| 摘要 |
<p>In an optical device including a Bragg grating (4), such as a gas or vapour sensor, a planar optical waveguide layer (2) is carried on a substrate (1) and has a cladding layer (3). Light from a source (7) is transmitted via an input fibre (6) along the waveguide layer (2) to be incident on the Bragg grating (4) at an angle which results in Bragg scattering from it. The scattered radiation is monitored to determine the concentration of the gas to which the sensor is exposed, the effective index of the waveguide (2) varying with changes in concentration of the gas. To obtain high sensitivity, edge surface (5) of the substrate (1) and waveguide layer (2) is curved, permitting the input fibre (6) to be adjusted in position to satisfy the Bragg angle at the grating (4) for a particular device geometry. Thus variations in dimensions of the device because of manufacturing tolerances may be accommodated. Also, the same device may be used with different light sources by suitably positionning the input fibre (6) relative to the grating (4).</p> |
