Yes it has Opi, the japanese invented that but it’s a complicated thing to make and it’s not perfect either, you get some obvious light loss from the fiber.
Not that these materials aren’t as complicated. We’ve already been seeing patents on the negative index of refraction material. Interesting stuff. It has two major drawbacks for an invisibility cloak right now.
1. they don’t have any materials for the visible light spectrum yet. With time that’s presumed to be overcome.
2. They only work on a narrow band of frequency ranges. i.e. one might bend red light but won’t work for green. The problem is that it’s a spatially constructed material and has to be made for a specific wavelength. The real trick will be to cover the entire range that visible light does.
On the whole negative index of refraction materials are really cool and have some more practical applications than just making one invisible. Remember, even if they do get them to work your eyes have to be exposed and visible or you won’t be able to see.
Well now that isn’t all true either, the advances in fibers and what the material of the fiber is. Some fibers can still act as a lense as well. We all know you can buy fish eye lenses…Wide angle… Might be as simple as the way you cut yours.