EP0115445A2
Expired / Lapsed
EP
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Optical heterodyne detection pulse receiving system and method
Assignee: NEC Corp
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Filing: 1984-01-31
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Granted: —
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Expires: 2004-01-31
Abstract
Abstract A photodiode (4) detects an intermediate frequency signal from an incoming pulse-modulated light carrier (1) and a local oscillator light beam (6) superimposed by means of a half-silvered mirror (2). The intermediate frequency (e.g. 128 MHz) is a multiple (e.g. 4 times) the modulating pulse repetition frequency (e.g. 32 MHz) which is extracted by a timing circuit (10). The intermediate frequency is divided in divider (14) by the said multiple and then phase-compared with the pulse repetition frequency in an oscillator control circuit (15) completing a phase-locked loop for the laser oscillator (5) which generates the local oscillator light beam (6). Jitter and wave form distortion problems with the regenerated pulses are thus avoided even with a significantly lower intermediate frequency than has heretofore been necessary.
Inventors
- 👤 Kouichi Minemura
- 👤 Minoru Shikada
- 👤 Katsumi Emura
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 20:57
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/60; G; G01; G01J; G01J9/00; G01J9/04; H04B10/61; H04B10/64; H04B14/00; H04B14/02; H04L; H04L27/00; H04L27/02; H04L27/06; H04L27/18; H04L27/22; H04L27/233; H04L27/2331
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
98 words
An optical heterodyne detection pulse receiving method, comprising the steps of mixing a local oscillator light wave and an optical carrier modulated with a pulse signal and extracting a signal having an intermediate frequency equal to the difference between the frequency of the local oscillator light wave and that of the optical carrier, and regenerating the pulse signal by demodulating this intermediate frequency signal, characterised in that the Nth multiple (where N is a positive integer) of the half cycle of the intermediate frequency is synchronized with the full cycle of the repeating frequency of the pulse signal.
Claim 2
Dependent Claim
98 words
An optical heterodyne detection pulse receiving method, comprising the steps of mixing a local oscillator light wave and an optical carrier modulated with a pulse signal and extracting a signal having an intermediate frequency equal to the difference between the frequency of the local oscillator light wave and that of the optical carrier, and regenerating the pulse signal by demodulating this intermediate frequency signal, characterised in that the Nth multiple (where N is a positive integer) of the half cycle of the intermediate frequency is synchronized with the full cycle of the repeating frequency of the pulse signal.
Claim 3
Dependent Claim
24 words
A method as claimed in Claim 1, characterised in that the optical carrier modulated with a pulse signal is a pulse phase-modulated optical carrier.
Claim 4
Dependent Claim
23 words
A method as claimed in Claim 1, characterised in that the carrier modulated with a pulse signal is a pulse amplitude-modulated optical carrier.
Claim 5
Dependent Claim
183 words
An optical heterodyne detection pulse receiving system, comprising local oscillator means (5) for generating a laser light wave; means (2) for aligning the wave fronts of the local laser light wave and of a modulated light wave, resulting from the modulation of a laser carrier with a pulse signal; photoelectric conversion means (4) for receiving the local laser light wave and the modulated light wave, and generating an electric signal having a frequency equal to ' the difference between the light wave frequencies; timing means (19) for extracting the timing signal of the pulse signal from the electric signal; characterised by means (13) for extracting from the electric signal an intermediate frequency signal equivalent to the frequency difference between the local laser light wave and the said laser carrier; and means (14, 15) for comparing the intermediate frequency signal and the timing signal and so controlling the local oscillator means (5) as to synchronize the Nth multiple (where N is a positive integer) of the half cycle of the intermediate frequency with the full cycle of the repeating frequency of the pulse signal.
Claim 6
Dependent Claim
183 words
An optical heterodyne detection pulse receiving system, comprising local oscillator means (5) for generating a laser light wave; means (2) for aligning the wave fronts of the local laser light wave and of a modulated light wave, resulting from the modulation of a laser carrier with a pulse signal; photoelectric conversion means (4) for receiving the local laser light wave and the modulated light wave, and generating an electric signal having a frequency equal to ' the difference between the light wave frequencies; timing means (19) for extracting the timing signal of the pulse signal from the electric signal; characterised by means (13) for extracting from the electric signal an intermediate frequency signal equivalent to the frequency difference between the local laser light wave and the said laser carrier; and means (14, 15) for comparing the intermediate frequency signal and the timing signal and so controlling the local oscillator means (5) as to synchronize the Nth multiple (where N is a positive integer) of the half cycle of the intermediate frequency with the full cycle of the repeating frequency of the pulse signal.
Claim 7
Dependent Claim
26 words
An optical heterodyne detection pulse receiving system as claimed in Claim 6, characterised in that the modulated light wave is pulse amplitude-modulated with said pulse signal.
Claim 8
Dependent Claim
26 words
An optical heterodyne detection pulse receiving system as claimed in Claim 6, characterised in that the modulated light wave is pulse phase-modulated with said pulse signal.
Claim 9
Dependent Claim
66 words
An optical heterodyne detection pulse receiving system as claimed in claim 4, 5 or 6, characterised in that the extracted intermediate frequency signal has a frequency equal to the said frequency difference and in that the comparing means comprise a divider (16) for dividing the intermediate frequency by N/2 and a phase comparator (15) comparing the signals from the divider (16) and the timing means (10).
References Cited (Backward Citations)
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