BROADBAND ARBITRARY WAVELENGTH MULTICHANNEL LASER SOURCE
A multi-channel laser source, including: a bus waveguide coupled, at an output end of the bus waveguide, to an output of the multi-channel laser source; a first semiconductor optical amplifier; a first back mirror; a first wavelength-dependent coupler, having a first resonant wavelength, on the bus waveguide; a second semiconductor optical amplifier; a second back mirror; and a second wavelength-dependent coupler, on the bus waveguide, having a second resonant wavelength, different from the first resonant wavelength. In some embodiments the first semiconductor optical amplifier is coupled to the bus waveguide by the first wavelength-dependent coupler, which is nearer to the output end of the bus waveguide than the second wavelength-dependent coupler, the second semiconductor optical amplifier is coupled to the bus waveguide by the second wavelength-dependent coupler, and the first wavelength-dependent coupler is configured to transmit light, at the second resonant wavelength, along the bus waveguide.
1 . A multi-channel laser source, comprising:
a bus waveguide coupled, at an output end of the bus waveguide, to an output of the multi-channel laser source;
a first semiconductor optical amplifier;
a first back mirror;
a first wavelength-dependent coupler having a first resonant wavelength;
a second semiconductor optical amplifier;
a second back mirror; and
a second wavelength-dependent coupler having a second resonant wavelength, different from the first resonant wavelength;
the first semiconductor optical amplifier comprising:
a first end coupled to the first back mirror, and
a second end,
the first wavelength-dependent coupler comprising:
a channel port connected to the second end of the first semiconductor optical amplifier;
a bus output connected to a first portion of the bus waveguide; and
a bus input, connected to a second portion of the bus waveguide more distant from the output end of the bus waveguide than the first portion of the bus waveguide;
the second semiconductor optical amplifier being coupled to the bus waveguide through the second wavelength-dependent coupler,
the first wavelength-dependent coupler being nearer to the output end of the bus waveguide than the second wavelength-dependent coupler,
the first wavelength-dependent coupler being configured to transmit light, at the second resonant wavelength, from the bus input of the first wavelength-dependent coupler to the bus output of the first wavelength-dependent coupler.
2 . The multi-channel laser source of claim 1 , further comprising an output coupler at the output end of the bus waveguide, wherein the first wavelength-dependent coupler is configured to transmit light at the first resonant wavelength from the channel port of the first wavelength-dependent coupler to the bus output of the first wavelength-dependent coupler.
3 . The multi-channel laser source of claim 1 , wherein the first wavelength-dependent coupler is configured to reflect a first portion of light received at the first resonant wavelength at the channel port of the first wavelength-dependent coupler, and to transmit, to the bus output of the first wavelength-dependent coupler, a second portion of light received at the first resonant wavelength at the channel port of the first wavelength-dependent coupler.
4 . The multi-channel laser source of claim 3 , wherein the first portion is at least 10% of the light received, and the second portion is at least 40% of the light received.
5 . The multi-channel laser source of claim 1 , wherein the first wavelength-dependent coupler is configured to transmit, to a fourth port of the first wavelength-dependent coupler, light received at the channel port at the second resonant wavelength.
6 . The multi-channel laser source of claim 5 , wherein the fourth port of the first wavelength-dependent coupler is connected to an optical absorber.
7 . The multi-channel laser source of claim 1 , wherein the first back mirror and the first semiconductor optical amplifier are configured as a reflective semiconductor optical amplifier.
8 . The multi-channel laser source of claim 1 , wherein the first wavelength-dependent coupler comprises a first ring resonator.
9 . The multi-channel laser source of claim 8 , wherein the first wavelength-dependent coupler further comprises a second ring resonator, the first ring resonator and the second ring resonator being configured to operate as a vernier ring resonator filter.
10 . The multi-channel laser source of claim 1 , wherein the first wavelength-dependent coupler comprises a grating assisted co-directional coupler.
11 . The multi-channel laser source of claim 10 , wherein the first wavelength-dependent coupler further comprises a distributed Bragg reflector connected in cascade with the grating assisted co-directional coupler.
12 . The multi-channel laser source of claim 1 , wherein the first wavelength-dependent coupler comprises a wavelength actuator for adjusting the first resonant wavelength.
13 . The multi-channel laser source of claim 1 , further comprising a phase shifter between the first back mirror and the first wavelength-dependent coupler.
14 . The multi-channel laser source of claim 1 , further comprising an amplitude modulator between the first back mirror and the first wavelength-dependent coupler.
15 . The multi-channel laser source of claim 1 , wherein the first semiconductor optical amplifier is the same semiconductor optical amplifier as the second semiconductor optical amplifier.
16 . The multi-channel laser source of claim 1 , wherein the first semiconductor optical amplifier comprises a first waveguide in a first semiconductor chip and the second semiconductor optical amplifier comprises a second waveguide in the first semiconductor chip.
17 . The multi-channel laser source of claim 1 , wherein the first semiconductor optical amplifier comprises a waveguide in a first semiconductor chip, and the second semiconductor optical amplifier comprises a waveguide in a second semiconductor chip, different from the first semiconductor chip.
18 . The multi-channel laser source of claim 1 , further comprising:
a wavelength sensor configured to receive a portion of, and to sense a wavelength of, light emitted by the first semiconductor optical amplifier; and
a control system configured:
to receive a wavelength sensing signal from the wavelength sensor,
to calculate a difference between the wavelength sensing signal and a wavelength setpoint, and
to apply a wavelength correction signal to a wavelength actuator, to reduce the difference between the wavelength sensing signal and the wavelength setpoint.
19 . The multi-channel laser source of claim 18 , further comprising a phase shifter between the first back mirror and the first wavelength-dependent coupler, wherein the wavelength actuator comprises the phase shifter.
20 . The multi-channel laser source of claim 18 , wherein the first wavelength-dependent coupler comprises a coupler wavelength actuator for adjusting the first resonant wavelength, wherein the wavelength actuator comprises the coupler wavelength actuator.
21 . The multi-channel laser source of claim 18 , wherein the wavelength sensor is configured to receive light from a fourth port of the first wavelength-dependent coupler.
22 . The multi-channel laser source of claim 18 , wherein the wavelength sensor comprises a Mach-Zehnder interferometer having a first arm and a second arm, longer than the first arm, and a temperature control system configured to control the temperature of a portion of the second arm.
23 . The multi-channel laser source of claim 18 , wherein:
the first semiconductor optical amplifier comprises a waveguide in a first semiconductor chip; and
the wavelength sensor comprises a photodiode, the photodiode being in the first semiconductor chip.
24 . A multiplexed multi-channel laser source comprising:
a first multi-channel laser source according to claim 1 ,
a second first multi-channel laser source according to claims 1 , and
a multiplexer,
the multiplexer comprising:
a first input,
a second input, and
an output,
the multiplexer being configured:
to transmit light from first input to the output, and
to transmit light from second input to the output.