Do optical modules in data center switches cause RE radiation issues?

Although the optical modules of data center switches transmit signals via fiber optic cables, the metal casing of the SFP cage, connected to the PCB ground, may couple digital noise, becoming a source of radiation. Measured near-field radiation intensity of a 10G SFP+ module at the 625MHz clock harmonic frequency reached 75dBμV/m, coupled to the motherboard ground plane through the cage pins. Suppression measures: A 90V SMD1812-091 gas discharge tube from EAST Electronics was connected in series between the SFP cage and signal ground to provide ESD discharge and isolate high-frequency noise; the contact resistance between the cage fixing spring and the chassis ground was <5mΩ; a PBZ1608A-600Z0T ferrite bead (60Ω@100MHz) was added to the power pins. After rectification, the overall radiation at the 625MHz frequency point decreased by 16dB, meeting the Class B limit.