Modulated light source

1. A modulated light source comprising:

an optical amplifier which includes a reflective film at one end;

a light wavelength filter which has band-pass characteristics and modulates a transmission center wavelength;

a light reflection mechanism which feeds back light having passed through the light wavelength filter to the optical amplifier and an optical resonator is formed between which and the reflective film; and

a wavelength adjustment mechanism which adjusts the transmission center wavelength to coincide with a specific oscillation wavelength when light oscillation selectively occurs at the specific oscillation wavelength depending on the band-pass characteristics of the light wavelength filter,

wherein the light wavelength filter is a ring modulator including a P-type doping region and an N-type doping region in a ring-state optical waveguide, and a modulation electrode applying a reverse bias voltage or a forward bias voltage between the P-type doping region and the N-type doping region in accordance with a modulation signal.

2. The modulated light source according to claim 1 ,

wherein the light wavelength filter has a transmission band in which the specific oscillation wavelength is selected from among a plurality of oscillation wavelengths each having a wavelength spacing determined by an optical path length of the resonator and light oscillation occurs at the specific oscillation wavelength.

3. The modulated light source according to claim 1 ,

wherein the wavelength adjustment mechanism includes: a detection part which detects a light power at the optical resonator; and a control part which outputs a control signal corresponding to an adjustment amount of the transmission center wavelength to make the transmission center wavelength coincide with the specific oscillation wavelength based on the light power detected by the detection part.

4. The modulated light source according to claim 3 ,

wherein the wavelength adjustment mechanism includes a heater part which heats the light wavelength filter in accordance with the control signal.

5. The modulated light source according to claim 1 ,

wherein the light wavelength filter is a ring modulator including a first modulation electrode which modulates the resonant wavelength based on a modulation signal in accordance with an intensity of the modulation signal.

6. The modulated light source according to claim 3 ,

wherein the light wavelength filter is a ring modulator including a first modulation electrode which modulates the resonant wavelength based on a modulation signal in accordance with an intensity of the modulation signal and a second modulation electrode to which the control signal is input.

7. The modulated light source according to claim 1 ,

wherein the light wavelength filter has two kinds of optical waveguides:

one of the optical waveguides corresponds to the light wavelength filter and the light reflection mechanism is disposed at one end; and

one end of the other of the optical waveguides is an output port and the other end is connected to the optical amplifier.

8. The modulated light source according to claim 1 , further comprising:

a plurality of light modulation units which each include a light wavelength filter, a light reflection mechanism, and a wavelength adjustment mechanism,

wherein in the plurality of light modulation units,

the resonant wavelengths of the respective light wavelength filters are set to different values, and

the respective wavelength adjustment mechanisms adjust the respective resonant wavelengths to coincide with a plurality of specific oscillation wavelengths when light oscillations selectively occur at the plurality of specific oscillation wavelengths depending on the band-pass characteristics of the respective light wavelength filters.

9. The modulated light source according to claim 1 , further comprising:

a plurality of light modulation units which each include a light wavelength filter and a wavelength adjustment mechanism,

wherein in the plurality of light modulation units,

the optical amplifier includes a plurality of optical amplification waveguides;

each light wavelength filter corresponds to each optical amplification waveguide and the resonant wavelengths are set to different values; and

the respective wavelength adjustment mechanisms adjust the respective resonant wavelengths to coincide with a plurality of specific oscillation wavelengths when light oscillations selectively occur at the plurality of specific oscillation wavelengths depending on the band-pass characteristics of the respective light wavelength filters.

10. The modulated light source according to claim 9 ,

wherein the light reflection mechanism is provided in common to the plurality of light modulation units.

11. The modulated light source according to claim 9 ,

wherein each light wavelength filter has two kinds of optical waveguides;

the light reflection mechanism is disposed at one end of one of the optical waveguides, and the other end is an output port; and

the other of the optical waveguides corresponds to each of the light wavelength filters, and one end of the optical waveguide is connected to each optical amplification waveguide.