Wavelength tunable comb source

1. A wavelength tunable optical comb source, providing an output, comprising:

a) a Fabry-Pérot semiconductor laser having a lasing cavity;

b) a RF source providing a RF signal for gain switching of the Fabry-Pérot semiconductor laser;

c) a DC bias source configured to provide a DC bias current to the Fabry-Pérot semiconductor laser; and

d) a tunable single mode laser,

e) an optical circulator comprising at least three ports, the optical circulator being optically coupled to the tunable single mode laser at a first port and optically coupled to the Fabry-Pérot semiconductor laser at a second port so that the comb source is configured such that the output from the single mode laser is injected into the lasing cavity of the Fabry-Pérot semiconductor laser with the output of the comb source provided by the Fabry-Pérot semiconductor laser from a third port of the optical circulator.

2. A wavelength tunable optical comb source according to claim 1 , wherein the tunable single mode laser is detuned with respect to the comb output.

3. A wavelength tunable optical comb source according to claim 1 , wherein the tunable single mode laser is detuned with respect to the comb output by a wavelength difference of between 0.01 nm and 0.2 nm.

4. A wavelength tunable comb source according to claim 1 , wherein the tunable single mode laser is configured to provide an optical power output into the lasing cavity of the Fabry-Pérot semiconductor laser in the range of −5 dBm and −20 dBm.

5. A wavelength tunable comb source according to claim 1 , further comprising a polarization controller positioned between the tunable single mode laser and the first port for adjusting the polarization of the light from the tunable single mode laser.

6. A wavelength tunable comb source according to claim 1 , wherein the comb source is configured to prevent light from the Fabry-Pérot semiconductor laser passing to the single mode laser.

7. A comb source according to claim 6 , wherein the comb source is configured to allow the injected light from the single mode laser to enter the cavity of the Fabry-Pérot semiconductor laser through the rear facet of the Fabry-Pérot semiconductor laser.

8. A wavelength tunable comb source according to claim 1 , wherein the single mode laser is selected from one of the following:

a) a single mode laser exhibiting wavelength tunability;

b) a tunable external cavity laser;

c) a sampled grating distributed feedback laser;

d) a grating-assisted co-directional coupler with sampled reflector; and

e) a multi-section slotted Fabry-Pérot laser, and

f) an integrated DFB laser (for example an ITLA laser).

9. A wavelength tunable comb source according to claim 1 , wherein the RF source is provided to as a drive signal to the Fabry-Pérot semiconductor laser with the bias signal through a bias Tee.

10. A wavelength tunable comb source according to claim 1 , further comprising a phase modulator for modulating the comb output with the RF signal from the RF source.

11. A comb source according to claim 10 , further comprising a polarization controller for adjusting the polarization of the comb output before the phase modulator.

12. A wavelength tunable comb source according to claim 10 , further comprising a RF delay for delaying the RF signal provided to the phase modulator.

13. A method of providing a wavelength tunable optical comb comprising the steps of:

a) gain switching a Fabry-Pérot semiconductor laser with a RF signal where the Fabry-Pérot semiconductor laser is biased with a DC bias; and

b) seeding the Fabry-Pérot semiconductor laser with light from a tunable single mode laser by optically coupling an optical circulator comprising at least three ports to the tunable single mode laser at a first port and optically coupling the optical circulator to the Fabry-Pérot semiconductor laser at a second port, wherein the output from the Fabry-Pérot semiconductor laser provides an optical comb output through a third port of the optical circulator.

14. A method of providing a wavelength tunable optical comb in accordance with claim 13 , further comprising detuning the tunable single mode laser from a selected mode of the Fabry-Pérot semiconductor laser.

15. A method of providing a wavelength tunable optical comb in accordance with claim 4 , wherein the tunable single mode laser is detuned with respect to the comb output by a wavelength difference of between 0.01 nm and 0.2 nm.

16. A method of providing a wavelength tunable optical comb according to claim 13 , wherein the tunable single mode laser is operated to provide an optical power output into the lasing cavity of the Fabry-Pérot semiconductor laser in the range of −5 dBm and −20 dBm.

17. A method of providing a wavelength tunable optical comb according to claim 13 , wherein the single mode laser is selected from one of the following:

a) a single mode laser exhibiting wavelength tunability;

b) a tunable external cavity laser;

c) a sampled grating distributed feedback laser;

d) a grating-assisted co-directional coupler with sampled reflector; and

e) a multi-section slotted Fabry-Pérot laser, and

f) an integrated DFB laser (for example an ITLA laser).

18. A wavelength tunable optical comb source comprising:

a) a Fabry-Pérot semiconductor laser having a lasing cavity;

b) a RF source providing a RF signal for gain switching of the Fabry-Pérot semiconductor laser;

c) a DC bias source configured to provide a DC bias current to the Fabry-Pérot semiconductor laser;

d) a tunable single mode laser, wherein the comb source is configured such that the output from the single mode laser is injected into the lasing cavity of the Fabry-Pérot semiconductor laser and the output of the comb source is provided by the Fabry-Pérot semiconductor laser, and wherein the comb source is further configured to prevent light from the Fabry-Pérot semiconductor laser passing to the single mode laser.

19. A wavelength tunable optical comb source comprising:

a) a Fabry-Pérot semiconductor laser having a lasing cavity;

b) a RF source providing a RF signal for gain switching of the Fabry-Pérot semiconductor laser;

c) a DC bias source configured to provide a DC bias current to the Fabry-Pérot semiconductor laser;

d) a tunable single mode laser, wherein the comb source is configured such that the output from the single mode laser is injected into the lasing cavity of the Fabry-Pérot semiconductor laser and the output of the comb source is provided by the Fabry-Pérot semiconductor laser, and

e) a phase modulator for modulating the comb output with the RF signal from the RF source.