Reference values give a good indication that the sources are operating as expected. They DO NOT give any assurance that the test reference cords are good. If you are reading this article because you are getting negative loss readings, you should review this article.
As a guide, when setting a reference, you should expect better than:
- DTX-SFM2: -5.5 dBm ～ -8.0 dBm
where -6.5 dBm is better than -8.0 dBm.