A multiwavelength laser source is demonstrated with a high power erbium-doped fiber amplifier as the gain medium. A highly nonlinear photonic crystal fiber (PCF) is inserted in the ring cavity to provide nonlinear gain by four-wave mixing. A Sagnac loop is incorporated in the ring cavity serving as a comb-like multichannel filter. The comparison between fiber ring laser without PCF and with PCF shows that the highly nonlinear PCF can generate a larger number of excited wavelengths and help stabilize the output power.

We demonstrate the novel flat-top modulational instability gain for a wide range of modulation frequencies in the anomalous dispersion regime of highly dispersive and nonlinear media. All the analytical results are compared with numerical simulation.

An optical switch structure which combines a planar lightwave circuit and liquid crystal is proposed and experimentally demonstrated. The switching is realized by inducing total internal reflection through controlling the refractive index of the liquid crystal. The principle and the design of the integrated optical switch are described. Experimental results suggest that anchoring of the liquid crystal molecules on nonplanar structures is very crucial in affecting the switching performance.

We demonstrate both width and wavelength-tunable optical pulse train generation based on four-wave mixing in highly nonlinear photonic crystal fiber. By tuning the delay time between two pulse trains, the pulsewidth of the generated pulse train is continuously tuned. By tuning the wavelength of one of the pulse trains, the wavelength of the generated pulse train is also continuously tuned. In our experiment, the pulsewidth of a 5-GHz repetition rate pulse train is tuned from 88 to 19ps and the pulsewidth of a 10-GHz pulse train is tuned from 39 to 19ps. The 3-dB wavelength tuning range is about 70 nm

A stable and broad bandwidth multiwavelength fiberring laser suitable for use in dense wavelength-division-multiplexing systems is demonstrated. A highly nonlinear photonic crystal fiber is inserted in the ring cavity to stabilize the power fluctuation and broaden the output spectrum. A thin-film Fabry-Pérot etalon filter is used to get stable wavelength lasing. A Sagnac filter is employed to achieve uniform power distribution at each wavelength at the laser output. A laser with a power fluctuation about 0.1dB in each wavelength within 20min and with wavelength shift of less than 0.016 nm within 10min is achieved. A stable 24-wavelength lasing operation with wavelength spacing of 0.8 nm within the 3-dB spectral range of 1573-1594 nm and signal-to-noise ratio better than 48dB is observed experimentally.