Optical telecommunications system using phase compensation interferometry
First Claim
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1. An optical telecommunication system comprising:
- a first transmission unit having;
a source of radiant energy having a coherence length;
separate first and second optical paths having a path length difference of Δ
L1 which is greater than said coherence length;
means for dividing radiant energy from said source into first and second portions for passage respectively along said first and second optical paths and for recombining said first and second optical portions after passage along said first and second optical paths;
a phase modulator in said first optical path operable for applying a telecommunication signal to said first portion;
said first transmission unit operably connected to provide said recombined portions with a phase difference corresponding to Δ
L1 to a transmission path having a first end adjacent said first transmission unit and a second end; and
a first receiver unit operably connected to said second end of said transmission path and having;
separate first and second reception paths, each having a Faraday rotating mirror at an end to reflect back radiant energy;
means for reseparating said first and second portions for passage separately and respectively on said first and second reception paths and for recombining said first and second portions; and
a first sensor connected to said means for reseparating and recombining, said first sensor operable to sense radiant energy for detection of the telecommunication signal applied at the first transmission unit; and
wherein said first transmission unit, transmission path, and said first receiver unit collectively are an interferometer.
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Abstract
Optical telecommunications systems use phase compensation interferometry wherein receiver units have interferometer configurations with path length differences identical to path length differences of arms in interferometer configurations at corresponding transmitter units. Faraday rotating mirrors are used to minimize sensitivity to polarization effects. A modified Michelson interferometer structure is used to provide optical signals which convert to electrical signals in a form allowing relatively easy demodulation. A demodulation circuit uses the property whereby two signals have a 90° phase shift.
53 Citations
20 Claims
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1. An optical telecommunication system comprising:
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a first transmission unit having; a source of radiant energy having a coherence length; separate first and second optical paths having a path length difference of Δ
L1 which is greater than said coherence length;means for dividing radiant energy from said source into first and second portions for passage respectively along said first and second optical paths and for recombining said first and second optical portions after passage along said first and second optical paths; a phase modulator in said first optical path operable for applying a telecommunication signal to said first portion; said first transmission unit operably connected to provide said recombined portions with a phase difference corresponding to Δ
L1 to a transmission path having a first end adjacent said first transmission unit and a second end; anda first receiver unit operably connected to said second end of said transmission path and having; separate first and second reception paths, each having a Faraday rotating mirror at an end to reflect back radiant energy; means for reseparating said first and second portions for passage separately and respectively on said first and second reception paths and for recombining said first and second portions; and a first sensor connected to said means for reseparating and recombining, said first sensor operable to sense radiant energy for detection of the telecommunication signal applied at the first transmission unit; and wherein said first transmission unit, transmission path, and said first receiver unit collectively are an interferometer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An optical telecommunication system comprising:
a first receiver unit having; separate first and second reception paths, each having a Faraday rotating mirror at an end to reflect back radiant energy; a means for reseparating first and second portions of radiant energy for passage separately and respectively on said first and second reception paths and for recombining said first and second portions, said first and second portions having been combined after separation and passage on different paths with a path length difference of Δ
L1, one of the paths having application of a telecommunication signal by phase modulation thereon;a first sensor connected to said means to reseparate and to recombine, said first sensor sensing radiant energy for detection of the telecommunication signal. - View Dependent Claims (12, 13, 14, 15)
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16. An optical telecommunication system comprising:
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a source of radiant energy having a coherence length; a first transmission unit having; separate first and second optical paths having a path length difference of Δ
L1 which is greater than said coherence length;means for dividing radiant energy from said source into first and second portions for passage respectively along said first and second optical paths and for recombining said first and second two portions after passage along said first and second optical paths; a phase modulator in said first optical path operable for applying a telecommunication signal to said first portion; said first transmission unit operably connected to provide said recombined portions with a phase difference corresponding to Δ
L1 to a transmission path having a first end adjacent said first transmission unit and a second end; anda first receiver unit operably connected to said second end of said transmission path and having; separate first and second reception paths, each having an end which reflects back radiant energy; means for reseparating said first and second portions for passage separately and respectively on said first and second reception paths and for recombining said first and second portions; and a first sensor connected to said means for reseparating and recombining, said first sensor operable to sense radiant energy for detection of the telecommunication signal applied at the first transmission unit; and said first transmission unit, said transmission path, and said first receiver unit collectively are an interferometer; and
wherein said means for reseparating and recombining is a 4 by 4 coupler/splitter having a first side closest to said second end of said transmission path and a second side, said first and second reception paths connected directly to said second side, said first sensor connected directly to said first side of said coupler/splitter by a first sensor path, and said first receiver unit further comprises a second sensor operable to sense radiant energy for detection of the telecommunication signal applied at the first transmission unit, and wherein said second sensor is connected directly to said first side of said coupler/splitter by a second sensor path. - View Dependent Claims (17, 18, 19)
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20. An optical telecommunication system comprising:
a first receiver unit having; separate first and second reception paths, each having an end which reflects back radiant energy; means for reseparating first and second portions of radiant energy for passage separately and respectively on said first and second reception paths and for recombining said first and second portions, said first and second portions having been combined after separation and passage on different paths with a path length difference of Δ
L1, one of the paths having application of a telecommunication signal by phase modulation thereon; anda first sensor connected to said means to reseparate and to recombine, said first sensor sensing radiant energy for detection of the telecommunication signal; and wherein said means for reseparating and recombining is a 4 by 4 coupler/splitter having a first side operable to receive a transmission signal and a second side, said first and second reception paths connected directly to said second side, said first sensor connected directly to said first side of said coupler/splitter by a first sensor path, and said first receiver unit further comprises a second sensor operable to sense radiant energy for detection of the telecommunication signal applied at the first transmission unit, and wherein said second sensor is connected directly to said first side of said coupler/splitter by a second sensor path.
Specification