| 摘要 |
PROBLEM TO BE SOLVED: To provide a steadily stable optical transmission waveform even if the phase of return light changes, in an element which suppresses return light noise by modulating the refractive index of an optical waveguide, by providing the optical waveguide which is coupled optically with the active region of an external modulator integrated semiconductor laser.SOLUTION: A distributed feedback laser 101 is used as a light source, and an electroabsorption modulator 102 is used as an outer modulator. The rear exit section of DFB-LD 101 is connected with an optical waveguide 103 transmitting the oscillation light of the DFB-LD 101, and terminated with a metal reflective surface 104. Output voltage amplitude Vf of BPF 113 is compared with the GND potential Vr by a comparator 114, and a PID controller 115 operates the deviation of the output voltage amplitude Vf from a target value, i.e., the GND potential Vr, and outputs a signal correlated with the deviation to a control waveguide drive circuit 116. The control waveguide drive circuit 116 outputs a voltage Vcnt applied to a control waveguide 103 on the basis of the output signal from the PID controller 115. |
