I understand that most ports that support SFP+ transceivers can step down to allow an SFP to be plugged into it, but my question is around the transceivers/optics themselves. Can an SFP+ transceiver run at 1GbE, for example a 10GBASE-SR SFP+, or would the only solution be to get an SFP specifically?
My understanding is that, SFP+ transceivers should be used for 10GbE and SFP for 1GbE and this lack of backward compatibility is one of the few reasons 10GBASE-T is appealing (due to auto-negotiation).
UPDATE - It appears that there are some dual-rate optics out there. Link to Finisar's offering: https://www.finisar.com/sites/default/files/downloads/finisar-ftlx8574d3bcv-1g-10g-850nm-multimode-datacom-sfp-transceiver-product-specification-revb.pdf