This article clarifies that in Junos Fusion, the SFP-1000BASE-BX10-U optics will not work in EX4300 satellite devices because they are not detected by the device. No workaround is currently available for this problem.

The SFP-1000BASE-BX10-U optics will work in EX4300 stand-alone devices but not in EX4300 satellite devices. At present, support is not available for SFP-1000BASE-BX10-U optics to be used in EX4300 satellite devices. There is also no workaround currently available for this.