Optical communication system

Claim 2

An optical communication system between two separate stations A and B in which: a. the station A is provided with: a light source for emitting a carrier, a modulator for modulating the light wave emitted from said carrier light source, means for transmitting the output of said modulator to the station B; b. the station B is provided with: means for dividing the modulated light signal transmitted from said station A, means for deriving (demodulating) the message of the station A from a divided portion of said signal, a message signal source of the station B, means for modulating a portion of the remainder of said divided modulated light signal with the message signal of the station B to use said divided modulated light signal as the carrier light source, and means for transmitting said modulated signal to said station A; and c. the station A is further equipped with: means for demodulating exclusively the message of the station B from said modulated light signal received from said station B.

Claim 3

An optical communication system between separate stations A and B in which; a. the station A is provided with: a carrier light source, means for obtaining a linearly polarized light wave from said light source, a message signal source, a light-modulator consisting of a crystal having an electro-optic effect for modulating said linearly polarized light wave emitted from said light source with a message signal of said message signal source, and demodulating means for deriving the signal of the station B from the modulated light wave received from the station B; b. the station B is provided with: means for dividing the modulated light signal transmitted from the station A, means for demodulating the message of the station A from a portion of said light signal divided by said dividing means, a first photoanalyzer adapted to pass therethrough only one of the polarized two components of another portion of the said divided light signal, said two components being so separated by passing said another portion of the divided light signal through said crystal having an electro-optic effect, a message signal source of the station B, a light-modulator consisting of a crystal having an electro-optic effect for modulating the output light signal of said photoanalyzer with said message signal of the station B to use said output light wave as the carrier light source, and means for transmitting the resulting modulated light signal emitted from said modulator.

Claim 4

An optical communication system between separate stations A and B in which; a. the station A is provided with: a carrier light source, means for obtaining a linearly polarized light wave from said light source, a message signal source, a light-modulator consisting of a crystal having an electro-optic effect for modulating said linearly polarized light wave emitted from said light source with a message signal of said message signal source, and demodulating means for deriving the signal of the station B from the modulated light wave received from the station B; b. the station B is provided with: means for dividing the modulated light signal transmitted from the station A, means for demodulating the message of the station A from a portion of said light signal divided by said dividing means, a first photoanalyzer adapted to pass therethrough only one of the polarized two components of another portion of the said divided light signal, said two components being so separated by passing said another portion of the divided light signal through said crystal having an electro-optic effect, a message signal source of the station B, a light-modulator consisting of a crystal having an electro-optic effect for modulating the output light signal of said photoanalyzer with said message signal of the station B to use said output light wave as the carrier light source, and means for transmitting the resulting modulated light signal emitted from said modulator.

Claim 5

An optical communication system between two separate stations A and B according to Claim 2, wherein a quarter-wave plate is provided between the output side of the light-modulator of the station A and the path of light beam of the demodulation means of the station B for giving a phase difference of 90 degrees to the two polarized light components so separated in optical axes x and y through said light-modulator of the station A consisting of a crystal having an electro-optic effect, and another quarter-wave plate is provided between the output side of the light-modulator of the station B and the demodulation means of the station A, said another quarter-wave plate being adapted to give a phase difference of 90 degrees to the polarized light components which have been separated into optical axes x and y by the modulator crystal of the station B.

Claim 6

An optical communication system between two separate stations A and B in which; a. the station A is provided with: a carrier light source, a message signal source, a high frequency oscillator, a first modulator for modulating a signal oscillated by said oscillator with a message signal of said message signal source, a second modulator for modulating the light wave emitted from said carrier light source, means for transmitting the resulting modulated light signal emitted from said second modulator to the station B located at a spaced site, and a demodulating means for deriving the message signal wave of the station B from a modulated light wave received from the station B, and b. the station B is provided with: means for dividing the modulated light wave transmitted from the station A, a message source of the station B, demodulating means for deriving the message signal of the station A from a portion of the signal divided by said dividing means, a modulator for modulating another portion of said divided light signal with said message signal of the station B to use said another portion of said divided light signal as the carrier light source, and means for transmitting the modulated output light signal of said modulator to the station A.

Claim 7

An optical communication system between two separate stations A and B in which; a. the station A is provided with: a carrier light source, a message signal source, a high frequency oscillator, a first modulator for modulating a signal oscillated by said oscillator with a message signal of said message signal source, a second modulator for modulating the light wave emitted from said carrier light source, means for transmitting the resulting modulated light signal emitted from said second modulator to the station B located at a spaced site, and a demodulating means for deriving the message signal wave of the station B from a modulated light wave received from the station B, and b. the station B is provided with: means for dividing the modulated light wave transmitted from the station A, a message source of the station B, demodulating means for deriving the message signal of the station A from a portion of the signal divided by said dividing means, a modulator for modulating another portion of said divided light signal with said message signal of the station B to use said another portion of said divided light signal as the carrier light source, and means for transmitting the modulated output light signal of said modulator to the station A.

Claim 8

An optical communication system between two separate stations A and B in which; a. the station A is provided with: a carrier light source, a message signal source, a modulator consisting of a crystal having an electro-optic effect and adapted to pass the linearly polarized light wave emitted from said light source through said crystal in a direction parallel with one of the polarization directions of the optical axis of said crystal and adapted to modulate the frequency or the phase of said light wave with said message signal, means for transmitting said modulated output light signal of said modulator to the station B located at a spaced communication site, and demodulating means for deriving the message signal of the station B from the modulated light signal transmitted from the station B, and b. the station B is equipped with: means for dividing the modulated light signal transmitted from the station A, a demodulating circuit for deriving the message of the station A from one portion of the divided signal, a message source of the station B, a modulator for modulating the amplitude of another portion of said divided light signal with said message signal to use said another portion of said divided light signal as the carrier light source, and means for transmitting the resulting light signal which has been modulated of its amplitude to the station A.

Claim 9

An optical communication system between two separate stations A and B in which; a. the station A is provided with: a carrier light source, a message signal source, a modulator consisting of a crystal having an electro-optic effect and adapted to pass the linearly polarized light wave emitted from said light source through said crystal in a direction parallel with one of the polarization directions of the optical axis of said crystal and adapted to modulate the frequency or the phase of said light wave with said message signal, means for transmitting said modulated output light signal of said modulator to the station B located at a spaced communication site, and demodulating means for deriving the message signal of the station B from the modulated light signal transmitted from the station B, and b. the station B is equipped with: means for dividing the modulated light signal transmitted from the station A, a demodulating circuit for deriving the message of the station A from one portion of the divided signal, a message source of the station B, a modulator for modulating the amplitude of another portion of said divided light signal with said message signal to use said another portion of said divided light signal as the carrier light source, and means for transmitting the resulting light signal which has been modulated of its amplitude to the station A.

Claim 10

The apparatus of claim 1, wherein said light is coherent light.

Claim 11

The apparatus of claim 2, wherein said light is coherent light.

Claim 12

The apparatus of claim 4, wherein said light is coherent light.

Claim 13

The apparatus of claim 5, wherein said light is coherent light.

Claim 16

The method of claim 10, wherein said light is polarized.