Hi Daniel,
We have been looking into this issue and have written an investigation report on the matter which includes our best guess at the issue, attempted solutions that won’t work, and workarounds for you to use as we further investigate the issue: Known Issue Report: GigaBlox SFP Compatibility Issue with Standard 1000BASE-X Switches
So far, the issue only seems to be presenting itself between certain specific third-party switches. We actually tested the UMC-GA1F2T switch in particular, and we were able to replicate the issue. The problem appears to be related to 1G serial PCS/SerDes interoperability rather than optical power, wavelength, fiber type, or cable quality, which means changing out the SFPs probably won’t help. Our current theory is that some link partners expect a specific serial link behavior, including auto-negotiation, in-band status, ordered sets, and link-up sequencing. Some devices are tolerant or auto-detect the mode successfully, while others require a stricter sequence and may not establish link with GigaBlox SFP. In simplest terms, both the chip on the GigaBlox SFP and the chip on the UMC-GA1F2T are slightly ‘picky’ in their serial link protocol, while other third-party switches (with newer chips) are less intolerant and therefore link up properly. More details can be found in the report.
For now, hopefully you can try one of the workarounds. During our testing, we also ordered a similar third-party switch (Omada TP-Link MC220L) and that one links up fine with GigaBlox SFP, but I’m not sure if that switch fits the specs you need for your design. In case it doesn’t, we recommend using the other GigaBlox SFP in place of your third-party switch.
Hope this helps!