Optical discriminators and systems and methods

Abstract

An optical multi-filter discriminator suitable for treating optical signals from an optical signal source, e.g., a direct modulated laser (“DML”), comprises a first optical filter, a second optical filter optically coupled to the first optical filter, an input port operative to receive optical signals from an optical signal source and oriented to launch the optical signals directly or indirectly to the first optical filter, and an output port oriented to receive optical signals treated by the multiple optical filters and operative to pass the optical signals directly or indirectly to an optical waveguide “downstream” of the discriminator. The first filter is transmissive (i.e., at the angle of incidence received from the input port) of at least a first wavelength band having a first center wavelength and reflective (again, meaning in this instance at the angle of incidence received from the input port) of at least a second wavelength band different from the first wavelength band. The optical multi-filter discriminator defines an optical path for optical signals in the first wavelength band received by the input port. The optical path includes at least (i) transmission from the input port directly or indirectly to and through the first optical filter, and (ii) then, prior to the output port, from the first optical filter directly or indirectly to the second optical filter at an angle of incidence at which the second optical filter is reflective of the first wavelength band. The at least two filters of the optical multi-filter discriminator can be packaged together in a common housing along with some or all of the other components, if any, of the optical multi-filter discriminator, e.g., lenses, isolators, mounting components, etc. An optical communication system comprises a DML or other optical signal source optically coupled to one or more of the aforesaid optical multi-filter discriminators. A method of operating an optical communication system comprises actuating an optical signal source to generate optical signals to one or more of the aforesaid optical multi-filter discriminators to increase the extinction ratio, and by passing the signals through the multi-discriminator to a downstream optical fiber or other optical waveguide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and features of the inventive subject matter disclosed here are further disclosed and described below with reference to the appended drawings wherein:

FIG. 1 is a schematic illustration of an optical dual discriminator in accordance with certain exemplary two-port embodiments of the inventive subject matter of the present disclosure;

FIG. 2 is a graph of the simulated spectra of a directly modulated laser, shown here modulated at 2.2 GHz;

FIG. 3 is a schematic illustration of a chip layout in accordance with certain exemplary embodiments of the inventive subject matter of the present disclosure, suitable for the optical dual discriminator of FIG. 1;

FIG. 4 is a schematic illustration of optical path angles for a chip layout suitable for the optical dual discriminator of FIG. 1;

FIG. 5 is a graph showing transmission profiles for the filter chips of an exemplary optical dual discriminator in accordance with FIGS. 1-4;

FIG. 6 is a schematic illustration of a component layout for an exemplary optical dual discriminator in accordance with FIGS. 1-5, where the dual discriminator is packaged as a separate component from a laser signal source and where, for simplicity of illustration, selected components, e.g., a housing, etc. are not shown;

FIG. 7 is a schematic illustration of a component layout for an exemplary optical dual discriminator in accordance with FIGS. 1-5, where the dual discriminator is integrated into a laser package and where, for simplicity of illustration, selected components, e.g., a housing, ferrules, etc. are not shown;

FIG. 8 is a schematic illustration of a two port optical dual discriminator in accordance with certain other exemplary embodiments of the inventive subject matter of the present disclosure;

FIG. 9 is a schematic illustration of a chip layout in accordance with certain exemplary embodiments of the inventive subject matter of the present disclosure, suitable for the optical dual discriminator of FIG. 8, where two optical chips each carries one of the two thin film filters of the dual discriminator;

FIG. 10 is a schematic illustration of a component layout for an exemplary optical dual discriminator in accordance with FIGS. 8 and 9, where, for simplicity of illustration, selected components, e.g., a housing, etc. are not shown;

FIG. 11 is a graph showing theoretical transmission and reflection plots for each of the two filter chips of an exemplary optical dual discriminator in accordance with FIGS. 8-10, along with a superimposed trace of the DML output showing an approximately 160 pm shift between the null or space and the mark or 1s expected for a 10 GHz optical signal system, where the first filter is tuned to transmit wavelengths near the 1s and to reflect wavelengths near the 0s.

FIG. 12 is a schematic illustration of a chip layout in accordance with certain exemplary embodiments of the inventive subject matter of the present disclosure, suitable for the optical dual discriminator of FIGS. 8-11;

FIG. 13 is a graph showing the theoretical and measured transmission for an exemplary optical dual discriminator in accordance with FIGS. 8-12;

FIG. 14 is a graph showing the chromatic dispersion (CD) profile for the first and second filters of a dual discriminator in accordance with FIGS. 8-13, including a negative CD region for the first filter; and

FIG. 15 is a schematic illustration of a component layout for an alternative exemplary optical dual discriminator in accordance with FIGS. 8 and 9, having a monitor port, where, for simplicity of illustration, selected components, e.g., a housing, etc. are not shown.

Claims

1. An optical multi-filter discriminator comprising: a. a first optical filter transmissive of at least a first wavelength band having a first center wavelength and reflective of at least a second wavelength band different from the first wavelength band; andb. a second optical filter optically coupled to the first optical filter; andc. an input port operative to receive optical signals from an optical signal source and oriented to launch the optical signals directly or indirectly to the first optical filter; andd. an output port oriented to receive optical signals treated by the first and second optical filters and operative to pass the optical signals directly or indirectly to an optical waveguide;wherein the optical multi-filter discriminator defines an optical path for optical signals in the first wavelength band received by the input port, the optical path comprising: from the input port directly or indirectly to and through the first optical filter, andfrom the first optical filter directly or indirectly to the second optical filter prior to the output port, at an angle of incidence at which the second optical filter is reflective of the first wavelength band.

2. The optical multi-filter discriminator of claim 1 wherein the second optical filter is reflective of the second wavelength band and transmissive of the first wavelength band, and the optical path for optical signals in the first wavelength band further comprises transmission through the second optical filter to the output port.

3. The optical multi-filter discriminator of claim 1 wherein the second optical filter is transmissive of the second wavelength band and reflective of the first wavelength band, and the optical path for optical signals in the first wavelength band further comprises reflection from the second optical filter back to the first optical filter and then again through the first optical filter to the output port.

4. The optical multi-filter discriminator of claim 1 wherein the first optical filter is disposed on a first surface of a first optical substrate, and the second optical filter is disposed on a first surface of a second optical substrate.

5. The optical multi-filter discriminator of claim 1 wherein the first optical filter is disposed on a first surface of a first optical substrate, and the second optical filter is disposed on a second surface of the first optical substrate.

6. The optical multi-filter discriminator of claim 1 wherein the first optical filter and the second optical filter each is a band pass filter.

7. The optical multi-filter discriminator of claim 1 wherein the first optical filter and the second optical filter each is a thin film Fabry-Perot filter.

8. The optical multi-filter discriminator of claim 1 wherein the first optical filter and the second optical filter are mounted together in a single, hermetically sealed housing.

9. The optical multi-filter discriminator of claim 8 wherein: the input port comprises a first optical fiber in a first ferrule fitted to the housing, andthe output port comprises a second optical fiber in a second ferrule fitted to the housing.

10. The optical multi-filter discriminator of claim 8 wherein: the input port comprises a first optical fiber in a first ferrule fitted to the housing, andthe output port comprises a second optical fiber in the first ferrule.

11. The optical multi-filter discriminator of claim 10 further comprising a third optical fiber in the first ferrule.

12. An optical communication system comprising: an optical signal source operative to generate optical signals;an optical multi-filter discriminator optically coupled to optical signal source, the optical multi-filter discriminator comprising:a. a first optical filter transmissive of at least a first wavelength band having a first center wavelength and reflective of at least a second wavelength band different from the first wavelength band; andb. a second optical filter optically coupled to the first optical filter; andc. an input port operative to receive optical signals from an optical signal source and oriented to launch the optical signals directly or indirectly to the first optical filter; andd. an output port oriented to receive optical signals treated by the first and second optical filters and operative to pass the optical signals directly or indirectly to an optical waveguide;

13. The optical communication system of claim 12 wherein the optical signal source comprises a directly modulated laser.

14. The optical communication system of claim 12 wherein the optical multi-filter discriminator is an optical dual filter discriminator wherein the first optical filter and the second optical filter are mounted together in a single, hermetically sealed housing.

15. The optical communication system of claim 15 wherein the optical signal source comprises a laser mounted in the single, hermetically sealed housing with the first optical filter and the second optical filter.

16. The optical communication system of claim 16 wherein the laser is a directly modulated laser.

17. The optical communication system of claim 15 wherein the second optical filter is transmissive of the second wavelength band and reflective of the first wavelength band and the optical path for optical signals in the first wavelength band further comprises transmission through the second optical filter to the output port.

18. The optical communication system of claim 15 wherein the second optical filter is reflective of the first wavelength band and transmissive of the second wavelength band, and the optical path for optical signals in the first wavelength band further comprises reflection from the second optical filter back to the first optical filter and then again through the first optical filter to the output port.

19. The optical communication system of claim 15 wherein the second optical filter is transmissive of the first wavelength band and reflective of the second wavelength band, and the optical path for optical signals in the first wavelength band further comprises transmission through the second optical filter to the output port.

20. The optical communication system of claim 12 wherein the first optical filter is disposed on a first surface of a first optical substrate, and the second optical filter is disposed on a first surface of a second optical substrate.

21. The optical communication system of claim 12 wherein the first optical filter is disposed on a first surface of a first optical substrate, and the second optical filter is disposed on a second surface of the first optical substrate.

22. A method of operating an optical communication system comprising: generating optical signals by modulating input current to an optical signal source;passing the optical signals to the input port of an optical multi-filter discriminator;launching the optical signals from the input port directly or indirectly to a first optical filter of the optical multi-filter discriminator at an angle of incidence, the first optical filter being transmissive of at least a wavelength band having a first center wavelength within the optical signals and reflective of other wavelengths within the optical signals;passing the optical signals through the first optical filter directly or indirectly to a second optical filter of the optical multi-filter discriminator at a second angle of incidence, the second optical filter being optically coupled to the first optical filter and being reflective of the first wavelength band at the second angle of incidence;following processing, if any, by optional addition optical filters of the optical multi-filter discriminator, passing the optical signals directly or indirectly to a second optical waveguide via an output port of the optical multi-filter discriminator, andcarrying the optical signals received from the optical multi-filter discriminator to a receiver at least in part via the second optical waveguide.

23. The method of claim 22 wherein the first center wavelength and the second center wavelength are in the C-Band.

24. The method of claim 23 wherein the first center wavelength is from 16 pm to 200 pm from the second center frequency.

25. The method of claim 24 wherein the optical signal source comprises a DML.

26. The method of claim 25 wherein processing the optical signals through the optical multi-filter discriminator increases the extinction ratio from a value less than 5 to a value greater than 5.

27. The method of claim 22 further comprising the second optical filter reflecting the first wavelength band back to the first optical filter and then again passing the first wavelength band through the first optical filter to the output port.

28. The method of claim 22 further comprising the second optical filter passing the first wavelength band to the output port.