Arrangements for detecting distorted optical pulses using a correlation technique

Claim 2

In an optical system wherein an optical pilot pulse and a train of overlapping information pulses are propagating, correlation means for resolving said overlapping information pulses comprising: means for generating a plurality of signal pairs, where each of said signal pairs is developed from said pilot pulse and a different information pulse of said train; the two signals of any one pair being proportional to the sum and difference, respectively, of the average energy of the pilot pulse and an information pulse, and a value on the crosscorrelation function of the latter two pulses; and means for forming a plurality of difference signals, each of which is proportional to the algebraic difference between the two signals of each of said signal pairs.

Claim 3

A correlation means in accordance with claim 1 wherein the time delay between adjacent information pulses is greater than the reciprocal of the information pulse bandwidth.

Claim 4

An optical transmission system comprising: means for generating a train of optical pulses comprising an optical pilot pulse followed by a train of information pulses; a dispersive optical transmission medium into which said pulses are coupled; and optical correlation means coupled to the output end of said medium for resolving said information pulses comprising: means for generating a plurality of signal pairs, where each of said signal pairs is developed from said pilot pulse and a different information pulse of said train; the two signals of any one pair being proportional to the sum and difference, respectively, of the average energy of the pilot pulse and an information pulse, and a value on the cross-correlation function of the latter two pulses; and means for forming a plurality of difference signals, each of which is proportional to the algebraic difference between the two signals of said signal pairs.

Claim 5

An optical transmission system comprising: means for generating a train of optical pulses comprising an optical pilot pulse followed by a train of information pulses; a dispersive optical transmission medium into which said pulses are coupled; and optical correlation means coupled to the output end of said medium for resolving said information pulses comprising: means for generating a plurality of signal pairs, where each of said signal pairs is developed from said pilot pulse and a different information pulse of said train; the two signals of any one pair being proportional to the sum and difference, respectively, of the average energy of the pilot pulse and an information pulse, and a value on the cross-correlation function of the latter two pulses; and means for forming a plurality of difference signals, each of which is proportional to the algebraic difference between the two signals of said signal pairs.

Claim 6

An optical transmission system in accordance with claim 3 wherein said means for forming a plurality of signal pairs comprises: a plurality of plates longitudinally distributed along the propagation direction of said pulses; each of said plates having a thickness equal to m lambda /4, and each being separated in space from the next adjacent plate by an amount vT/2, where lambda is the optical wavelength, m is an odd integer, v is the velocity of the pulses and T is the center to center spacing between adjacent information pulses; a mirror facing a surface of the last of said plurality of plates, said mirror being disposed a distance vT''/2 from said surface, where T'' is the time delay between said pilot pulse and said first information pulse; and means disposed on opposite sides of each of said plates for intercepting the optical wave energy scattered therefrom.

Claim 7

An optical transmission system in accordance with claim 4 wherein said means disposed on opposite sides of each plate comprises an optical square law detector which develops an electrical signal proportional to the intensity of the received optical wave energy.

Claim 8

An optical transmission system in accordance with claim 5 wherein said square law detectors have response times which are equal to the broadened width of the information pulses after they have propagated through said dispersive medium.

Claim 9

An optical transmission system in accordance with claim 3 wherein said means for forming a plurality of difference signals comprises a plurality of difference amplifiers.

Claim 10

An optical transmission system in accordance with claim 3 wherein said means for generating a plurality of signal pairs comprises: a plurality of optical plates distributed, at intervals of vT/2, along the propagation path of said pulses; each of said plates being inclined to said propagation path of said pulses, and each having a first surface for reflecting a first component of an incident information pulse along a first path and a second surface for reflecting a second component of the same information pulse along a second path; a plurality of mirrors, each of which is displaced a distance vT/2 from the propagation path of said pulses, and disposed such that it redirects the first and second components reflected by a different one of said plates back through said one plate and along third and fourth paths, respectively; a plurality of delay elements for imparting a delay of m lambda /2 to optical wave energy passing back and forth therethrough, where each of said delay elements lies along a different one of said second paths; a mirror disposed along said propagation path of said pulses, at a distance v(T''+T)/2 away from the last plate of said plurality, for redirecting said pilot pulse back through said plates; each of said plates reflecting first and second components of said redirected pilot pulse, as it passes therethrough, along the third and fourth paths, respectively, associated with each plate; and means for intercepting the optical wave energy propagating along the third and fourth paths associated with each plate.

Claim 11

An optical transmission system in accordance with claim 8, wherein the means for intercepting the optical wave energy propagating along the third and fourth paths associated with each plate comprises: a prism arranged such that two of its surfaces lie along said third and fourth paths, respectively; and two optical square law detectors, each disposed opposite to one of said two surfaces for receiving the optical wave energy reflected therefrom.

Claim 12

An optical transmission system in accordance with claim 9 wherein said square law detectors are gated to remain on only during the time and redirected pilot pulse is traversing their respective plate.