Optical filter
View Patent ↗An optical filter comprises a first mode converter converting an incident light signal propagating in an incident mode into a signal propagating in a propagation mode LPnm of order higher than that of said incident mode; a second mode converter converting the light signal of higher propagation order LPnm into a signal propagating in the incident propagation mode; and a slanted Bragg grating disposed between said first and second mode converters and adapted to couple the higher propagation order light signal LPnm in back-propagation into said incident mode. The filter is applicable to flattening gain and to multiplexing DWDM signals.
1. A non-reflecting optical filter comprising:
a first mode converter converting an incident light signal propagating in an incident mode into a signal propagating in a propagation mode LPnm of order higher than that of said incident mode;
a second mode converter converting the light signal of higher propagation order LPnm into a signal propagating in the incident propagation mode; and
a slanted Bragg grating disposed between said first and second mode converters and adapted to couple the higher propagation order light signal LPnm in back-propagation into said incident mode.
2. An optical filter according to claim 1 , characterized in that the incident light signal propagates in the fundamental mode LP 01 .
3. An optical filter according to claim 1 , characterized in that the higher-order mode is LP 11 mode.
4. An optical filter according to claim 1 , characterized in that the higher-order mode is LP 0 m mode.
5. A filter according to claim 1 , characterized in that the grating, and the first and second mode converters are integrated in a single continuous waveguide.
6. An optical filter according to claim 5 , characterized in that at least one of the mode converters is an optical waveguide taper.
7. An optical filter according to claim 1 , characterized in that at least one of the mode converters is a long-period grating.
8. An optical filter according to claim 1 , characterized in that at least one of the mode converters is a converter in free space.
9. An optical filter according to claim 1 , characterized in that the slanted Bragg grating is of varying period (chirp).
10. An optical filter according to claim 1 , characterized in that the slanted Bragg grating is apodized.
11. An optical filter according to claim 1 , characterized in that it comprises a plurality of concatenated slanted Bragg gratings.
12. An optical filter according to claim 1 , characterized in that the slanted Bragg grating is sampled.
13. A gain equalizer including an optical filter according to claim 1 .
14. A multiplexer including an optical filter according to claim 1 .
15. An optical filter according to claim 1 , wherein only a single light signal is propagated to the slanted Bragg grating.