| 摘要 |
<P>PROBLEM TO BE SOLVED: To perform the synchronous detection of a QAM signal without using a pilot signal, in an optical receiving circuit. <P>SOLUTION: The optical receiving circuit performs heterodyne detection using local oscillation light having a wavelength nearly equal to the wavelength of a received signal, samples the detected output with a clock signal extracted from the received optical signal, selects a symbol having a prescribed amplitude from the sampling output, finds the phase difference between a carrier of the received optical signal and the local oscillation light on the basis of a sampling output corresponding to the selected symbol, and demodulates data from the phase difference and the sampling output. <P>COPYRIGHT: (C)2009,JPO&INPIT |
