Compression-tuned single-frequency Bragg grating fiber laser.

Compressive stress has been used to continuously wavelength tune a single-frequency Bragg grating fiber laser over 32 nm without mode hopping. A master-oscillator/power-amplifier configuration and active noise reduction were implemented to maintain a constant, low-noise, 3-mW lasing power over the tuning range.

Fiber-optic Bragg grating strain sensor with drift-compensated high-resolution interferometric wavelength-shift detection.

The operation of a fiber Bragg grating strain sensor system that uses interferometric determination of strain-induced wavelength shifts and incorporates a reference channel to compensate for random thermal-induced drift in the output is described. This system is shown to be capable of resolving sub-microstrain changes in the quasi-static strain applied to a grating and has a resolution of ~6 x 10(-3) microstrain/ radicalHz at a strain perturbation frequency of 1 Hz.

Polarimetric heterodyning Bragg-grating fiber-laser sensor.

We report the operation of an active, single-frequency, polarimetric, Bragg-grating fiber-laser strain sensor. The short Bragg-grating fiber-laser design limited lasing to two orthogonal polarization modes that, when optically mixed, yielded a single beat frequency that varied at a rate of -4.1 MHz/mstrain for linear strain and -0.37 MHz/(deg/cm) for torsional strain.

Continuously tunable single-mode erbium fiber laser.

A single-mode linear-cavity fiber laser that utilizes intracore Bragg reflectors for cavity feedback has been continuously tuned, without mode hopping, when both the gratings and enclosed fiber are stretched uniformly. Continuous tuning is achieved in a 1.54-microm erbium fiber laser since the change in the reflected wavelength from a Bragg reflector tracks the change in the cavity resonance wavelength.

Formation of Bragg gratings in optical fibers by a transverse holographic method.

Bragg gratings have been produced in germanosilicate optical fibers by exposing the core, through the side of the cladding, to a coherent UV two-beam interference pattern with a wavelength selected to lie in the oxygen-vacancy defect band of germania, near 244 nm. Fractional index perturbations of approximately 3 x 10(-5) have been written in a 4.4-mm length of the core with a 5-min exposure. The Bragg filters formed by this new technique had reflectivities of 50-55% and spectral widths, at half-maximum, of 42 GHz.

Cross-talk fiber-optic temperature sensor.

The temperature sensitivity of cross talk between closely spaced cores in a common cladding is calculated and compared with measurements. A periodic variation in core contrast is observed when one core is illuminated and the temperature is changed. The variation in light distribution, which is ascribable to a change in coupling between the cores, agrees with theoretical predictions. It is shown that cross talk can be made to be a sensitive, predictable function of temperature or by proper selection of materials, wavelength, and fiber geometry essentially temperature independent.