Abstract: To resolve problems, with the invention, an optical transmitter comprises an encoder for generating an optical signal obtained by encoding multi-wavelength pulses corresponding to sending data by use of a method of time spread/wavelength hopping in accordance with an encoding pattern of the encoder itself. The encoder concurrently executes time delay for every wavelength component at encoding, and time delay due to pre-compensation processing to pre-compensate for difference in propagation time for every wavelength component, occurring due to chromatic dispersion characteristics of a transmission line by ?%. An optical receiver comprises a decoder for decoding the optical signal transmitted by the optical transmitter in accordance with a decoding pattern of the decoder itself.

Abstract: An optical signal encoder/decoder includes a grating waveguide having an identical number of uniform pitch gratings to the number of code chips of a binary phase optical code, the uniform pitch gratings being formed in a waveguide direction to reflect light of a predetermined wavelength. Here, adjacent gratings corresponding to a position at which the optical code value changes are disposed a spacing apart from each other to give a phase shift of (2m+1)?/2 to the light, and the remaining adjacent gratings are disposed a spacing apart from each other to give a phase shift of n? to the light (m, n: integer).

Abstract: A feature of a wavelength conversion device of this invention is the board range of selection of wavelengths which can be obtained by conversion. A wavelength conversion device of this invention comprises an SC light generation portion 12, which receives an excitation light pulse output from an excitation light pulse source and generates SC light, and an optical wavelength filter 14 which filters the SC light. An excitation light pulse source generates an excitation light pulse, of central wavelength ?S. When the excitation light pulse generated by the excitation light pulse source is incident on the SC medium, SC light having a flat spectral shape over the range from wavelength ?L to wavelength ?H (where ?L<?H) is generated. The optical wavelength filter has a characteristic such that the filtering transmitted central wavelengths are ?1, ?2, ?3, . . . , ?n (where n is a natural number). A further feature is that the following conditions (1) and (2-1), (2-2), . . .

Abstract: An optical signal encoder/decoder includes a grating waveguide having an identical number of uniform pitch gratings to the number of code chips of a binary phase optical code, the uniform pitch gratings being formed in a waveguide direction to reflect light of a predetermined wavelength. Here, adjacent gratings corresponding to a position at which the optical code value changes are disposed a spacing apart from each other to give a phase shift of (2m+1)?/2 to the light, and the remaining adjacent gratings are disposed a spacing apart from each other to give a phase shift of n? to the light (m, n: integer).

Abstract: A feature of a wavelength conversion device of this invention is the board range of selection of wavelengths which can be obtained by conversion. A wavelength conversion device of this invention comprises an SC light generation portion 12, which receives an excitation light pulse output from an excitation light pulse source and generates SC light, and an optical wavelength filter 14 which filters the SC light. An excitation light pulse source generates an excitation light pulse, of central wavelength &lgr;S. When the excitation light pulse generated by the excitation light pulse source is incident on the SC medium, SC light having a flat spectral shape over the range from wavelength &lgr;L to wavelength &lgr;H (where &lgr;L<&lgr;H) is generated. The optical wavelength filter has a characteristic such that the filtering transmitted central wavelengths are &lgr;1, &lgr;2, &lgr;3, . . . , &lgr;n (where n is a natural number). A further feature is that the following conditions (1) and (2-1), (2-2), . . .

Abstract: A central station and base station are connected by using an optical transmission path. Low frequency optical signals are transmitted via the optical transmission path. The base station and a wireless terminal are connected by using a wireless transmission path. The base station converts an optical signal that is input via the optical transmission path into an electrical signal, converts the electrical signal into a high frequency signal, and then converts this high frequency signal into a radio wave signal and outputs this signal. The wireless terminal inverts the received radio wave into an electrical signal and converts the electrical signal into a low frequency signal. By using low frequency optical signals and high frequency electrical signals, the costs of building the communication system can be reduced without any loss of communication speed.

Abstract: To resolve problems, with the invention, an optical transmitter comprises an encoder for generating an optical signal obtained by encoding multi-wavelength pulses corresponding to sending data by use of a method of time spread/wavelength hopping in accordance with an encoding pattern of the encoder itself. The encoder concurrently executes time delay for every wavelength component at encoding, and time delay due to pre-compensation processing to pre-compensate for difference in propagation time for every wavelength component, occurring due to chromatic dispersion characteristics of a transmission line by &agr;%. An optical receiver comprises a decoder for decoding the optical signal transmitted by the optical transmitter in accordance with a decoding pattern of the decoder itself.

Abstract: In a modulator integrated laser 100, a wave guide channel 200a in a modulator area 200 having a core constituted of an absorption layer 204 and a wave guide channel 250a at a laser area 250 having a core constituted of an active layer 254 are optically connected with each other by a wave guide channel 150a having a core constituted of a light wave guide layer 204b. The width of the light wave guide layer 204b increases in a continuous manner as the distance from the modulator area 200 increases and the width also increases in a continuous manner as the distance from the laser area 250 increases, with the width achieving its maximum in the vicinity of the middle area between the modulator area 200 and the laser area 250.

Abstract: A photonic switching method and a photonic switch utilizing the method are disclosed. Input electrical signals Ea.about.Ed are input through plural input ports 21a.about.21d are converted into optical signals with the pulse intervals of these input electrical signals being preserved unchanged. The converted optical signals are timing adjusted within the pulse interval and multiplexed in such a manner that these optical signals do not overlap with each other on the time axis. The resulting multiplexed optical signals are transferred to output ports 19a.about.19d. An optical signal, from among the multiplexed optical signals, which should be output at a target output port is separated by utilizing a mutual optical interactional function, for example, a four optical wave mixture.

Abstract: A second-harmonic generating device includes a laser diode for providing light of a fundamental wave, having end-facets at least one being an antireflection coated end-facet. An optical reflector forms an external resonator with one of the end-facets of the laser diode whereby a portion of the light from the laser diode is returned by the reflector to the laser diode. A second-harmonic generation element is disposed between the laser diode and the optical reflector, for producing a second-harmonic of the fundamental wave while the fundamental wave propagates in the second-harmonic generation element. In this way, the optical reflector determines the wavelength of the light of the fundamental wave so that the laser diode produces light with a wavelength satisfying a phase matching condition of the second-harmonic generation element.