Optical communication system using pulse position modulation

Claim 1

An optical pulse position modulated digital data signal transmitter comprising: a mode-locked laser producing recurrent optical pulses at a predetermined frequency; optical control means associated with said mode locked laser for optically outputting a selected one of said optical pulses in response to a respectively corresponding supplied electrical control signal; input processing means electrically coupled to said optical control means for recurrently accepting groups of n binary digital data bit signals having 2 n possible data values and for producing said electrical control signal in synchronism with the occurrence of a selected one of a group of N optical pulses, N being an integer greater than 2 n /n, wherein said predetermined frequency of recurrent optical pulses produced by the mode-locked laser is greater than 2 n /n times the occurrence rate of said binary digital data bit signals and is also synchronized with the occurrence rate of said groups of n bit signals.

Claim 3

A method of transmitting digital data having successive digits, said method including: deriving, from groups of digits of the data, first position modulated electrical pulses respectively representing the groups of digits by counting clock pulses at a time slot frequency until the count has a specific relationship to the group of digits and then generating one of said first position modulated electrical pulses, producing a succession of pulses of optical energy at the time slot frequency and in synchronization therewith from a mode locked laser, selecting and coupling for transmission one of N optical energy pulses from the succession in response to occurrences of said first position modulated pulses, N being an integer greater than one receiving the transmitted optical energy pulses and deriving from them second position modulated electrical pulses, coverting each second position modulated electrical pulse into a corresponding group of digital data digits by counting clock pulses at the time slot frequency for the time interval which occurs between a datum time and the occurrence of a second position modulated electrical pulse and using the count reached to generate the group of digital data digits, and producing as output the groups of digital data digits.

Claim 4

A method of transmitting digital data having successive digits, said method including: deriving, from groups of digits of the data, first position modulated electrical pulses respectively representing the groups of digits by counting clock pulses at a time slot frequency until the count has a specific relationship to the group of digits and then generating one of said first position modulated electrical pulses, producing a succession of pulses of optical energy at the time slot frequency and in synchronization therewith from a mode locked laser, selecting and coupling for transmission one of N optical energy pulses from the succession in response to occurrences of said first position modulated pulses, N being an integer greater than one receiving the transmitted optical energy pulses and deriving from them second position modulated electrical pulses, coverting each second position modulated electrical pulse into a corresponding group of digital data digits by counting clock pulses at the time slot frequency for the time interval which occurs between a datum time and the occurrence of a second position modulated electrical pulse and using the count reached to generate the group of digital data digits, and producing as output the groups of digital data digits.