Methods to reduce radiated emissions from optical transceivers

Telecommunication network equipment extensively uses optical transceivers to convert electrical signals into lightwave and vice-versa. The aperture (ferrule) of the transceiver where fiber will be attached cannot be completely RF shielded to prevent radiation in the frequency range of 8 to 40 GHz. Most telecommunication equipment is designed to operate in a frame without doors or covers and therefore, radiation must be stopped at circuit pack level in order to meet the regulatory and customer imposed radiated emission requirements. The radiation levels from optical transceivers increase with data-rate, transmit optical power-level, and fiber impedance. Transceivers of different manufacturers may be used in optical network platforms to increase the data throughput and rate. The radiated emissions emanating from transceivers are found to be different depending on their type and manufacturer. This paper discusses downward angular installation methods to reduce radiated emission levels from transceivers so that equipment has extra margin to compensate for increased radiated emission levels from certain transceivers. A theoretical calculation of transceiver placement angle to lower radiated emissions is presented. Also presented and results discussed is experimental data for different downward angular placement for a simulated transceiver and for transceivers installed in network equipment.