If you're lighting the glass from the sides instead of from behind you can use a combination of diffusion panels, softboxes, and flags to control the size and harshness of the side highlights. Still, if you want to limit the wrap of the light you need to have the lights behind the glass, even when side lighting it.
Yes, I am lighting the glass from behind and using diffusion panels to create the gradient. Right now, the diffuser on the left is smaller than the one on the right and they are both round. I'm going to have to splurge it looks like and get square diffusion panels. That's why I'm trying out what I have vs what I need for the look I'm trying for.
Here's the BTS look showing the two strip boxes aimed from behind and the two diffuser's parallel to each other to spread the light out. You can really tell the difference in the size of the two diffusers in this shot.