Abstract: WDMs have been used to separate a plurality of signals spatially by the difference of wavelengths in prior bidirectional multiwavelength optical communication network. For excluding WDMs, linear PD/LD modules adopt eigen-wavelength photodiodes sensing only the light of an eigen wavelength but allowing all the wavelengths longer than the eigen wavelength. An n-member PD/LD module aligns (n-1) eigen wavelength photodiodes, PD1, PD2, PD3, . . . , PDn-1 of .lambda.1, .lambda.2, .lambda.3, . . . ,.lambda.n-1 and an LD of .lambda. n which satisfy inequalities .lambda.1<.lambda.2<.lambda.3 <. . . <.lambda. n in series on a beam line in the order of increasing the eigen wavelengths. Otherwise, an n-member PD/LED module aligns k eigen wavelength PDs of .lambda.1, .lambda.2, .lambda.3, . . . , .lambda.k and (n-k) LEDs emitting light of different wavelengths of .lambda.k+1, .lambda.k+2, .lambda.k+3, . . . .lambda. n on the beam line in the same order. On the contrary, an n-member LD/PD module aligns a .

Abstract: Bidirectional optical communication system transmits optical signals with two different wavelengths .lambda..sub.1 and .lambda..sub.2 (.lambda..sub.1 <.lambda..sub.2) between a broadcasting station and a plurality of ONU terminals. Bisecting separation of .lambda..sub.1 and .lambda..sub.2 requires expensive WDMs. .lambda..sub.1 -selective photodiode which absorbs all the .lambda..sub.1 light and allows all the .lambda..sub.2 to pass through is proposed. The energy gap Eg.sub.1 of the light receiving layer is determined to be smaller than hc/.lambda..sub.2 and larger than hc/.lambda..sub.1. The .lambda..sub.1 -selective photodiode and the other photodiode are positioned in series on a beam line, which dispenses with WDMs.

Abstract: Alignment between an optical fiber and a laser diode is carried out by the steps of fixing a position sensitive detector and an optical fiber on a common supporting device, arranging a position sensitive detector opposite the laser diode, measuring the converging point of the light beams from the laser, calculating the difference between the converging point and the optical fiber, displacing the optical fiber relative to the laser diode by the calculated difference for harmonizing the converging point with the center of the optical fiber within a tolerance, moving minutely the optical fiber with the laser in the direction for increasing the light power emitted from the other end of the optical fiber and fixing the optical fiber at the point which gives the maximum power to the optical fiber.

Abstract: A semiconductor laser device in which a housing with an optical fiber inserted in is secured to a header with a semiconductor laser chip mounted on is integrated, the light emitting surface of the semiconductor laser chip and the end surface of the optical fiber are opposed to each other, and there is provided a photodiode chip for detecting the signal light emitted from the backside (rear end surface) of the light emitting surface of the semiconductor laser chip, in the top incidence type photodiode chip having a pn junction area of the structure as a photo-sensing region, the first region is surrounded by a second region of the second conductivity type formed at a portion of the semiconductor layer. The second region has the same or larger depth as or than that of the first region. Thus, even if a light is directed to the outside of the photo-sensing region, extra charges into the photo-sensing region is prevented.

Abstract: A semiconductor light detecting device in which a housing with an optical fiber is inserted in is secured to a header with a photodiode chip mounted on integral therewith, and a light detecting surface of the photodiode chip is opposed to a light emitting surface of the optical fiber, the photodiode chip having a pn junction, the first region is surrounded by a second region of the second conductivity type formed at a portion of the semiconductor layer. The second region has the same or larger depth as or than that of the first region. Thus, even if a light is directed to the outside of the photo-sensing region, extra charges into the photo-sensing region is prevented. As a result, no optical lens system is necessary, and if an optical lens system is used, an inexpensive optical system may be used. Further, the device itself can be fabricated at low costs and easily.

Abstract: A semiconductor light source for transmitting light signals of digital or analog data having a laser diode and a photodiode for monitoring the output power of the laser diode. The driving current of the laser diode is adjusted by the photocurrent of the monitoring photodiode. The photodiode has a light receiving region at a center enclosed by an annular electrode and a light non-receiving region outside the annular electrode. If leak light beams entered the non-receiving region, delayed photocurrent is produced. The delayed photocurrent misleads the control of the laser diode. This invention provides a non-receiving region of the photodiode with a dielectric layer for reflecting or absorbing light beams in order to preventing the light beams from producing the delayed photocurrent.

Abstract: A semiconductor photodetector comprising a photodiode chip, a header for mounting the chip, a receptacle, and a ferrule for holding an end of an optical fiber. The photodetector does without a lens. A dielectric layer covers a periphery of the photodiode chip for shielding it from incidence of extra light beams by reflecting or absorbing light. Omission of a lens reduces the costs of parts and assembly. Since no light beams enter the peripheral part of photodiode chip, no delayed photocurrent is produced. Reproduced signals are immune from deformation or delay of phase. The photodetector facilitates wide prevalence of optoelectronic communication.

Abstract: A method of making a holographic light guide comprising, in sequence, a substrate, a light guiding layer and a holographic recording layer that partially replaces the light guiding layer is disclosed. The substrate is made of a first bismuth sillenite group substance. The light guiding layer is made of a second bismuth sillenite group substance that has a higher refractive index than the first bismuth sillenite group substance and absorbs little of the light being guided. The holographic recording layer is made of a third bismuth sillenite group substance that has a higher refractive index than the first bismuth sillenite group substance and has a degree of photosensitivity.

Abstract: A magnetic field and electric current measuring device which uses bismuth silicon oxide (Bi.sub.12 SiO.sub.20) or bismuth germanium oxide (Bi.sub.12 GeO.sub.20) as a Faraday cell, and which is so adapted that polarized light which enters the cell is passed back and forth through the cell along the optic axis thereof to cancel any change in optical rotatory power ascribable to a variation in temperature. A magnetic field applied in the direction of the optic axis of the Faraday cell is measured based on the angle of rotation of the polarization plane of the polarized light. The surface of the Faraday cell may be coated with a transparent and electrically conductive thin film to eliminate the effects of external electric fields.

Abstract: A hologram recording material comprises one of bismuth silicon oxide and bismuth germanium oxide, and Fe added to these material. The density of Fe is 10 p.p.m.

Abstract: An optical voltage and electric field sensor for detecting the voltage or electric field applied to a device made of a single crystal of bismuth silicon oxide (Bi.sub.12 SiO.sub.20) or bismuth germanium oxide (Bi.sub.12 GeO.sub.20) is disclosed. The device comprises a plurality of crystal plates stacked in a direction perpendicular to the propagation direction of light, each plate having only one dimension reduced to a very small size.

Abstract: A voltage and electric field measuring device is disclosed. The device uses light, including a polarizer, an electro-optic crystal consisting of a material having an optical rotatory power, and an analyzer arranged in the stated order in the direction of advancement of applied light, with a quarter-wave plate being disposed between the polarizer and crystal or between the crystal and analyzer. The angle of orientation .psi. of the analyzer, relative to the optical axis of the crystal, is set to the product of .theta. and l, where .theta. represents the optical rotatory power, with respect to the applied light, of the crystal near a point at the center of a range of varying temperatures at the installation environment, and l represents the thickness of the crystal measured in the direction of advancement of light. The specified relation between .psi. and .theta..multidot.l maximizes the temperature stability of the device.

Abstract: A magneto-optical converter utilizing the Faraday effect is disposed between the opposed ends of an iron core having a magnetic field extending therebetween. The magneto-optical converter is comprised of a body of material exhibiting the Faraday effect which is provided with a light receiving surface and a light exiting surface. A polarizer in the form of a polarizing beam splitter is located adjacent the light receiving surface whereby an incident beam of light perpendicular to the magnetic field will be deflected and polarized at right angles to the incident beam of light and directed into the receiving surface of the body of material. An analyzer comprised of a polarizing beam splitter is located adjacent the light exiting surface whereby the beam of light from the body of material will be deflected and polarized and exit the analyzer at right angles to the magnetic field.

Abstract: A voltage and electric field measuring device using light as an operating parameter. An electro-optic crystal, a quarter-wave plate, and a polarization analyzer are arranged in that order in the direction of advancement of applied light. A voltage may be applied to the electro-optic crystal through electrodes arranged thereon. The electro-optic crystal belongs to a cubic system, such as bismuth silicon oxide or bismuth germanium oxide.