A hand-written memo on filter cavity part of KAGRA+ sensitivity calculation code.
I made up the formula there in by myself, since I could not find suitable references.
To make this formula reliable, I put this memo here, so that someone else can trace my calculation.
Mathematica version of KAGRA+ code: https://granite.phys.s.u-tokyo.ac.jp/svn/LCGT/trunk/sensitivity/Mathematica/KAGRAplus/
For Matlab version, ask some colleague around you.