| 摘要 |
PROBLEM TO BE SOLVED: To easily optimize a working point when the working point of an intensity modulator needs to be reviewed.SOLUTION: In an intensity modulator 100, a first light intensity detection unit 102 outputs a signal representing the intensity of light from a Mach-Zehnder optical modulation unit 101. A DC bias output unit 302a outputs the DC component of a bias voltage to the intensity modulator 100. A low-frequency signal output unit 303a outputs a low-frequency signal to the intensity modulator 100 as the AC component of the bias voltage. A synchronous detection unit 301A performs synchronous detection on the output from the first light intensity detection unit 102 using the low-frequency signal as a reference signal. Feedback control using the detection signal obtained by the synchronous detection unit 301A is exercised in the DC bias output unit 302a. A phase setting unit 305 sets a phase difference between the phase of the low-frequency signal inputted to the intensity modulator 100 and the low-frequency signal inputted to the synchronous detection unit 301A.SELECTED DRAWING: Figure 1 |
