Assume the distance between grating couplers is A, distance between adiabatic and grating couplers on X axis is B, distance between adiabatic coupler outputs approximately \(3\mu m\), bend radius is R, and L1 must be equal L2. So we need to find A2 or A1 to place adiabatic coupler.
Therefore \(L1=(A1-5)+3\pi R/2+(B-11.5)\) and \(L2=(A2-5)+3\pi R/2 +(B-3.5)\).
So \(A2=68.85398\).
To be more accurate all other nessesary lengths was adjusted by using Klayout.
And last one design have 20 90 degree bends on phase shifting waveguide, so we can clearly see bend influence on final result in this MZI scheme.