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US5210633A
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Apparatus and method for linearizing the operation of an external optical modulator
Assignee: Ciena Corp
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Filing: 1990-09-12
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Granted: 1993-05-11
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Expires: 2010-09-12
Abstract
Abstract A modulating signal is predistorted to linearize the output of an optical intensity modulator. The modulating signal is split into first and second paths. In the first path, the signal is phase shifted. In the second path, distortion components are introduced. The phase shifted signal from the first path is then combined with the distorted signal from the second path to provide a predistorted signal for use in modulating a light source. The distortion generator can comprise a diode pair coupled with opposite polarities in parallel. Both diodes are forward biased, and the pair is coupled in series with the input signal to provide the desired predistortion.
Inventors
- 👤 Yudhi Trisno
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 18:36
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/32; H03F1/3241; H03F1/3252; H03F1/3276; H04; H04B; H04B10/00; H04B10/50; H04B10/58; H04B10/588
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
105 words
External optical intensity modulator apparatus having reduced third order distortion products comprising: means for splitting an analog input signal into first and second paths; phase shift means coupled to said first path for shifting the input signal phase; distortion generator means coupled to said second path for introducing distortion components into said input signal; means for combining the phase shifted input signal from said first path with the distorted input signal from said second path to provide a predistorted analog modulation signal; and an external optical intensity modulator having an input for receiving said predistorted analog modulation signal for use in modulating a light source.
Claim 2
Dependent Claim
105 words
External optical intensity modulator apparatus having reduced third order distortion products comprising: means for splitting an analog input signal into first and second paths; phase shift means coupled to said first path for shifting the input signal phase; distortion generator means coupled to said second path for introducing distortion components into said input signal; means for combining the phase shifted input signal from said first path with the distorted input signal from said second path to provide a predistorted analog modulation signal; and an external optical intensity modulator having an input for receiving said predistorted analog modulation signal for use in modulating a light source.
Claim 3
Dependent Claim
57 words
Apparatus in accordance with claim 1 wherein said distortion generator means comprise: a diode pair coupled with opposite polarities in parallel; a first current source for forward biasing one of said diodes; a second current source for forward biasing the other of said diodes; and means for coupling said diode pair in series with said second path.
Claim 4
Dependent Claim
19 words
Apparatus in accordance with claim 1 wherein said phase shift means is adjustable to provide a desired phase delay.
Claim 5
Dependent Claim
19 words
Apparatus in accordance with claim 1 further comprising: a variable gain amplifier coupled to adjustably amplify said distortion components.
Claim 6
Dependent Claim
19 words
Apparatus in accordance with claim 4 wherein said phase shift means is adjustable to provide a desired phase delay.
Claim 7
Dependent Claim
57 words
Apparatus in accordance with claim 5 wherein said distortion generator means comprise: a diode pair coupled with opposite polarities in parallel; a first current source for forward biasing one of said diodes; a second current source for forward biasing the other of said diodes; and means for coupling said diode pair in series with said second path.
Claim 8
Dependent Claim
26 words
Apparatus in accordance with claim 4 wherein said variable gain amplifier is coupled in said second path between said distortion generator means and said combining means.
Claim 9
Dependent Claim
19 words
Apparatus in accordance with claim 7 further comprising: an attenuator coupled between said distortion generator means and said amplifier.
Claim 10
Dependent Claim
23 words
Apparatus in accordance with claim 4 wherein said variable gain amplifier is coupled to amplify the predistorted signal provided by said combining means.
Claim 11
Dependent Claim
31 words
Apparatus in accordance with claim 9 wherein said combining means subtracts the phase shifted input signal from the distorted input signal to provide a predistorted signal comprising primarily said distortion components.
Claim 12
Dependent Claim
28 words
Apparatus in accordance with claim 10 further comprising: means for summing said input signal with the distortion components from the combining means to provide said analog modulation signal.
Claim 13
Dependent Claim
22 words
Apparatus in accordance with claim 11 further comprising: amplifier means for amplifying said input signal prior to summation with said distortion components.
Claim 14
Dependent Claim
28 words
Apparatus in accordance with claim 1 wherein said combining means add the phase shifted input signal to the distorted input signal to provide said predistorted analog modulation signal.
Claim 15
Dependent Claim
22 words
Apparatus in accordance with claim 13 wherein said external optical intensity modulator is a Mach Zehnder modulator for modulating said light source.
Claim 16
Dependent Claim
22 words
Apparatus in accordance with claim 1 wherein said external optical intensity modulator is a Mach Zehnder modulator for modulating said light source.
Claim 17
Dependent Claim
16 words
Apparatus in accordance with claim 1 wherein said distortion generator means provide odd order distortion components.
Claim 18
Independent Claim
117 words
A method for linearizing the output of an external analog optical modulator comprising the steps of: providing an analog modulating signal for use in modulating an external optical modulator; adjusting the phase of said modulating signal in a first path to compensate for a phase shift introduced by said modulator; predistorting said modulation signal in a second path with odd order distortion components similar to but opposite in polarity than distortion components introduced by said modulator; combining the phase adjusted modulating signal from said first path with the predistorted modulation signal from said second path to provide a predistorted, phase shifted signal; and coupling said predistorted, phase shifted signal to a modulating signal input of said modulator.
Claim 19
Independent Claim
117 words
A method for linearizing the output of an external analog optical modulator comprising the steps of: providing an analog modulating signal for use in modulating an external optical modulator; adjusting the phase of said modulating signal in a first path to compensate for a phase shift introduced by said modulator; predistorting said modulation signal in a second path with odd order distortion components similar to but opposite in polarity than distortion components introduced by said modulator; combining the phase adjusted modulating signal from said first path with the predistorted modulation signal from said second path to provide a predistorted, phase shifted signal; and coupling said predistorted, phase shifted signal to a modulating signal input of said modulator.
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