US5339185A
Expired / Lapsed
US
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Optical timing extraction circuit
Assignee: NEC Corp
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Filing: 1992-07-29
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Granted: 1994-08-16
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Expires: 2012-07-29
Abstract
Abstract An optical timing extraction circuit is capable of extracting an optical clock signal of greater than tens of Gb/sec from a NRZ modulated signal. The light intensity level of a light signal modulated in intensity by an NRZ signal is amplified to a level sufficient to cause the optical Kerr effect, and combined with a CW light from a semiconductor laser which is modulated in frequency by the amplified light signal in an optical converting circuit by utilizing the optical Kerr effect. This frequency-modulated light is passed through a narrow band-pass optical filter to cause a signal intensity-modulated pulsed light at each intensity changing point of the modulated signal. Next, after the pulsed light is amplified up to a required optical intensity level, it is passed through another narrow band-pass optical filter, which is an optical tank for extracting the optical clock, to extract an optical clock signal.
Inventors
- 👤 Kazuhisa Kaede
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 13:43
CPC Classifications
H; H04; H04L; H04L7/00; H04L7/0075
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
186 words
An optical timing extraction circuit comprising: converting means for converting an intensity modulated signal to an optical frequency modulated signal, said converting means modulating an optical frequency of a second light by a first light, said first light being modulated in intensity by an NRZ signal whose transmission rate is B bit/sec and said second light being a CW light; first narrow band-pass optical filter means receiving said second light, for selectively reflecting said second light which has been modulated in frequency by said converting means, a transmission center frequency of said first narrow band-pass optical filter means coinciding with a central frequency of said second light, a transmission bandwidth of said first narrow band-pass optical filter means being substantially equal to a modulated width of the frequency of said second light; and second narrow band-pass optical filter means having a free spectral range substantially equal to B Hz for extracting and emitting an optical clock signal of sinusoidal form whose frequency is B Hz, said optical clock signal being extracted from said second light modulated in intensity by said first narrow band-pass optical filter means.
Claim 2
Dependent Claim
186 words
An optical timing extraction circuit comprising: converting means for converting an intensity modulated signal to an optical frequency modulated signal, said converting means modulating an optical frequency of a second light by a first light, said first light being modulated in intensity by an NRZ signal whose transmission rate is B bit/sec and said second light being a CW light; first narrow band-pass optical filter means receiving said second light, for selectively reflecting said second light which has been modulated in frequency by said converting means, a transmission center frequency of said first narrow band-pass optical filter means coinciding with a central frequency of said second light, a transmission bandwidth of said first narrow band-pass optical filter means being substantially equal to a modulated width of the frequency of said second light; and second narrow band-pass optical filter means having a free spectral range substantially equal to B Hz for extracting and emitting an optical clock signal of sinusoidal form whose frequency is B Hz, said optical clock signal being extracted from said second light modulated in intensity by said first narrow band-pass optical filter means.
Claim 3
Dependent Claim
200 words
An optical timing extraction circuit comprising: first narrow band-pass optical filter means, receiving a first light FSK-modulated by an NRZ signal whose transmission rate is B bit/sec, for converting said first light into an intensity modulated light signal, a transmission center frequency of said first filter means coinciding with a central frequency of said FSK-modulated first light; converting means for converting said intensity modulated light signal to an optical frequency modulated signal, said converting means receiving said first light, which has passed through said first narrow band-pass optical filter means to be converted into said intensity modulated light signal, and a second light, which is a CW light, said converting means modulating the optical frequency of said second light by said intensity modulated light signal; second narrow band-pass optical filter means, receiving said second light, modulated in frequency by said converting means, for converting said second light into a light modulated in intensity at each time point corresponding to a frequency change in said FSK-modulated first light; and third narrow band-pass optical filter means for extracting and emitting an optical clock signal of sinusoidal form from said second light which was passed through said second narrow band-pass optical filter means.
Claim 4
Dependent Claim
200 words
An optical timing extraction circuit comprising: first narrow band-pass optical filter means, receiving a first light FSK-modulated by an NRZ signal whose transmission rate is B bit/sec, for converting said first light into an intensity modulated light signal, a transmission center frequency of said first filter means coinciding with a central frequency of said FSK-modulated first light; converting means for converting said intensity modulated light signal to an optical frequency modulated signal, said converting means receiving said first light, which has passed through said first narrow band-pass optical filter means to be converted into said intensity modulated light signal, and a second light, which is a CW light, said converting means modulating the optical frequency of said second light by said intensity modulated light signal; second narrow band-pass optical filter means, receiving said second light, modulated in frequency by said converting means, for converting said second light into a light modulated in intensity at each time point corresponding to a frequency change in said FSK-modulated first light; and third narrow band-pass optical filter means for extracting and emitting an optical clock signal of sinusoidal form from said second light which was passed through said second narrow band-pass optical filter means.
Claim 5
Dependent Claim
115 words
An optical timing extraction circuit as set forth in claim 2 wherein a transmission center frequency of said second narrow band-pass optical filter means coincides with one peak optical frequency of said frequency-modulated second light, a central optical frequency of said second light lying substantially at one end of the transmission bandwidth, a portion of a frequency bandwidth of said second filter means ranging from the central optical frequency of said second light up to another peak optical frequency forming a reflecting frequency bandwidth, and the free spectral range of said third narrow band-pass optical filter means being approximately B Hz to emit an optical clock signal of sinusoidal form whose frequency is B Hz.
Claim 6
Dependent Claim
86 words
An optical timing extraction circuit as set forth in claim 2 wherein a transmission center frequency of said second narrow band-pass optical filter means substantially coincides with the frequency of said second light before its frequency is modulated by said converting means, and whose transmission band-width is below the modulation width of said second light; and the free spectral range of said third narrow band-pass optical filter means is approximately 2B Hz to emit an optical clock signal of sinusoidal form whose frequency is 2B Hz.
Claim 7
Dependent Claim
41 words
An optical timing extraction circuit as set forth in claim 1 wherein said optical frequency modulation of said second light by said first light is carried out by the optical Kerr effect in a polarization-maintaining fiber, each light being linearly polarized.
Claim 8
Dependent Claim
41 words
An optical timing extraction circuit as set forth in claim 2 wherein said optical frequency modulation of said second light by said first light is carried out by the optical Kerr effect in a polarization-maintaining fiber, each light being linearly polarized.
Claim 9
Dependent Claim
41 words
An optical timing extraction circuit as set forth in claim 3 wherein said optical frequency modulation of said second light by said first light is carried out by the optical Kerr effect in a polarization-maintaining fiber, each light being linearly polarized.
Claim 10
Dependent Claim
41 words
An optical timing extraction circuit as set forth in claim 4 wherein said optical frequency modulation of said second light by said first light is carried out by the optical Kerr effect in a polarization-maintaining fiber, each light being linearly polarized.
References Cited (Backward Citations)
US4991975A
Cited
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