Patent US5896216A successfully refreshed from Google Patents.
US5896216A
Expired / Lapsed
US
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AM/PM converter and optical signal transmission system
Assignee: NTT Inc
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Filing: 1996-06-25
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Granted: 1999-04-20
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Expires: 2016-06-25
Abstract
Abstract The AM/FM converter of the present invention comprises an optical frequency modulation section which receives multi-channel AM video signals and outputs an optical-frequency-modulated optical signal beam; and an optical heterodyne detection section comprising an optical frequency oscillator composed of a semiconductor local laser which outputs a local oscillator optical beam having an optical frequency separated by a designated intermediate frequency, an optical coupler, and a photoelectric converter composed of a photodiode, which receives the optical signal beam and outputs an electrical batched FM modulation signal which is frequency-modulated and frequency-converted to the intermediate frequency. By means of this configuration, the invention offers an AM/FM converter wherein the frequency band is made considerably wider.
Inventors
- 👤 Koji Kikushima
- 👤 Nori Shibata
- 👤 Kouichi Suto
- 👤 Katsushi Iwashita
- 👤 Satoshi Ikeda
- 👤 Hiroshi Nakamoto
- 👤 Chisei Kishimoto
- 👤 Kiyomi Kumozaki
- 👤 Naoya Sakurai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 20:08
CPC Classifications
H; H04; H04N; H04N7/00; H04N7/22
Claims Analysis
Total Claims: 33
Claim 1
Independent Claim
102 words
An AM/FM converter, comprising: optical frequency modulation means for receiving an electrical signal and outputting an optical-frequency-modulated optical signal beam; and an optical heterodyne detection section, having optical frequency oscillation means for outputting a local oscillator optical beam with an optical frequency separated from that of said optical signal beam by a designated intermediate frequency, optical coupling means for coupling said optical signal beam and said local oscillator optical beam, and a photoelectric converter for obtaining an output as an electrical signal, which receives said optical signal beam and outputs a modulation signal which is frequency-modulated and frequency-converted to said intermediate frequency.
Claim 2
Dependent Claim
102 words
An AM/FM converter, comprising: optical frequency modulation means for receiving an electrical signal and outputting an optical-frequency-modulated optical signal beam; and an optical heterodyne detection section, having optical frequency oscillation means for outputting a local oscillator optical beam with an optical frequency separated from that of said optical signal beam by a designated intermediate frequency, optical coupling means for coupling said optical signal beam and said local oscillator optical beam, and a photoelectric converter for obtaining an output as an electrical signal, which receives said optical signal beam and outputs a modulation signal which is frequency-modulated and frequency-converted to said intermediate frequency.
Claim 3
Dependent Claim
54 words
An AM/FM converter according to claim 1, wherein: the value of a ratio P FM /P LO between the power P FM of said optical signal beam and the power P LO of said local oscillator optical beam when inputted to said photoelectric converter is at least -8 dB and at most +8 dB.
Claim 4
Dependent Claim
55 words
An AM/FM converter according to claim 2, wherein: said optical frequency modulation means receives a multi-channel AM video signal as said electrical signal; the value of said ratio P FM /P LO is set so that the carrier-to-noise ratio of an amplitude-modulated video signal obtained by frequency-demodulating said modulation signal is at least 42 dB.
Claim 5
Dependent Claim
36 words
An AM/FM converter according to claim 3, further comprising unnecessary intensity component elimination means for eliminating unnecessary intensity components generated by at least one of said optical frequency modulation means and said optical frequency oscillation means.
Claim 6
Dependent Claim
60 words
An AM/FM converter according to claim 4, wherein said unnecessary intensity component elimination means comprises distribution means, inserted directly in front of said optical frequency modulation means, for distributing said input electrical signal; and combining means for combining one of the outputs of said distribution means with the output of said optical heterodyne detection section in an opposite phase relation.
Claim 7
Dependent Claim
30 words
An AM/FM converter according to claim 4, wherein said unnecessary intensity component elimination means comprises two photoelectric converters in a balanced receiver configuration provided in said optical heterodyne detection section.
Claim 8
Dependent Claim
85 words
An AM/FM converter according to either claim 5 or 6, further comprising: frequency-demodulation means for frequency-demodulating the modulation signal outputted by said optical heterodyne detection section; and feedback means, for extracting optical frequency fluctuations of said optical signal beam and said local oscillator optical beam from the output signal of said frequency-demodulation means, and applying negative feedback control to the optical frequency of at least one of said optical frequency modulation means and said optical frequency oscillation means based on the results of said extraction.
Claim 9
Dependent Claim
30 words
An AM/FM converter according to claim 3, further comprising a predistortion circuit for predistorting the input electrical signal before said electrical signal is inputted to said optical frequency modulation means.
Claim 10
Dependent Claim
81 words
An AM/FM converter according to claim 3, further comprising: frequency-demodulation means for frequency-demodulating the modulation signal outputted by said optical heterodyne detection section; and feedback means, for extracting optical frequency fluctuations of said optical signal beam and said local oscillation beam from the output signal of said frequency-demodulation means, and applying negative feedback control to the optical frequency of at least one of said optical frequency modulation means and said optical frequency oscillation means based on the results of said extraction.
Claim 11
Dependent Claim
36 words
An AM/FM converter according to claim 2, further comprising unnecessary intensity component elimination means for eliminating unnecessary intensity components generated by at least one of said optical frequency modulation means and said optical frequency oscillation means.
Claim 12
Dependent Claim
60 words
An AM/FM converter according to claim 10, wherein said unnecessary intensity component elimination means comprises distribution means, inserted directly in front of said optical frequency modulation means, for distributing said input electrical signal; and combining means for combining one of the outputs of said distribution means with the output of said optical heterodyne detection section in an opposite phase relation.
Claim 13
Dependent Claim
30 words
An AM/FM converter according to claim 10, wherein said unnecessary intensity component elimination means comprises two photoelectric converters in a balanced receiver configuration provided in said optical heterodyne detection section.
Claim 14
Dependent Claim
85 words
An AM/FM converter according to either claim 11 or 12, further comprising: frequency-demodulation means for frequency-demodulating the modulation signal outputted by said optical heterodyne detection section; and feedback means, for extracting optical frequency fluctuations of said optical signal beam and said local oscillator optical beam from the output signal of said frequency-demodulation means, and applying negative feedback control to the optical frequency of at least one of said optical frequency modulation means and said optical frequency oscillation means based on the results of said extraction.
Claim 15
Dependent Claim
30 words
An AM/FM converter according to claim 2, further comprising a predistortion circuit for predistorting the input electrical signal before said electrical signal is inputted to said optical frequency modulation means.
Claim 16
Dependent Claim
81 words
An AM/FM converter according to claim 2, further comprising: frequency-demodulation means for frequency-demodulating the modulation signal outputted by said optical heterodyne detection section; and feedback means, for extracting optical frequency fluctuations of said optical signal beam and said local oscillation beam from the output signal of said frequency-demodulation means, and applying negative feedback control to the optical frequency of at least one of said optical frequency modulation means and said optical frequency oscillation means based on the results of said extraction.
Claim 17
Dependent Claim
36 words
An AM/FM converter according to claim 1, further comprising unnecessary intensity component elimination means for eliminating unnecessary intensity components generated by at least one of said optical frequency modulation means and said optical frequency oscillation means.
Claim 18
Dependent Claim
60 words
An AM/FM converter according to claim 16, wherein said unnecessary intensity component elimination means comprises distribution means, inserted directly in front of said optical frequency modulation means, for distributing said input electrical signal; and combining means for combining one of the outputs of said distribution means with the output of said optical heterodyne detection section in an opposite phase relation.
Claim 19
Dependent Claim
30 words
An AM/FM converter according to claim 16, wherein said unnecessary intensity component elimination means comprises two photoelectric converters in a balanced receiver configuration provided in said optical heterodyne detection section.
Claim 20
Dependent Claim
74 words
An AM/FM converter according to claim 16, wherein said unnecessary intensity component elimination means comprises distribution means, inserted directly in front of said optical frequency modulation means, for distributing said input electrical signal; and optical intensity modulation means, inserted between an output of said optical frequency modulation means and an input of said optical heterodyne detection section, for intensity-modulating said optical signal beam by means of one of the outputs of said distribution means.
Claim 21
Dependent Claim
99 words
An AM/FM converter according to claim 16, wherein said unnecessary intensity component elimination means comprises: optical beam splitting means for splitting the output of said optical frequency modulation means into two optical beams; optical intensity modulation means, connected to one of the outputs of said optical beam splitting means, for outputting to said optical heterodyne detection section; and a third photoelectric converter, connected to the other output of said optical beam splitting means, for outputting an electrical signal converted from an optical signal and inputting to said optical intensity modulation means at opposite phase, to perform optical intensity modulation.
Claim 22
Dependent Claim
30 words
An AM/FM converter according to claim 1, further comprising a predistortion circuit for predistorting the input electrical signal before said electrical signal is inputted to said optical frequency modulation means.
Claim 23
Dependent Claim
82 words
An AM/FM converter according to claim 1, further comprising: frequency-demodulation means for frequency-demodulating the modulation signal outputted by said optical heterodyne detection section; and feedback means, for extracting optical frequency fluctuations of said optical signal beam and said local oscillator optical beam from the output signal of said frequency-demodulation means, and applying negative feedback control to the optical frequency of at least one of said optical frequency modulation means and said optical frequency oscillation means based on the results of said extraction.
Claim 24
Dependent Claim
81 words
An AM/FM converter according to claim 1, further comprising: multiplexing means for superimposing a pilot signal onto the input electrical signal of said optical frequency modulation means; and noise elimination means for extracting a first component relating to said input electrical signal and a second component relating to said pilot signal from said modulation signal, and eliminating noise arising from fluctuations in said optical signal beam and said local oscillator optical beam by mixing said first component and said second component.
Claim 25
Dependent Claim
166 words
An optical signal transmission system, comprising: an optical transmission device having an AM/FM converter, comprising optical frequency modulation means for receiving an electrical signal and outputting an optical-frequency-modulated optical signal beam, and an optical heterodyne detection section, having optical frequency oscillation means for outputting a local oscillator optical beam with an optical frequency separated from that of said optical signal beam by a designated intermediate frequency, optical coupling means for coupling said optical signal beam and said local oscillator optical beam, and a photoelectric converter for obtaining an output as an electrical signal, which receives said optical signal beam and outputs a modulation signal which is frequency-modulated and frequency-converted to said intermediate frequency; and a transmission means for outputting a transmission optical beam intensity-modulated by the output of said AM/FM converter; an optical transmission path; and an optical receiving device, connected to said optical transmission device via said optical transmission path, comprising a photoelectric converter and frequency-demodulation means for frequency-demodulating the output of said photoelectric converter.
Claim 26
Dependent Claim
166 words
An optical signal transmission system, comprising: an optical transmission device having an AM/FM converter, comprising optical frequency modulation means for receiving an electrical signal and outputting an optical-frequency-modulated optical signal beam, and an optical heterodyne detection section, having optical frequency oscillation means for outputting a local oscillator optical beam with an optical frequency separated from that of said optical signal beam by a designated intermediate frequency, optical coupling means for coupling said optical signal beam and said local oscillator optical beam, and a photoelectric converter for obtaining an output as an electrical signal, which receives said optical signal beam and outputs a modulation signal which is frequency-modulated and frequency-converted to said intermediate frequency; and a transmission means for outputting a transmission optical beam intensity-modulated by the output of said AM/FM converter; an optical transmission path; and an optical receiving device, connected to said optical transmission device via said optical transmission path, comprising a photoelectric converter and frequency-demodulation means for frequency-demodulating the output of said photoelectric converter.
Claim 27
Dependent Claim
56 words
An optical signal transmission system according to claim 24, wherein: the value of a ratio P FM /P LO between the power P FM of said optical signal beam and the power P LO of said local oscillator optical beam when inputted to said photoelectric converter is at least -8 dB and at most +8 dB.
Claim 28
Dependent Claim
57 words
An optical signal transmission system according to claim 25, wherein said optical frequency modulation means receives a multi-channel AM video signal as said electrical signal; the value of said ratio P FM /P LO is set so that the carrier-to-noise ratio of an amplitude-modulated video signal obtained by frequency-demodulating said modulation signal is at least 42 dB.
Claim 29
Dependent Claim
43 words
An optical signal transmission system according to claim 24, wherein said optical transmission device further comprises unnecessary intensity component elimination means for eliminating unnecessary intensity components generated by at least one of said optical frequency modulation means and said optical frequency oscillation means.
Claim 30
Dependent Claim
32 words
An optical signal transmission system according to claim 24, further comprising a predistortion circuit for predistorting the input electrical signal before said electrical signal is inputted to said optical frequency modulation means.
Claim 31
Dependent Claim
89 words
An optical signal transmission system according to claim 24, wherein said optical transmission device further comprises: frequency-demodulation means for frequency-demodulating the modulation signal outputted by said optical heterodyne detection section; and feedback means, for extracting optical frequency fluctuations of said optical signal beam and said local oscillator optical beam from the output signal of said frequency-demodulation means, and applying negative feedback control to the optical frequency of at least one of said optical frequency modulation means and said optical frequency oscillation means based on the results of said extraction.
Claim 32
Dependent Claim
88 words
An optical signal transmission system according to claim 24, wherein said optical transmission device further comprises: multiplexing means for superimposing a pilot signal onto the input electrical signal of said optical frequency modulation means; and noise elimination means for extracting a first component relating to said input electrical signal and a second component relating to said pilot signal from said modulation signal, and eliminating noise arising from fluctuations in said optical signal beam and said local oscillator optical beam by mixing said first component and said second component.
Claim 33
Dependent Claim
57 words
An optical signal transmission system according to claim 24, wherein: said optical frequency modulation means receives a multi-channel AM video signal as said electrical signal; the value of said ratio P FM /P LO is set so that the carrier-to-noise ratio of an amplitude-modulated video signal obtained by frequency-demodulating said modulation signal is at least 42 dB.
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