shown in fig2 similarly the pon 14 has three levels of split including a first splitter 26 associated with the ring 18 and having a 2 u00d7 4 way split the second level of split is constituted by four splitters 27 each having a 16 way split the third level of split is constituted by sixteen splitters 28 each having a 16 way split the splitters 28 can be considered as dps respective optical fibres 29 lead from each of the splitters 28 to associated customer premises 30 for reasons of clarity not all the splitters 26 27 and 28 and the associated fibres and customer premises are shown in fig2 in order to provide resilience some of the customer premises of the ring 15 identified by the reference numerals 25 39 are connected to nearby splitters 28 of the ring 18 by respective optical fibres 24 39 similarly some of the customer premises of the ring 18 identified by the reference numerals 30 39 are connected to nearby splitters of the ring 15 by respective optical fibres 29 39 the customer premises 25 39 and 30 39 are therefore each connected to both the rings 15 and 18 thereby ensuring that those premises receive service if their main fibres 24 and 29 fail or if.