| 摘要 |
A micro-mechanical attenuator comprising a straight-edged occulting shutter moved across into the small gap between the ends of two co-aligned single mode optical fibres, or the gap between two beam-expanding lens-terminated optical fibres, is found to introduce a measure of polarisation sensitivity that may be unacceptably large for certain applications, whether that shutter is electrically conductive or not. (Different phenomena are involved in the two instances.) By appropriate shaping of the leading edge of the shutter so that it presents a mirror symmetry of orthogonally oriented edge portions to the beam that it occults, this polarisation sensitivity can be substantially eliminated.
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