| 摘要 |
PROBLEM TO BE SOLVED: To output an optical 4 value modulation signal, which enhances the multi-level code efficiency, is free from a waveform distortion and stable. SOLUTION: The optical 4 value modulator comprises a laser diode 3 for generating a continuous light, a first driving circuit 2a for outputting a first bit pattern signal which modulates 2 optical values and has a desired first amplitude voltage, a second driving circuit 2b for outputting a second bit pattern signal, different from that of the first driving circuit 2a, which modulates 2 values and has a desired second amplitude voltage, a 2 electrode type Mach- Zehnder optical modulator 1 for intensibly modulating a continuous light generated by the laser diode 3, with the first bit pattern signal, for modulating 2 optical values, to be inputted into a first electrode 1a and the second bit pattern signal, for modulating 2 optical values, to be inputted into a second electrode 1b, and a DC bias applying part 5 for applying DC bias to the second electrode 1b. The sum voltage of the first amplitude voltage and the second amplitude voltage is made to be not more than an amplitude when the 2 electrode type Mach- Zehnder optical modulator 1 carries out 100% modulation. |
