摘要:
The present invention pertains to a strain sensor. The strain sensor is comprised of an optical waveguide, a device for providing optical pulses to the optical waveguide and a device for sensing localized strain in the optical waveguide. The sensing device determines shifts in arrival times of the optical pulses at the sensing device that correspond to the localized strain. In a preferred embodiment the sensing device includes a device for reflecting a portion of the optical pulses at predetermined positions in the optical waveguide and a device for detecting the shift in arrival times of the portion of the optical pulses which are reflected.
摘要:
The present invention pertains to a strain sensor. The strain sensor is comprised of an optical wave guide, a device for providing optical pulses to the optical wave guide and a device for sensing localized strain in the optical waveguide. The sensing device determines shifts in arrival times of the optical pulses at the sensing device that correspond to the localized strain. The apparatus includes a light source, a light detector, and a waveguide connecting the source with the detector. The apparatus also includes means for generating light pulses from the source through the waveguide and means for repeatedly propagating at least one of the light pulses in a closed loop. The light source detects arrival times of the light pulses.
摘要:
The present invention pertains to an optical splice. The optical splice includes a member having an alignment cavity which receives optical waveguides and allows light to pass there between. The member is made of a material that is moldable such that when an optical waveguide is received by the member, the alignment cavity expands but constricts about the optical waveguide in a predetermined position. The member has a plurality of funnels which communicate with the alignment cavity and guide an optical waveguide into the alignment cavity where it is received thereby. The present invention also pertains to a method for making a funnel in a member. The method includes the steps of placing a drawn-down end of a capillary into a mold; inserting an alignment rod into the mold and the capillary through the drawn-down end thereof; filling the mold with a curable material; allowing the material to cure to form the member; and removing the alignment rod and capillary from the member to form in the member an alignment cavity with a funnel. In a preferred embodiment the member is an optical splice.
摘要:
Uniformity of optical coupling of optical elements such as star couplers and splitters is improved by heat treatment which causes dopants in the core of an optical fiber to diffuse into material from the cladding layer of the optical fibers from which the optical element is formed, resulting in a substantially homogeneous interior region of the star coupler or splitter. Increased lossiness of the optical element thus formed may be limited by termination of the heat treatment before dopant diffusion reaches equilibrium throughout the fibers so that a portion of the cladding layer of the fibers remains surrounding the substantially homogeneous region where the fibers have been fused together.
摘要:
Optic fiber coupler fabrication stations allow one-step packaging and reduce fabrication time. The optic fiber coupler fabrication stations produce a single piece construction of the coupler package with improved uniformity. Two linear translation stages are driven in opposing directions using left and right hand threaded rods connected to a common drive shaft driven by a small electric motor. Fibers to be coupled are clamped into the station to provide the necessary tension during the tapering process. The fibers are tied together using cotton thread, and an oxy-propane torch is used to fuse the fibers together while the two translation stages pull the fibers to form a biconical tapered region in the fibers.
摘要:
Two-mode, elliptical-core optic fibers with a permanent photo-induced index change are used as sensors with sensitivity varying as a function of length. The optic fiber sensors act as vibrational-mode filters thereby performing initial signal processing of the sensor signal. The sensors are based on photo-induced refractive index changes. These refractive index changes affect the differential phase modulation between the LP.sub.01 and the LP.sub.11.sup.even modes. The change in beat-length is dependent on the amount of strain induced in the fiber while the grating is being formed. The pattern is thus varied along the length of the fiber by straining the fiber in a specific fashion while the grating is being written. This changes the sensitivity, of the sensor along its length. By choosing an appropriate weighting function in the manufacture of the sensor, it is possible to implement vibrational-mode analysis, vibrational-mode filtering and other functions that are critical in control system applications.
摘要:
A fiber optic sensor is fully compensated for light source intensity variation, fiber losses and modal power distribution by providing input to one end of an optical fiber from a relatively broad band light source containing at least two spectrally separated wavelengths. At least one of these spectrally separated wavelengths is reflected back into the optical fiber by a filter located between a second end of the optical fiber and a reflective transducer. The filter is preferably of the interference edge filter type and has a nominal cut-off wavelength within the spectral band of the light source or between the two spectrally separated wavelengths. Therefore, the paths traversed by light of the spectrally separated wavelengths will differ only by twice traversing the reflective transducer. Temperature measurement or compensation can also be provided by sensing of reflected light intensity or power at approximately the nominal cut-off frequency of the filter. Reflective transducers of both the intensity-based and interferometric types are usable with the invention.
摘要:
Tapered two-mode optic fibers are used as sensors with sensitivity varying as a function of length. The optical fiber sensors act as vibrational-mode filters thereby performing initial signal processing of the sensor signal. The sensors are based on the differential propagation constant in a two-mode fiber that is directly dependent on the normalized frequency or V-number. Tapering the fiber changes the V-number and hence can change the sensitivity of the sensor along its length. By choosing an appropriate weighting function in the manufacture of the sensor, it is possible to implement vibrational-mode analysis, vibrational-mode filtering and other functions that are critical in control system applications.
摘要:
Uniformity of optical coupling of optical elements such as couplers and splitters is improved by heat treatment which causes dopants in the core of an optical fiber to diffuse into material from the cladding layer of the optical fibers from which the optical element is formed, resulting in a substantially homogeneous interior region of the star coupler or splitter. Increased lossiness of the optical element thus formed may be limited by termination of the heat treatment before dopant diffusion reaches equilibrium throughout the fibers so that a portion of the cladding layer of the fibers remains surrounding the substantially homogeneous region where the fibers have been fused together. Dopant diffusion is constrained to a substantially radial direction in each fiber by uniformity of heating over a region where at least two fibers are twisted together. Thus dopant diffusion is highly repeatable and can be readily regulated to provide highly selective, wavelength-dependent coupling between fibers, particularly for multiplexing and demultiplexing applications.
摘要:
The fibers are bound together about 1 cm apart. An oxy-propane torch is used to heat the fibers so that they fuse together. At the same time, the two relatively movable translational stages to which the fibers are clamped are pulled apart to form a biconical tapered region in the fibers. The fibers are tapered until a desired coupling ratio is achieved. After the insertion loss is measured, the torch is reintroduced into the taper region and one side (e.g., the right side) of the taper region is rotated with a minimal increase in the taper length, i.e., the distance between the two stations is increased only enough to keep an even tension in the taper region.