Abstract: A method to produce an optical module, in particular, a module to transmit an analog data to enhance a yield thereof is disclosed. The method comprises (a) taking an I-L characteristic and its slope efficiency, (b) taking a gradient of a linear approximation between the slope efficiency and a current applied to an LD, and (c) taking an optimum current for the CSO characteristic as varying the current. Steps (a) to (c) give a correlation between the gradient of the linear approximation and the optimum current and are performed in advance to the practical production.

Abstract: A method to produce an optical module, in particular, a module to transmit an analog data to enhance a yield thereof is disclosed. The method comprises (a) taking an I-L characteristic and its slope efficiency, (b) taking a gradient of a linear approximation between the slope efficiency and a current applied to an LD, and (c) taking an optimum current for the CSO characteristic as varying the current. Steps (a) to (c) give a correlation between the gradient of the linear approximation and the optimum current and are performed in advance to the practical production.

Abstract: An optielectronic device comprising a substrate crystal whose crystal plane is a (n11) plane tilted from the (100) plane toward the [110] direction, or [110] direction where (n>1). When the substrate is applied to an AlGaInP semiconductor laser, the optical device can be cleaved into a rectangular shape, as in the case of a (100) substrate crystal, resulting in easy handling of the chips and also is effective for making the lasting wavelength shorter, lowering the threshold current density for lasing, improving the continuous lasing temperature, etc. Furthermore, semiconductor lasers of different lasing wavelengths can be prepared under good control. Furthermore, a doping efficiency having no dependence on a tilt angle can be obtained by proper selection of a dopant. For example, Si is suitable as an n-type dopant entering sites of group III atom on an (n11) A plane (n.gtoreq.2).

Abstract: A semiconductor laser having a double hetero structure comprises a cladding layer of In.sub.1-x-y Ga.sub.x Al.sub.y P.sub.1-z As.sub.z (0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0.ltoreq.z.ltoreq.0.5, 0.5.ltoreq.x+y.ltoreq.1) and an active layer of a strained-layer-superlattice of In.sub.1-x-y Ga.sub.x Al.sub.y P.sub.1-z As.sub.z (0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0.ltoreq.z.ltoreq.1, 0.ltoreq.x+y.ltoreq.1) system, thus enabling the lasing of wavelength ranges from infra-red to green.

Abstract: A photocoupler comprises a light-emitting element and a light-receiving element which are optically coupled through a soft light-transmissive resin and covered by a light-blocking resin. The light-emitting element is covered by a light-transmissive protective hard resin and hence is protected against external pressure.

Abstract: A selenium-base chalcogenide glass for use as optical fibers suitable for transmitting with low loss infrared rays, particularly that of 10.6 .mu.m in wavelength, is provided. The infrared optical fibers with low transmission loss, which is suitable for practical use, are obtained by incorporating 2 to 100 ppm of at least one of Al Ga, and In into a selenium-base chalcogenide glass, thereby to reduce the absorption due to the vibration of Ge--O bond formed by the contamination with oxygen. The infrared optical fibers made of such a glass material show a transmission loss of 3-4 dB/m which is less than 1/2.5 of the loss (10 dB/m) of a reference glass.

Abstract: Optical glass is produced by heating a porous gel to a high temperature to partly sinter it, heating it in a chlorine-containing atmosphere to subject it to hydroxyl group removal treatment, and then further heating it to sinter it. The optical glass produced by this process does not rise in bubbles even when heated.

Abstract: A method for producing optical glass, which comprises charging a mixed solution capable of forming a high-silica-content gel by hydrolysis reaction into a vessel, the inner wall face of which is composed of a material unwettable to the mixed solution, such as a fluorocarbon resin or silicone resin, causing gelation of the mixed solution in the vessel, drying the obtained gel, and heating and sintering the obtained dry gel. When electrodes are placed in the mixed solution at the gelation step and an electric voltage is applied, the time required for formation of the gel is shortened. Furthermore, at the gel-drying step, if the amount of materials evaporated from the gel is detected or the weight of the gel is measured, the detected amount of the evaporated materials or the change of the weight of the gel is fed back to a factor regulating the drying speed, such as the drying temperature to control the drying speed to an appropriate level.

Abstract: A process for producing a mother rod useful for the production of an optical fiber which comprises hydrolyzing a silicon alkoxide to prepare a gel of a desired shape, and drying and sintering the gel to produce a block made of a silica glass. The process has the advantages that it is well adapted for mass-production, that a glass made of a B.sub.2 O.sub.3 --SiO.sub.2 system may be produced thereby and that a glass block of arbitrary shape may be readily produced.

Abstract: A method for producing silica glass wherein a dry silica gel subjected to a water desorption treatment and a carbon removal treatment is heated and has its temperature raised in an atmosphere containing chlorine, to perform a hydroxyl group removal treatment, the resultant silica gel is thereafter heated to a temperature of approximately 1,000.degree. C.-1,100.degree. C. in an atmosphere containing at least 1% of oxygen, to perform a chlorine removal treatment, and the resultant silica gel is further heated to a temperature of 1,050.degree. C.-1,300.degree. C. in He or in vacuum, to perform a sintering treatment. The silica glass thus produced does not form bubbles even when heated to high temperatures of or above 1,300.degree. C. Therefore, it is easily worked and it is free from the lowering of transparency attributed to the bubble formation.

Abstract: A method for producing an optical fiber comprises (i) the step of depositing a barrier layer on the inner wall surface of a glass tube by the CVD (chemical vapor deposition) process, said barrier layer being capable of preventing the diffusion of impurities and being made of high-silica glass which has a refractive index that is substantially equal to that of the glass tube and which contains at least one substance for lowering the refractive index of silica and at least one substance for raising the refractive index of silica, (ii) the step of depositing a glass film of desired refractive index on the barrier layer by the CVD process, (iii) the step of heating and collapsing the resultant glass tube into a composite rod or the so-called optical fiber preform, and (iv) the step of heating and drawing said optical fiber preform into the optical fiber, whereby the optical fiber which has the impurity diffusion-preventing layer between the core and the outside glass layer can be easily produced.

Abstract: A method of producing an optical fiber comprising (i) the step of depositing a glass film of desired refractive index onto the inner wall surface of a quartz tube by the CVD (chemical vapor deposition) process, (ii) the step of heating the quartz tube to a high temperature while the gas of a compound which forms an oxide, enhancing the refractive index of the glass film, in an oxidizing atmosphere at the high temperature is kept flowing into the quartz tube along with an oxidizing gas, (iii) the step of heating and collapsing the quartz tube into a solid rod or the so-called preform, and (iv) the step of heating and drawing the optical fiber preform into the optical fiber.In the optical fiber produced by this method of manufacture, the lowering of the refractive index of the central part of the optical fiber is sharply reduced.