Cascaded fiber fabry-perot filters

1. A cascaded tunable filter which comprises two or more tunable all-fiber Fabry-Perot component filters optically coupled in sequence wherein the FSRS of the Fabry-Perot component filters are selected to achieve a vernier configuration of filters, wherein the two portion of the fiber of each component filter are held within a fiber ferrule and the Fabry-Perot cavity of each filter is formed in bare fiber between the ferrules.

2. The cascaded tunable filter of claim 1 wherein the component filters are temperature tunable.

3. The cascaded tunable filter of claim 1 wherein the component filters are electromechanically tunable.

4. The cascaded tunable filters of claim 1 wherein the component filters are compression tunable.

5. The cascaded tunable filter of claim 1 having two component filters.

6. The cascaded tunable filter of claim 1 having more than two component filters.

7. The cascaded tunable filter of claim 1 wherein the Fabry-Perot cavities of the component filters are formed by bonding of fiber ends one of which carries a reflector to form a fiber embedded reflector.

8. The cascaded tunable filter of claim 1 wherein the fiber ferrules holding the fiber carrying the Fabry-Perot cavity are held within ferrule holders and wherein the distance between the ferrule holders can be changed to change the cavity length and tune the filter.

9. The cascaded tunable filter of claim 1 wherein the component filters comprise a Fabry-Perot cavity formed in a bare section of fiber and the fiber of the filter is bonded to a metal substrate.

10. The cascaded tunable filter of claim 9 wherein the metal is aluminum.

11. The cascaded tunable filter of claim 1 wherein vernier multipliers are employed to achieve the vernier configuration and the vernier multipliers are the reciprocals of a series of consecutive integers which are not multiples of each other.

12. The cascaded tunable filter of claim 11 wherein the vernier multipliers are selected from the series 1/11, 1/12, 1/13, 1/14, 1/15, 1/16, 1/17, 1/18, 1/19 and 1/20.

13. The cascaded tunable filter of claim 11 wherein the vernier multipliers are selected from the series 1/20, 1/21, 1/22, 1/23, 1/24, 1/25, 1/26, 1/27, 1/28, 1/29 and 1/30.

14. A method for generating a selected wavelength spectrum employing a cascaded tunable filter of claim 1 wherein tuning is performed by coordinated tuning of the component filters.

15. An all-fiber Fabry-Perot interferometer wherein the Fabry-Perot cavity is formed in bare fiber and wherein the length of the Fabry-Perot cavity is changed thermally or electromechanically to tune the wavelengths transmitted by the interferometer, wherein the fiber containing the Fabry-Perot cavity is bonded into a groove of a metal substrate.

16. The interferometer of claim 15 which is tuned thermally by changing the temperature of the metal substrate.

17. The interferometer of claim 15 wherein the fiber containing the Fabry-Perot cavity is bonded to two metal substrates such that the Fabry-Perot cavity of the fiber bridges a gap between the two substrates.

18. The interferometer of claim 17 which is tuned by changing the length of the gap between the metal substrates.

19. The interferometer of claim 18 further comprising a piezoelectric element attached to both substrates wherein the gap between the substrates is changed by application of a voltage to the piezoelectric transducer.

20. The interferometer of claim 15 which is tuned by compression of the fiber.