A single-mode optical fiber that reduces the chromatic dispersion of an optical pulse due the laser chirp in an optical communication system operating in the O-band has a cable cutoff wavelength less than 1250 nm, a zero-dispersion wavelength greater than 1334 n, and a nominal mode field diameter of said fiber at 1310 nm between 8.6 and 9.5 microns.

A single-core polarization-maintaining dispersion compensation micro-structured optical fiber comprises a fiber core, a first layer of air holes surrounding the fiber core, the cladding defects on the x-axis, the cladding defects on the y-axis, and the cladding. The air holes in the fiber cross section are arranged in the equilateral triangle lattice. Three consecutive air holes are omitted to form a solid area. This solid area is the fiber core. There are two cladding defects along the x-axis. Their centers are respectively located at the two vertices of the hexagon on the x-axis, which is formed by the fourth air hole ring from the core exclusive the central air hole. Each cladding defect along the x-axis contains 7 air holes and goes through from the core by only 1 layer of air holes. There are also two cladding defects along the y-axis.

A distributed Brillouin sensor system comprising a pump laser, a Brillouin sensor fiber, and a detector system is described. The pump laser is arranged so as to send a pump signal into a first end of the Brillouin sensor fiber, and the detector system is arranged to detect Brillouin backscattering from the Brillouin sensor fiber. The Brillouin sensor fiber is characterized by having a negative dispersion, and further by an effective area of the sensor fiber being less than or equal to 50 m.sup.2.

A distributed Brillouin sensor system comprising a pump laser, a Brillouin sensor fiber, and a detector system is described. The pump laser is arranged so as to send a pump signal into a first end of the Brillouin sensor fiber, and the detector system is arranged to detect Brillouin backscattering from the Brillouin sensor fiber. The Brillouin sensor fiber is characterized by having a negative dispersion, and further by an effective area of the sensor fiber being less than or equal to 50 m.sup.2.