Abstract: An optical transmission apparatus includes a Mach-Zehnder modulator, transmission lines which transmit modulation data to the Mach-Zehnder modulator, a phase varying section which is connected to at least one of the transmission lines, and a phase synchronization loop which is connected to the phase varying section, and which applies a control voltage on which a dither signal is superimposed to the phase varying section. The phase varying section adjusts a skew between the transmission lines to remain constant, based on the control voltage on which the dither signal is superimposed.

Abstract: An optical transmitter includes a modulation unit, an optical coupler, a photodetector and a control unit. The modulation unit sets up a phase difference between first and second optical signals acquired by branching an input light. The modulation unit modulates the first and second optical signals based on first and second input data signals, respectively. The optical coupler couples the first and second optical signals to generate a phase-modulated optical signal. The photodetector generates a received signal based on the phase-modulated optical signal. The control unit superimposes a dither signal having a frequency on at least one of the first and second optical signals. The control unit performs detection on the dither signal that is included in the received signal output from the photodetector. The control unit controls the phase difference that is to be set up by the modulation unit. The control of the phase difference is made based on a result of the detection.

Abstract: An optical receiver in which a failure in a certain channel affects no other channels is provided. An optical receiver inputs DQPSK optical signals supplied from the outside into each of first and second delay interferometers and reproduces optical output from the first and second delay interferometers as binary non-return-to-zero (NRZ) signals of first and second channels by first and second An optical receiving elements. The delay time of the first and second delay interferometers is performed a feedback control by a control system independent for each of the first and second channels.

Abstract: A two-optical signal generator is provided for generating two optical signals, where a difference between optical frequencies or optical wavelength of the two optical signals can be adjusted. A first optical modulator modulates a single-mode optical signal generated by a first light source according to an inputted signal, and outputs a modulated optical signal including predetermined specific two optical signals having a predetermined optical frequency difference, while a second light source generates a multi-mode optical signal including predetermined two further optical signals having substantially the same wavelengths as those of the predetermined specific two optical signals of the modulated optical signal, respectively.

Abstract: A two-optical signal generator is provided for generating two optical signals, where a difference between optical frequencies or optical wavelength of the two optical signals can be adjusted. A first optical modulator modulates a single-mode optical signal generated by a first light source according to an inputted signal, and outputs a modulated optical signal including predetermined specific two optical signals having a predetermined optical frequency difference, while a second light source generates a multi-mode optical signal including predetermined two further optical signals having substantially the same wavelengths as those of the predetermined specific two optical signals of the modulated optical signal, respectively.

Abstract: A two-optical signal generator is provided for generating two optical signals, where a difference between optical frequencies or optical wavelength of the two optical signals can be adjusted. A first optical modulator modulates a single-mode optical signal generated by a first light source according to an inputted signal, and outputs a modulated optical signal including predetermined specific two optical signals having a predetermined optical frequency difference, while a second light source generates a multi-mode optical signal including predetermined two further optical signals having substantially the same wavelengths as those of the predetermined specific two optical signals of the modulated optical signal, respectively.

Abstract: A two-optical signal generator is provided for generating two optical signals, where a difference between optical frequencies or optical wavelength of the two optical signals can be adjusted. A first optical modulator modulates a single-mode optical signal generated by a first light source according to an inputted signal, and outputs a modulated optical signal including predetermined specific two optical signals having a predetermined optical frequency difference, while a second light source generates a multi-mode optical signal including predetermined two further optical signals having substantially the same wavelengths as those of the predetermined specific two optical signals of the modulated optical signal, respectively.

Abstract: A two-optical signal generator is provided for generating two optical signals, where a difference between optical frequencies or optical wavelength of the two optical signals can be adjusted. A first optical modulator modulates a single-mode optical signal generated by a first light source according to an inputted signal, and outputs a modulated optical signal including predetermined specific two optical signals having a predetermined optical frequency difference, while a second light source generates a multi-mode optical signal including predetermined two further optical signals having substantially the same wavelengths as those of the predetermined specific two optical signals of the modulated optical signal, respectively.

Abstract: A receptacle-type optical module has a semiconductor laser device, and a glass rod arranged to be contacted tightly with an optical fiber ferrule to guide light emitted from the semiconductor laser device to an optical fiber. A marker is formed on the physical contact face of the glass rod to position the optical axis of the semiconductor laser device. The semiconductor laser device is caused to emit light, and at the same time, the marker image on the physical contact face and the image of the light emitted from the semiconductor laser device are picked up with an infrared camera and subjected to two-dimensional image processing by an image processing unit, thereby detecting the positional shift of the semiconductor laser device from the desired position. A fine adjustment stage is driven in the direction perpendicular to the optical axis of the semiconductor laser device on the basis of the information of the positional shift to position the semiconductor laser device.

Abstract: Each optical transceiver comprises a photoemissive device for generating a signal light of near-infrared rays, a photoreceptor for receiving the signal light of the near-infrared rays, and an optical lens for converting the signal light outputted from the photoemissive device into a substantially collimated light so as to emit the light into a desired direction and for guiding the signal light from the same direction to the photoreceptor. Directivities of the respective optical transceivers are directed to the same portion on the indoor optical diffusing surface such as a ceiling.

Abstract: An optical multiplexing and demultiplexing device of a type using a lens and a diffraction grating, which incorporates a waveguide array having waveguide channels with narrow spacings for facilitating high resolution, where the narrow spacings are realized by forming an etching groove between each adjacent waveguide channels and providing a measure for preventing optical coupling among the waveguide channels in the form of an air gap, or a layer having a refractive index lower than a cladding layer, or a layer for absorbing/reflecting light, which is provided in the etching groove. The device also incorporates a reflection mirror for reflecting the initially diffracted lights from the diffraction grating back to the diffraction grating, such that the diffracting grating diffracts the diffracted lights reflected back from the reflection mirror again to produce wavelength division multiplexed/demultiplexed optical signals in high resolution.

Abstract: An integrated optical multiplexer-and-demultiplexer comprising an arrayed waveguide having an optical delay portion imparting an optical band-pass characteristic, a lens secured to one end of the arrayed waveguide, and a diffraction grating opposing the lens. The optical delay portion is made of a light-transmitting medium selected from the group consisting of air and material composed of at least two substances exhibiting a minimum temperature coefficient to an optical length.