A single mode optical fiber having a core made from silica and less than or equal to about 6.5 weight % germania and having a maximum relative refractive index .sub.1MAX. The optical fiber also has an inner cladding surrounding the core and having a minimum relative refractive index .sub.2MIN. A difference between a softening point of the core and a softening point of the inner cladding is less than or equal to about 20 C., and .sub.1MAX>.sub.2MIN. The single mode optical fiber may also have an outer cladding surrounding the inner cladding made from silica or SiON. The outer cladding has a maximum relative refractive index .sub.3MAX, and .sub.3MAX>.sub.2MIN. A method for manufacturing an optical fiber includes providing a preform to a first furnace, the preform, drawing the optical fiber from the preform, and cooling the drawn optical fiber in a second furnace.

Layered glass structures and fabrication methods are described. The methods include depositing soot on a dense glass substrate to form a composite structure and sintering the composite structure to form a layered glass structure. The dense glass substrate may be derived from an optical fiber preform that has been modified to include a planar surface. The composite structure may include one or more soot layers. The layered glass structure may be formed by combining multiple composite structures to form a stack, followed by sintering and fusing the stack. The layered glass structure may further be heated to softening and drawn to control linear dimensions. The layered glass structure or drawn layered glass structure may be configured as a planar waveguide.

There is provided an optical fiber for providing increased sensitivity in sensing applications by increasing the Rayleigh backscatter coefficient of the fiber while maintaining tolerable levels of signal attenuation (e.g., less than 20% over 10 km). Such an optical fiber comprises a core, a first cladding layer and a second cladding layer. The core comprises at least one core dopant selected from the range of: germanium, phosphorus, aluminium, boron, fluorine. The at least one core dopant is used to increase the core refractive index and enhance the core Rayleigh backscatter coefficient. The first cladding layer comprises at least one dopant selected from: germanium, phosphorus, aluminium, boron, fluorine; wherein at least one first cladding layer dopant is used to reduce the first cladding layer refractive index. The signal attenuation generated in the fiber is less than 20% over 1 km.

According to embodiments, an optical fiber may include a core portion comprising an outer radius r.sub.C and a maximum relative refractive index .sub.Cmax. A cladding may surround the core portion and include a low-index trench and an outer cladding. The low index trench may surround the core portion and includes an outer radius r.sub.T and relative refractive index .sub.T. The outer cladding may surround and be in direct contact with the low-index trench. The outer cladding may be formed from silica-based glass comprising greater than 1.0 wt. % bromine and has a relative refractive index .sub.OC, wherein .sub.Cmax>.sub.OC>.sub.T. The optical fiber may have a cable cutoff of less than or equal to 1530 nm. An attenuation of the optical fiber may be less than or equal to 0.185 dB/km at a wavelength of 1550 nm.

A fiber sensor includes an optical fiber configured for operation at a wavelength from about 800 nm to about 1600 nm. The optical fiber includes a cladding that is defined by a fiber outer diameter and a core that is surrounded by the cladding. The core of the optical fiber has a Rayleigh scattering coefficient, .sub.s, that is controlled by controlling a concentration of one or more dopants in the core. The Rayleigh scattering coefficient is tuned to be within a predetermined range of an optimum Rayleigh scattering coefficient for a given total length, L, of the optical fiber. The predetermined range is from about 70% of the optimum .sub.s to about 130% of the optimum .sub.s.

A quartz glass tube as a semi-finished product for an optical component that has an inner bore extending along a tube center axis for the acceptance of a core rod and a tube wall limited by an inner casing surface and an outer casing surface is already known; within said tube wall an inner region made of a first quartz glass and an outer region made of a second quartz glass with a different index of refraction surrounding the inner region contact one another at a contact surface which runs around the center axis. In order to provide a quartz glass on this basis that facilitates the production of optical components for special applications such as laser-activated optical components in wand or fiber form, the invention states that the contact surface has a non-round course in the radial cross-section and the inner casing surface has a circular course.

Layered glass structures and fabrication methods are described. The methods include depositing soot on a dense glass substrate to form a composite structure and sintering the composite structure to form a layered glass structure. The dense glass substrate may be derived from an optical fiber preform that has been modified to include a planar surface. The composite structure may include one or more soot layers. The layered glass structure may be formed by combining multiple composite structures to form a stack, followed by sintering and fusing the stack. The layered glass structure may further be heated to softening and drawn to control linear dimensions. The layered glass structure or drawn layered glass structure may be configured as a planar waveguide.

Methods for producing an optical fiber by elongating a silica glass blank or a coaxial group of silica glass components, on the basis of which a fiber is obtained that comprises a core zone, an inner jacket zone enclosing the core zone and a ring zone surrounding the inner jacket zone, are known. In order to provide, proceeding from this, a method, a tubular semi-finished product and a group of coaxial components for the cost-effective production of an optical fiber, which is characterized by a high quality of the boundary between the core and jacket and by low bending sensitivity, according to the invention, the silica glass of the ring zone is provided in the form of a ring zone tube made of silica glass having a mean fluorine content of at least 6000 weight ppm and the tube has an inner tube surface and an outer tube surface, wherein via the wall of the ring zone tube, a radial fluorine concentration profile is adjusted which has an inner fluorine depletion layer with a layer thickness of at least 1 m and no more than 10 m, in which the fluorine content decreases toward the inner tube surface and is no more than 3000 weight ppm in a region close to the surface which has a thickness of 1 m.

A method for preparing a doped optical fibre preform includes formulating, a rare earth material or a functional metal material and a co-doping agent into a doping solution, mixing a high-purity quartz powder with the doping solution, drying same at a temperature of 100C.-150C. for 12-48 hours, crushing and screening the same to obtain a doped quartz powder; depositing the doped quartz powder onto the surface of a target rod to form a doped core layer; replacing the doped quartz powder with the high-purity quartz powder, and depositing the high-purity quartz powder onto the surface of the doped core layer to form a quartz outer cladding; and removing the target rod, and gradually collapsing the entirety formed from the doped core layer and the quartz outer cladding at a high temperature to obtain the doped optical fibre preform.

An embodiment of the invention relates to an optical device which is capable of realizing a secondary nonlinear optical phenomenon. The optical device is a fiber-type optical device which is comprised of glass containing SiO.sub.2, and includes a core region, a first cladding region, and a second cladding region. At least a part of a glass region configured by the core region and the first cladding region has such a repetition structure that a first section serving as a poled crystal region and a second section serving as an amorphous region are alternately disposed along a longitudinal direction of the optical device.