Patent ID: 7945171

Claim:
An optical code division multiplexing transmission method, comprising: an encoding step of encoding an optical pulse signal by using an encoding optical phase code to generate an encoded optical pulse signal; and a decoding step of decoding said encoded optical pulse signal by using a decoding optical phase code to generate an autocorrelation waveform of the optical pulse signal, said decoding optical phase code being based on said encoding optical phase code, wherein said encoding step and said decoding step are executed by using optical pulse time spreaders, each of which time-spreads an optical pulse to form a series of chip pulses that are sequentially arranged on a time axis to provide a chip pulse stream, by using encoding that employs an optical phase code, and that outputs said chip pulse stream, and wherein each optical pulse time spreader includes an optical waveguide having a phase control means for generating said chip pulse stream, wherein said phase control means comprises a plurality of unit diffraction gratings having a periodic refractive index modulation structure that are arranged in a row and correspond one for one with code values constituting said optical phase code, said unit diffraction gratings being arranged in series in a waveguide direction of the optical waveguide, and wherein the phase difference of Bragg reflected light from two unit diffraction gratings that adjoin one another from front to back and provide equal code values is given by: 2πM+(π/2) (expression 1), and the phase difference of Bragg reflected light from two unit diffraction gratings that adjoin one another from front to back and provide different code values is given by: 2πM+(2N+1)π+(π/2) (expression 2) (where M and N are integers).