摘要:
A dual two-beam differential interferometer that measures both the amplitude and orientation of propagating, broadband surface acoustic waves. Four beams are focused on a surface. The four reflected beams are separated into two pairs. The two pairs are detected to produce two signals that are used to compute amplitude and orientation.
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:
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:
An electrostatic self-assembly method of fabricating electrostrictive and piezoelectric thin film assemblies not only provides a thinner film than is attainable by conventional methods, but provides excellent molecular-level uniformity and precise structural control, and thus large, effective piezoelectric coefficients. The method produces a thin film assembly including (a) a substrate, and (b) a film having one or a plurality of layers disposed upon the substrate, wherein at least one of the layers includes a dipolar material, and this layer of dipolar material has a uniform thickness of at most 500 nm.
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:
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:
A piezoelectric crystal with several concentric ring electrodes on one side of the crystal. A resistor network applies different amplitudes of an AC source to each of the several electrodes. A plot of the different amplitudes from the outermost electrode to the innermost electrode is the first half of a Gaussian function. Consequently, the output of the crystal from the side opposite the electrodes has a Gaussian profile.
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.