Optical Variable Gain Tilt Filter And Its Control System With Temperature Stabilized Operation

In the dense wavelength division multiplexing (DWDM) transmission system, the wavelength-related gain or loss within optical amplifiers, dispersion effects, optical media, and other optical components, as well as the dynamic changing in the different channels in the optical networking systems will cause power imbalance between different channels. It will cause the system error rate increases significantly. Therefore dynamic gain equalization devices, which are able to equalize varying power in different links, is needed. Optical Variable Gain Tilt Filter (VGTF), also known as the sine filter, which has its amplitude and phase can be tuned by means of electro-optic control method, can be used for dynamic gain equalization devices.In the first part of this paper, a systematic study in OptoCeramic^?series of transparent ferroelectric ceramic materials based VGTF has been carried out. Through analyzing how to use ferroelectric ceramic and birefringent crystal materials to construct the VGTF devices, the transmission function of VGTF is demonstrated.In the second part, a universal serial bus (USB) based real-time control circuit for the VGTF is designed. After analyzing temperature effects of transparent ferroelectric ceramic and birefringent materials, the temperature-dependent properties of VGTF are deeply investigated and a temperature-dependent calculation model is established, wherein the temperature-dependent coefficients can be obtained by experimental and numerical methods. Through the real-time temperature surveillance, the control voltages can be dynamically adjusted with a corresponding value. The VGTF transmission spectrum achieves precise control and remains stable within temperature varying.In the last part, VGTF based applications, erbium-doped fiber amplifier (EDFA) gain tilt balance and two-tap tunable microwave photonic filter, has been displayed. The results show that the temperature stabilized control system has greatly improved the temperature stability of VGTF based applications.