| 摘要 |
A modulator arrangement comprises two Mach-Zehnder modulators, a main modulator (2) and a compensation modulator (3) having non-linear transmission functions. The modulators (2, 3) are controlled by a modulating control signal (V), via electrodes (16, 17). A carrier wave (S1) from a laser (7) is power divided (a, 1-a) into part-waves in a power divider (5) between the modulators (2, 3). The modulated part-waves (S2, S3) are superimposed at an output (14) to produce a resultant modulated wave (S4). A linearized transmission function between the control voltage (V) and the power of the resultant modulated wave (S4) has a radius of curvature whose length is maximized within a control voltge range, so as to minimize intermodulation distortion. The mean slope of the transmission function is maximized within this range. At a common control voltage (V) for the modulators (2, 3), the modulator arrangement has an optimal transmission function at a length ratio b = 2ROOT 3:1 between the modulators (2, 3), and a power ratio between the part-waves of 2ROOT 3:9. The main modulator (2) is the shortest and modulates the strongest part-wave. |
