Fiber lasers may exhibit instabilities and self-pulsed regimes that can have catastrophic consequences on their components. One of the self-pulsing regimes is the recently observed self-induced laser line sweeping (SLLS). The SLLS is characterized by periodic wavelength drift over broad spectral interval of several nanometers followed by quick bounce backward. The sweeping rate is relatively slow, of the order of nm per second. Thanks to narrow line width and simple construction, the SLLS fiber lasers are attractive sources for testing of photonics components, interrogation of optical fiber sensor arrays and for laser spectroscopy. The SLLS can be explained by creation of a standing wave built up by laser longitudinal mode and consequent spatial-hole burning and refractive-index grating inscription. We review an evaluation of reflection spectra of transient fiber Bragg gratings that are created in SLLS fiber lasers. The evaluation is shown using example of ytterbium fiber laser in Fabry-Perot configuration of the laser cavity. We discuss also the effect of the laser wavelength self-sweeping on the triggering of the self-Q-switched regime and the generation of giant laser pulses. and Vláknové lasery mohou vykazovat nestabilní pulzní režimy. Jedním z režimů se samovolnou generací impulzů je nedávno pozorovaný jev spontánního rozmítání vlnové délky vláknového laseru. Tento jev je doprovázen charakteristickým periodickým posunem vlnové délky laseru v širokém rozsahu vlnových délek několika nanometrů. Rychlost rozmítání je relativně pomalá, řádově nanometry za sekundu. Díky úzké šířce čáry a jednoduché konstrukci jsou tyto lasery atraktivními zdroji záření, mj. pro systémy optických vláknových senzorů, charakterizaci optických komponent a laserovou spektroskopii. Samovolné rozmítání vlnové délky lze vysvětlit vytvořením stojaté vlny určené podélným módem rezonátoru. Vznik stojaté vlny vede k podélné modulaci indexu lomu - zápisu mřížky. V tomto příspěvku podáváme shrnutí dosud prezentovaných prací týkajících se modelování odrazivosti braggovských mřížek ve vláknových laserech se spontánním rozmítáním vlnové délky. Popisujeme experimentální ytterbiový vláknový laser s tímto typem nestability, následovaný teoretickým popisem braggovské mřížky a ukázkou výpočtu odrazivosti pro laser odpovídající experimentu. Je též diskutován význam spontánního rozmítání na spouštění režimu samočinného Q-spínání a generaci gigantických laserových pulzů.
Hydrologic cycle in the Liz catchment is described with an anomaly in the vegetation seasons 1992-1996. Experimental catchment Liz is located in the Šumava Mts. in the Czech Republic. The fully forested watershed is covered by mature spruce forest, and its basic characteristics are as follows: drainage area 0.99 km2, mean discharge 0.01m3 s-1, runoff coefficient 0.38, mean annual air temperature 6.30 oC, average slope 17 %, basin length 1.45 km, water course length 1.43 km, elevation 828-1074 m a.s.l., precipitation sum 851 mm year-1, and runoff depth 324 mm year-1. Air temperature, precipitation, global radiation, and discharge in the closing profile are measured in the catchment. It is characteristic for hydrologic cycle in the catchment that the share of seasonal sums of both the global radiation and temperature was nearly constant in 1983-2000. However, the seasonal sums of both the global radiation and temperature were changed considerably in 1983-2000. Similarly, the share of seasonal sums of both the rainfall and runoff was nearly constant in 1983-1991 and 1997-1999. An anomalous course of climate was registered in 1992-1996, manifested by a deviation on the double mass curve of the seasonal sums of rainfall and runoff. Stabilised elsewhere, the ratio of rainfall and runoff is changed during the vegetation seasons 1992-1996. Starting from the 1997 season, this ratio has obtained the value held before 1992. The reason of the 1992-1996 anomaly of hydrologic cycle in the experimental catchment had to be significant external phenomenon, most likely explosion of the Mount Pinatubo volcano in Philippines on June 15, 1991. and Hydrologic cycle in the Liz catchment is described with an anomaly in the vegetation seasons 1992- 1996. Experimental catchment Liz is located in the Šumava Mts. in the Czech Republic. The fully forested watershed is covered by mature spruce forest, and its basic characteristics are as follows: drainage area 0.99 km2 , mean discharge 0.01m3 s -1, runoff coefficient 0.38, mean annual air temperature 6.30 ºC, average slope 17 %, basin length 1.45 km, water course length 1.43 km, elevation 828-1074 m a.s.l., precipitation sum 851 mm year-1, and runoff depth 324 mm year-1. Air temperature, precipitation, global radiation, and discharge in the closing profile are measured in the catchment. It is characteristic for hydrologic cycle in the catchment that the share of seasonal sums of both the global radiation and temperature was nearly constant in 1983-2000. However, the seasonal sums of both the global radiation and temperature were changed considerably in 1983-2000. Similarly, the share of seasonal sums of both the rainfall and runoff was nearly constant in 1983-991 and 1997-1999. An anomalous course of climate was registered in 1992-1996, manifested by a deviation on the double mass curve of the seasonal sums of rainfall and runoff. Stabilised elsewhere, the ratio of rainfall and runoff is changed during the vegetation seasons 1992-1996. Starting from the 1997 season, this ratio has obtained the value held before 1992. The reason of the 1992-1996 anomaly of hydrologic cycle in the experimental catchment had to be significant external phenomenon, most likely explosion of the Mount Pinatubo volcano in Philippines on June 15, 1991.