| 摘要 |
A laser (10) produces a primary beam (18) and a phase network (20), placed near the optical fibre (22), forms the secondary beams. The fringe separation is varied by an optical system comprising two lenses (14, 16) whose relative separation is variable. The displacement is controlled (28) simultaneously with the longitudinal displacement of the optical fibre so as to vary discretely the spacing of the Bragg grating in successive new segments of the fibre. Alternatively, the different segments may be identified by using a movable angled mirror to reflect the beam through 90 degrees onto a stationary phase network and fibre, allowing greater precision in the juxtaposition of the segments. The wavelength of the laser is 240 nm. |
