The number of molecules in the mode volume is introduced into the rate equations of a microcavity laser, and the resultant equations are analyzed. It is predicted that the laser does not oscillate and the output power is saturated unless the product of the number of molecules in the mode volume and the spontaneous emission coupling ratio exceeds a certain constant. The step height in a log-log plot of the input-output characteristics is not necessarily equal to the logarithm of the reciprocal spontaneous emission coupling ratio.

Because of increase of communication bandwidth demand, upgrading the speed of optical fiber networks is a future issue. However, in the case of high speed transmission at wavelength of 1.5 μm band on the existing single mode fiber, transmission distance is limited due to chromatic dispersion. Thus, in addition to chromatic dispersion compensation devices, automatic optimization methods of the compensation value are important especially in the case of photonic networks, on which transmission distances often change dynamically. But problems remain such that signal quality measuring instruments are expensive under existing automatic chromatic dispersion compensation methods.In this report, focusing on spectrum profile change by long transmission of optical signals, a simple automatic control method of chromatic dispersion compensation is proposed. And some results of basic experiments are described. By doing feedback control for optimizing the chromatic dispersion compensation value, an error-free state of a 10 Gbps optical signal is demonstrated even if the dispersion value of the transmission line is rapidly changed.

SUMMARYWe propose an interferometer-type multistate optical switch and an interferometer-type digital performance switch using a fiber Bragg grating (FBG) and the phase reversal effect. The effect is a reversing phenomenon of optical phase difference between the reflected and transmitted light from an FBG on a reflectivity spectrum dip between the main reflection band and first sideband. By combining this effect and reflectivity change, the multistate switch including only a single FBG can perform as a four-state switch. In this paper we describe the principle of the phase reversal effect and some novel optical switch structures, and also the results of experimental examination.

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