Patent ID: 7974541
Filing Date: 2011-07-05
Classification: H04B

Abstract:
1. A high frequency signal optical transmission system that transmits a high frequency signal over a long distance by an optical fiber, comprising: two-lightwave generating means for generating an optical signal of a first wavelength and an optical signal of a second wavelength which are apart from each other by a frequency of a first microwave signal from an input laser beam by using the first microwave signal that is the high frequency signal; light distributing means for distributing two optical signals that are generated by the two-lightwave generating means; light direction converting means for changing a direction of one of the two optical signals which are distributed by the light distributing means, guiding the two optical signals including the optical signal of the second wavelength whose phase is controlled to the optical fiber, changing directions of the two optical signals that are returned from a receiving side by the optical fiber, and guiding the two optical signals including the optical signal of the second wavelength whose phase is again controlled to a direction different from the optical fiber; phase shift control means for controlling the phase of the optical signal of the second wavelength in the two optical signals to be transmitted which are guided by the light direction converting means based on a calculated phase difference to return the optical signal to the light direction converting means, and controlling the phase of the optical signal of the second wavelength in the two optical signals that are guided by the light direction converting means and returned from the receiving side to return the optical signal to the light direction converting means; receiving side processing means for detecting a difference frequency of the two optical signals that are transmitted by the optical fiber as a second microwave signal, frequency-shifting the transmitted two optical signals by a third microwave signal, and rotating polarization by 90 degrees to guide the two optical signals to the optical fiber; and phase calculating means for mixing two optical signals including the remaining one of the two optical signals which are distributed by the light distributing means and the optical signal of the second wavelength that is guided by the light direction converting means, returned from the receiving side, and again controlled in phase together, splitting the mixed signal into the optical signal of the first wavelength and the optical signal of the second wavelength, detecting a beat frequency of the microwave signals of the first wavelength and the second wavelength, and calculating a phase difference between the first microwave signal and the second microwave signal to output a calculation result to the phase shift control means.