The characteristics including mean wavelength stability, linewidth, and output power of a double-pass backward (DPB) Er-doped superfluorescent fiber source (SFS) are theoretically analyzed in details. The effects of the variations in fiber length, pump wavelength, fiber mirror reflectance, optical feedback, and erbium concentration on the characteristics are investigated. The analysis results show that an SFS in DPB configuration may serve as light source for the navigation-grade fiber-optic gyroscope applications.

A general methodl of analyzing misalignment tolerance of coupling light from an astigmatic laser diode to a single-mode fiber is described. We apply the method to derive the 3 dB tolerances caused by Ilongitudinal, lateral, and angular misalignments in the optimal coinditions for two kinds of coupling schemes. One is by the use of a rotationally symmetric optical system, and the other by a rod which is a special case of utilizing a rotationally asymmetric optical system. In the latter coupling case, the misalignment caused by a laser is found to have a much less 3 dB tolerance in the vertical direction than that caused by a fiber.

GEORGES, T., MONERIE, M., and POUMELLEC, B.: 'Behaviour of spectral transmissions of Bragg gratings written in germania-doped fibres : Writing and erasing experiments using pulsed or CW uv exposure',

We demonstrate a new technique to generate a high-power multiwavelength fiber source (MWFS) by inserting cascaded long-period fiber gratings (LPFG's) in double-pass Er-doped fiber (EDF) superfluorescent fiber sources. 20 channels with extinction ratios larger than 10 dB can be obtained between 1525-1560 nm with appropriate EDF lengths. Though the total output power decreases due to the insertion of the cascaded LPFG's, the power in each channel for the proposed MWFS is larger than that obtained by using the spectrum slicing technique because of power redistribution. We also demonstrate that by using another LPFG in such a source to reduce the power variation among the desired channels. The wavelength stability of the source is shown to be determined by the cascaded LPFG's rather than by the EDF.

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