Each of optical fibers has a core and stress applying members disposed around the core. In an exemplary method, a substrate is provided which includes a first material and a second material. The shadow cache lines are provided with additional entries so that if newly referenced data is added to a particular local cache line by \u201csilently\u201d removing an entry in the local cache line, the newly referenced data may be added to the shadow cache line without forcing the \u201cblind\u201d removal of an entry in the shadow cache line. The bracket is attached to the first retaining member. This system is particularly suitable for use in ADSL and VDSL modems which can be used to give broad band access over copper networks.