Abstract: A SDH receiver which comprises a first polarization beam splitter 11, a second polarization beam splitter 13, a first separator 15, a second separator 17, a third separator 19, a fourth separator 21, a first 90-degree polarization rotor 23, a second 90-degree polarization rotor 25, a first hybrid detector 31, a second hybrid detector 33, a third hybrid detector 35, a fourth hybrid detector 37, and a signal processor 39.

Abstract: The receiver 11 for self-homodyne detection comprises a coherent detection system and a direct detection system. The receiver comprises a polarization splitter 13, a first splitter 15, a 90 degree polarization rotor 17, a hybrid detector 19, a first balanced detector 21, and a processor 23.

Abstract: A SDH receiver which comprises a first polarization beam splitter 11, a second polarization beam splitter 13, a first separator 15, a second separator 17, a third separator 19, a fourth separator 21, a first 90-degree polarization rotor 23, a second 90-degree polarization rotor 25, a first hybrid detector 31, a second hybrid detector 33, a third hybrid detector 35, a fourth hybrid detector 37, and a signal processor 39.

Abstract: The receiver 11 for self-homodyne detection comprises a coherent detection system and a direct detection system. The receiver comprises a polarization splitter 13, a first splitter 15, a 90 degree polarization rotor 17, a hybrid detector 19, a first balanced detector 21, and a processor 23.

Abstract: A device for coupling a multicore/multimode fiber that can transmit a large quantity of information. This multicore/multimode fiber coupling device has a first fiber group (11), a first light converging system (13), a first mode converter (15), a second fiber group (21), a second light converging system (23), and light converging system (33) for multicore fibers. By means of the first mode converter (15), light from the first fiber group (11) is subjected to mode conversion en masse. A space coupling system (33) for multicore fibers transmits light derived from the second fiber group (21) and light derived from the first fiber group (11) subjected to mode conversion to the multicore fibers (31).

Abstract: To provide a self-homodyne detection communication system capable of using a space-division multiplexing signal as a signal for communication. The present invention relates to a space-division multiplexing apparatus 12 including a multi-core fiber 11 having multiple cores. The space-division multiplexing apparatus 12 uses cores other than a core 13 for self-homodyne detection among the multiple cores included in the multi-core fiber 11 as cores 16 for communication. The space-division multiplexing apparatus is configured to include a pilot-tone guiding unit 14 and a self-homodyne detection unit 15.

Abstract: To provide a self-homodyne detection communication system capable of using a space-division multiplexing signal as a signal for communication. The present invention relates to a space-division multiplexing apparatus 12 including a multi-core fiber 11 having multiple cores. The space-division multiplexing apparatus 12 uses cores other than a core 13 for self-homodyne detection among the multiple cores included in the multi-core fiber 11 as cores 16 for communication. The space-division multiplexing apparatus is configured to include a pilot-tone guiding unit 14 and a self-homodyne detection unit 15.

Abstract: It is an object of the present invention to provide a rare earth doped fiber whose transient response is suppressed and an optical amplifier for optical packet communication having a good characteristic even if there is little traffic. The above-mentioned problem is solved by an optical amplifier for optical packet communication comprising a first rare earth doped fiber (EDFA) having an active region whose diameter is between 3.4 ?m and 10 ?m, inclusive, an intermediate gain equalizing filter, and a second EDF, wherein the first EDFA is shorter than the second EDFA, and wherein the intermediate gain equalizing filter adjusts the intensity of each wavelength channel so as to equalize the light intensity of each wavelength channel having transmitted through the second EDF.

Abstract: It is an object of the present invention to provide a rare earth doped fiber whose transient response is suppressed and an optical amplifier for optical packet communication having a good characteristic even if there is little traffic. The above-mentioned problem is solved by an optical amplifier for optical packet communication comprising a first rare earth doped fiber (EDFA) having an active region whose diameter is between 3.4 ?m and 10 ?m, inclusive, an intermediate gain equalizing filter, and a second EDF, wherein the first EDFA is shorter than the second EDFA, and wherein the intermediate gain equalizing filter adjusts the intensity of each wavelength channel so as to equalize the light intensity of each wavelength channel having transmitted through the second EDF.