shrinkage or entrapped gas. The validity of this method of evaluation was shown by comparing two different regions with different ratios of pores formed by shrinkage and gas. It was shown that the proposed evaluation can be used as a quantitative indication of porosity.     

Relationships between 4-hydroxy-2-nonenal, 2-thiobarbituric acid reactive substances and n-6 polyunsaturated fatty acids in refrigerated and frozen pork

The relationships between 4-hydroxy-2-nonenal (HNE), 2-thiobarbituric acid reactive substances (TBARS) and n-6 polyunsaturated fatty acids (n-6 PUFAs) were investigated for pork stored at 0, -20 and -80 degrees C. A significant linear correlation was apparent between HNE and TBARS for the pork stored at each temperature. However, the n-6 PUFA content remained unchanged during storage.     

Optical loss measurement results on an experimental optical fibre submarine cable of 30 km length

A continuous length of 30 km optical fibre submarine cable was successfully manufactured and laid on the sea bed about 1000 m deep. After the sea trial of 17 months, the cable was recovered from the sea bed. No significant degradation was observed in the optical loss of the recovered cable.     

Estimation of long-term transmission loss increase in silica-basedoptical fibers under hydrogen atmosphere

The irreversible loss increase in silica-based optical fibers due to hydrogen is discussed on the basis of results of various high-temperature tests. The results show that germanium-doped-core fibers have different behavior with respect to irreversible loss increase, and that a pure-silica-core fiber fabricated under optimum conditions is very stable against irreversible loss increase. The estimation of long-term transmission loss stability is also discussed, and high-temperature testing is certified to be effective for estimating the long-term loss stability under low temperature     

Loss spectra of optical fibres under hydrogen and deuterium

Assignment of the frequencies at the loss peaks due to hydrogen permeation is clarified on the basis of the loss spectra in silica glass fibre under deuterium. As a result, it is concluded that the loss peaks due to hydrogen permeation in silica glass fibre are related to the combinational vibrations of hydrogen molecular vibration and SiO4 tetrahedral vibrations.     

Dopant effect on transmission loss increase due to hydrogen permeation

The transmission loss increase due to hydrogen permeation in a GeO2-doped silica fibre and a P2O5-doped silica fibre are investigated. As a result, the difference of the loss increase between them is observed, and is considered to be due to the difference of the electronegativity between silica, germanium and phosphorus.     

Chromatic dispersion measurement over a 100 km dispersion-shifted single-mode fibre by a new phase-shift technique

Chromatic dispersion of a 100.7 km concatenated dispersion-shifted single-mode fibre has been measured by a two wavelengths division multiplexing phase-shift technique utilising four laser diodes in the 1.3~1.6 ?m spectral region. Measurement accuracies of dispersion and zero-dispersion wavelength were good and within ±0.025 ps/km nm and ±0.3 nm, respectively. The measured result of dispersion coincided with the arithmetic mean of those of the constituent fibres.     

Absorption loss in optical fibres due to hydrogen

It is shown that OD formation in optical fibres due to the deuterium molecule can become a barrier to OH formation in optical fibres exposed to hydrogen, although it cannot be a barrier to the absorption due to the hydrogen molecule in a fibre. The mechanism is discussed.     

Polarisation fluctuation of submarine-cabled single-mode optical fibres in ocean installation

Polarisation fluctuations of the power spectrum with time in an optical fibre submarine cable installation are reported for the first time. It was found that the power spectrum of polarisation fluctuation was less than 60 Hz, and the maximum power spectrum was between 5Hz and 10Hz during the cable installation within a maximum cable tension of 18 kN (?1.8 tons) and a cable laying speed of 3.5 n mile/h, respectively.