A distributed fiber optic intrusion sensor capable of detecting intruders from the pressure of their weight on the earth's surface was investigated in the laboratory and in field tests. The presence of an intruder above or in proximity to the buried sensor induces a phase shift in light propagating along the fiber which allows for the detection and localization of intrusions. Through the use of an ultra-stable erbium-doped fiber laser and phase sensitive optical time domain reflectometry, disturbances were monitored in long (several km) lengths of optical fiber. Narrow linewidth and low frequency drift in the laser were achieved through a combination of optical feedback and insulation of the laser cavity against environmental effects. The frequency drift of the laser, characterized using an all-fiber Mach Zehnder interferometer, was found to be less than 1 MHz/min, as required for operation of the intrusion detection system. Intrusions were simulated in a laboratory setting using a piezoelectric transducer to produce a controllable optical phase shift at the 2 km point of a 12 km path length. Interrogation of the distributed sensor was accomplished by repetitively gating light pulses from the stable laser into the sensing fiber. By monitoring the Rayleigh backscattered light with a photodetector and comparing traces with and without an induced phase shift, the phase disturbances were detected and located. Once the feasibility of such a sensor was proven in the laboratory, the experimental set up was transferred to Texas A&M's Riverside Campus. At the test site, approximately 40 meters of fiber optic cable were buried in a triangle perimeter and then spliced into the 12 km path length which was housed inside the test facility. Field tests were conducted producing results comparable to those found in the laboratory. Intrusions over this buried fiber were detectable on the φ-OTDR trace and could be localized to the intrusion point. This type of sensor has the potential benefits of heightened sensitivity, covertness, and greatly reduced cost over the conventional seismic, acoustic, infrared, magnetic, and fiber optic sensors for monitoring long (multi-km) perimeters.

Linear tuning the frequency of an erbium-doped fiber ring laser using both a Fabry-Perot filter and an electro-optic tunable filter has been experimentally demonstrated. The rate of frequency change is determined by monitoring the fringes produced by laser light transmitted through a fiber Fabry-Perot interferometer. The fiber ring laser has been tuned over a 50 nm spectral range when using the Fabry-Perot filter and a tuning rate of 16480 nm/s has been achieved. The spectral width of the laser is 0.049 nm and the nearest sidelobe to the main peak is more than 30 dB below the central lobe. When the electro-optic tunable filter is used, a spectral range of 11 nm is reached. The spectral width is 2.33 nm and is in close agreement with the filter theoretical results. The sidelobe to main peak difference is around 13 dB.

Several genes thought to confer susceptibility to dyslexia have been identified, and the purpose of this study is to 1) determine the expression pattern of one of these gene products and 2) characterize the function of the product of one of these genes, namely KIAA0319-Like (KIAA0319L), using the developing chick visual system as a model. Whole mount in situ hybridization was performed for KIAA0319L on embryonic day (E)3 – E5 and in situ hybridization on sections was performed at later stages. Engineered microRNA (miRNA) constructs targeting KIAA0319L were prepared and their specificity and efficiency for knocking down KIAA0319L were tested. miRNAs were electroporated in E5 optic tecta (OT). Embryos were sacrificed at E12. OT were removed, sectioned and analyzed. Results demonstrate that KIAA0319L is expressed in the developing chick visual system. Knockdown of KIAA0319L in the OT results in abnormal migration indicating that KIAA0319L is necessary for this process.

Several genes thought to confer susceptibility to dyslexia have been identified, and the purpose of this study is to 1) determine the expression pattern of one of these gene products and 2) characterize the function of the product of one of these genes, namely KIAA0319-Like (KIAA0319L), using the developing chick visual system as a model. Whole mount in situ hybridization was performed for KIAA0319L on embryonic day (E)3 – E5 and in situ hybridization on sections was performed at later stages. Engineered microRNA (miRNA) constructs targeting KIAA0319L were prepared and their specificity and efficiency for knocking down KIAA0319L were tested. miRNAs were electroporated in E5 optic tecta (OT). Embryos were sacrificed at E12. OT were removed, sectioned and analyzed. Results demonstrate that KIAA0319L is expressed in the developing chick visual system. Knockdown of KIAA0319L in the OT results in abnormal migration indicating that KIAA0319L is necessary for this process.

Fiber-optic networks are an integral part of todays digital communication system. In these networks, distances of typically 400 km to 6000 km are linked together, and information is transfered at extremely high data rates. As the demands for capacity increases, finding new methods for cost effective long-haul transmission systems that can be used to increase the capacity becomes of high interest. In this work Orthogonal Frequency Division Multiplexing (OFDM), which is a standard digital modulation format in many wireless communication systems, for instance the IEEE 802.11n, is adapted to the optical domain and used for data transmission. The advantage of OFDM in the optical domain is that it transforms a high data rate stream into many simultaneously low bit rate streams that are efficiently frequency multiplexed. By doing so high spectral efficiency is achieved and many of the impairments encountered in high data rate transmissions are avoided. The disadvantage is however, that OFDM has inherently a high peak-to-average power ratio. As a result, OFDM suffers from nonlinearities occurring along the transmission line. The low nonlinear tolerance of OFDM in fiber optic applications restricts the feasible transmission distance. The goal of this work is to assess the suitability of OFDM in fiber-optic communications

Fiber Fabry-Perot Interferometers (FFPI) are optical sensors which can be used to measure changes in stress or temperature, but efforts continue to improve them. Calculations show that the response can be dramatically altered with a gain inducing medium in the cavity. In order to induce gain, a highly doped Erbium (Er) fiber is incorporated in the FFPI. A pump wavelength of 1480 nm is used with a wavelength near 1550 nm. The pump must be at a significantly higher power level than the signal for gain. In order to correctly interpret responses, it is necessary to characterize the response of the measurement equipment. This includes everything from the laser and photodetector to system losses and the titanium oxide coated fibers. Fabrication of FFPIs involves fusing titanium oxide coated fibers to standard single mode fibers. Directly fusing an Er - doped fiber to a titanium oxide coated fibers was not possible because of incompatible splice conditions required in each case. Instead, an intermediate standard single mode fiber was spliced between them. This lengthened the cavity. Experimental results from the Er - doped Fiber Fabry-Perot Interferometer verified the hypothesis that improvements are obtainable. Overall, the measurements showed a 1.3 dB improvement in the maximum-to-minimum Insertion Loss Ratio.

The fiber-optic microampere current sensor used two metal-coated single mode optical fibers to detect the current when it pass through the coated part which existing a thermal resistance effect.When the optical fiber experience temperature change,variation of the phase shift would be incurred by the change of refractive index and geometric structure of the fiber.Then we can observe the phase amplitude to know the input current.Besides we combine the all-fiber Michelson interferometer with the Faraday rotator mirror to build up a polarization-insensitive structure.Final using the phase-generated carrier technique(PGC) to stabilize demodulate the phase signal.

Linear tuning the frequency of an erbium-doped fiber ring laser using both a Fabry-Perot filter and an electro-optic tunable filter has been experimentally demonstrated. The rate of frequency change is determined by monitoring the fringes produced by laser light transmitted through a fiber Fabry-Perot interferometer. The fiber ring laser has been tuned over a 50 nm spectral range when using the Fabry-Perot filter and a tuning rate of 16480 nm/s has been achieved. The spectral width of the laser is 0.049 nm and the nearest sidelobe to the main peak is more than 30 dB below the central lobe. When the electro-optic tunable filter is used, a spectral range of 11 nm is reached. The spectral width is 2.33 nm and is in close agreement with the filter theoretical results. The sidelobe to main peak difference is around 13 dB.

A fiber optic system for measuring magnetic heading and pitch of one or more compass heads in a towed acoustic array has been developed as a cooperative effort between engineers at Fiber Dynamics, Inc., and faculty and graduate students at Texas A&M. An unconventional photolithographic process for producing a bar-code pattern on a curved (spherical) surface was successfully implemented. First, an absorption process for applying a thin layer of photoresist uniformly to the gold-coated surface of a glass sphere was perfected. Then, a system for defining the patterns in the metal was assembled. A LabView computer program controlled the system as required to define the bar code pattern in the metal. High-quality bar code patterns were produced on floating spheres by this method. The data acquisition/signal processing system digitized and processed the raw data returning from the compass heads, and computed magnetic heading and pitch from the data. Processing of the signal from a single compass head required readout of a 7-bit binary code giving coarse heading, using timing information to obtain fine heading, and measuring the apparent width of an analog bar to determine pitch. When monitoring multiple compass heads distributed along the fiber, a time-division demultiplexing technique was used for separating the data from the individual compass heads. For testing the system, the cylindrical sensor head was mounted on a machinist's table for rotating it through 360?? in the horizontal plane to vary the heading, and through ??10?? about a horizontal axis to vary pitch. Measured resolutions of the system were 0.044?? for heading, and 0.85?? for pitch.

Programmable two-port polarization independent electro-optically wavelength tunable filters based on asymmetric Mach-Zehnder structure in LiNbO3 substrate have been developed for 1.55 µm application. The operation principle is based on Mach-Zehnder interference and TE↔TM polarization conversion. Fabrication parameters for channel waveguides, polarization converters and bandpass filters have been optimized. Straight channel waveguides 7 µm in width were produced by diffusing 1116 Å thick Ti into LiNbO3 substrate at 1035°C for 10 hours. Single mode guiding has been realized for both TE and TM polarization. Insertion loss of 2.9 dB for TE polarization input and 3.3 dB for TM polarization input were achieved on a 46 mm long sample. Single sideband programmable polarization mode converters were produced with 16 electrode sets, each containing 64 grating periods. Programmability was achieved by applying spatially periodic weighted independent voltages to interdigital electrode sets, and controlled electronically via a personal computer through a digital-to-analog converter array chip. Maximum conversion efficiency of more than 99% was realized for both TM→TE and TE→TM, and was observed at 1530.48 nm. Two-port polarization independent electro-optically tunable wavelength filters were produced based on the results obtained above. The 3 dB bandwidth is 1.1 nm and the nearest side lobes to the main transmission are down by about 9 dB for uniform coupling. Side lobes are reduced to about 20 dB below peak transmission after apodization, and the 3 dB bandwidths increased to ~ 1.3 nm as a result. Seven channels (channel -4, -2, -1, 0, +1, +2 and +4) were selectable by programming the voltages on each electrode set. Channel spacing is 1.1~1.2 nm. The tuning ranges from 1524.04 to 1533.56 nm. Fiber-to-fiber insertion loss of the filter at center frequency is 4.3 dB for TE input and 4.2 dB for TM input. The polarization dependent loss is < 0.5 dB for all selectable channels. The temporal response to a 21 V step change in applied voltages was measured to be 586 ns for the 10%-90% rise time and 2.308 µs for the 90%-10% fall time. This research work provides a convenient scheme for making programmable two-port tunable bandpass filters and ROADMs.