A manufacturing method for an optical fiber, includes: drawing, while heating in a heating furnace, a lower end of an optical fiber preform that is to be an optical fiber having a core consisting of silica glass containing a rare earth element compound. The heating furnace has a temperature profile in which a temperature of the heating furnace increases to a maximum temperature T.sub.max and then decreases from an upstream side of the heating furnace toward a downstream side of the heating furnace. The temperature profile has a changing point at which the temperature decreases more steeply on the downstream side from a position where the maximum temperature T.sub.max is reached. At the maximum temperature, a temperature of the silica glass is higher than or equal to a glass transition temperature and the silica glass is in a single phase.

A low-dispersion single-mode fiber includes a core and claddings covering the core. The core layer has a radius in a range of 3-5 μm and a relative refractive index difference in a range of 0.15% to 0.45%. The claddings comprise a first depressed cladding, a raised cladding, a second depressed cladding, and an outer cladding arranged sequentially from inside to outside. The first depressed cladding has a unilateral width in a range of 2-7 μm and a relative refractive index difference in a range of −0.4% to 0.03%. The raised cladding has a unilateral width in a range of 2-7 μm and a relative refractive index difference in a range of 0.05% to 0.20%. The second depressed cladding has a unilateral width in a range of 0-8 μm and a relative refractive index difference in a range of 0% to −0.2%. The outer cladding is formed of pure silicon dioxide glass.

A high-density optical fiber ribbon is formed by two or more cladding-strengthened glass optical fibers each having an outer surface and that do not individually include a protective polymer coating. A common protective coating substantially surrounds the outer surfaces of the two or more cladding-strengthened glass optical fibers so that the common protective coating is common to the two or more cladding-strengthened glass optical fibers. A fiber ribbon cable is formed by adding a cover assembly to the fiber ribbon. A fiber ribbon interconnect is formed adding one or more optical connectors to the fiber ribbon or fiber ribbon cable. Optical data transmission systems that employ the fiber ribbon to optically connect to a photonic device are also disclosed. Methods of forming the cladding-strengthened glass optical fibers and the high-density optical fiber ribbons are also disclosed.

A single mode optical fiber having a core made from silica and less than or equal to about 11 weight % germania and having a maximum relative refractive index Δ.sub.1MAX. The optical fiber also has an inner cladding surrounding the core and having a minimum relative refractive index Δ.sub.2MIN, a first outer cladding surrounding the inner cladding and a second outer cladding surrounding the first outer cladding. The viscosity at 1650° C. of the second outer cladding minus the viscosity at 1650° C. of the first outer cladding is greater than 0.1e.sup.7 Poise, and Δ.sub.1MAX>Δ.sub.2MIN. The single mode optical fiber may also have an outer cladding surrounding the inner cladding made from silica or SiON. The first outer cladding has a maximum relative refractive index Δ.sub.3MAX, and Δ.sub.3MAX>Δ.sub.2MIN.

A sensor that can be used for real time monitoring of load and structural health in engineering structures is provided. The sensor may include a patch with a portion of an optical fiber embedded therein. There may also be triboluminescent materials dispersed within the patch, on and/or near the portions of the optical fiber embedded in the patch. There may be micro-excitors located in proximity to the triboluminescent materials and on the surface of the optical fiber. Loading events and/or damage to the monitored structure may result in a triboluminescent emission from the triboluminescent material that can be guided via the optical fiber. Analysis of the triboluminescent emission may provide information on the magnitude of the applied load as well as the occurrence, severity and location of damage in the structure.

The present disclosure relates to an optical fiber having a core and a cladding, where the cladding is doped with a dopant. The cladding has a dopant concentration gradient in the radial direction such that a concentration of the dopant changes with respect to radial distance from a core-cladding interface. Doping the cladding of the optical fiber enables ablation of the fiber surface with a line source to provide an ablated wedge or crack such that cleaving can be achieved by applying a stress force to the fiber after ablation or by applying a pull force during ablation.

The high-density FAU comprises a support substrate having a grooved front-end section that supports glass end sections of the small diameter low-attenuation optical fibers. A cover is disposed on the front-end section and secured thereto to hold the glass end sections in place. The substrate and the cover can be made of the same glass or glasses having about the same CTE. The glass end sections have a diameter d4 so that the pitch P2 of the fibers at the front end of the FAU can be equal to or greater than d4, wherein d4=2r.sub.4, with r.sub.4 being the radius of the glass end section as defined by the optical fiber cladding. The glass end section has a radius r.sub.4 less than 45 microns, allowing for a high-density FAU and a high-density optical interconnection device.

An optical fiber has a structure uniform in a longitudinal direction. This optical fiber includes a core and a cladding that surrounds the core in a cross-section perpendicular to the longitudinal direction. A refractive index of the cladding is lower than a refractive index of the core. The cladding has, in the cross-section, an inner cladding layer including an inner circumferential surface of the cladding, and an outer cladding layer including an outer circumferential surface of the cladding. The inner cladding layer contains fluorine. The inner and outer cladding layers have refractive indexes different from each other. The outer cladding layer includes a local maximum portion where a residual stress, which is a tensile stress, becomes local maximum. A radial distance between the local maximum portion and an inner circumferential surface of the outer cladding layer is 10 μm or less.

An optical fiber according to an embodiment includes a core and a cladding. The average value n1_ave of the refractive index of the core, the minimum value nc_min of the refractive index of the cladding, and the refractive index n0 of pure silica glass satisfy relationships of n1_ave>nc_min and nc_min<n0. The cladding contains fluorine. The fluorine concentration in the cladding is adjusted to be minimum in the outermost portion of the cladding including the outer peripheral surface of the cladding.

In this invention there is provided an illumination system for a photosynthetic organism-growing medium. This system comprises a waterproof housing arranged to be inserted into a photosynthetic organism-growing medium and having a length along a longitudinal axis that is greater than a width. It also comprises a light source arranged to provide illumination along the length of the housing, and a diffuser arranged within the waterproof housing, the diffuser having a narrow end directed towards the light source and a wider end away from the light source and having a diffusive reflective surface arranged to diffusively reflect light from the light source to outside the housing.