Patent US5119447A successfully refreshed from Google Patents.
US5119447A
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Apparatus and method for externally modulating an optical carrier
Assignee: Ciena Corp
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Filing: 1990-11-06
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Granted: 1992-06-02
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Expires: 2010-11-06
Abstract
Abstract An external electrooptic modulator is provided offering high linearity and low intermodulation distortion. A Mach Zehnder modulator is followed by a directional coupler. The Mach Zehnder modulator is modulated with a first pair of electrodes at a first polarity. The modulating signal is scaled by a factor η and applied to a separate pair of electrodes for the directional coupler at a second polarity opposite to the first polarity. Separate DC bias electrodes can be provided in the Mach Zehnder modulator. The modulator is particularly appropriate for use in optical transmission systems for cable television applications.
Inventors
- 👤 Yudhi Trisno
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:34
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/29; G02F1/31; G02F1/313; G02F1/3136; H; H04; H04B; H04B10/00; H04B10/50; H04B10/501; H04B10/503; H04B10/505; G02F2203/00; G02F2203/19
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
101 words
An optical modulator comprising: means for splitting an optical signal for communication over first and second paths, wherein at least said first path comprises an electrooptic material; means for coupling a modulating signal to apply an electrical field of a first polarity across said first path to phase modulate the signal therein; an electrooptic directional coupler coupled to said first and second paths; and means for coupling said modulating signal to apply an electric field of a second polarity opposite to said first polarity across said coupler to couple optical signals from said first and second paths into an output signal.
Claim 2
Dependent Claim
101 words
An optical modulator comprising: means for splitting an optical signal for communication over first and second paths, wherein at least said first path comprises an electrooptic material; means for coupling a modulating signal to apply an electrical field of a first polarity across said first path to phase modulate the signal therein; an electrooptic directional coupler coupled to said first and second paths; and means for coupling said modulating signal to apply an electric field of a second polarity opposite to said first polarity across said coupler to couple optical signals from said first and second paths into an output signal.
Claim 3
Dependent Claim
23 words
An optical modulator in accordance with claim 1 further comprising: means for biasing said first path to provide a substantially 45° phase shift.
Claim 4
Dependent Claim
26 words
An optical modulator in accordance with claim 2 wherein said biasing means comprise a set of electrodes for applying an electric field across said first path.
Claim 5
Dependent Claim
51 words
An optical modulator in accordance with claim 3 wherein: said means for applying said first polarity electric field comprise a first set of modulating signal electrodes adjacent said first path; and said means for applying said second polarity electric field comprise a second set of modulating signal electrodes adjacent said coupler.
Claim 6
Dependent Claim
18 words
An optical modulator in accordance with claim 4 wherein said splitting means comprise a Y-branch optical power splitter.
Claim 7
Dependent Claim
51 words
An optical modulator in accordance with claim 1 wherein: said means for applying said first polarity electric field comprise a first set of modulating signal electrodes adjacent said first path; and said means for applying said second polarity electric field comprise a second set of modulating signal electrodes adjacent said coupler.
Claim 8
Dependent Claim
35 words
An optical modulator in accordance with claim 1 wherein said second path comprises an electrooptic material, and further comprising: means for applying an electric field across said second path to phase modulate the signal therein.
Claim 9
Dependent Claim
20 words
An optical modulator in accordance with claim 1 wherein said directional coupler has a nominal effective coupling length of π/4.
Claim 10
Dependent Claim
39 words
An optical modulator in accordance with claim 1 wherein distortions in the output signal are minimized by scaling the magnitude of said modulating signal to provide said second polarity field at a different magnitude than said first polarity field.
Claim 11
Dependent Claim
26 words
An optical modulator in accordance with claim 1 wherein said splitting means divide the optical power of said signal equally into said first and second paths.
Claim 12
Dependent Claim
18 words
An optical modulator in accordance with claim 10 wherein said splitting means comprise a Y-branch optical power splitter.
Claim 13
Dependent Claim
18 words
An optical modulator in accordance with claim 1 wherein said splitting means comprise a Y-branch optical power splitter.
Claim 14
Independent Claim
111 words
A method for externally modulating an optical carrier comprising the steps of: splitting an optical carrier into first and second portions for input to a Mach Zehnder modulator; modulating at least said first portion in said Mach Zehnder modulator by applying a modulating signal to a first set of electrodes associated with the Mach Zehnder modulator at a first polarity; applying the first and second portions from the Mach Zehnder modulator to a directional coupler: and combining said first and second portions in said directional coupler by applying said modulating signal to a second set of electrodes associated with the directional coupler at a second polarity opposite to said first polarity.
Claim 15
Independent Claim
111 words
A method for externally modulating an optical carrier comprising the steps of: splitting an optical carrier into first and second portions for input to a Mach Zehnder modulator; modulating at least said first portion in said Mach Zehnder modulator by applying a modulating signal to a first set of electrodes associated with the Mach Zehnder modulator at a first polarity; applying the first and second portions from the Mach Zehnder modulator to a directional coupler: and combining said first and second portions in said directional coupler by applying said modulating signal to a second set of electrodes associated with the directional coupler at a second polarity opposite to said first polarity.
Claim 16
Dependent Claim
29 words
A method in accordance with claim 13 comprising the further step of: scaling the magnitude of said modulating signal prior to applying it to said second set of electrodes.
Claim 17
Dependent Claim
34 words
A method in accordance with claim 14 comprising the further step of: biasing said Mach Zehnder modulator to provide a substantially 45° phase shift to said first portion when no modulating signal is present.
Claim 18
Dependent Claim
34 words
A method in accordance with claim 13 comprising the further step of: biasing said Mach Zehnder modulator to provide a substantially 45° phase shift to said first portion when no modulating signal is present.
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