We report active Q-switching of an all-fiber laser using a Bragg grating based acousto-optic modulator. Q-switching is performed by modulating a fiber Bragg grating with an extensional acoustic wave. The acoustic wave modulates periodically the effective index profile of the FBG and changes its reflection features. This allows controlling the Q-factor of the cavity. Using 1 m of 300 ppm erbium-doped fiber and a maximum pump power of 180 mW, Q-switch pulses of 10 W of peak power and 82 ns wide were generated. The pulse repetition rate of the laser can be continuously varied from few Hz up to 62.5 kHz.

The elasto-optic effect in optical fibers under axial strain can be characterized by means of the whispering gallery mode (WGM) resonances of the fiber itself. This technique enables a direct measurement of the anisotropy, the determination of the individual Pockels’ coefficients, and the study of the wavelength dependence. The method is based on a rigorous theoretical study of WGM resonances in cylindrical microresonators. The shift of the WGM resonances as a function of strain was measured for the TE and TM modes, showing a strong modal anisotropy. In particular, the shift rate for TE modes was 1.84 times the one for TM modes. From these measurements, experimental values for the Pockels’ coefficients were obtained: $p_{11}=0.116$ and $p_{12}=0.255$ at 1531 nm, and $p_{11}=0.131$ and $p_{12}=0.267$ at 1064 nm. The dispersion of $p_{44}$ with wavelength was shown to be $5\%{\mathrm{\mu m}}^{-1}$.

We report a high-repetition rate actively Q-switched all-fiber laser. The acousto-optic interaction controls the coupling between co-propagating core and cladding modes and is used to modulate the optical losses of the cavity, which permits to perform active Q-switching. Using 1.4 m of 300 ppm Er-doped fiber and a maximum pump power of 120 mW, we have obtained up to 1 W peak power pulses, with a pulse repetition rate that can be continuously varied from 1 Hz to 120 kHz and a pulse width that changes from 70 ns to 2.2 μs.

Active mode locking of an erbium-doped all-fiber laser with a Bragg-grating-based acousto-optic modulator is demonstrated. The fiber Bragg grating was acoustically modulated by a standing longitudinal elastic wave, which periodically modulates the sidebands at twice the acoustic frequency. The laser has a Fabry–Perot configuration in which cavity loss modulation is achieved by tuning the output fiber Bragg grating to one of the acoustically induced sidebands. Optical pulses at $9\mathrm{MHz}$ repetition rate, $120\mathrm{mW}$ peak power, and $780\mathrm{ps}$ temporal width were obtained. The output results to be stable and has a timing jitter below $40\mathrm{ps}$. The measured linewidth, $2.8\mathrm{pm}$, demonstrates that these pulses are transform limited.

We report a novel dynamic fiber-optic add-drop multiplexer that combines the properties of Bragg gratings and the acousto-optic effect in optical fibers. It is a noninterferometric, nonfrequency shifting device that allows adding/dropping a certain optical channel when it is required. The prototype presented here exhibits a time response of /spl sim/95/spl mu/s.