Diameter-boundedness conjecture for tight distance-regular graphs

Let $\Gamma$ be a tight distance-regular graph. Let $b=b_1/(1+\theta_1)$, where $b_1$ is an intersection number of $\Gamma$ and $\theta_1$ is the second largest eigenvalue of $\Gamma$. Assume that $b\geq 2$.

Diameter-boundedness conjecture. The diameter of $\Gamma$ is bounded by a function in $b$.

The conjecture seeks a uniform diameter bound for tight distance-regular graphs in terms of the parameter $b$. The paper proves such a bound under additional hypotheses and presents this as a goal for further generalization; the unrestricted statement remains open in the supplied source.