We report a novel kind of all-optical dynamic grating based on Brillouin scattering in a polarization maintaining fiber (PMF). A moving acoustic grating is generated by stimulated Brillouin scattering between writing beams in one polarization and used to reflect an orthogonally polarized reading beam at different wavelengths. The center wavelength of the grating is controllable by detuning the writing beams, and the $3\mathrm{dB}$ bandwidth of $\sim 80\mathrm{MHz}$ is observed with the tunable reflectance of up to 4% in a $30\mathrm{m}$ PMF.

An efficiently prepared graphene from a bulk graphite using mechanical exfoliation is experimentally investigated for the first practical application to ultrafast photonics. Overcoming the limitations of the method in its size and atomic layer control, the multilayered graphene guarantees a nonlinear intensity modulation. After confirming its excellent crystal quality and few-layered nanostructure employing Raman analysis and atomic force microscopy the graphene layer is introduced into a fiber laser as an intracavity saturable absorber to realize the passive mode-locking that produces picosecond pulses at the repetition rate of 10.9 MHz. Extinction ratio of the resultant pulsed output is higher than 40 dB.

We passively generate picosecond $6.5\mathrm{nJ}$ optical pulses directly from a single-stage oscillator using carbon nanotube mode locker. The mode locker immunized to the high optical power induced damage employs the evanescent field interaction of propagating light with the nanotubes. The mode locker endures the intracavity power of up to $27.7\mathrm{dBm}$ . For the enhanced interaction, vertically aligned nanotubes are synthesized and applied. The output pulses are monitored for $200\mathrm{h}$ to find that there is no significant degradation of average power and spectral width.

A kind of high-repetition-rate distributed Brillouin sensor is proposed and experimentally demonstrated based on optical correlation-domain analysis with differential frequency modulation, where the optical frequencies of the pump and the probe waves are modulated at slightly different RFs so that the temporal position of the measurement is continuously and repeatedly swept along a fiber under test. A distribution map of Brillouin frequency variation along a $100\mathrm{m}$ optical fiber is acquired at a repetition rate of $20\mathrm{Hz}$ with an accuracy of $\pm 2.5\mathrm{MHz}$ and a spatial resolution of about $80\mathrm{cm}$.

Large increase of effective sensing points in Brillouin optical correlation domain analysis (BOCDA) is achieved by simultaneously applying double modulation and optical time gate based on differential measurement scheme. The noise substructure of Brillouin gain spectrum induced by the double modulation is effectively suppressed by the differential measurement, leading to 2,000 times enlargement of the measurement range. Distributed strain and temperature sensing along a 10.5 km fiber with spatial resolution of less than 1 cm is experimentally demonstrated which corresponds to over 1 million effective sensing points.