Fluctuation induced conductivity (FIC) analysis on dc resistivity versus temperature data of as-prepared and oxygen post-annealed <$Eroman {TlBa sub 2 (Ca} sub 2-y {roman Mg} sub y ) Cu sub 3 O sub {10- delta }> (y = 0, 0,25, 0,5, 0,75, 1,0) superconductor samples are carried out by using Aslamazov - Larkin model for excess conductivity. The microscopic parameters such as zero temperature coherence length along c axis {<$Exi sub c (0)>}, interlayer coupling (J), intergrain coupling (<$Ealpha>), critical exponent (<$Elambda>) and dimensionality of superconducting fluctuations are calculated with the help of aforementioned model. The crossover temperature (To) is shifted towards higher temperature values with the increase of Mg contents up to y = 0,5 and then start to decrease but still remains greater than those values of undoped samples. The increase in <$Exi sub c (0)> and J after Mg-doping at Ca sites shows the improvement of interplane coupling in <$Eroman {TlBa sub 2 (Ca} sub 2-y {roman Mg} sub y ) Cu sub 3 O sub {10- delta }> samples. The appreciable change in all the microscopic parameters extracted from the FIC analysis indicates the optimization of oxygen in all the oxygen post-annealed samples. The increase in relative intensity of almost all the oxygen modes indicates the oxygen diffusion in the unit cell after oxygen post-annealing. The diffusion of oxygen can take place at intergranular sites along with intragranular sites, which increases the grains size, intergrain connectivity and carrier density in CuO2 planes.

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