Optical FM source based on intra-cavity phase and amplitude modulation in lasers

1. A fiber optic communication system comprising:

an optical signal source adapted to receive a binary base signal having a bit period T, and generate a first signal, wherein the first signal is frequency modulated; and

an optical spectrum reshaper (OSR) adapted to reshape the first signal into a second signal, wherein the second signal is amplitude modulated and frequency modulated;

characterized in that:

the optical signal source is a laser in which frequency modulation is generated by modulating the loss of the laser cavity;

wherein the frequency modulation excursion of the source is between 0.2 times ½ T and 0.8 times ½ T.

2. A system according to claim 1 wherein modulation of the loss in the laser cavity is achieved by a change in the absorption of a semiconductor material by the application of a voltage to that material.

3. A system according to claim 2 wherein modulation of the loss in the laser cavity is achieved by using one from the group consisting of (i) the quantum confined stark effect (QCSE); and (ii) the Franz-Keldysh effect.

4. A system according to claim 1 wherein the laser comprises one from the group consisting of (i) distributed feedback (DFB) lasers; (ii) distributed Bragg reflector (DBR) lasers; (iii) sampled grating distributed Bragg reflector (SG-DBR) lasers; and (iv) Y branch DBR lasers.

5. A system according to claim 1 wherein the laser comprises one from the group consisting of, (i) external cavity lasers (ii) vertical cavity surface emitting lasers (VCSEL); and (iii) Fabry Perot lasers.

6. A system according to claim 5 , wherein the external cavity lasers include at least one of Bragg gratings, ring resonators, planar lightwave circuit (PLC) Bragg gratings, arrayed waveguide gratings (AWG), and grating filters as external cavities.

7. A method for transmitting a signal, comprising:

receiving a binary base signal having a bit period T, and generating a first signal, wherein the first signal is frequency modulated; and

reshaping the first signal into a second signal, wherein the second signal is amplitude modulated and frequency modulated;

characterized in that:

the first signal is frequency modulated by using a laser in which frequency modulation is generated by modulating the loss of the laser cavity;

wherein the frequency excursion of the source is between 0.2 times ½ T and 0.8 times ½ T.

8. A method according to claim 7 wherein modulation of the loss in the laser cavity is achieved by a change in the absorption of a semiconductor material by the application of a voltage to the material.

9. A method according to claim 8 wherein modulation of the loss in the laser cavity is achieved by using one from the group consisting of (i) the quantum confined stark effect (QCSE); and (ii) the Franz-Keldysh effect.

10. A method according to claim 7 wherein the laser comprises one from the group consisting of (i) distributed feedback (DFB) lasers; (ii) distributed Bragg reflector (DBR) lasers; (iii) sampled grating distributed Bragg reflector (SG-DBR) lasers; and (iv) Y branch DBR lasers.

11. A method according to claim 7 wherein the laser comprises one from the group consisting of, (i) external cavity lasers (ii) vertical cavity surface emitting lasers (VCSEL); and (iii) Fabry Perot lasers.

12. A method according to claim 11 , wherein the external cavity lasers include at least one of Bragg gratings, ring resonators, planar lightwave circuit (PLC) Bragg gratings, arrayed waveguide gratings (AWG), and grating filters as external cavities.

13. A fiber optic communication system comprising:

an optical signal source adapted to receive a binary base signal having a bit period T, and generate a first signal, wherein the first signal is frequency modulated; and

an optical spectrum reshaper (OSR) adapted to reshape the first signal into a second signal, wherein the second signal is amplitude modulated and frequency modulated;

characterized in that:

the optical signal source is a laser in which frequency modulation is generated by modulating the phase of the laser cavity;

wherein the frequency modulation excursion of the source is between 0.2 times ½ T and 0.8 times ½ T.

14. A system according to claim 13 wherein the laser comprises one from the group consisting of, (i) external cavity lasers (ii) vertical cavity surface emitting lasers (VCSEL); and (iii) Fabry Perot lasers.

15. A system according to claim 14 , wherein the external cavity lasers include at least one of Bragg gratings, ring resonators, planar lightwave circuit (PLC) Bragg gratings, arrayed waveguide gratings (AWG), and grating filters as external cavities.

16. A system according to claim 13 wherein modulation of the phase in the laser cavity is achieved by a change in the refractive index of a semiconductor material by the application of a voltage to that material.

17. A system according to claim 16 wherein modulation of the phase in the laser cavity is achieved by using one from the group consisting of (i) the quantum confined stark effect (QCSE); and (ii) the Pockels effect.

18. A system according to claim 13 wherein the laser comprises one from the group consisting of (i) distributed feedback (DFB) lasers; (ii) distributed Bragg reflector (DBR) lasers; (iii) sampled grating distributed Bragg reflector (SG-DBR) lasers; and (iv) Y branch DBR lasers.