Improvements relating to optical fibre communication systems

摘要

An optical fibre communication system in which modulator means 2 is provided at the transmitter end of the system for modulating the relative phase between orthogonally polarised signals derived from a coherent light source 1 in accordance with data or information to be transmitted over an optical fibre communication path to the receiver 4 end of the system where the signals will be demodulated. In order to reduce noise resulting from delay differentials between polarised signals transmitted over the optical fibre path L, it is includes sections of polarisation maintaining optical fibre 3 which are angularly rotated through 90 DEG or thereabouts relatively to one another so that the overall delay for the respective polarised signals over the entire length of the communication path is substantially the same.