Abstract: Systems and methods for encoding a data signal as a pulse position modulation (PPM) signal and decoding a PPM signal to output the original data signal. The method of encoding may comprise receiving an input data signal; converting the data within the input data signal to a sequence of PPM symbol values; and generating a PPM signal comprising an alternating sequence of synchronisation pulses and data pulses. The PPM signal may be generated by generating a plurality of synchronisation pulses at a fixed pulse repetition rate; and generating a sequence of data pulses with each data pulse having a time delay from a preceding synchronisation pulse, whereby the sequence of data pulses represent the sequence of PPM symbol values.

Abstract: Systems and methods for encoding a data signal as a pulse position modulation (PPM) signal and decoding a PPM signal to output the original data signal. The method of encoding may comprise receiving an input data signal; converting the data within the input data signal to a sequence of PPM symbol values; and generating a PPM signal comprising an alternating sequence of synchronisation pulses and data pulses. The PPM signal may be generated by generating a plurality of synchronisation pulses at a fixed pulse repetition rate; and generating a sequence of data pulses with each data pulse having a time delay from a preceding synchronisation pulse, whereby the sequence of data pulses represent the sequence of PPM symbol values.

Abstract: The present invention relates to an improved quantum signal transmitter, which has a plurality of quantum output channels having at least one optical source and at least one optical splitter acting on the output of said at least one source. Such a transmitter can easily be used with existing passive optical network (PON) systems and can be a compact piece of equipment.

Abstract: Methods and apparatus for use in quantum key distribution (QKD) are described. A quantum QKD signal is generated at a source and transmitted through a fiber optic network to an endpoint, a key being agreed with communication over a classical QKD channel. The classical QKD channel contains additional information relevant to a network over which keys are distributed, and may be processed at nodes intermediate between the source and the endpoint.

Abstract: The invention relates to methods and apparatus for Quantum key distribution. Such methods including authenticating a first node in a communications network with a remote node in the communications network. The authentication may include connecting an authentication device to the first node, agreeing a quantum key between the first node and the remote node based on a quantum signal transmitted or received by the first node and performing an authentication step between the authentication device and the remote node on an encrypted channel. Authentication between the authentication device and remote node may be taken as authentication of the first node.

Abstract: Methods and apparatus for use in quantum key distribution (QKD) are described. A quantum QKD signal is generated at a source and transmitted through a fibre optic network to an endpoint, a key being agreed with communication over a classical QKD channel. The classical QKD channel contains additional information relevant to a network over which keys are distributed, and may be processed at nodes intermediate between the source and the endpoint.

Abstract: The invention relates to methods and apparatus for Quantum key distribution. Such methods including authenticating a first node in a communications network with a remote node in the communications network. The authentication may include connecting an authentication device to the first node, agreeing a quantum key between the first node and the remote node based on a quantum signal transmitted or received by the first node and performing an authentication step between the authentication device and the remote node on an encrypted channel. Authentication between the authentication device and remote node may be taken as authentication of the first node.

Abstract: The present invention relates to an improved quantum signal transmitter, which has a plurality of quantum output channels having at least one optical source and at least one optical splitter acting on the output of said at least one source.