A tree-structured 4x4 switch array in lithium niobate with attached fibers and proton-exchange polarizers.

Several Lithium Niobate switch arrays with excellent crosstalk values have been reported. These measurements are taken using highly polarized input light which is injected directly into the LiNbO sub 3 crystal. Once fiber arrays are attached to a device (for packaging), the crystal no longer sees highly polarized input light. A typical application of a packaged device would involve a -20dB polarized diode-laser transmitter with PM fibers, and possibly an in-line fiber compensator. Because less than perfectly polarized light reaches the crystal, the crosstalk characteristics of packaged devices typically degrade. An example of this is a recent device whose measurements for the cross state degraded from -35dB to -24dB (ave). To address this problem, we attached proton-exchange polarizers and PM fibers to the 4x4 Duobanyan switch array, a device known to have good crosstalk values. The crosstalk characteristics went from >34dB to >37dB for the cross state and from >40dB to >44dB (measurement limited) for the bar state.