  Motivated by identifying the origin of the bias dependence of tension
propagation we investigate methods for measuring tension propagation
quantitatively in computer simulations of driven polymer translocation. Here
the motion of flexible polymer chains through a narrow pore is simulated using
Langevin dynamics. We measure tension forces, bead velocities, bead distances,
and bond angles along the polymer at all stages of translocation with
unprecedented precision. Measurements are done at a standard temperature used
in simulations and at zero temperature to pin down the effect of fluctuations.
The measured quantities were found to give qualitatively similar
characteristics, but the bias dependence could be determined only using tension
force. We find that in the scaling relation $\tau \sim N^\beta f_d^\alpha$ for
translocation time $\tau$, the polymer length $N$, and the bias force $f_d$ the
increase of the exponent $\beta$ with bias is caused by center-of-mass
diffusion of the polymer toward the pore on the \textit{cis} side. We find that
this diffusion also causes the exponent $\alpha$ to deviate from the ideal
value $-1$. The bias dependence of $\beta$ was found to result from combination
of diffusion and pore friction and so be relevant for polymers that are too
short to be considered asymptotically long. The effect is relevant in
experiments all of which are made using polymers whose lengths are far below
the asymptotic limit. Thereby our results also corroborate the theoretical
prediction by Sakaue's theory [Polymers 8(12), 424 (2016)] that there should
not be bias dependence of $\beta$ for asymptotically long polymers. By
excluding fluctuations we also show that monomer crowding at the pore exit
cannot have a measurable effect on translocation dynamics under realistic
conditions.
