Method and apparatus for transmitting information

A transmitter for transmitting information as a series of binary digits, each having one of two values, said transmitter comprising:

• a source of optical soliton pulses providing at an output port a series of n optical soliton pulses, where n is an integer>1, at each occurrence of one of the binary digit values, and
• optical coupling means optically connected to said output port for coupling or not coupling the series of n soliton pulses into an optical fibre as a function of said binary digit values,
• said source means including:
• a source of optical soliton pulses;
• a beam splitter located to split the stream of optical pulses into two subsidiary streams;
• a pair of reflective means to reflect the two subsidiary streams back to the beam splitter;
• the reflective means being positioned such that the two subsidiary streams are combined by the beam splitter to form an output stream of optical soliton pulses alternate pulses of which derive from different ones of the subsidiary streams.

A method of transmitting digital data in the form of a sequence of bits in successive bit periods, said method comprising the steps of:

• producing a soliton pulse series;
• deriving from the soliton pulse series at least first and second subsidiary streams of soliton pulses, each of said subsidiary streams corresponding to the soliton pulse series;
• combining the subsidiary streams to produce a carrier pulse stream wherein each of the bit periods includes soliton pulses from each of the subsidiary streams;
• and
• modulating the carrier stream according to the digital data, whereby successive bits of the digital data are represented by the presence or absence of a plurality of soliton pulses during each successive bit period.

Apparatus for transmitting digital data in the form of a sequence of bits in successive bit periods, said apparatus comprising:

• a digital data source;
• an optical source producing an optical soliton pulse series;
• means for deriving from the soliton pulse series at least first and second subsidiary streams of soliton pulses, each of said subsidiary streams corresponding to the soliton pulse series;
• combining means for combining the subsidiary streams to produce a carrier pulse stream wherein each of the bit periods includes soliton pulses from each of the subsidiary streams;
• and
• modulator means for modulating the carrier stream according to the data from the digital data source, whereby successive data bits of the digital data are represented by the presence or absence of a plurality of soliton pulses during each successive bit period.