thereon however in the arrangement of fig3 insulation 122 is divided into a first inner layer 122 a and a second outer layer 122 b in a first arrangement inner layer 122 a is made from a solid pei pvc polyolefin etc material typically a polymer which has a low dielectric constant and which is good for electrical performance and ideally with good with flame retardant properties outer layer 122 b is then made from foamed polysulfone psu in such an arrangement the polysulfone outer layer 122 b will generally be of the same material type as in the example shown above in fig2 however it is possible that the void percentage in the foam can be increased due to inner layer 122 a being used as a support structure in one exemplary embodiment the thicknesses of layers 122 a and 122 b may depend on the cable design and electrical criteria however in one exemplary design the ratio of thicknesses is 20 80 and vice versa generally the thickness of inner layer 122 a is about 0 004 u2033 to 0 008 u2033 and the thickness of outer layer 122 b is about 0 004 u2033 to 0 008 u2033 such a dual layer insulation 122 a 122 b should be slightly smaller than its solid counter part due to the foaming of the insulation allows a reduction in od outside diameter of the cable while still achieving the same electrical results in the case of using polyolefins as solid material for inner layer 122 a and foamed polysulfone as outer layer 122 b the polyolefin can provide good electrical properties and increased crush resistance at a low cost for inner layer 122 a without have to worry.