Analysis, fabrication and properties of single-mode fibres exhibiting extremely low polarization birefringence

There is currently a great deal of interest in the development of single-mode fibres, capable of transmitting linearly-polarized light. Conventional monomode fibres exhibit linear birefringence; they therefore have an output state which is, in general, elliptically polarized and different from that at the input. Apart from the possible curtailment of the transmission bandwidth caused by this birefringence, the indeterminacy of the output polarization is a considerable disadvantage when coupling fibres to polarization-sensitive integrated-optics receivers. In addition, several interesting devices which utilise single-mode fibres have recently emerged and it has been found that the intrinsic retardance present in the fibres accompanied by the uncertainty in output polarization imposes a limitation on performance. Amongst these, the best known are the Faraday-effect current transducer, the fibre Raman laser and the fibre gyroscope