Then Elango

Thanks Amrita for the reply. 

But, when I simulate for bent waveguide, there are higher modes generated for the same dimension, which are higher than the effective indices of the substrate. 

For eg, a rectangular waveguide hads, 2 guided modes, now i enable bend waveguide anaylsis for  calculating modes in circular bend, and I get more than 2 modes which are much higher effective index than straight waveguide. 



also, based on the radius, the effective index values differ and the first order modes look like this:  



As the radius is increased, there is optimum effective index with 2  modes. 

What could this be?