hi arpita
i have gone through your .osd degn pic.what i saw in your attached pic is that you are using the mux and demux……
1.but we use mux and demux while we are transmitting at several wavelengths.and you are using only one wavelength.hence in my view your .osd design is logically wrong. you are using time divison for single wavelenth which is optical timing division multiplexing(OTDM).
2. i think you are trying to form hybrid network i.e time divison wavelength multiplexing.
with regards