Patent EP0251062A2 successfully refreshed from Google Patents.
EP0251062A2
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EP
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Dual balanced optical signal receiver
Assignee: Fujitsu Ltd
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Filing: 1987-06-19
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Granted: —
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Expires: 2007-06-19
Abstract
Abstract An optical signal receiver comprising an optical mixing/polarization splitting unit (l0l) for producing IF optical signals having two orthogonally polarized components, an optical signal receiving unit (l02-l05) for producing four corresponding IF electric signals, and a combining circuit (l06) for combining two IF electric signals having one polarization with the other two IF electric signals having the other polarization, suppressing fluctuation of the polarization and the intensity noise of the related local optical signal. The intensity noise suppression is also effective for IF electric signals having a higher frequency range.
Inventors
- 👤 Hideo Kuwahara
- 👤 Terumi Chikama
- 👤 Tetsuya Kiyonaga
- 👤 Chiaki Ohsawa
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 17:38
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/60; H04B10/61; H04B10/614; H04B10/63; H04B10/64
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
134 words
A dual balanced optical signal receiver, comprising: an optical mixing/polarization splitting means for producing optical signals having an intermediate frequency (IF) by mixing a received optical signal with a local oscillation optical signal. and then splitting the thus mixed signal into two orthogonally polarized components, or by splitting a received optical signal into two orthogonally polarized components and then mixing each of the thus split orthogonally polarized components with a local oscillation optical signal; an optical signal receiving means for receiving IF optical signals and transforming said IF optical signals into corresponding electric signals having an intermediate frequency (IF), and; a combining means for receiving the IF electric signals and combining the two of said IF electric signals having one type of polarization with two other IF electric signals having another type of polarization.
Claim 2
Dependent Claim
134 words
A dual balanced optical signal receiver, comprising: an optical mixing/polarization splitting means for producing optical signals having an intermediate frequency (IF) by mixing a received optical signal with a local oscillation optical signal. and then splitting the thus mixed signal into two orthogonally polarized components, or by splitting a received optical signal into two orthogonally polarized components and then mixing each of the thus split orthogonally polarized components with a local oscillation optical signal; an optical signal receiving means for receiving IF optical signals and transforming said IF optical signals into corresponding electric signals having an intermediate frequency (IF), and; a combining means for receiving the IF electric signals and combining the two of said IF electric signals having one type of polarization with two other IF electric signals having another type of polarization.
Claim 3
Dependent Claim
80 words
A receiver as set forth in claim l, wherein said receiver is further provided with a modulation means for modulating a local oscillation optical signal to be input to said optical mixing/polarization splitting means, and a control means for extracting a modulation signal component from a signal output by said combining means and controlling an input or output of said optical signal receiving means in such a manner that a level of the thus extracted modulation signal component is minimized.
Claim 4
Dependent Claim
66 words
A receiver as set forth in claim l, wherein said optical mixing/polarization splitting means is comprised of a mixing part which mixes a received optical signal with a local oscillation optical signal to produce two mixed optical signals and a polarization splitting part which separates said two mixed optical signals into two orthogonally polarized components and produces a total of four mixed and split optical signals.
Claim 5
Dependent Claim
39 words
A receiver as set forth in claim 3, wherein a polarization direction of said local oscillation optical signal is adjusted in such a manner that the two orthogonally polarized components thereof have substantially a same intensity as each other.
Claim 6
Dependent Claim
44 words
A receiver as set forth in claim 4, wherein said local oscillation optical signal is supplied to said mixing part by way of a polarization-maintaining fiber, and a polarization plane thereof is rotated relative to a longitudinal axis thereof by an angle of 45°.
Claim 7
Dependent Claim
39 words
A receiver as set forth in claim 3, wherein said optical signal receiving means has four optical signal receiving elements which transform the four mixed and split optical signals from said polarization splitting part into corresponding electric signals, respectively.
Claim 8
Dependent Claim
71 words
A receiver as set forth in claim 6, wherein said optical signal receiving elements are connected with a subtracting means for receiving outputs from the four optical signal receiving elements and producing two independent IF electric signals by subtracting, on one hand, two IF electric signals having one polarization from each other, and on the other hand, subtracting the other two IF electric signals having the other polarization from each other.
Claim 9
Dependent Claim
33 words
A receiver as set forth in claim 7, wherein said combining means further contains a switching circuit which selects from said IF electric signals the IF electric signal having a better S/N ratio.
Claim 10
Dependent Claim
55 words
A receiver as set forth in claim 7, wherein said combining means further contains a phase control means for matching phases of two IF electric signals having the same polarization and phases of the other two IF electric signals having the other polarization and a summing means for summing the phase-matched two IF electric signals.
Claim 11
Dependent Claim
41 words
l0. A receiver as set forth in claim 9, wherein said combining means further contains a signal intensity control means for equalizing an intensity of each of the two IF electric signals and applying the same to said phase control means.
Claim 12
Dependent Claim
80 words
A receiver as set forth in claim l, wherein said optical mixing/polarization splitting means is comprised of a polarization splitting part for receiving said received optical signal and said local oscillation optical signal and separating each of these two optical signals into two orthogonally polarized components and a mixing part which mixes the two polarized components having one polarization and mixes the other two polarized components having the other polarization, which polarized components are given from said polarization splitting part.
Claim 13
Dependent Claim
36 words
A receiver as set forth in claim ll, wherein a polarization direction of said local oscillation optical signal is adjusted in such a manner that the two orthogonally polarized components thereof have substantially the same intensity.
Claim 14
Dependent Claim
37 words
A receiver as set forth in claim l2, wherein said local oscillation optical signal is projected onto said polarization splitting part with a polarization plane rotated relative to the optical axis thereof by an angle of 45°.
Claim 15
Dependent Claim
38 words
A receiver as set forth in claim ll, wherein said optical signal receiving means has four optical signal receiving elements which transforms the four mixed and split optical signals from said mixing part into corresponding electric signals, respectively.
Claim 16
Dependent Claim
71 words
A receiver as set forth in claim l4, wherein said optical signal receiving elements are connected with a subtracting means for receiving outputs from said four optical signal receiving elements and producing two independent IF electric signals by subtracting, on one hand, two IF electric signals having one polarization from each other, and on the other hand, subtracting the other two IF electric signals having the other polarization from each other.
Claim 17
Dependent Claim
34 words
A receiver as set forth in claim l5, wherein said combining means further contains a switching circuit which selects from the two IF electric signals the IF electric signal having the better S/N ratio.
Claim 18
Dependent Claim
57 words
A receiver as set forth in claim l6, wherein said combining means further contains a phase control means for matching the phases of two IF electric signals having the same polarization and the phases of the other two IF electric signals having the same polarization, and a summing means for summing the phase-matched two IF electric signals.
Claim 19
Dependent Claim
38 words
A receiver as set forth in claim l7, wherein said combining means further contains a signal intensity control means for equalizing the intensity of the two IF electric signals and applying the same to said phase control means.
Claim 20
Dependent Claim
140 words
A dual balanced optical signal receiver, comprising: a photomixing means for mixing a received optical signal with a local oscillation optical signal and producing two optical signals each having an intermediate frequency (IF); an optical signal receiving means for receiving said IF optical signals and transforming said optical signals into two corresponding electric signals having an intermediate frequency (IF); a combining means for producing an output signal by subtracting each of the two IF electric signals from each other; a modulation means for modulating said local oscillation optical signal to be input to said photomixing means, and; a control means for extracting the modulation signal component from the output signal of said combining means and controlling the input or the output of said optical signal receiving means such that the level of the thus extracted modulation signal component is minimized.
Claim 21
Dependent Claim
140 words
A dual balanced optical signal receiver, comprising: a photomixing means for mixing a received optical signal with a local oscillation optical signal and producing two optical signals each having an intermediate frequency (IF); an optical signal receiving means for receiving said IF optical signals and transforming said optical signals into two corresponding electric signals having an intermediate frequency (IF); a combining means for producing an output signal by subtracting each of the two IF electric signals from each other; a modulation means for modulating said local oscillation optical signal to be input to said photomixing means, and; a control means for extracting the modulation signal component from the output signal of said combining means and controlling the input or the output of said optical signal receiving means such that the level of the thus extracted modulation signal component is minimized.
Claim 22
Dependent Claim
22 words
A receiver as set forth in claim l9, wherein said control means controls the output level of said optical signal receiving means.
Claim 23
Dependent Claim
23 words
2l. A receiver as set forth in claim l9, wherein said control means controls the phase of each of said IF electric signals.
References Cited (Backward Citations)
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