Optical receiver and optical reception method
An optical receiver includes: an interference unit generating a first interference light signal (ILS 1 ) and a second interference light signal (ILS 2 ) with an approximately inverse phase to that of the first interference light signal, by causing a received light signal to interfere with local oscillator light; a first interference light subtraction unit generating a first interference light subtraction signal (ILSS 1 ) representing the difference between signals obtained by photoelectric conversion of ILS 1 and a local oscillator light proportional signal having light intensity based on the light intensity of the local oscillator light; a second interference light subtraction unit generating a second interference light subtraction signal (ILSS 2 ) representing the difference between a signal obtained by photoelectric conversion of ILS 2 and the signal obtained by photoelectric conversion of the local oscillator light proportional signal; and a difference output unit outputting a signal representing the difference between ILSS 1 and ILSS 2.
1. An optical receiver comprising:
an interference unit which generates a first interference light signal and a second interference light signal with an approximately inverse phase to that of the first interference light signal, by causing a received light signal to interfere with local oscillator light;
a first interference light subtraction unit which generates a first interference light subtraction signal representing the difference between a signal obtained by photoelectric conversion of the first interference light signal and a signal obtained by photoelectric conversion of a light signal having a light intensity based on the light intensity of the local oscillator light;
a second interference light subtraction unit which generates a second interference light subtraction signal representing the difference between a signal obtained by photoelectric conversion of the second interference light signal and a signal obtained by photoelectric conversion of the light signal having the light intensity based on the light intensity of the local oscillator light; and
a difference output unit which outputs a signal representing the difference between the first interference light subtraction signal and the second interference light subtraction signal.
2. The optical receiver according to claim 1 , wherein
the difference output unit is configured by a differential amplification unit which amplifies and subsequently outputs the signal representing the difference.
3. The optical receiver according to claim 1 , wherein
the interference unit generates the light signal having the light intensity based on the light intensity of the local oscillator light by attenuating the local oscillator light to adjust intensity of the local oscillator light, and outputs the generated light signal to the first interference light subtraction unit and the second interference light subtraction unit.
4. The optical receiver according to claim 1 further comprising
an optical attenuating unit which generates the light signal having the light intensity based on the light intensity of the local oscillator light by attenuating the local oscillator light to adjust intensity of the local oscillator light, and outputs the generated light signal to the first interference light subtraction unit and the second interference light subtraction unit.
5. The optical receiver according to claim 1 , wherein,
in at least one of the first interference light subtraction unit and the second interference light subtraction unit, the capacitance of a photodetection unit for performing photoelectric conversion of the light signal having the light intensity based on the light intensity of the local oscillator light is smaller than the capacitance of a photodetection unit for performing photoelectric conversion of either the first or second interference light signals.
6. The optical receiver according to claim 1 , wherein
the light intensity of the light signal having the light intensity based on the light intensity of the local oscillator light is smaller than the light intensity of the local oscillator light.
7. The optical receiver according to claim 1 , wherein
at least one of the first interference light subtraction unit and the second interference light subtraction unit is formed in a single substrate.
8. An optical reception method comprising:
generating a first interference light signal and a second interference light signal with an approximately inverse phase to that of the first interference light signal, by causing a received light signal to interfere with local oscillator light;
generating a first interference light subtraction signal representing the difference between a signal obtained by photoelectric conversion of the first interference light signal and a signal obtained by photoelectric conversion of a light signal having a light intensity based on the light intensity of the local oscillator light;
generating a second interference light subtraction signal representing the difference between a signal obtained by photoelectric conversion of the second interference light signal and a signal obtained by photoelectric conversion of the light signal having the light intensity based on the light intensity of the local oscillator light; and
outputting a signal representing the difference between the first interference light subtraction signal and the second interference light subtraction signal.
9. The optical reception method according to claim 8 , wherein
the light signal having a light intensity based on the light intensity of the local oscillator light is generated by attenuating the local oscillator light to adjust its intensity.
10. An optical receiver comprising:
an interference unit which generates a first interference light signal and a second interference light signal with an approximately inverse phase to that of the first interference light signal, by causing a received light signal to interfere with local oscillator light;
a first interference light subtraction unit which generates a first interference light subtraction signal representing the difference between a signal obtained by photoelectric conversion of the first interference light signal and an electrical signal having an intensity based on the light intensity of the local oscillator light;
a second interference light subtraction unit which generates a second interference light subtraction signal representing the difference between a signal obtained by photoelectric conversion of the second interference light signal and the electrical signal having the intensity based on the light intensity of the local oscillator light; and
a difference output unit which outputs a signal representing the difference between the first interference light subtraction signal and the second interference light subtraction signal.
11. The optical receiver according to claim 2 , wherein
the interference unit generates the light signal having the light intensity based on the light intensity of the local oscillator light by attenuating the local oscillator light to adjust intensity of the local oscillator light, and outputs the generated light signal to the first interference light subtraction unit and the second interference light subtraction unit.
12. The optical receiver according to claim 2 further comprising
an optical attenuating unit which generates the light signal having the light intensity based on the light intensity of the local oscillator light by attenuating the local oscillator light to adjust intensity of the local oscillator light, and outputs the generated light signal to the first interference light subtraction unit and the second interference light subtraction unit.
13. The optical receiver according to claim 2 , wherein,
in at least one of the first interference light subtraction unit and the second interference light subtraction unit, the capacitance of a photodetection unit for performing photoelectric conversion of the light signal having the light intensity based on the light intensity of the local oscillator light is smaller than the capacitance of a photodetection unit for performing photoelectric conversion of either the first or second interference light signals.
14. The optical receiver according to claim 3 , wherein,
in at least one of the first interference light subtraction unit and the second interference light subtraction unit, the capacitance of a photodetection unit for performing photoelectric conversion of the light signal having the light intensity based on the light intensity of the local oscillator light is smaller than the capacitance of a photodetection unit for performing photoelectric conversion of either the first or second interference light signals.
15. The optical receiver according to claim 4 , wherein,
in at least one of the first interference light subtraction unit and the second interference light subtraction unit, the capacitance of a photodetection unit for performing photoelectric conversion of the light signal having the light intensity based on the light intensity of the local oscillator light is smaller than the capacitance of a photodetection unit for performing photoelectric conversion of either the first or second interference light signals.
16. The optical receiver according to claim 2 , wherein
the light intensity of the light signal having the light intensity based on the light intensity of the local oscillator light is smaller than the light intensity of the local oscillator light.
17. The optical receiver according to claim 3 , wherein
the light intensity of the light signal having the light intensity based on the light intensity of the local oscillator light is smaller than the light intensity of the local oscillator light.
18. The optical receiver according to claim 4 , wherein
the light intensity of the light signal having the light intensity based on the light intensity of the local oscillator light is smaller than the light intensity of the local oscillator light.
19. The optical receiver according to claim 5 , wherein
the light intensity of the light signal having the light intensity based on the light intensity of the local oscillator light is smaller than the light intensity of the local oscillator light.
20. The optical receiver according to claim 2 , wherein
at least one of the first interference light subtraction unit and the second interference light subtraction unit is formed in a single substrate.