| 摘要 |
A method of controlling the depth of modulation of an optical source in a frequency shift keyed intensity modulation optical transmitter, the method including the steps of impressing on a digitally modulated drive signal for the source an amplitude modulation at a first frequency less than that of the digital signal, impressing on the digital signal a dither modulation at a second frequency less than that of the first frequency, extracting at 26 from the transmitter output the second harmonic of the first frequency, multiplying the second harmonic with the second frequency and driving therefrom a control signal to control the depth of modulation of the source. <IMAGE>
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