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We demonstrate stable single-frequency and polarization operation of a traveling-wave, Er(3+)-doped fiber loop laser by incorporating an unpumped Er(+3)-doped fiber section butted against a narrow-band feedback reflector. The saturable absorber acts as a narrow bandpass filter that automatically tracks the lasing wavelength, thus ensuring single-frequency operation. Output powers up to 6.2 mW at 1535 nm were obtained for launched pump powers of 175 mW at 1064 nm. At this output, the relative intensity noise was less than -112 dBy/Hz at frequencies above 200 kHz and a laser linewidth of less than 0.95 kHz, whereas the lasing frequency was observed to drift slowly (~170 MHz/h) because of environmental effects.

Through a periodic sinc modulation of the refractive index-profile in fibre Bragg gratings we demonstrate gratings with multiple equally spaced and identical wavelength channels. We show 10 cm long gratings with 4, 8 and 16 identical uniform wavelength channels separated by the ITU spacing of 100 GHz and a 22.5 cm long grating with 4 identical dispersion compensating channels with a 200 GHz separation designed to dispersion compensate 80 km data transmission through standard fibre at 1.55 µm.

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We report, for the first time to our knowledge, the experimental observation of quasi-cw nonlinear switching and multiple gap-soliton formation within the bandgap of a fiber Bragg grating. As many as five gap solitons with 100-500-ps durations were generated from a 2-ns pulse at a launched peak intensity of approximately 27 GW/cm(2). A corresponding increase in the grating transmission from 3% to 40% of the incident pulse energy was observed.