Abstract: When the subscribers are connected with the switching system by the optical fibers, in order to realize the signal exchange without converting the optical signals sent by the optical fibers into the electric signal, the optical switching system is constituted by: an optical time division multiplexer for time division multiplexing the optical signals which were sent by a plurality of fiber optic cables corresponding to a plurality of subscribers; an optical time switch for changing the time arrangement of the output signals of the optical time division multiplexer; and an optical time division demultiplexer for distributing the time sequential signal of the output signals of the optical time switch to the optical fibers of a plurality of subscriber lines.

Abstract: A waveguide type optical multiplexer/demultiplexer in which a directional coupler made of a three-layer structure wherein core waveguides (refractive index n.sub.c : n.sub.c >n.sub.b) and a cladding (refractive index n.sub.r : n.sub.r <n.sub.c) are successively stacked on a low refractive index layer (refractive index n.sub.b), is provided with a thin film heater in or on the cladding, and a voltage is applied across the heater.

Abstract: A waveguide type light merging and branching device, in which a resistance layer is disposed on a surface of a substrate or at least on one side therein and a low refractive index layer (refractive index n.sub.b), a core waveguide layer (refractive index n.sub.c, n.sub.c >n.sub.b), and a cladding layer (refractive index n.sub.n, n.sub.n >n.sub.c) superposed thereon on each other, the resistance layer having electrode terminals at the two extremities thereof, to which a voltage is applied.

Abstract: This invention relates to an optical multi/demultiplexer which will be useful for optical wavelength-division multiplexing communication using an optical fiber.In order to obtain high isolation, the optical multi/demultiplexer of the present invention constitutes three, mutually the same optical multi/demultiplexers by use of a main waveguide and first, second and third branch waveguides. Two rays of light having mutually different wavelenths, which are incident into the main waveguide, are isolated completely by the three optical multi/demultiplexers and are outputted.

Abstract: A waveguide type optical device in which a waveguide layer for propagating light is provided on the front surface of a substrate, and a compensation layer having a coefficient of thermal expansion substantially equal to that of the waveguide layer formed on the front surface is provided on the rear surface of the substrate.

Abstract: A two-way optical transmission system in which a plurality of light signals of wavelengths differing one from another are transmitted through a single optical fiber from one end thereof to the other end and from the other end to the one end. One or more assemblies each including an electrooptic transmitter, a dielectric thin-film filter and a rod lens and one or more assemblies each including a rod lens, a dielectric thin-film filter and an opto-electric receiver are connected to the single optical fiber at both ends thereof, respectively.

Abstract: An optical waveguide device comprises a low refractive index layer having a refractive index n.sub.b, a core layer having a refractive index n.sub.c (where n.sub.c >n.sub.b) and a cladding layer having a refractive index n.sub.c1 (where n.sub.c1 <n.sub.c) formed on a substrate. Thermal expansion coefficients of the low refractive index layer, the core layer and the cladding layers, respectively, are made substantially equal to each other at respective boundaries.

Abstract: Formed on a low refractive index layer (refractive index n.sub.b) is a core waveguide (refractive index n.sub.c, n.sub.c >n.sub.b) and formed on the core waveguide is a cladding whose refractive index n.sub.cl (n.sub.cl <n.sub.c, n.sub.cl .noteq.n.sub.b) is varied in the propagation direction of optical signals. Formed on a low refractive index layer (refractive index n.sub.b) is a core waveguide whose refractive index n.sub.c (n.sub.c >n.sub.b) is continuously varied in the propagation direction of optical signals and formed on the entire core waveguide is a cladding (refractive index n.sub.cl, n.sub.cl <n.sub.c).

Abstract: An optical star coupler having a biconically tapered optical star coupler suspensively inserted in a protection tube and the method for manufacturing the same are disclosed, and the manufacturing method is that an optical fiber bundle is inserted into a protection tube such as hollow glass tube, then the optical fiber bundle is twisted and pulled while it is indirectly heated through the protection tube, thereby to form a twisting, fusing and pulling portion, and both ends of the protection tube are sealed with an adhesive agent to fix the optical fiber bundle to the protection tube. This optical star coupler can be constructed so as to be connected in tandem without any splicing. The optical star coupler of the present invention, naturally in the case of an optical star coupler using multi-mode optical fiber, particularly in the case of one equally divided optical star coupler using single-mode optical fiber, also provides low insertion loss, less power deviation and low manufacturing cost.

Abstract: While a middle part of a plastic optical fiber bundle in a lengthwise direction thereof is being heated, it is twisted, and it is pulled in axial directions of the bundle. A biconically tapered portion is formed at the middle part of the bundle by the twisting and the pulling. When the biconically tapered portion has been formed into a predetermined shape, the heating is stopped, and simultaneously, a gas is blown against an outer periphery of the biconically tapered portion so as to rapidly cool this tapered portion. The biconically tapered portion is solidified to the predetermined shape by the rapid cooling.

Abstract: A two-way optical fiber transmission network comprises: a center that transmits and receives information; a plurality of areas each containing a plurality of subscribers using information from the center; an optical start coupler connected at least with the plurality of subscribers in the area which is in the shortest distance to the center; an optical fiber cable connecting the optical star coupler with the center; and optical fiber cables connecting the plurality of subscribers in the remaining areas with the center.

Abstract: An optical filter is formed by providing a plurality of gaps, which have a desired width and such a depth that is larger than the thickness of the waveguide layer, in a slab or a waveguide layer in a three-dimensional optical waveguide so as to extend in the light propagating direction at desired period intervals. These gaps are filled with a film of a material, the refractive index of which is different from that of the waveguide layer, to complete the optical filter. A multiplex wavelength transmission device is formed monolithically by providing at least one optical filter, which is formed in the above-mentioned manner, in an optical waveguide, and arranging one or both of a light-emitting semiconductor element and a photodetector on the side of an optical signal which has passed through the optical filter, and on the side of an optical signal which has been reflected on the same optical filter.

Abstract: An optical multi/demultiplexer comprising a first waveguide for inputting/outputting light, second and third waveguides which are respectively arranged on both sides of the first waveguide, and first and second open-waveguides which are respectively arranged on sides of the second and third waveguides remote from the first waveguide.

Abstract: An optical star coupler having a biconically tapered optical star coupler inserted and suspended in a protection tube and the method for manufacturing the same are disclosed. The manufacturing method provides that an optical fiber bundle is inserted into a protection tube such as hollow glass tube, then the optical fiber bundle is twisted and pulled while it is indirectly heated through the protection tube, thereby forming a twisting, fusing and pulling portion. Both ends of the protection tube are then sealed with an adhesive agent to fix the optical fiber bundle to the protection tube. This optical star coupler can be constructed so as to be connected in tandem without any splicing. The optical star coupler of the present invention, in the case of an optical star coupler using multi-mode optical fibers, and particularly in the case of one equally divided optical star coupler using single-mode optical fiber, also provides low insertion loss, less power deviation and low manufacturing costs.

Abstract: An optical coupling system between a semiconductor laser and an optical fiber is disclosed. The system is characterized in that a medium having a refractive index greater than 1 but smaller than the refractive index of the semiconductor laser material is packed between the end surface of a distributed feedback type or distributed Bragg reflector type semiconductor laser and the end surface of an optical fiber.

Abstract: A method for producing an optical fiber preform comprising the steps of blowing, through at least one nozzle, gaseous material producing glass material soot by a CVD reaction to permit the glass material soot to be deposited on a target to produce a soot rod which grows in size, and heating and rendering transparent the soot rod produced in the first step, wherein a pipe is arranged substantially concentrically with the glass material soot so as to permit gas to flow through a clearance between the deposited glass material soot and the inner wall surface of the pipe in a direction in which the soot rod grows in size. The method makes it possible to prevent the outer peripheral portion of the soot rod from becoming porous and to satisfactorily control the diameter of the soot rod.

Abstract: Apparatus for producing an optical fiber including apparatus for heating an optical fiber preform, apparatus for drawing out the optical fiber from the optical fiber preform whose fore end part has been made molten by the heating and for taking up the drawn out fiber, apparatus for causing a gas to flow along the outer peripheral surface of the molten part of the optical fiber preform, and apparatus for controlling both the flow rate of the gas and the drawing-out speed of the optical fiber according to a fluctuation in the diameter of the optical fiber.

Abstract: For drawing an optical fiber from an optical fiber preform there are provided means for heating an optical fiber preform, means for pulling out an optical fiber from the optical fiber preform whose fore end part has been fused by heating, and means for causing gas to flow along the outer peripheral surface of the fused part of the optical fiber preform. By further controlling the flow rate of the gas and/or the pulling-out velocity for the optical fiber according to fluctuations in the fiber diameter of the optical fiber, an optical fiber of uniform fiber diameter is easily provided.

Abstract: An optical wave guide comprises a cylindrical body which is made of a first transparent dielectric, and a second transparent dielectric which is concentrically formed on the outer periphery of the cylindrical body and which has an index of refraction lower than that of the first dielectric, the central part of the wave guide being hollow.