Extended precision in video bandwidth analog to digital converter using optical techniques

Claim 2

An optical analog-to-digital converter comprising: an optical conversion unit including a first electro-optic modulator and a second electro-optic modulator formed from a single mode waveguide for generating optical modulator signal outputs, wherein said modulators are driven in parallel by an input analog signal V(t) and said optical modulator signal outputs are identical except for a relative phase bias θ; LSB means for detecting, digitizing, and processing the optical modulator signal outputs to form a least significant bits representation LSB of V(t); MSB means for digitizing said input analog signal V(t) to form a most significant bits MSB representation; and means for interleaving said LSB representation and said MSB representation to form a final binary representation of said input analog signal V(t).

Claim 3

An optical analog-to-digital converter as claimed in claim 1, wherein said LSB digitizing means comprises a first electronic analog-to-digital converter to receive and convert the detected output from said first modulator to digital form, and a second electronic analog-to-digital converter to receive and convert the detected output from said seccnd modulator to digital form.

Claim 4

An optical analog-to-digital converter as claimed in claim 1, wherein said LSB processing means comprises means to compare said digitized representations of the detected optical modulator signal outputs and to choose the digitized value closest to a designated reference value essentially in a predetermined midrange of possible analog-to-digital converter outputs.

Claim 5

An optical analog-to-digital converter as claimed in claim 1, wherein said MSB means comprises an electronic analog-to-digital converter fed directly by the input analog signal V(t).

Claim 6

An optical analog-to-digital converter as claimed in claim 1, wherein said interleaving means comprises binary logic gates.

Claim 7

An optical analog-to-digital converter as claimed in claim 1, wherein said single mode waveguide is formed in a substrate of lithium tantalate.

Claim 8

An optical analog-to-digital converter as claimed in claim 1, wherein said single mode waveguide is formed in a substrate of lithium niobate.

Claim 9

An optical analog-to-digital converter as claimed in claim 3, wherein said means to compare said digitized representations of the detected optical modulator signal outputs and to choose the digitized value closest to a designated reference value essentially in a predetermined midrange of possible analog-to-digital converter outputs comprises read only memory (ROM) logic.

Claim 10

An optical analog-to-digital converter comprising: an optical conversion unit including two interferometric electro-optic modulators formed from single-mode waveguides in a single crystal substrate of a Pockels (linear) electro-optic material for generating optical modulator signal outputs, wherein said modulators are driven in parallel by an input analog signal and wherein said modulator optical signal outputs are identical except for a relative phase bias θ; a repetitively pulsed light source for sampling the optical output signals from said modulators; a first photodetector to convert the transmitted optical signal from one of said modulators into electrical signals essentially proportional in voltage to the amplitude of the optical signals; a second photodetector to convert the transmitted optical signal from the second modulator into electrical signals essentially proportional in voltage to the amplitude of the optical signals; a first electronic analog-to-digital converter to digitize the signal detected by the first photodetector; a second electronic analog-to-digital converter to digitize the signal detected by the second photodetector; LSB means for forming a least significant bit LSB representation of the input analog signal from the outputs of said electronic analog to digital converters; a third electronic analog-to-digital converter fed directly by the input analog signal to form a most significant bits MSB representation of the input analog signal; and an interleaving logic stage to form a final binary representation of said input analog signal V(t) by interleaving said least significant bits representation LSB and said most significant bits representation MSB.

Claim 11

An optical analog-to-digital converter comprising: an optical conversion unit including two interferometric electro-optic modulators formed from single-mode waveguides in a single crystal substrate of a Pockels (linear) electro-optic material for generating optical modulator signal outputs, wherein said modulators are driven in parallel by an input analog signal and wherein said modulator optical signal outputs are identical except for a relative phase bias θ; a repetitively pulsed light source for sampling the optical output signals from said modulators; a first photodetector to convert the transmitted optical signal from one of said modulators into electrical signals essentially proportional in voltage to the amplitude of the optical signals; a second photodetector to convert the transmitted optical signal from the second modulator into electrical signals essentially proportional in voltage to the amplitude of the optical signals; a first electronic analog-to-digital converter to digitize the signal detected by the first photodetector; a second electronic analog-to-digital converter to digitize the signal detected by the second photodetector; LSB means for forming a least significant bit LSB representation of the input analog signal from the outputs of said electronic analog to digital converters; a third electronic analog-to-digital converter fed directly by the input analog signal to form a most significant bits MSB representation of the input analog signal; and an interleaving logic stage to form a final binary representation of said input analog signal V(t) by interleaving said least significant bits representation LSB and said most significant bits representation MSB.

Claim 12

An optical analog-to-digital converter as recited in claim 9, wherein said LSB means comprises read only memory (ROM) logic.

Claim 15

A method of converting input analog signals to digital form, as recited in claim 11, wherein the sampling step is performed by a mode locked laser.

Claim 16

A method of converting input analog signals to digital form, as recited in claim 11, wherein forming a least significant bits representation comprises: digitizing the optical output of said electro-optic modulators; and comparing said digitized optical output and to choose the output value closest to a designated reference value essentially in a predetermined midrange of possible analog-to-digital converter outputs.

Claim 17

A method of converting input analog signals to digital form, as recited in claim 13, wherein the digitizing step is performed by, a first electronic analog-to-digital converter serially connected to the output of said first modulator, and a second electronic analog-to-digital converter serially connected to the output of said second modulator.

Claim 18

A method of converting input analog signals to digital form, as recited in claim 13, wherein said comparing step is performed by read only memory (ROM) logic.

Claim 19

A method of converting input analog signals to digital form, as recited in claim 11, wherein said interleaving step is performed by binary logic gates.