A wide band linearly chirped erbium-doped fiber laser has been developed. The erbium-doped fiber laser using a rotating mirror/grating combination as one of the reflectors in a Fabry-Perot laser cavity has been tuned over a 46 nm spectral range. Linearization of the chirp rate has been achieved using feedback from a fiber Fabry-Perot interferometer (FFPI) to adjust the voltage ramp which drives the rotating mirror. In a demonstration of monitoring an array of two fiber Bragg grating (FBG) sensors, a wavelength resolution of 1.7 pm has been achieved. The linearly chirped fiber laser has been used in measuring the optical path difference (OPD) of interferometric fiber optic sensors by performing a Fourier transform of the optical signal. Multiplexing of an array of three FFPI sensors of different lengths has been demonstrated, with an OPD resolution ranging from 3.6 nm to 6.3 nm. Temperature was measured with one of the sensors over the range from 20°C to 610°C with a resolution of 0.02°C. Short FBGs are used to form the two mirrors of a fiber Bragg grating pair interferometer (FBGPI) sensor, so that the mirror reflectances change gradually as a function of temperature. Modulating the drive current of a DFB laser produces chirping of the laser frequency to scan over ~2.5 fringes of the FBGPI reflectance spectrum. Because the fringes are distinguished due to the FBG reflectance change, the ambient temperature can be determined over the range from 24 oC to 367 oC with a resolution of 0.004 oC. Multiplexing of FBGPI sensors of different lengths with a linearly chirped fiber laser has demonstrated improved sensitivity and multiplexing capacity over a conventional FBG WDM system. The FBG spectral peak position and the phase shift of an FBGPI are determined through the convolution of the sensor reflected signal with an appropriately matched reference waveform, even though the reflectance spectra for the FBGs from different sensors overlap over a wide temperature range. A spectral resolution for the FBG reflectance peak of 0.045 GHz (0.36 pm), corresponding to a temperature resolution of 0.035 oC, has been achieved.

No description available.

We propose a linear mean square error channel estimator that exploits the joint space-time-frequency (STF) correlations of the wireless fading channel for applications in multiple-antenna orthogonal frequency division multiplexing systems. Our work generalizes existing channel estimators to the full dimensions including transmit spatial, receive spatial, time, and frequency. This allows versatile applications of our STF channel estimator to any fading environment, ranging from spatially-uncorrelated slow-varying frequency-flat channels to spatially-correlated fast-varying frequency-selective channels. / The proposed STF channel estimator reduces to a time-frequency (TF) channel estimator when no spatial correlations exist. In another perspective, the lower-dimension TF channel estimator can be viewed as an STF channel estimator with spatial correlation mismatch for space-time-frequency selective channels. / Computer simulations were performed to study the mean-square-error (MSE) behavior with different pilot parameters. We then evaluate the suitability of our STF channel estimator on a space-frequency block coded OFDM system. Bit error rate (BER) performance degradation, with respect to perfect coherent detection, is limited to less than 2 dB at a BER of 10-5 in the modified 3GPP fast-fading suburban macro environment. Modifications to the 3GPP channel involves reducing the base station angle spread to imitate a high transmit spatial correlation scenario to emphasize the benefit of exploiting spatial correlation in our STF channel estimator.

No description available.

Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references. / vi, 47 leaves, bound ill. 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references (leaves 44-45). / viii, 45 leaves, bound ill. 29 cm

Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references (leaves 152-160). Also available via World Wide Web.

Thesis (Ph.D) -- McMaster University, 1997. / Includes bibliographical references (leaves 183-190). Also available via World Wide Web.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph. D.)--Ohio University, August, 1994. / Title from PDF t.p.