The effects of thermal and polarization fluctuations on 3/spl times/3 coupler performance

For the Gould 3/spl times/3 coupler studied here, changes in input SOP produce measurable changes in the power transfer properties of the coupler while temperature-induced changes are almost negligible over the range 0-100/spl deg/C. When used for passive demodulation in interferometric systems, changes in SOP will cause noise and inaccuracies in the calculated phase, even in systems employing Faraday rotator mirrors to prevent fringe visibility fading. Hence, the effects of polarization must be controlled by, for example, using a depolarized source or by realtime monitoring of the coupler phase angles. Future studies will extend the investigation to a variety of coupler types and to an investigation of the dependence of the complex scattering matrix on wavelength.