Abstract:
This thesis presents a novel optical fibre switch useful in telecommunication networks and optical sensor systems. The switch uses an optical fibre inserted into a piezoelectric ceramic tube and switches optical signals from one input to one of the output fibres (1 x2 or 1 x4). The piezoelectric tube deflects by applying a voltage to the electrodes on the tubes' surface thereby moving the input fibre. This moving fibre opto-mechanical switch is simpler and more scalable than many current opto-mechanical switches.
The piezoelectric tube actuators presented in this thesis were fabricated with an electrophoretic deposition (EPD) process. These tubes have a smaller diameter and a thinner wall than commercial piezoelectric tubes. New equations for thin- and thickwalled tubes were developed to more accurately predict the tip deflection of these tubes, accounting for their unique electrode arrangement. The accuracy of the equations was experimentally verified.
A number of piezoelectric switch prototypes were constructed. The output fibres were aligned in silicon v-grooves using precision translation stages. The input fibre was bonded inside the piezoelectric tube and the protruding fibre was strengthened by a graphite rod. The piezoelectric tube was driven by a power supply unit constructed with a DC-DC converter providing drive voltages ofup to ±200 V.
Tests showed that the 1 x2 multimode fibre switch prototype had an insertion loss of <1 dB, a crosstalk of <-55 dB and a switching time of <8 ms. The prototype was tested in different orientations with reliability over 1.6 million switching cycles. The cost of the switch was estimated at NZD 220. The switch was also successfully tested in the optical network of the University of Auckland. A multiple-output switch with 1 x4 configuration was also implemented showing similar optical performance as the 1 x2 switch. This demonstrated that the concept could be extended to multiple outputs without introducing extra complexity. In addition, thermally expanded core (TEC) fibres were used to fabricate a single-mode fibre switch prototype. TEC fibres relaxed the required alignment i
accuracy between the input and outputs resulting in a switch with an insertion loss of <1.5 dB. In summary, the test results of different optical switch prototypes proved that the piezoelectric optical switching concept is feasible. Further use of micro-machining technologies would take the prototypes closer to commercial realisation.