Abstract: A quartz etalon having light reflecting film layers on the Z-cut surfaces and electrode layers on the X-cut surfaces are axially supported in the X-cut surface electrode layers. A dither signal is applied to this axially supported portion to resonate the etalon. In this state, laser-beam is transmitted through the Z-cut surfaces of the etalon. The transmitted light is photo-electrically converted and subjected to synchronous detection by a dither signal. On the basis of an error signal obtained by the detection output, the oscillation wavelength of the semiconductor laser is controlled. Since the etalon resonates as its axially supported central portion functions as a node, the mechanical loss is small, and the Q value upon mechanical resonance is extremely large. This makes the synchronous detection output about 100 times as large as the conventional value. This increases the signal-to-noise ratio of the photoelectric conversion signal, and increases the wavelength accuracy.

Abstract: An optical communication system for optically transmitting transmission data from a transmitting station to a transmitting device includes an adder for adding an intermediate frequency subcarrier signal modulated with data to be transmitted to a pilot carrier signal as a sinusoidal wave, and an electro-optical converter for electro-optically converting the above sum signal to an optical signal by directly modulating a semiconductor laser element having a resonant frequency fr in accordance with the sum signal and transmitting the signal to an optical fiber for a down link. The frequency fIF of the intermediate frequency subcarrier signal and the frequency fLO of the pilot carrier signal satisfy fLO?fIF?1[GHz], 2×fIF<fLO<(?)×fr, fIF<1[GHz], and 2 [GHz]<fLO.

Abstract: A quartz etalon having light reflecting film layers on the Z-cut surfaces and electrode layers on the X-cut surfaces are axially supported in the X-cut surface electrode layers. A dither signal is applied to this axially supported portion to resonate the etalon. In this state, laser-beam is transmitted through the Z-cut surfaces of the etalon. The transmitted light is photo-electrically converted and subjected to synchronous detection by a dither signal. On the basis of an error signal obtained by the detection output, the oscillation wavelength of the semiconductor laser is controlled. Since the etalon resonates as its axially supported central portion functions as a node, the mechanical loss is small, and the Q value upon mechanical resonance is extremely large. This makes the synchronous detection output about 100 times as large as the conventional value. This increases the signal-to-noise ratio of the photoelectric conversion signal, and increases the wavelength accuracy.

Abstract: An optical communication system for optically transmitting transmission data from a transmitting station to a transmitting device includes an adder for adding an intermediate frequency subcarrier signal modulated with data to be transmitted to a pilot carrier signal as a sinusoidal wave, and an electro-optical converter for electro-optically converting the above sum signal to an optical signal by directly modulating a semiconductor laser element having a resonant frequency fr in accordance with the sum signal and transmitting the signal to an optical fiber for a down link.

Abstract: An optical communication system for optically transmitting transmission data from a transmitting station to a transmitting device includes an adder for adding an intermediate frequency subcarrier signal modulated with data to be transmitted to a pilot carrier signal as a sinusoidal wave, and an electro-optical converter for electro-optically converting the above sum signal to an optical signal by directly modulating a semiconductor laser element having a resonant frequency fr in accordance with the sum signal and transmitting the signal to an optical fiber for a down link. The frequency fIF of the intermediate frequency subcarrier signal and the frequency fLO of the pilot carrier signal satisfy fLO−fIF≧1 [GHz], 2×fIF<fLO<(2/3)×fr, fIF<1 [GHz], and 2 [GHz]<fLO.

Abstract: The present invention provides a light transfer system comprising a plurality of slave stations each equipped with a light transmitter for outputting an optical signal corresponding to an information signal and a master station for receiving an optical multiplex signal obtained by optically multiplexing the optical signals sent from the plurality of slave stations, wherein the plurality of slave stations adjusts an amount of heat radiated from an exothermic-effect-only heat source of the optical transmitter to thereby control a wavelength of the optical signal output from a laser diode of the light transmitter.

Abstract: In this invention, there is provided an optical communication system comprising a plurality of sub-stations and a main station connected to the plurality of sub-stations via an optical transmission path. The plurality of sub-stations respectively comprise modulation section for modulating a wavelength of an optical signal which is transmitted from the respective sub-station to the main station via the transmission path containing information signals by using a control signal having a unique frequency allocated to the sub-station, arbitrary pairs of control signals having different frequency differences.

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: A dial gauge with a simplified structure and reductions in number of parts and production costs. In the dial gauge having a case 10 which is composed of a case body 11, a front case member 21 provided on the front of the case body 11, and a rear case member 31 provided on the rear of the case body 11, the case body 11 and the front case member 21 are combinedly formed by using plastic materials. The rear case member 31 includes a rear cover and a reinforcing plate covering the rear of the case body 11.

Abstract: A wavelength division multiplexing optical transmission apparatus comprises an optical wavelength demultiplexer which demultiplexes, for each wavelength, the wavelength division multiplex optical signal transmitted via an optical fiber, receivers which receive the output beams from the optical wavelength demultiplexer, a wavelength detector that detects the difference between the wavelength of a transmitter and a wavelength minimizing the loss in the optical wavelength demultiplexer, and an alarm generator that determines an abnormality when the wavelength difference has exceeded an allowable value and raises the alarm.

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.

Abstract: Light beams emitted from an optical fiber are converted into parallel light beams by a lens, and then allowed to pass through a Faraday device, followed by being converged to an incident end of the optical fiber by a lens. The Faraday device is applied with a magnetic field in a direction of the optical axis thereof from a coil. Moreover, the Faraday device is applied with a magnetic field in a direction perpendicular to the optical axis by a pair of magnets. When an electric current flowing in a coil 74 is changed from I to -I, the direction of a synthesized magnetic field can be rotated. Therefore, by arbitrarily changing the electric current flowing in the coil, polarization of transmission light can be controlled.

Abstract: An optical communication system suitable for selective reception of multiple services, which facilitates the adaptation of the already existing service network to an expansion of the service of the system by incorporating additional services, inexpensively, without causing the inconvenience to the subscribers of the system. In the system, the intensity modulated light signals with a first wavelength and the angle modulated light signals with a second wavelength are transmitted through the optical fiber communication lines in a form of multiplexed light signals. Then, the intensity modulated light signals in the multiplexed light signals are received and demodulated by using a direct detection, while the angle modulated light signals in the multiplexed light signals transmitted are received and demodulated from the multiplexed light signals. The selective detection of the angle modulated light signals is preferably made by a balanced optical heterodyne/homodyne receiver.

Abstract: In an optical coupler of this invention, second and third single mode optical fibers are arranged to be parallel with each other with a first single mode optical fiber intervening therebetween, and a region in which the second and third optical fibers are linearly symmetrical with each other about the first optical fiber as the center is distribution-coupled. The coupling length of distributed coupling is set such that when the first and second light waves having a wavelength .lambda.1 and a wavelength .lambda.2 different from the wavelength .lambda.1 are incident on one port of the first optical fiber, the first light wave is emitted from the other port of the first optical fiber and the second light wave is emitted from the second and third optical fibers.

Abstract: In a device for mixing a first input optical signal and a second input optical signal, a polarization beam splitter receives the first and second input optical signals. Each of the first and second input optical signals is separated into polarized optical signals having different polarization planes. Each polarized optical signal is divided into divided optical signals being transmitted in directions with an acute crossed angle in a mixer which mixes the divided optical signals corresponding to the first and second input optical signals. The mixed optical signals are then focused.

Abstract: In a semiconductor laser apparatus of the invention, a laser beam emitted from a semiconductor laser is collimated by an optical leans, and is subsequently split by a beam splitter in two directions. One split laser beam component is focused on a first photodetector through an optical lens. The other laser beam component is incident on a Fabry-Perot resonator, and is changed in intensity thereby. The laser beam component is then focused on a photodetector through an optical lens. The Fabry-Perot resonator is integrally designed such that dielectric multilayer films are respectively deposited on both the end faces of a crystalized quartz bulk, which is shaped into a columnar shape extending in the C-axis direction, so as to form a pair of reflect filters. Since the bulk is made of crystalized quartz it is not easily influenced by changes in temperature.

Abstract: In a television camera having a color resolving prism system for forming monochromatic images on the image pickup surfaces of a plurality of image pickup devices by an objective lens the color resolving prism system has first, second, third and fourth prisms as is named in the order from a side of the objective lens along the optic axis of the objective lens, the first and second prisms, with their refracting angles opening in opposite directions, are edisposed with an air layer interposed therebetween or are joined together with a dichroic layer interposed therebetween, the second and third prisms are disposed with an air layer interposed therebetween, the third and fourth prisms are joined together with a second dichroic layer interposed therebetween, and the values of the refracting angles of the first .theta..sub.10 or .theta..sub.21), second .theta..sub.10 +.theta..sub.11 or .theta..sub.22, third .theta..sub.23 and fourth .theta..sub.

Abstract: An adapter with built-in shutter arranged to be attached between a master lens and a camera body, includes a first lens group having a negative power and disposed at a position on the master lens side of an image forming plane of the master lens, a second lens group having a positive power and arranged to receive a bundle of rays passing the first lens group, and a shutter for controlling an exposure.

Abstract: A high-speed pickup apparatus in which a rotary shutter is disposed on the intermediate image plane between a photo-taking lens and a relay lens.