In this paper, an analysis was made on the variation of oscillating mode numbers of a semiconductor laser at high speed pulse modulation by solving multi-mode rate equations which relate a quasi-Fermi level to photon numbers. The laser gain was assumed to be homogeneous and has a dependency of (), where is ωE_g (relative photon energy). Single mode oscillation conditions for short pulse modulation were obtained associated with following two cases. A) One is the criterion how wide the mode separation must be made as of a short cavity laser and of an integrated twin-guide (ITG) laser. B) The other is the condition how large we must give an excess loss to the unwanted modes such as of the ITG laser, of a distributed feedback (DFB) laser, and of a distributed Bragg reflector (DBR) laser.

A New carrier recovery subsystem for binary PSK systems using synchronized push-pull oscillator is described. A property that the push-pull oscillator has two stable states of which the phase difference is π, can be well applied for this purpose. This new subsystem does not include phase-locked loop (PLL), therefore pull-in time and pull-in range are not limited by the loop delay of PLL. The circuit of this push-pull oscillator is very simple. Yet, it is proven to achieve rather good performance, if a limiter which normalizes the input amplitude, when practically deformed on account of the band-limiting, is attached. Our experiments have had good agreement with the theory and computer simulation.

Experimental results and theoretical consideration of the slant path rain attenuation characteristics and site diversity effects are described, together with the prediction method. The slant path rain attenuation has been measured by using 17 and 27 GHz sun-tracking radiometers at Yokosuka Electrical Communication Laboratory in Japan for 3 years. At a distance of 33 km from the laboratory, the atmospheric noise was also measured by using 18 GHz passive radiometer for the above-mentioned period to know the site diversity operation characteristics. It is shown that calculated values of slant path rain attenuation and site diversity effects agree well with measured values. For example, calculated and measured values of the rain attenuation, at 17 GHz for 0.1% of time within the time interval when the elevation angle of the sun is from 30 to 60, are 5.5 and 5.1 dB, respectively. Experimental results using 18 GHz passive radiometers fixed at 20 and 55 elevation angles indicate that the rain attenuation has the elevation angle dependence.

The error-rate performance of digital FM with discriminator-detection under the fast Rayleigh fading environment is theoretically analyzed in the presence of Gaussian noise and co-channel interference. While the effect of intersymbol interference caused by band width lmitations and time-delay spread is neglected, the fading spectrum effect is taken into consideration. The error-rate including not only the Rayleigh envelope fading effect but also the random FM noise effect is given in a simple closed form.

In this paper we derive several results on the dependent 2-unit system with single repair facility. The dependency means that it is allowed for the two units to fail at the same time. First, for the dependent 2-unit warm standby system, we obtain the following results: Laplace transform of the system reliability by using the conditional transform, limit theorems for the system reliability and mean time to the system failure (MTSF), distribution of the number of repairs completed during (0, t] and Laplace transform of the system reliability and MTSF in the case that the repair facility is capable of only n repairs. Second we discuss on the effects of repair policies to the availability of the dependent 2-unit hot standby system.

Usually, for the definitions on n-variable positive real functions, the properties on 2n-dimentional domain are used as the conditions of the definition, as examplified below. On the domain D {(p₁, p₂, , p_n)|Re p₁0, Re p₂0, , Re pn0)}, |Re w(p₁, p₂, , p_n) must be positive." In the present paper, the approach is simplified by the following two items.
(i) Fixing all variables except for one on the axis (real axis or imaginary axis), the problems on multi-variables are reduced to the one's on singlevariable.
(ii) The problems are discussed only on one-dimentional domain, that is, on the axes.
Simplifying the problems concerning with multi-variable positive real function by the two items stated above, the definitions of several classes of positive real function are presented. Clearly, these definitions may simplify extremely the verification of positive realness of any given function, and may give an effective means for the studies of multi-variable positive real function.

On the transient wave form of the oscillation at 4416 Å in a He-Cd II hollow cathode laser excited by the square wave discharge, a sharp peak is found in the initial region where the peak value of the discharge current is high. The excitation mechanism for the peak is due to the direct collision between electrons and Cd atoms.

A narrow-bandwidth optical wave filter was constructed by a stacked directional coupler with two slab waveguides of different materials. The matched phase constant β₀ defines the center wave-length of the filter, whereas the different dispersion relations and the inhomogeneity of the guides define the filter bandwidth. The narrowest 3 dB bandwidth was 0.2 nm at the center wavelength of 616.8 nm.