Dielectric fibres for low-loss transmission of millimetre waves and its application in couplers and splitters

We present a dielectric fibre and two splitters made of polyethylene, which are well suited for the guidance of millimeter waves. A successful construction of a 3-dB coupler and a 1 × 4 splitter is reported. The fibre has a diameter of 3 mm and offers a very low absorption of 0.03 dB/cm at a frequency of 70 GHz. Since the radiation is guided mainly inside the fibre, the waveguide is insensitive to mechanical contact. The fibre has been tested to work effectively for frequencies up to 300 GHz. Therefore, such fibres and derived devices are relevant for practical applications such as endoscopes and fibre arrays. The use of fibre arrays can for example increase the measurement speed in continuous wave imaging.