Dopant diffusion loss mechanism in high-birefringent-fiber fused couplers.

The observation of dopant diffusion during the tapering of high-birefringent fibers that increases with initial modal birefringence is reported. The resulting reduction in the core-cladding index difference is postulated to result in an increased taper transmission loss and is shown to correspond to increased 3-dB fused-coupler insertion loss.

Internal rotation of the birefringence axes in polarization-holding fibers.

An internal rotation of the birefringence axes has been measured in a variety of polarization-holding fibers. The rotation of the axes causes coupling of the major-field components of the fundamental modes, which limits the polarization-extinction ratio in short lengths of birefringent fibers to -45 dB in some cases. A practical consequence of the rotation of the axes is a reduction of the polarization-holding ability of devices such as fiber couplers that are made with these fibers.

9 x 9 single-mode fiber-optic star couplers.

A 9 x 9 single-mode fiber-optic star coupler that displays an excess loss of 1.46 dB and a uniformity of 1.50 dB is described. Design and fabrication are discussed, and performance data are presented.

All-fiber gyroscope with polarization-holding fiber.

An all-fiber gyroscope is reported that is constructed entirely of polarization-holding fiber. The random-drift coefficient was 5 x 10(-3) deg/ radicalh. Gyro bias drift is shown to be stable over periods of hundreds of hours. Device construction details and some thermal dependence of components are given.

Comparison of cutoff wavelength measurements for single-mode waveguides.

The intrinsic cutoff wavelength of the LP11 mode is investigated using three different types of measurement for an ITT single-mode fiber. Characterization of the far-field pattern of the LP01 mode gives a cutoff value approximately 660 nm, a near-field transmission experiment gives approximately 690 nm, and a refracted power measurement gives approximately 830 nm. We conclude that the refracted power technique is the best experimental method for the determination of the intrinsic cutoff wavelength of a fiber sample. The effect of the loss of coupling efficiency into the LP11 mode as cutoff is approached on the transmission and refracted power experiments is noted.

Fiber-optic gyroscope with polarization-holding fiber.

A fiber gyroscope is reported that uses polarization-holding fiber in the coil, the phase modulator, and the coupler. The random-drift coefficient, calculated from rms noise levels, was 8.10(-4) deg/ radicalh, within a factor of 2 of an experimentally determined quantum and thermal limit. White-noise behavior was observed for integration time constants from 1 to 40 sec. Device characteristics and performance are presented.

Birefringence correction for single-mode fiber couplers.

We apply a two-port, lumped-element birefringence model to single-mode fiber couplers. By application of twist and compression to output leads, the effects of circular and linear birefringence can be essentially eliminated. Resulting output polarization states are linear and unrotated for any linear inputs in both splitters and combiners. Compensation stability is investigated.