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Control circuit for control of the extinction ratio of a semiconductor laser
Control circuit for control of the extinction ratio of a semiconductor laser
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机译:用于控制半导体激光器的消光比的控制电路
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摘要
In an optical communications system, it is necessary to control the extinction ratio of a laser device (192) of an optical transmission unit. The laser device (192) is typically used to transmit a signal that can be approximated by a pseudo-random bit stream. The bit stream is monitored by collecting light from a back facet of the laser device (192) using a photodiode (194) in a control loop. Due to band limiting effects of the photodiode (194) and parasitic circuit track capacitances, a feedback signal generated by the photodiode (194) becomes distorted, leading to difficulties in controlling the extinction ratio. The present invention therefore provides an apparatus that simulates a signal generated by the photodiode (194) and subsequent processing of the photodiode signal. The simulated signal and the processed photodiode signal are compared so as to generate a control signal for controlling modulation amplitude of the laser device (192) and hence the extinction ratio.
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