Research Works On The Wavelength Monitors Fabricated With Integrated Waveguides

Wavelength is a fundenmetal characteristic of the lightwave. Wavelength measurement is a basic and important requirement in optical communication system, especially in the fiber Bragg grating (FBG) based optical sensing systems, the multichannel dense wavelength-division multiplexing (DWDM) optical communication systems, and the optical interconnect system.In order to measure the wavelength of the signal light, we need to measure a physical quantity which is related to the wavelength, and then demodulate the measurement results to get the wavelength. There are many methods to measure the wavelength of the light, but most of them are cumbersome, bulky, slow, and power costly. As a result, they are insuitable for the integrated optical system. The purpose of the thesis is to demonstrate wavelength monitors fabricated with integrated waveguides which can be used in integrated optical system.Among all the methods for the wavelength measurement, the ratio-metric wavelength measuring method, which is based on the filter characteristic of the edge filter, is the most potential technique which can be realized by using the integrated waveguides. The ratio-metric wavelength monitor has the advantages of simple configuration, high-speed measurement, low power consumption, and no mechanical movement. We designed and fabricated ratio-metric wavelength monitors based on ion-exchange waveguides on glass and silicon-based waveguides on SOI (silicon on insulator) substrate. The wavelength measurement performance of the devices are measured and analysed. The main works are listed as follows:1. Dual Mach-Zender Interferometer (MZI) based integrated X-type ratio-metric wavelength monitor on glass. We design and fabricate an integrated ratio-metric wavelength monitor based on ion-exchange waveguides on glass. The device consists of two unbalanced MZIs acting as edge filters. They are designed to have "X-TYPE" spectral response. The output ratio of them is monotonic to the wavelength in the functional range of the wavelength monitor. The measured resolution is about0.1nm ranging from1522to1576nm, which can potentially be improved to15pm after packaged. The polarization dependency of the device is also discussed. Our work makes it possible to build a high performance integrated sensing and detecting optical system on one single chip.2. Ratio-metric wavelength monitor with a double measurement structure. The measureable wavelength range and the resolution of the ratio-metric wavelength monitor are limited by each other in a conventional structure. A double measurement structure is demonstrated in order to overcome this problem. We designed and fabricated a high performance integrated ratio-metric wavelength measurement device on glass by the method of ion-exchange. It contains a rough wavelength measurement with wide range and a fine wavelength measurement with high resolution. The device is consisted by four unbalanced MZIs. The highest measured resolution can reach0.01nm. By heating the unbalanced MZI, the performance of the fine wavelength monitor can be improved.3. Microring based ratio-metric wavelength monitor on silicon. Compared to the ion-exchange waveguides, the size of the optical devices fabricated with the silicon-based waveguides is very small. The wavelength monitor based on silicon-based waveguides can be used in integrated optical system convienetly. An integrated dual-ring ratio-metric wavelength monitor (DR-RMWM) with ultra high wavelength resolution and compact size is demonstrated. Two microrings are used as the edge filters and designed to achieve an "X-TYPE" spectral response in a particular wavelength range. It is fabricated with the CMOS (Complementary Metal-Oxide Semiconductor) compatible fabrication process on the silicon-on-insulator (SOI). The measured wavelength resolution is5pm in a1.2nm wide wavelength range. The effective scale of the device is only120×150μm.By tuning the resonant wavelength thermally, the functional wavelength range can be shifted. The DR-RMWM can find applications in wavelength monitoring systems, especially the on-chip systems.