EMI shielding collar with dimpled fingers which may have a lap-joint

An electromagnetic interference collar 50 is mounted via a band portion 60 onto a housing 21 of a pluggable optical transceiver module 20 that can fit into a cage (10 fig 1). Preferably the band has ends forming a lap-joint 80 which may be welded (eg spot or laser welded) and thus caused to tighten as it cools around the housing 21. The collar band carries spring fingers 70 whose outer surface contact the inside of the cage. The fingers have dimples / indentations 100 that provides two contact points 110 (see also fig 6) at each end. These additional contacts results in a reduction in the size of the maximum EMI aperture dimension of the collar, which improves the ability of the collar to attenuate EMI signals, even EMI signals having high frequencies. The dimple length end-to-end is preferably a quarter, more preferably an eighth and most preferably a tenth of the wavelength of an EMI signal to be attenuated.