I had a look on Wikipedia, and it seems that your equation:
delta_t = 2 omega R L / (c^2-v^2)
only applies to a circular path.
In the China-Japan experiment, the path is extremely non-circular, almost a straight line. In that case, the general equation is:
delta_t = 4 A omega / c^2
A is the area enclosed by the paths.
If the signals travel along the same path in both directions, then A = 0, so no time difference is expected.
Putting 90ns into this equation gives A=3e13 m^2. Which is a square 5000km on a side. Sounds like more than any seperation of the two paths would give, so I'm a bit confused. Where can I find this Sagnac explanation for the 90ns? Was it just a causal opinion, or the result of an investigation?
A small lab experiment would have trouble detecting Earth's rotation because:
delta_t = 2 omega R L / c^2
R ~= 1m
L ~= 6m
omega = 7.3e-5 rad/s
delta_t = 1e-20 s = TINY!!!!
Have I made some mistake?
