An optical fiber loop has a gain medium having a gain at an oscillation wavelength and optical circulators 13 and 14. Collimate lenses 22 and 24 enlarge light bean taken from the optical circulators 13 and 14. A polygon mirror 25 is provided on the light axis, and is rotated. A diffraction grating 27...http://www.google.se/patents/US7382809?utm_source=gb-gplus-sharePatent US7382809 - Tunable fiber laser light source
