Optical receivers
A packaged optical receiver, comprising: a photodiode configured to receive an optical signal; a transimpedance amplifier (TIA) coupled to the photodiode; and a signal pin; wherein the optical receiver is configured to receive, via the signal pin, a reset signal; and wherein the optical receiver is configured to output in response to the reset signal, via the signal pin, a received signal strength indication (RSSI) for the received optical signal.
1. A packaged optical receiver, comprising:
a photodiode configured to receive an optical signal;
a transimpedance amplifier (TIA) coupled to the photodiode; and
a signal pin;
wherein the optical receiver is configured to receive, via the signal pin:
a reset signal; and
a rate select signal indicating a bit rate of the received optical signal, the rate select signal switchable between a first voltage indicative of a first bit rate of the received optical signal and a second voltage indicative of a second bit rate of the received optical signal different from the first bit rate; and
wherein the optical receiver is configured to output in response to the reset signal, via the signal pin, a received signal strength indication (RSSI) for the received optical signal.
2. The optical receiver of claim 1 , wherein a sensitivity of the transimpedance amplifier is adjusted based on the rate select signal.
3. The optical receiver of claim 1 , wherein, on a first transition of the reset signal, the optical receiver is configured to sample the rate select signal received before the first transition of the reset signal.
4. The optical receiver of claim 1 , wherein the first voltage and the second voltage are lower than a reset voltage of the reset signal.
5. The optical receiver of claim 1 , further comprising:
a first comparator having a first inverting input coupled to a first reference voltage; and
a second comparator having a second inverting input coupled to a second reference voltage;
wherein a first non-inverting input of the first comparator and a second non-inverting input of the second comparator are coupled to the signal pin.
6. The optical receiver of claim 5 , further comprising a flip-flop having:
a clock input coupled to a first output of the first comparator;
a data input coupled to a second output of the second comparator; and
a digital rate select output.
7. The optical receiver of claim 6 , further comprising a delay element coupled between the data input and the second output of the comparator.
8. The optical receiver of claim 1 , wherein the optical receiver is configured to output the RSSI at the signal pin after a first transition of the reset signal.
9. The optical receiver of claim 1 , comprising:
current driver circuitry configured to output the RSSI at the signal pin in response to an enable signal.
10. The optical receiver of claim 9 , wherein the current driver circuitry comprise:
a switch; and
a load resistor coupled between the switch and a ground reference voltage, wherein the switch is configured to switch the RSSI from the load resistor to the signal pin in response to the enable signal.
11. The optical receiver of claim 10 , wherein the switch comprises a differential pair of switches.
12. A packaged optical receiver, comprising:
a photodiode configured to receive an optical signal;
a transimpedance amplifier (TIA) coupled to the photodiode;
current driver circuitry; and
a signal pin;
wherein the optical receiver is configured to receive, via the signal pin, a reset signal; and
wherein the current driver circuitry is configured to output in response to the reset signal, via the signal pin, a received signal strength indication (RSSI) for the received optical signal.