US5504608A
Expired / Lapsed
US
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Adjustable filter for tuning multimode optical signals
Assignee: AT&T Inc
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Filing: 1995-05-25
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Granted: 1996-04-02
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Expires: 2015-05-25
Abstract
Abstract This invention provides an apparatus and a method of filtering a MM Wavelength Division Multiplexed (WDM) signal operating in the 1548 to 1560 nm region. The wavelengths of the MM are spaced 1-12 nm apart and centered about 1558 nm. The adjustable filters for tuning MM optical signals encompass a carousel and a mechanical system for positioning one of the filters in the path of the MM WDM signal and tracking the signal. An algorithm controls the mechanical system for tracking and positioning one of the filters in the path of the MM WDM signal. The filter in position filters one of a plurality of wavelengths and tunes the filter to compensate for temperature changes.
Inventors
- 👤 Arthur E. Neeves
- 👤 William E. Watters
- 👤 James E. Williams
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 17:20
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/60; H04B10/66; H04B10/67; H04B10/671; H04B10/675; G; G02; G02B; G02B6/00; G02B6/24; G02B6/26; G02B6/28; G02B6/293; G02B6/29346; G02B6/29361; G02B6/2937; G02B6/29379; G02B6/29395; H04B10/25; H04B10/2581
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
126 words
A method for receiving the passband of an optical beam carrying multimode, wavelength division multiplexed optical signals, where each wavelength of said signals has peaks defining a bandpass region, where said region has maximum optical power, and tuning said bandpass region, said method comprising: (a) selecting one of a plurality of optical filter elements arranged in a carousel where each filter element has a different center wavelength for passing at least one wavelength from a plurality of wavelength division multiplexed signals; (b) centering the selected filter element in the path of the optical beam; (c) positioning the selected filter element to tune said bandpass region of said at least one selected wavelength; and (d) tracking the tuned bandpass region of said selected at least one wavelength.
Claim 2
Independent Claim
126 words
A method for receiving the passband of an optical beam carrying multimode, wavelength division multiplexed optical signals, where each wavelength of said signals has peaks defining a bandpass region, where said region has maximum optical power, and tuning said bandpass region, said method comprising: (a) selecting one of a plurality of optical filter elements arranged in a carousel where each filter element has a different center wavelength for passing at least one wavelength from a plurality of wavelength division multiplexed signals; (b) centering the selected filter element in the path of the optical beam; (c) positioning the selected filter element to tune said bandpass region of said at least one selected wavelength; and (d) tracking the tuned bandpass region of said selected at least one wavelength.
Claim 3
Dependent Claim
21 words
The method according to claim 1, wherein the selected filter element is positioned for passing a two millimeter diameter optical beam.
Claim 4
Dependent Claim
24 words
The method according to claim 1, wherein the wavelengths of the optical beam are in the range of around 1548 to around 1560 nm.
Claim 5
Dependent Claim
16 words
The method according to claim 3, wherein the adjacent wavelengths are spaced approximately 2 nm apart.
Claim 6
Dependent Claim
16 words
The method according to claim 1, wherein the wavelengths are within 12 nm of one another.
Claim 7
Dependent Claim
26 words
The method according to claim 1, wherein a processor controlled motor is used to drive the carousel for centering and positioning the selected optical filter element.
Claim 8
Dependent Claim
21 words
The method according to claim 1, wherein the optical filter elements are circular, each having a diameter of around five millimeters.
Claim 9
Dependent Claim
37 words
The method according to claim 7, wherein the tilt angle of the selected optical filter element can be physically changed by a control motor to allow isolation of a single wavelength signal from the incident NDM signal.
Claim 10
Dependent Claim
65 words
The method according to claim 1, further comprising the steps of: (e) determining with an optical receiver feedback whether the selected filter is in position to tune the bandpass region of said one wavelength; and (f) controlling with a processor and associated stored programs said selected filter element to get maximum transmission of said bandpass region of said one wavelength through said selected filter element.
Claim 11
Dependent Claim
25 words
The method according to claim 9, wherein said processor and associated programs repeatedly checks to determine whether the selected optical filter element stays in position.
Claim 12
Dependent Claim
102 words
The method according to claim 10, wherein said processor and associated stored programs periodically issues commands to the carousel for selective rotation and scanning with a plurality of filter elements a wavelength spectrum region to determine if any wavelength division multiplexed optical signal peaks are present, wherein when any peaks are detected, said processor and associated stored programs issues commands to tune said bandpass region of said detected peaks, wherein said processor and associated stored programs proceeds to track said detected peaks without losing said one wavelength should said one wavelength or said selected filter element drift due to a temperature change.
Claim 13
Dependent Claim
22 words
The method according to claim 1, wherein the optical signals are collimated before said bandpass region of said one wavelength is tuned.
Claim 14
Dependent Claim
18 words
The method according to claim 12, wherein GRIN (Graded Index) lenses are used to collimate the optical signals.
Claim 15
Dependent Claim
16 words
The method according to claim 12, wherein aspheric lenses are used to collimate the optical signals.
Claim 16
Dependent Claim
24 words
The method according to claim 1, wherein each of said plurality of optical filter elements is a two or three cavity, multi-layer interference type.
Claim 17
Independent Claim
111 words
A method for extracting a single channel electrical signal, said electrical signal having peaks defining a bandpass region, from an optical beam carrying multimode, wavelength division multiplexed optical signals, in a system having a plurality of optical filter elements, said method comprising: (a) selecting one out of a plurality of optical filter elements where each filter element has a different center wavelength; (b) positioning the selected filter element in the path of said optical beam; (c) shifting the positioned optical filter element to tune said bandpass region of one of said multimode optical signals to form said electrical signal; and (d) feeding said electrical signal to an analog to digital converter.
Claim 18
Independent Claim
111 words
A method for extracting a single channel electrical signal, said electrical signal having peaks defining a bandpass region, from an optical beam carrying multimode, wavelength division multiplexed optical signals, in a system having a plurality of optical filter elements, said method comprising: (a) selecting one out of a plurality of optical filter elements where each filter element has a different center wavelength; (b) positioning the selected filter element in the path of said optical beam; (c) shifting the positioned optical filter element to tune said bandpass region of one of said multimode optical signals to form said electrical signal; and (d) feeding said electrical signal to an analog to digital converter.
Claim 19
Dependent Claim
23 words
The method according to claim 16, wherein said multimode optical signals have wavelengths in the range of around 1548 to around 1560 nm.
Claim 20
Dependent Claim
37 words
The method according to claim 16, wherein said method further comprises: (e) monitoring feedback measurements of optical power from the electronic converter; and (f) inspecting to detect wavelength shifts among said multimode optical signals and said signal.
Claim 21
Dependent Claim
23 words
The method according to claim 17, wherein said multimode optical signals have wavelengths spaced approximately 1-12 nm apart and centered around 1558 nm.
Claim 22
Independent Claim
150 words
A system for receiving an optical beam carrying multimode, wavelength division multiplexed optical signals, where each of said signals has peaks defining a bandpass region, where said region has maximum optical power, and tuning said bandpass region, said system comprising: signal peak detection means for detecting the presence of a peak of one of said wavelength division multiplexed signals; selection means for selecting one out of a plurality of optical filter elements arranged in a carousel wherein each of said filter elements has a different center wavelength for passing said detected wavelength from a plurality of wavelength division multiplexed signals; centering means for centering the selected filter element in the path of the optical beam; positioning means for positioning the centered filter element to tune the bandpass region; and tracking means for tracking the tuned bandpass region without losing said detected wavelength should said detected wavelength or selected filter drift.
Claim 23
Independent Claim
150 words
A system for receiving an optical beam carrying multimode, wavelength division multiplexed optical signals, where each of said signals has peaks defining a bandpass region, where said region has maximum optical power, and tuning said bandpass region, said system comprising: signal peak detection means for detecting the presence of a peak of one of said wavelength division multiplexed signals; selection means for selecting one out of a plurality of optical filter elements arranged in a carousel wherein each of said filter elements has a different center wavelength for passing said detected wavelength from a plurality of wavelength division multiplexed signals; centering means for centering the selected filter element in the path of the optical beam; positioning means for positioning the centered filter element to tune the bandpass region; and tracking means for tracking the tuned bandpass region without losing said detected wavelength should said detected wavelength or selected filter drift.
Claim 24
Dependent Claim
19 words
The system according to claim 20, wherein the optical filter elements are circular, each having a five millimeter diameter.
Claim 25
Dependent Claim
30 words
The system according to claim 20, wherein the plurality of optical filter elements each have an optical receiver feedback means for determining whether the selected filter element is in position.
Claim 26
Dependent Claim
33 words
The system according to claim 20, wherein the selected filter element is positioned in a manner such that a two millimeter diameter of the optical beam can transmit through the selected filter element.
Claim 27
Dependent Claim
24 words
The system according to claim 20, wherein the wavelengths of the optical beam are in the range of around 1548 to around 1560 nm.
Claim 28
Dependent Claim
20 words
The system according to claim 24, wherein the wavelengths are spaced approximately 1-12 nm apart and centered around 1558 nm.
Claim 29
Dependent Claim
13 words
The system according to claim 20, wherein said carousel includes seven filter elements.
Claim 30
Dependent Claim
25 words
The system according to claim 20, wherein each said filter element has a center wavelength in the range of around 1548 to around 1560 nm.
Claim 31
Dependent Claim
40 words
The system according to claim 20, further including means for limiting tuning loss to approximately 1 dB while maintaining insertion loss at less than 4 dB when positioning angle of said selected filter element is between 0 to 7 degrees.
Claim 32
Dependent Claim
27 words
The system according to claim 20, further including a motor and motor control means for driving the carousel for centering and positioning the selected optical filter element.
Claim 33
Dependent Claim
19 words
The system according to claim 20, further including means for collimating said optical signals before tuning the bandpass region.
Claim 34
Dependent Claim
17 words
The system according to claim 30, further including GRIN (Graded Index) lenses for collimating said optical signals.
Claim 35
Dependent Claim
14 words
The system according claim 30, further including aspheric lenses for collimating said optical signals.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1999-04-02 | 1999-10-02 | 2000-04-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-04-02 | 2003-10-02 | 2004-04-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-04-02 | 2007-10-02 | 2008-04-02 | $7700.00 | Window Closed / Lapsed |