| 摘要 |
<p>The band pass filter is formed of a fibre module and comprises one or more fibre Bragg gratings arranged one behind the other. The cutoff region of the filter is determined by the bandwidth of the grating. The gratings are arranged at a given angle to the fibre axis to reduce reflection back to the input of the module by contra-directional mode coupling. A multi-mode fibre is used to obtain optimal coupling. In the cutoff region, one or more pass bands are provided for letting out corresponding grid sections. The pass bands have the same or different attenuation.</p> |
