| 摘要 |
<p>The optical transmitter described contains a laser diode (2) and a photodiode (3) optically coupled with it as a monitor diode. The photocurrent of the monitor diode (3) is used for controlling the light power of the laser diode (2). The optical transmitter also contains modulators for modulating the laser diode current (IL) with an information signal (bn) and a pilot signal (Bk). To prevent, among other things, jitter in the light signal, the following are provided: 1.1 Means for multiplying (7a, 7b) a control current (Is) by the information signal (bn), the control current (Is) being a direct current modulated with the pilot signal (Bk), 1.2 Filter means (11, 12) by means of which the amplitude of that component of the photocurrent of which the frequency corresponds to the fundamental frequency of the pilot signal (Bk) is isolated, and means (8, 9, 10, U1, 17) for controlling the amplitude of the alternating component of the control current (Is) in such a manner that the amplitude of the said component in the photocurrent of the monitor diode (3) remains constant, 1.3 Means (16. 18.19) by means of which the modulation percentage of the control current (Is) is kept constant and 1.4 Filter means (21) by means of which the direct component of the photocurrent of the monitor diode is determined, and means (21, 22, U2, 23, 20) for controlling the bias current (Iv) of the laser diode (2) in such a manner that the direct component of the photocurrent also remains constant. <IMAGE></p> |
