Overall pictures
Back
Front
Waveforms
Tx
This is the voltage on the cathode of the transmit laser, or TX0/pin 7 of the OPT3101 :
The overall repetition rate is ~4kHz which matches up with the datasheet. The inner modulation frequency is 10.4MHz.
Rx
It’s not possible to probe the Rx directly:
So I removed the RF can:
Probing anywhere within the photodiode area (either side, or on the cap) gives a signal like this:
This looks kind of promising until you realize:
- It does not change phase or amplitude with range
- It’s only the higher harmonics
- Actually, you see the same thing probing from the outer ground to the photodiode can ground (they are separate) So this is clearly just crosstalk from the Tx, which is a shame.
I don’t think this would be possible to probe then without a diff probe directly on the package pins or something like that.
Not much else to learn here really. The whole product is a pretty standard implementation of the TI OPT3101, so reading the datasheet would tell you everything about this product.