CMOS-COMPATIBLE TUNABLE MICROWAVE PHOTONIC BAND-STOP FILTER

• US 20090214223A1
• Filed: 02/22/2008
• Published: 08/27/2009
• Est. Priority Date: 02/22/2008
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Rasras, Mahmoud, Chen, Young-Kai, Tu, Kun-Yii, Patel, Sanjay
• Granted Patent: US 8,014,676 B2
• Time in Patent Office: Days
• US Class Current: 398/183
• CPC Class Codes: H04B 10/00 Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
• CPC Class Codes: H04B 2210/006 Devices for generating or processing an RF signal by optical means

Abstract

According to one embodiment, a microwave photonic band-stop (MPBS) filter uses an electrical input signal to drive an optical Mach-Zehnder modulator. A modulated optical carrier produced by the modulator is applied to an optical filter having at least two tunable spectral attenuation bands that are located substantially symmetrically on either side of the carrier frequency. The resulting filtered optical signal is applied to an optical-to-electrical (O/E) converter to produce an electrical output signal.

Claims

1. A device, comprising:

an optical modulator adapted to modulate an optical signal having an optical carrier frequency to generate a modulated optical signal, said modulation being based on an electrical input signal;

an optical filter having first and second spectral attenuation bands and adapted to filter said modulated optical signal to produce a filtered optical signal, wherein the optical carrier frequency is substantially centered between said first and second spectral attenuation bands; and

an optical-to-electrical (O/E) converter adapted to convert the filtered optical signal into an electrical output signal.

2. The invention of claim 1, wherein:

the optical filter further has third and fourth spectral attenuation bands;

the optical carrier frequency is substantially centered between said third and fourth spectral attenuation bands; and

spectral separation between the first and second spectral attenuation bands is different from spectral separation between the third and fourth spectral attenuation bands.

3. The invention of claim 1, wherein the optical filter comprises:

a Mach-Zehnder interferometer having first and second internal interferometer arms, both coupled between two optical couplers;

first and second optical resonators, each coupled to the first interferometer arm, wherein;

optical losses induced by the first optical resonator result in the first spectral attenuation band; and

optical losses induced by the second optical resonator result in the second spectral attenuation band.

4. The invention of claim 3, wherein the optical filter further comprises third and fourth optical resonators, each coupled to a corresponding one of the first and second interferometer arms via a corresponding tunable optical coupler.

5. The invention of claim 4, wherein each of said tunable optical couplers is configured to provide a substantially zero optical coupling strength between the respective optical resonator and the interferometer arm.

6. The invention of claim 5, wherein both the third optical resonator and the fourth optical resonator are coupled to the first interferometer arm or to the second interferometer arm.

7. The invention of claim 4, wherein:

the optical filter further has third and fourth spectral attenuation bands;

optical losses induced by the third optical resonator result in the third spectral attenuation band;

optical losses induced by the fourth optical resonator result in the fourth spectral attenuation band; and

both the third optical resonator and the fourth optical resonator are coupled to the first interferometer arm.

8. The invention of claim 7, wherein:

the optical carrier frequency is substantially centered between the third and fourth spectral attenuation bands; and

spectral separation between the first and second spectral attenuation bands is different from spectral separation between the third and fourth spectral attenuation bands.

9. The invention of claim 1, further comprising a control circuit adapted to configure the optical filter to change spectral separation between the first and second attenuation bands.

10. The invention of claim 9, wherein the spectral separation is continuously tunable between zero and 20 GHz.

11. The invention of claim 1, further comprising:

a coherent light source adapted to generate the optical signal having said optical carrier frequency; and

a driver circuit adapted to convert the electrical input signal into a drive signal for driving the optical modulator.

12. The invention of claim 1, wherein the optical modulator is a double-sided Mach-Zehnder modulator.

13. The invention of claim 1, wherein the device is an integrated circuit fabricated using CMOS technology.

14. A method of processing electrical signals, comprising:

modulating an optical signal having an optical carrier frequency to generate a modulated optical signal, said modulation being based on an electrical input signal;

filtering said modulated optical signal in an optical filter having first and second spectral attenuation bands to produce a filtered optical signal, wherein the optical carrier frequency is substantially centered between said first and second spectral attenuation bands; and

converting the filtered optical signal into an electrical output signal.

15. The invention of claim 14, wherein:

the optical filter further has third and fourth spectral attenuation bands;

the optical carrier frequency is substantially centered between said third and fourth spectral attenuation bands; and

spectral separation between the first and second spectral attenuation bands is different from spectral separation between the third and fourth spectral attenuation bands.

16. The invention of claim 14, further comprising configuring the optical filter to change spectral separation between the first and second spectral attenuation bands.

17. The invention of claim 14, further comprising generating the optical signal having said optical carrier frequency with a coherent light source.

18. The invention of claim 14, wherein the optical filter comprises:

a Mach-Zehnder interferometer having first and second internal interferometer arms, both coupled between two optical couplers;

first and second optical resonators, each coupled to the first interferometer arm, wherein;

optical losses induced by the first optical resonator result in the first spectral attenuation band; and

optical losses induced by the second optical resonator result in the second spectral attenuation band.

19. The invention of claim 18, wherein:

the optical filter further comprises third and fourth optical resonators, each coupled to the first interferometer arm via a corresponding tunable optical coupler;

the optical filter further has third and fourth spectral attenuation bands;

optical losses induced by the third optical resonator result in the third spectral attenuation band;

optical losses induced by the fourth optical resonator result in the fourth spectral attenuation band

the optical carrier frequency is substantially centered between the third and fourth spectral attenuation bands; and

spectral separation between the first and second spectral attenuation bands is different from spectral separation between the third and fourth spectral attenuation bands.

20. The invention of claim 14, wherein:

an electrical input signal is a multi-frequency signal having an undesired frequency component; and

the method further comprises selecting spectral separation between the first and second attenuation bands to suppress said undesired frequency component in the electrical output signal.