I have been doing a simulation of TAMA optical bench using OptoCAD. Here attached interim results. It has not been completed. You can convert an attached text file into a fortran source code by changing .txt to .f90 for eample (depending on your environment). For some unknown reason (probably a problem of windows OS), I couldn't divide code into multiple files (like a main program and some external files beside it) as is a common method to gain readability of a long code. Consequently, the source code got complete mess. Basically it is just a list of optical component so you caan just add components which will be placed later on. For a green beam part at least it is consistent to the actual situation. For an IR beam part it should be changed afterwards.