Abstract: A communication system includes a termination-side optical transmitter comprising a reflective semiconductor optical amplifier, a reflective unit configured to reflect output light from the termination-side optical transmitter, and a terminal station-side optical receiver connected to the termination-side optical transmitter via a transmission line and configured to receive the output light from the termination-side optical transmitter by limiting a frequency band of the output light. The reflective semiconductor optical amplifier amplifies the output light reflected by the reflective unit, modulates the amplified output light based on an electric signal, and outputs the modulated output light.

Abstract: To suppress occurrence of axial hole burning in a phase shift portion of a diffraction grating, provided is a semiconductor optical device including: a diffraction grating layer including a diffraction grating and a phase shift portion; and an optical waveguide layer including an active layer that has a gain with respect to an emission wavelength and an optical waveguide region that has no gain with respect to the emission wavelength. The optical waveguide region is formed at least on the lower side of the phase shift portion.

Abstract: Some semiconductor lasers have an initial failure mode that is advanced as the amount of optical power therein, namely, the amount of optical output observed from the outside increases in almost independent of the temperature. The initial failure mode that is advanced as the amount of optical output increases is not sufficiently screened, so that the initial failure rate is somewhat higher than that of the semiconductor laser having the conventional active layer material. It is effective to introduce a test with large optical output at lower temperature than average operating temperature such as room temperature, during the manufacturing process. This helps to eliminate elements having the initial failure mode that is advanced as the amount optical output increases, thereby to extend the expected life of the laser diodes.

Abstract: During the polishing of a semiconductor substrate, the semiconductor wafer that has been reduced in thickness, and hence in strength, by polishing, suffers outer-surface damage (or cracking) due to the initial damage caused by the use of polishing quartz. In order to solve these problems, the present invention applies a semiconductor substrate fixing jig formed with, on the face for fixing the semiconductor substrate, a groove(s) of almost the same diameter as that of the semiconductor substrate. Semiconductor substrate damage and cracking can be suppressed by applying this jig.

Abstract: Some semiconductor lasers have an initial failure mode that is advanced as the amount of optical power therein, namely, the amount of optical output observed from the outside increases in almost independent of the temperature. The initial failure mode that is advanced as the amount of optical output increases is not sufficiently screened, so that the initial failure rate is somewhat higher than that of the semiconductor laser having the conventional active layer material. It is effective to introduce a test with large optical output at lower temperature than average operating temperature such as room temperature, during the manufacturing process. This helps to eliminate elements having the initial failure mode that is advanced as the amount optical output increases, thereby to extend the expected life of the laser diodes.

Abstract: During the polishing of a semiconductor substrate, the semiconductor wafer that has been reduced in thickness, and hence in strength, by polishing, suffers outer-surface damage (or cracking) due to the initial damage caused by the use of polishing quartz. In order to solve these problems, the present invention applies a semiconductor substrate fixing jig formed with, on the face for fixing the semiconductor substrate, a groove(s) of almost the same diameter as that of the semiconductor substrate. Semiconductor substrate damage and cracking can be suppressed by applying this jig.