US4577924A
Expired / Lapsed
US
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Optical recursive filter
Assignee: Tacan Corp
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Filing: 1985-01-02
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Granted: 1986-03-25
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Expires: 2005-01-02
Abstract
Abstract An optical RF bandpass filter employing a noncoherent optical carrier. The filter consists of a section of multimode optical fiber having a length equal to half the modulation wavelength with mirrors deposited at each end of the fiber. The fiber section functions as a resonant cavity for the intensity modulated light which is directed into the fiber and which exits at one end through one of the partially reflecting mirrors.
Inventors
- 👤 Ronald F. Mathis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 17:06
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/24; G02B6/26; G02B6/28; G02B6/293; G02B6/29346; G02B6/29356; G02B6/2804; G02B6/2852; G02B6/29331; G02B6/29335
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
176 words
An optical recursive RF bandpass filter for extracting light varying in intensity at a predetermined intensity modulation frequency from light varying in intensity over a band of intensity modulation frequencies, comprising: a segment of multimode optical fiber; a first mirror on one end of said fiber; a second mirror on the other end of said fiber; and means for directing light varying in intensity over a band of intensity modulation frequencies at a substantially constant optical wavelength into said fiber; wherein said fiber has a length equal to half the wavelength of a predetermined intensity modulation frequency in said band of intensity modulation frequencies in said fiber, said fiber with said first and second mirrors on opposite ends thereof defining a resonant cavity which permits resonance of light at said predetermined intensity modulation frequency, a portion of the resonating light within said resonant cavity exiting through one of said first and second mirrors as filtered output light varying in intensity at said predetermined intensity modulation frequency with said filtered output light being at said optical wavelength.
Claim 2
Dependent Claim
176 words
An optical recursive RF bandpass filter for extracting light varying in intensity at a predetermined intensity modulation frequency from light varying in intensity over a band of intensity modulation frequencies, comprising: a segment of multimode optical fiber; a first mirror on one end of said fiber; a second mirror on the other end of said fiber; and means for directing light varying in intensity over a band of intensity modulation frequencies at a substantially constant optical wavelength into said fiber; wherein said fiber has a length equal to half the wavelength of a predetermined intensity modulation frequency in said band of intensity modulation frequencies in said fiber, said fiber with said first and second mirrors on opposite ends thereof defining a resonant cavity which permits resonance of light at said predetermined intensity modulation frequency, a portion of the resonating light within said resonant cavity exiting through one of said first and second mirrors as filtered output light varying in intensity at said predetermined intensity modulation frequency with said filtered output light being at said optical wavelength.
Claim 3
Dependent Claim
24 words
The filter recited in claim 1 wherein said first and second mirrors are formed of a dielectric material deposited on the respective fiber ends.
Claim 4
Dependent Claim
15 words
The filter recited in claim 1 wherein said light directing means comprises a directional coupler.
Claim 5
Dependent Claim
21 words
The filter recited in claim 3 wherein said directional coupler comprises a light injection fiber coupled to said multimode optical fiber.
Claim 6
Dependent Claim
35 words
The filter recited in claim 1 wherein said light directing means comprises an axial hole through one of said first and second mirrors and an injecting fiber axially aligned with and closely adjacent said hole.
Claim 7
Dependent Claim
15 words
The filter recited in claim 5 wherein said injecting fiber is a single mode fiber.
Claim 8
Dependent Claim
19 words
The filter recited in claim 1 wherein said optical fiber comprises a core and cladding of different refractive index.
Claim 9
Dependent Claim
24 words
The filter recited in claim 1 or 2 wherein the reflectance of the output mirror is less than the reflectance of the other mirror.
Claim 10
Dependent Claim
16 words
The filter recited in claim 1 or 2 wherein the reflectances of said mirrors are equal.
Claim 11
Dependent Claim
53 words
The filter recited in claim 1 wherein the length L of said filter is given by the relationship L=λ/2=c/(2nf.sub.c) where λ is the wavelength of said predetermined intensity modulation frequency, c is the speed of light, n is the effective refractive index of said fiber, and f c is the center modulation frequency.
Claim 12
Dependent Claim
27 words
The filter recited in claim 1 wherein the light directed into said resonant cavity exists as noncoherent light therein which resonates at said predetermined intensity modulation frequency.
Claim 13
Dependent Claim
16 words
The filter recited in claim 11 wherein the light directed into said resonant cavity is noncoherent.
Claim 14
Dependent Claim
16 words
The filter recited in claim 11 wherein the light directed into said resonant cavity is coherent.
Claim 15
Dependent Claim
28 words
The filter recited in claim 13 wherein the length of said fiber has a value other than one half the wavelength of the light directed into said fiber.
Claim 16
Dependent Claim
25 words
The filter of claim 11 wherein said filtered output light has a predetermined 3 dB intensity modulation frequency bandwidth about said predetermined intensity modulation frequency.
Claim 17
Dependent Claim
28 words
The filter recited in claim 1 wherein the length of said fiber has a value other than one half the wavelength of the light directed into said fiber.
Claim 18
Independent Claim
172 words
A method for filtering light varying in intensity over a band of intensity modulation frequencies to provide light varying in intensity at a predetermined intensity modulation frequency, comprising the steps of: providing a multimode optical fiber having a pair of mirrors each on a respective end of said fiber, said fiber having a length equal to half the wavelength of a predetermined intensity modulation frequency within a band of intensity modulation frequencies in said fiber, said fiber with said pair of mirrors defining a resonant cavity which permits resonance of light at said predetermined intensity modulation frequency, directing light varying in intensity over a band of intensity modulation frequencies at a substantially constant optical wavelength into said fiber, said light directed into said resonant cavity resonating at said predetermined intensity modulation frequency; and extracting a portion of the resonating light in said resonant cavity through one of said mirrors as filtered output light varying in intensity at said predetermined intensity modulation frequency with said filtered output light being at said optical wavelength.
Claim 19
Independent Claim
172 words
A method for filtering light varying in intensity over a band of intensity modulation frequencies to provide light varying in intensity at a predetermined intensity modulation frequency, comprising the steps of: providing a multimode optical fiber having a pair of mirrors each on a respective end of said fiber, said fiber having a length equal to half the wavelength of a predetermined intensity modulation frequency within a band of intensity modulation frequencies in said fiber, said fiber with said pair of mirrors defining a resonant cavity which permits resonance of light at said predetermined intensity modulation frequency, directing light varying in intensity over a band of intensity modulation frequencies at a substantially constant optical wavelength into said fiber, said light directed into said resonant cavity resonating at said predetermined intensity modulation frequency; and extracting a portion of the resonating light in said resonant cavity through one of said mirrors as filtered output light varying in intensity at said predetermined intensity modulation frequency with said filtered output light being at said optical wavelength.
Claim 20
Dependent Claim
27 words
The method recited in claim 17 wherein the light resonating in said resonant cavity exists as noncoherent light therein which resonates at said predetermined intensity modulation frequency.
Claim 21
Dependent Claim
16 words
The method recited in claim 18 wherein the light directed into said resonant cavity is noncoherent.
Claim 22
Dependent Claim
16 words
The method recited in claim 18 wherein the light directed into said resonant cavity is coherent.
Claim 23
Dependent Claim
28 words
The method recited in claim 18 wherein the length of said fiber has a value other than one half the wavelength of said light directed into the fiber.
References Cited (Backward Citations)
US4307933A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-03-24 | 1989-09-23 | 1990-03-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-03-24 | 1993-09-23 | 1994-03-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-03-24 | 1997-09-23 | 1998-03-25 | $7700.00 | Window Closed / Lapsed |