[time-nuts] RTC DS3231: how well can it be regulated?

[MLewis]

I was watching the PPS LED on my M8T board vs. the LED I put on the RTC 
DS3231's SQW output enabled for 1 Hz for a PPS. As expected they're not 
aligned, and the drift of that misalignment shows they're obviously not 
at the same frequency.

It got me wondering. Between the DS3231's Aging Trim, insulating and 
perhaps a heater for some temperature control, does anyone know if the 
DS3231's PPS could be synced and stabilized into a reasonable PPS source 
through an opto-isolator?

Might a fibre-optic line be useful as a transmission cable, gapping two 
LEDs functioning as an opto-isolator, thereby providing both isolation 
and high-speed coupling for the PPS to the device that wants to read the 
PPS?

I don't know if the onboard temperature sensor is precise/stable enough 
to be useful for maintaining a stable temperature with a heater. It's 
accuracy is listed as +/- 3 C, but that doesn't speak to the stability 
of the temperature it reports.

The SQW output can be set to 1 Hz, 1.025 kHz, 4.096 kHz or 8.192 kHz.

It also has a 32 kHz output pin. I don't know if that's actually 32 kHz 
or 2^15 = 32,768 Hz.
Ah, there it is. "outputs a 32.768kHz square-wave signal".

Has anyone done this, or does it seem like it may be worthwhile?

Thanks,

Michael