Abstract: An optical fiber with low attenuation of light transmission comprising a core and a cladding, wherein the core is made of a polymer comprising units of deuterated methyl methacrylate containing 10 to 40% of a methacrylic ester the ester moiety of which has an alicyclic hydrocarbon group of from 6 to 20 carbon atoms, and the cladding is made of a transparent polymeric material having a refractive index of at least 3% smaller than that of the core, which optical fiber has excellent heat and humidity resistance as well as good flexibility.

Abstract: A plastic optical fiber comprising a core and a cladding, wherein the core is made a polymer comprising units of methyl methacrylate and of a methacrylate ester, the ester moiety of which has an alicyclic hydrocarbon of 8 to 20 carbon atoms, and the cladding is made of a fluorine-containing polymer comprising units of the formula: ##STR1## wherein R.sub.1 and R.sub.2 are each hydrogen or C.sub.1 -C.sub.3 alkyl, R.sub.f1 is fluorine or trifluoromethyl, an R.sub.f2 is C.sub.2 -C.sub.10 fluoroalkyl, which units (I) are derived from fluoroalkyl .alpha.-fluoroacrylate or trifluoromethacrylate, which has short- and long-time heat and humidity resistance as well as low attenuation of light transmission.

Abstract: In this information transmission system, a PCM encoder is provided for time-division multiplexing multichannel audio signals and a digital character information signal to generate a time-division multiplexed, or TDM, information signal. The TDM information signal is angle-modulated by the modulator to generate an angle-modulated information signal. This signal is supplied to a frequency-division multiplexer, which multiplexes the angle-modulated information signal and an image signal so as to generate a frequency-division multiplexed, or FDM, information signal which is adapted to be supplied to a certain subscriber.

Abstract: A contention-type data communication system such as an optical star-configured network comprises a plurality of stations connected with one another through data bus. To detect a signal collision quickly, each of the stations is arranged to transmit a collision-detecting packet which has a predetermined time length T.sub.1 and a predetermined pulse pattern, and then transmit a data packet after a time interval T.sub.2. The number or pattern of pulses received during a time period T.sub.1 +T.sub.2 from the start of reception of a collision-detecting packet is compared with that of the self-transmitted collision-detecting packet so that the signal collision is detected when noncoincidence occurs.

Abstract: An optical communication system includes a plurality of stations and at least two passive optical couplers. Each of the couplers has at least four pairs of ports, each pair including an input port and an output port. An optical signal inputted to any one of the input ports is outputted to all of the output ports except the output port of the pair into which the optical signal was inputted. A plurality of optical signal transmission lines interconnect the passive optical couplers and connect the passive optical couplers to the stations. Passive optical couplers of both the transmission type and the reflection type are disclosed. The transmission type passive optical couplers rely either upon the direct interconnection of the appropriate input ports and output ports or upon diffraction to guide optical signals to the correct output ports.

Abstract: Highly dielectric organic compounds can be obtained by cyanoethylating a dihydroxyalkylate of a water-soluble polysaccharide or a derivative thereof with acrylonitrile.

Abstract: A laser apparatus including first and second frequency sweeping laser devices, the sweep frequency range of each being different. The output laser beams of the first and second laser devices are multiplexed by a multiplexer. The output laser beam of the multiplexer is transmitted to a photodetector for detecting the difference in frequency between those of the first and second laser devices. A frequency monitor, coupled to the photodetector, provides a signal to a control circuit which causes the first and second laser devices to sequentially sweep their respective sweep frequency ranges.

Abstract: The invention is to provide the methods for producing highly water-absorbable and water-retainable hydrogels having a large particle diameter together with a sufficient gel strength. The method is characterized by use of a specific dispersing agent in the water-in-oil type inverse phase suspension polymerization of an .alpha.,.beta.-unsaturated carboxylic acid and/or its alkali metal salt. Due to the high water-absorbability and water-retainability, along with the superior gel strength and the stable gel structure, the hydrogels of the invention enlarge the conventional range of usages.

Abstract: A method for producing a hydrophilic gel comprising polymerizing acrylic acid and/or methacrylic acid in the presence of polyvinyl alcohol to obtain a polymer (A) which is then subjected to neutralization followed by heat treatment or to heat treatment followed by neutralization, or polymerizing a neutralized product of acrylic acid and/or methacrylic acid in the presence of polyvinyl alcohol to obtain a polymer (B) which is then subjected to heat treatment, wherein said polymerization is carried out in an aqueous solution having a total concentration of acrylic acid and/or methacrylic acid or its neutralized product (the weight of the neutralized product is converted to the acid basis) and polyvinyl alcohol of 10 to 60% by weight, said heat treatment temperature is 50.degree. to 150.degree. C., and the weight ratio of polyvinylalcohol is acrylic acid and/or methacrylic acid or its salt (the weight of the neutralized product is converted to the acid basis) is 5 to 95: 95 to 5.

Abstract: A method for the preparation of water-insoluble gels containing at least a hydroxyl group and a carboxylate group in molecules thereof which comprises saponifying copolymers comprising a vinyl ester component and an acrylic or methacrylic acid ester component or terpolymers comprising said two components and an ethylene component in the presence of an alkali catalyst and a solvent under conditions in which said copolymers or terpolymers are not dissolved.