High speed pulse modulation of the injection lasers at non-bias condition has been studied to reduce the pattern effect. Rate equations involving the effect of spontaneous emission enable us to analyze the pulse response of carriers and photons both starting from zero in the cavity. The increase of threshold current and the decrease of delay time are derived as a function of the width of driving pulse current at the non-bias condition. Theoretical results were in good agreement with the experiments. The effect of accumulation carriers in the active region is analyzed in details. It is pointed out that the effect of accumulation carriers in the active region limits the rate of pulse repetition when the pattern effect is required to be small. To overcome this effect a new method which utilizes the application of reverse pulse to a laser diode immediately after the emission of light pulse is proposed. This method has been proved experimentally to be effective. A series capacitance to a laser diode was used to produce reverse pulse, and in this way two pulses have been applied at the interval of 2 nsec. Further investigation on the pulse repetition rate together with the consideration of series resistance in the driving circuit has lead to the conclusion that a few Gbit/sec is possible with AlGaAs DH lasers at the non-bias condition. In these lasers, however, very thin active layers with low impurity concentration are required.

By application of Zolotarev polynomial, a difference pattern of a monopulse array antenna and a sum (conventional) pattern of an array antenna with an even number of elements are synthesized. The resulting patterns are optimum in a Chebyshev sense for monopulse array antennas and for even element arrays with the element spacing less than a half wavelength, respectively. Design procedure for difference and sum patterns is shown by numerical calculations.

The waveguide bandpass filter with dielectric resonators is usually constructed with a cutoff waveguide including dielectric resonators inside and waveguides which are connected at both ends of the cutoff waveguide. The coupling coefficient between dielectric resonators was obtained by S.B. Cohn. The external Q of a dielectric resonator, however, was not reported in the past, which is necessary for the design of the filter. In this paper, the external Q is obtained by calculating the radiation power by using the displacement current inside the dielectric resonator. The theoretical values of the external Q are obtained corresponding to the distance between input waveguide and a resonator. The results were compared with the experimental results and they were in a good agreement. The external Q is also calculated by using the radiation power from a magnetic dipole source of a resonator. It takes more error than the method by using a displacement current.

An optical-transmission error-rate experiment is described in which a single-mode fibre up to 5.9 km long is used as a transmission medium. It is shown that impairments of the transmission was mainly determined by material dispersion and wave-guide-delay distorsion of the transmission medium.