Passively temperature-compensated nontunable fibre Fabry-Perot etalons

A temperature-insensitive, nontunable fibre Fabry-Perot etalon is demonstrated. This compensation has been obtained for an etalon with a cavity length of 740 μm (free spectral range = 135 GHz), and the principle may be applied for etalons of arbitrary length. This device may prove useful in setting frequencies for WDM applications.