Phase lock loop circuit using optical correlation detection

Optical correlation detecting circuit comprising:

• optical combining means for combining an optical signal pulse and an optical clock pulse possessing a sufficiently narrow pulse width including nth harmonics, n being a natural number, component of a repetition frequency;
• optical fiber for outputting a product of intensities of said optical signal pulse and said optical clock pulse;
• and
• optical splitting means for extracting from an optical output signal of said optical fiber only a correlation component of said optical signal pulse and said optical clock pulse;
• wherein, said optical signal and said optical clock respectively possess wavelengths in a vicinity of a zero dispersion wavelength of said optical fiber.

Optical correlation detecting circuit comprising:

• optical combining means for combining an optical signal pulse and an optical clock pulse possessing a sufficiently narrow pulse width including nth harmonics, n being a natural number, component of a repetition frequency;
• optical fiber for outputting a product of intensities of said optical signal pulse and said optical clock pulse;
• and
• optical splitting means for extracting from an optical output signal of said optical fiber only a correlation component of said optical signal pulse and said optical clock pulse;
• wherein a loop is formed by optically coupling said optical combining means, said optical fiber, and said optical splitting mean, and wherein said optical combining means separately includes a means for receiving said optical signal pulse and means for receiving said optical clock pulse.