| 摘要 |
An optical transceiver having a transimpedance amplifier with an in-situ optical power meter is disclosed which realizes that the common mode voltage of a peak-to-peak voltage signal derived from impinging light is related to the optical power of the impinging light. The peak-to-peak voltage signals, moreover, can be imposed on the common mode voltage so that the optical power measurements can be derived with existing electrical contacts. In the preferred embodiment, the optical power meter takes advantage of certain functions within a transimpedance amplifier of the optical receiver. First, the use of an nfet and a capacitor smooth the peak-to-peak voltage to create the control signal for the common mode voltage. Then the common mode current is mirrored into a bank of pfets at the output stage to create a current sink. Depending upon the potential of the common mode voltage, more or less current will be drawn from the peak-to-peak voltage signals that are output from a final differential amplifier stage of the transimpedance amplifier. If there are no limitations regarding the number of outputs from the transimpedance amplifier, the common mode voltage can be output directly. Alternatively, a decoding circuit in a post amplifier can extract the common mode voltage from the peak-to-peak voltage and provide an optical power signal to a host interface. Under the circuit specifications shown herein, the common mode voltage is accurately linear to the optical power of the received light.
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