calculate the band of Fabry-Parot Filter -A Fabry-Parot Filter consist of the cavity formed by two highly reflective mirrors placed parallel to each other , as shown in the figure 1.The input light beam to the filter enters the first mirror at right angles to its surface. The output of the filter is the light beam leaving the second mirror. This filter is called Fabry-Parot or etalon. This is a classical device that has been used widely in interferometric applications. Fabry-Parot filters have been used for WDM in several optical network test beds. There are better filters today, such as thin film resonant multi cavity filter and they can still be viewed as Fabry-Perot filter. This type of filter transmits a narrow band of wavelengths and rejects wavelengths outside of that band. An interesting feature of this type of filter is its ability to "select" a different peak wavelength as the filter is tilted