Polarization-independent tunable spectral slicing filter in Ti:LiNbO3.

A two-port polarization-independent tunable spectral slicing filter at the 1530 nm wavelength regime is presented. The design utilizes an asymmetric interferometer with a sparse index grating along its arms. The sparse grating makes it possible to select equally spaced frequency channels from an incident WDM signal and to place nulls between them to coincide with the signal comb frequency.

Intrinsic fiber Fabry-Perot temperature sensor with fiber Bragg grating mirrors.

A fiber Fabry-Perot interferometer (FFPI) sensor is formed with broadband (~3 nm, 3-dB bandwidth) fiber Bragg grating (FBG) mirrors. Repetitively modulating a distributed-feedback laser produces chirping that modulates the reflectance of the FFPI. Because the reflectance of the FBG mirrors varies with optical frequency, the fringes in the sensor reflectance modulation are distinguishable, making it possible to extend the sensor dynamic range versus that of a FFPI sensor with conventional wavelength-dependent mirrors.

Multiplexed fiber Fabry-Perot temperature sensor system using white-light interferometry.

A novel monitoring system for a fiber Fabry-Perot interferometer (FFPI) temperature sensor has yielded a resolution of 0.013 degrees C (0.0025 fringe).

Field test of a distributed fiber-optic intrusion sensor system for long perimeters.

Field tests in desert terrain of a distributed sensor system for detecting and locating intruders based on the phase-sensitive optical-time-domain reflectometer (phi-OTDR) are described. The sensing element is a single-mode telecommunications fiber in a 4.5 mm diameter cable buried in a trench filled with loose sand.

Fabry-Perot optical binary switch for aircraft applications.

An optical binary switch for aircraft applications is demonstrated. A fiber Fabry-Perot interferometer (FFPI) bonded to a cantilever is used as the sensing element. A white-light interferometry system with two bulk Michelson interferometers sharing the same motor-driven translation stage is utilized to monitor the elongation of the FFPI.

Narrowband Bragg reflectors in Ti:LiNbO3 optical waveguides.

Bragg grating reflectors etched in amorphous silicon overlay films have been integrated with Ti:LiNbO3 optical waveguides to obtain a narrow (0.05 nm) reflectance spectrum with a > 20 dB dip in the transmittance spectrum. These results were realized at a wavelength of 1542.

Polarization discrimination in a phase-sensitive optical time-domain reflectometer intrusion-sensor system.

A distributed sensor system for detecting and locating intruders based on a phase-sensitive optical time-domain reflectometer (phi-OTDR) that utilizes polarization discrimination is described. The sensing element is a single-mode telecommunications fiber in a 3 mm diameter cable buried along a monitored perimeter in a 20-46 cm deep, 10 cm wide trench in clay soil. Light pulses from a continuous-wave Er fiber Fabry-Perot laser with a narrow (< 3 kHz) instantaneous linewidth and low (a few Kilohertz per second) frequency drift are injected into one end of the fiber, and the orthogonal polarizations of the backscattered light are monitored with separate receivers.

Photolithographic fabrication of a high-precision bar-code pattern on the surface of a sphere.

Bar-code patterns were produced upon gold-coated glass spheres 8 mm in diameter with a novel projection photolithography exposure system that included a computer-controlled rotation stage-and-shutter arrangement. The patterns extended in an equatorial band about the entire 360 degrees periphery of the sphere. To obtain uniform thickness of the photoresist layer, we dip coated the spheres and removed the excess with an absorption pad.

Polarization dependence of the coupling ratio in LiTaO3 directional couplers.

The effect of design and fabrication parameters on the polarization dependence of the splitting ratio in directional couplers produced in LiTaO3 by Zn diffusion has been investigated experimentally at a wavelength of 1558 nm. The directional couplers featured various combinations of waveguide width, separation gaps between waveguides, bending angle, and diffusion conditions. In each case the coupling region was 3.

Digital and analog readout systems for fiber-optic strain sensors as applied to the monitoring of roller element bearing systems.

A rotating machinery test rig was instrumented with fiber Fabry-Perot interferometer strain sensors for condition monitoring of rolling element bearings. Strain variations produced by ball passes were observed and analyzed in the time and frequency domain. Wavelength division multiplexing was utilized to simultaneously monitor the sensors with analog and digital readout systems--analog for high bandwidth and digital for high dynamic range and the monitoring of multiple sensors.

Spectrally scanned, repetitively pulsed erbium-doped fiber laser for spectral and temporal multiplexing of fiber Bragg grating sensors.

An erbium-doped fiber laser that emits a series of spectrally scanned pulses is used to monitor an array of fiber Bragg grating (FBG) sensors. The cavity for this Fabry-Perot laser is formed by two spectrally selective reflectors: a rotating mirror-grating combination for scanning the reflectance peak wavelength and a fiber Fabry-Perot interferometer (FFPI) with a periodic reflectance spectrum. During a scan of the rotating mirror, the laser produces a set of Q-switched pulses over the 1522-1568-nm spectral range at each of the FFPI reflectance peak wavelengths.

Interferometric fiber-optic sensor embedded in a spark plug for in-cylinder pressure measurement in engines.

Pressure sensing in an internal combustion engine with an intrinsic fiber Fabry-Perot interferometer (FFPI) integrated with a spark plug is demonstrated for the first time. The spark plug was used for the ignition of the cylinder in which it was mounted. The FFPI element, protected with a copper/gold coating, was embedded in a groove in the spark-plug housing.

Monitoring and multiplexing technique for interferometric fiber optic sensors with a linearly chirped Er:fiber laser.

The monitoring of interferometer fiber optic sensors using a laser that is scanned over a wide frequency range is investigated. The interrogation technique is based on the principle that if the light-source frequency varies linearly with time, the optical signal reflected or transmitted is intensity modulated at a frequency that is proportional to the optical path difference (OPD) in the interferometer. Fourier components in the detected optical output signal then correspond to the OPDs of any interferometers that have contributed to this modulation.

Polarization dependence in Ti-diffused LiNbO3 directional couplers.

The effect of design and fabrication parameters on the dependence on polarization of the splitting ratio in directional couplers produced by Ti diffusion in LiNbO3 has been investigated experimentally at a wavelength of 1.54 microm. The parametric study was carried out at a diffusion temperature of 1025 degrees C, which was found to suppress outdiffusion effects.