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.     

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.     

50 km, two-repeaters sea trial of optical-fibre submarine cable system

The experimental optical-fibre submarine cable system with 50 km cable and two repeaters was successfully laid in early June 1982. Optical loss changes of the cable during laying were less than 0.003 dB/km. The experiment will be continued during two or three years to obtain data on the cable and the repeaters.     

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.     

Optimal control of sensory evaluation of the sake mashing process

In the sake mashing process, we established the following four stages for optimal control of sensory evaluation. (1) To estimate the sensory evaluation value from the component concentrations of sake. (2) To create a model that can approximate the time series of the estimated sensory evaluation value and ethanol production rate from temperature data as the control variable. (3) To calculate the optimal trajectory of the ethanol production rate by using stages (1) and (2). (4) To perform trajectory control. As a result, sake having an optimal value of sensory evaluation was obtained by the above procedure.     

Prediction control for a cycloconverter of a power distortioncompensation system

Control methods of a flywheel mechanical energy storage system composed of a flywheel-synchronous machine and a current-controlled cycloconverter are described. Improvements to the current control abilities of the cycloconverter, applying modern control and information theories, are discussed. To obtain good current follow characteristics, both deadbeat control and prediction control are applied. The dead-beat scheme possesses one sample delay in its controlled signal which can compensate by predicting reference signals of the next sample time. To predict the load currents at the next sample time, two prediction methods are used. One of the predictions, which has learning ability for repetitive waves using correlation functions of the current, is composed of 256 digital filters. The weighting coefficients of the filters are determined instantaneously to minimize RMS (root mean square) errors. The other prediction, which has a high-frequency response, is applied to compensate random components and high-frequency components. The system is controlled by two digital signal processors for prediction of the currents, and a 16-bit microprocessor for control of the cycloconverter. Experimental results show excellent compensation abilities, not only for repetitive harmonics but also for high-frequency random components     

Novel core alignment method for low-loss splicing of single-mode fibres utilising uv-excited fluorescence of Ge-doped silica core

A novel core alignment method for single-mode fibre low-loss splicing without optical power monitoring is proposed. The method is based on the fluorescence of a Ge-doped silica core excited by ultraviolet light. The efficiency of the novel core alignment is investigated.