摘要:
A device for changing the power levels of signals transmitted by an optical fiber, along with signal modulation and wavelength routing, comprises a length of optical fiber in which for a predetermined section of the length of the fiber, the fiber core is surrounded by a cladding having one or more variable refractive index (VRI) regions disposed therein in close proximity to the core. The VRI regions are fabricated with a material having an index of refraction higher than that of the cladding and may comprise a variable attenuator.
摘要:
A device for changing the power levels of signals transmitted by an optical fiber, along with signal modulation and wavelength routing, comprises a length of optical fiber in which for a predetermined section of the length of the fiber, the fiber core is surrounded by a cladding having one or more variable refractive index (VRI) regions disposed therein in close proximity to the core. A grating region is disposed along the length of the fiber overlapping the VRI region. The VRI regions have an index of refraction lower than that of the core to change the effective index of the guided light and thereby define a tunable grating.
摘要:
Embodiments of the invention include an optical system apparatus and method for modulating the strength of a grating such as a long period grating (LPG) within optical systems and devices by varying the light transmission and loss characteristics of the cladding mode, rather than varying the effective refractive index of the fiber layers. According to embodiments of the invention, the use of a light-scattering or light absorptive material in the cladding of the optical fiber or other optical energy transmission medium causes the cladding to switch between a first state that effectively allows coherent coupling of cladding modes and a second state that effectively prevents coherent coupling of cladding modes. The light-scattering materials include electro-optic materials that cause the cladding to switch between the first and second states based on the presence (or absence) of an electric field, magneto-optic materials that cause the cladding to switch between the first and second states based on the presence (or absence) of a magnetic field, and materials capable of phase transitions that cause the cladding to switch between the first and second states based on temperature. The light-absorptive materials include dopants that cause the cladding to switch between the first and second states based on the wavelength of the optical energy. Embodiments of the invention differ from conventional optical media in that, according to embodiments of the invention, the cladding mode loss (attenuation) is varied rather than conventional changes in the index of refraction. The magnitude of the loss according to embodiments of the invention depends on the specification arrangements employed, but such loss typically is defined in dB per unit length in the given cladding mode.
摘要:
Disclosed are non-periodic microstructured optical fibers that guide radiation by index guiding. By appropriate choice of core region and cladding region, the effective refractive index difference .DELTA. between core region and cladding can be made large, typically greater than 5% or even 10 or 20%. Such high .DELTA. results in small mode field diameter of the fundamental guided mode (typically
摘要:
A tunable optical fiber device comprises a length of fiber having a core having a certain refractive index; a cladding peripherally surrounding the core with a refractive index less than the refractive index of the core; and at least one hollow region disposed within the cladding in proximity to the core or within the core itself. Fluid (typically liquid) controllably moved within the hollow region modifies the effective index of the fiber and thereby tunes its characteristics.
摘要:
The invention involves providing a microstructured fiber having a core region, a cladding region, and one or more axially oriented elements (e.g., capillary air holes) in the cladding region. A portion of the microstructured fiber is then treated, e.g., by heating and stretching the fiber, such that at least one feature of the fiber microstructure is modified along the propagation direction, e.g., the outer diameter of the fiber gets smaller, the axially oriented elements get smaller, or the axially oriented elements collapse. The treatment is selected to provide a resultant fiber length that exhibits particular properties, e.g., mode contraction leading to soliton generation, or mode expansion. Advantageously, the overall fiber length is designed to readily couple to a standard transmission fiber, i.e., the core sizes at the ends of the length are similar to a standard fiber, which allows efficient coupling of light into the microstructured fiber length.
摘要:
A fiber optic system comprises an optical transmitter, an optical receiver, and an optical fiber transmission path that optically couples the transmitter and the receiver to one another. The transmission path includes a first section that has negative dispersion at an operating wavelength &lgr;0 greater than about 1300 nm and a second section that includes a MOF. The MOF has relatively large anomalous dispersion at &lgr;0 and is sufficiently long to compensate the accumulated negative dispersion in the first section. In one embodiment the MOF comprises a core, a lower index cladding that includes one or more layers of air holes surrounding the core, characterized in that the diameter of the core is less than about 8 &mgr;m and the difference in effective refractive index between the core and cladding is greater than about 0.1 (10%). Preferably, the cladding contains no more than 2 layers of air holes and the distance between the nearest edges of adjacent air holes is less than about 1 &mgr;m.
摘要:
A method of fabricating a glass body that includes a multiplicity of constituents, at least one of which is a dopant (e.g., a rare-earth element) having a low vapor pressure (LVP) precursor includes the steps of: (a) generating an aerosol from the LVP precursor; (b) separately generating vapors of the other constituents; (c) convecting the aerosol and vapors to deposition system including a substrate; and (d) forming at least one doped layer on a surface of the substrate. In one embodiment, the method also includes filtering the aerosol so as to remove aerosol particles outside of a particular range of sizes. Also described is a unique aerosol generator that is particularly useful in generating aerosols of rare-earth dopants. Particular embodiments directed to the fabrication of Yb-doped optical fibers are described.
摘要:
Applicants have determined that much of the nonuniformity in solution doped preforms is due to nonuniformity of the soot layer caused by the high temperature necessary for complete reaction, and that MCVD fabrication using reaction temperature lowering gases such as nitrous oxide (N.sub.2 O) can produce more uniform soot layers. The conventional oxygen/reactant gas mixture presents a very small temperature window in which a uniform silica soot layer can be deposited without sintering. If the temperature in oxygen is too low, SiCl.sub.4 will not react completely and silicon oxychlorides will form. This degrades the soot layer and makes it unusable. If the temperature is too high the soot layer begins to sinter, decreasing the surface area and porosity. Adding a reaction temperature lowering gas lowers the reaction temperature and enables deposition of soot on the tube wall at a temperature substantially lower than the sintering temperature. This results in a more uniform, porous soot layer along the length of the preform and from one preform to another; and, in turn, the greater uniformity permits more uniform solution doping.
摘要:
A method of fabricating a glass body that includes a multiplicity of constituents, at least one of which is a dopant (e.g., a rare-earth element) having a low vapor pressure (LVP) precursor comprises the steps of: (a) generating an aerosol from the LVP precursor; (b) separately generating vapors of the other constituents; (c) convecting the aerosol and vapors to deposition system including a substrate; and (d) forming at least one doped layer on a surface of the substrate. In one embodiment, the method also includes filtering the aerosol so as to remove aerosol particles outside of a particular range of sizes. Also described is a unique aerosol generator that is particularly useful in generating aerosols of rare-earth dopants. Particular embodiments directed to the fabrication of Yb-doped optical fibers are described.