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: A measuring instrument of magnetic field utilizing Faraday rotation is disclosed in which a medium exhibiting Faraday rotation includes at least one thin magnetic garnet film magnetized in a propagation direction of light and having a composition expressed by a general formula R.sub.3-x Q.sub.x (Fe.sub.5-y M.sub.y)O.sub.12 (where R indicates at least one element selected from a group consisting of Y, La, Lu, Ca, Sm and Bi, Q indicates at least one element selected from a group consisting of Gd, Eu, Er, Tm, Tb, Yb, Ho and Dy, M is at least one element selected from a group consisting of Ga, Al, Ge, Si, Sc, Mn, In, V and Cr, the value of x lies in a range expressed by a formula 0.1.ltoreq.x.ltoreq.3.0, and the value of y lies in a range expressed by a formula 0.ltoreq.y.ltoreq.5.0). According to this instrument, stable measured values are obtained independently of temperature variation.

Abstract: An electric-field measuring apparatus utilizing electrooptic effect for measuring the intensity of an electric DC field includes a material exhibiting both electrooptic effect and photoelectric effect or both a material exhibiting the electrooptic effect and a material exhibiting the photoelectric effect which material or materials are irradiated with a continuous light ray of a wavelength capable of inducing the electrooptic effect and an intermittently interrupted light ray of a wavelength capable of inducing the photoelectric effect.

Abstract: A method of producing a preform for a single-polarization optical fiber wherein a glass rod to become a core or a glass rod to become a clad is inserted into a quartz tube which has on its inner wall surface a glass thin film to become a clad layer, a glass thin film to become a jacket layer or glass films to become a jacket layer and a clad layer, and wherein under a state under which the internal pressure of the quartz tube is reduced, the quartz tube is heated to become solid, whereby at least one of the clad and the jacket of the optical fiber preform becomes elliptic in cross section.

Abstract: In an optical gyroscope comprising a coil of an optical fiber having opposite ends on which linearly polarized input light beams are incident and from which output light beams are derived which create an interference pattern to be detected, the optical fiber has orthogonal principal axes along which the light beams propagate at a large propagation constant difference. The application of the linearly polarized input light beams to the opposite ends of the optical fiber coil is such that the polarization plane of the linearly polarized light beam coincides with the same principal axis on the opposite ends. Thus, polarization characteristics of the output light beam from the optical fiber coil becomes time invariant and the light paths for the two light beams coincide with each other. In particular, in order to minimize the influence of external disturbances, the optical fiber has a structure defined by.vertline.N.sub.x -N.sub.y .vertline.>.lambda./R.sub.owhere N.sub.x and N.sub.

Abstract: A glass layer is formed inside a silica glass tube and another glass layer having a refractive index higher than that of the abovementioned glass layer is formed on said glass layer. After these glass layers are formed, one end of the glass tube is collapsed. While the internal pressure of the glass tube is being reduced below the atmospheric pressure, the glass tube is caused to collapse by heating, thereby yielding a preform for an optical fiber. The optical fiber produced from this preform has the difference in the refractive indices of the two orthogonal major axes of at least 1.6.times.10.sup.-4 and maintains the linear polarization plane.

Abstract: A single-mode-transmission optical fiber comprises a core of a radius a having an arbitrary (non constant) refractive index distribution n(r) in the radial direction r, the index distribution being expressed by n.sup.2 (r)=n.sub.1.sup.2 {1-2.DELTA..sub.o f(r)}, and a cladding having a constant refractive index n.sub.2, the radius a of the core being: ##EQU1## In these expressions, n.sub.1 denotes a maximum refractive index of the core, .lambda.

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 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.