ABSTRACT
Thermo-optic VOA is based on the Thermo-optic effect to achieve the attenuation. In general, the production of thermo-optic VOA requires the use of micro-processing technology in the formation of thin film interconnect as a heating electrode on the optical waveguide. After the electrode is energized, heat will be transferred to the optical waveguide and the temperature field distribution will be generated. Finally changes the refractive index of the waveguide and attenuates the optical signal. Figure 1 gives the structure of a thermo-optic VOA. The input and output single-mode waveguides are connected to the optical fiber and they have the same matching coefficients. The heating electrode is at an angle β to the plane of the multimode waveguide so that the attenuation ratio of the optical signal is conformed to the design claim. After the electrode is energized, the refractive index of the waveguide decreases as the temperature
1 INTRODUCTION
With the rapid development of optical communication industry, themo-optical devices with the characteristics of small size, low driving power, low cost and easy manufacture, represented by Variable Optical Attenuator (VOA) and optical switch, have been widely applied (Xingjian Lv et al. 2004, Junxing Yu 2014). However, the device size has being growing obviously along with the fast increasing of channels. For example, a typical commercial available thermo-optical VOA has 16 channels for the early products. When the channel number is improved to 20, the overall size of the device has increased 1.5 times. According to the working principle of thermo-optic devices, each channel requires a film interconnect as the role of heater to establish a temperature gradient and achieve light attenuation. The requirements for high integration and miniaturization of the device are needed in the size and spacing of the thin film interconnects. At present, there are a lot of researches on the problems of size optimization and reliability of the thin film interconnects, but there is little research on the spacing optimization.
