The nature of pairing mechanism and the superconducting state of bi-layer o
ptimised hole doped Yttrium based cuprates have been theoretically investig
ated using the strong coupling theory. An interaction potential is set up w
hich incorporates various interactions as hole-hole, hole-phonon and hole-p
lasmon with proper layered structure of the system. For the admissible valu
e of interlayer phonons the deduced value of coupling strength favours the
strong coupling regime and screening parameter infers the effective screeni
ng of holes as carriers. The transition temperature with the use of model c
oupling parameters is estimated as T-c(Ph) = 73.45 K. Incorporating the 2-D
acoustic plasmons the T,, enhances to 90 K, which is in the measured range
. The approach is further applied Co evaluate the isotope exponent and the
reduced total isotope exponent suggests a transition from phonon mediated s
uperconductivity to dual phonon-electronic boson mechanism in high-T-c Yttr
ium based systems. The energy gap ratio is substantially larger than BCS ra
tio and infers that the strong coupling effects are important. The implicat
ions of the cc-operative phonon-plasmon approach are discussed.