The present disclosure provides an optical device comprising a first optical fibre portion having a first region and further regions between which the first region is positioned. The optical device also comprises a second optical fibre portion having a second region and further regions between which the second region is positioned. Further, the optical fibre comprises at least one member to which the first and second optical fibre portions are attached at the first and second regions. The first and second regions are positioned at opposite sides of an area defined between the first and second regions and spaced apart from each other by a first distance and wherein adjacent further regions are spaced apart by a second distance that is smaller than the first distance.