Patent EP0532021A2 successfully refreshed from Google Patents.
EP0532021A2
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Coherent subcarrier multiplexed optical communication system
Assignee: Fujitsu Ltd
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Filing: 1992-09-11
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Granted: —
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Expires: 2012-09-11
Abstract
Abstract A light is modulated in a sending equipment according to a composed signal obtained by mixing a signal frequency-multiplexed at the microwave level in a coherent SCM optical communication system with an unmodulated signal out of the frequency band of the frequency-multiplexed signal. The resultant modulated light is optical-heterodyne-detected. A demodulating unit (811) demodulates a frequency-multiplexed signal according to an electric signal delayed by a delay unit (810) by the time equal to the time delay in an unmodulated component extracting unit (809). Only the frequency components of a frequency-multiplexed signal and an unmodulated signal must be received in a receiving equipment (807), without need of receiving the component in a broad frequency band from the frequency component to the main carrier component of the frequency-multiplexed signal. <IMAGE>
Inventors
- 👤 Shigeki c/o FUJITSU LIMITED Watanabe
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 01:26
CPC Classifications
H; H04; H04J; H04J14/00; H04J14/02; H04J14/0298
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
240 words
An optical communication system for communicating a data signal by modulating and transmitting a light, comprising: a plurality of electric stage modulating means (1301), provided corresponding to each transmission signal (D₁ - D N ) for a plurality of channels, for modulating each carrier signal having a different microwave frequency according to each of said transmission signals, frequency multiplexing means (1302) for frequency-multiplexing each modulated signal from each of said electric stage modulating means (1301), frequency multiplexing means (1305) for mixing a frequency-multiplexed signal from said frequency multiplexing means (1302) with an unmodulated signal having a frequency out of the frequency band of said frequency-multiplexed signal, light modulating means (1303) for modulating a light according to a composed signal obtained by said multiplexing means (1305) and outputting a resultant modulated light, light receiving means (1306 -1308) for detecting said modulated light and converting it to an electric signal, unmodulated component extracting means (1402) for extracting from said electric signal from said light receiving means a frequency component (I₁₆) in said unmodulated signal, delay means (1401) for delaying said electric signal from said light receiving means (1306 - 1308) by the time equal to the signal delay time in said unmodulated component extracting means (1402), and demodulating means (1310) for canceling phase noise according to said electric signal (I₁₅) from said delay means (1401) and said unmodulated signal extracted by said unmodulated component extracting means (1402) and demodulating said transmission signal.
Claim 2
Dependent Claim
67 words
The optical communication system according to Claim 1, wherein plural sets of a plurality of said electric stage modulating means (1301), said frequency multiplexing means (1302), or said another frequency multiplexing means(1305), and said light modulating means (1303), and light multiplexing means for multiplexing each of said modulated lights from each of said light modulating means (1303) and outputting a resultant modulated light as said modulated light.
Claim 3
Dependent Claim
69 words
The optical communication system according to Claim 1, wherein said light receiving means (1306 - 1308) comprises: local oscillating means (1306) for generating a local oscillator light, mixing means (1305) for mixing said local oscillator light from said local oscillator means (1306) with said modulated light, and light receiving element means (1307) for detecting a mixed light from said mixing means (1305) and converting it to an electric signal.
Claim 4
Dependent Claim
95 words
The optical communication system according to Claim 3, wherein said optical communication system is a light distributing network having the configuration such that said modulated lights transmitted from a transmitter (A) to a light transmission line (1504) are mixed by said local oscillating means (1506) and said mixing means (1505) provided in a repeater (B) before being branched, and each of said branched mixed lights is received by a plurality of receivers each comprising said light receiving element means (1507), said unmodulated component extracting means (1402), said delay means (1401), and said demodulating means (1510).
Claim 5
Dependent Claim
22 words
The optical communication system according to Claim 4, further comprising: light amplifying means (1508,1808) before or after said branch in said repeater.
Claim 6
Dependent Claim
125 words
The optical communication system according to Claim 3, wherein a transmitter (A) comprises said local oscillating means (1602), said mixing means (1601), and a polarization control means (1603) for controlling such that the polarization state of said modulated light coincides with that of said local oscillator light from said local oscillating means (1602), and said modulated light and said local oscillator light are mixed by said mixing means (1601) with each of said polarization states controlled by said polarization controlling means (1603), and said mixed light from said mixing means (1601) is transmitted to a light transmission line leading to a receiver (C) comprising said light receiving element means (1507), said unmodulated component extracting means (1202), said delay means (1201), and said demodulating means (1510).
Claim 7
Dependent Claim
37 words
The optical communication system according to Claim 6, wherein said transmitter (A) further comprises light amplifying means (1701) for transmitting to said light transmission line (1504) said mixed light from said mixing means (1601) after being amplified.
Claim 8
Dependent Claim
81 words
The optical communication system according to Claim 6, wherein said light communication system is a light distributing network having the configuration such that said mixed light transmitted from said transmitter (A) to said light transmission line (1504) is branched at said repeater (B), and each of said branched mixed lights is received by a plurality of said receivers each comprising said light receiving element means (1507), said unmodulated component extracting means (1202), said delay means (1201), and said demodulating means (1510).
Claim 9
Dependent Claim
23 words
The optical communication system according to Claim 8, wherein light amplifying means (1508, 1808) provided before and/or after said branch in said repeater.
References Cited (Backward Citations)
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