The MEMS Organic Thin Film For Variable Optical Attenuator Applications

The variable optical attenuator is a critical optical component in WDM fiber-optic communication system. It can be used to equalize the optical gain, block the optical signal, and prevent the saturation of the receiver. In this thesis, we design a novel reflection type variable optical attenuator. It not only includes the characteristic of low PDL, but also can be easily fabricated compared to the common reflection type VOA. The VOA is made by an optical fiber collimator and a deformable mirror. Due to the defocus effect, the optical power could be adjusted by controlling the curvature of the deformable mirror.
According to the material selection chart, the low stress organic material is applied to compose the deformable mirror. By micromachining fabrication, the 6 mm X 6 mm deformable mirror was successfully fabricated and tested without crack. The residual stress and Young’s modulus are measured as low as 3.5 Mpa and 15 Gpa, respectively. Due to these mechanical properties of organic thin films, the curvature of the deformable mirror as large as 20 mm is achieved by pneumatic force. The 8 dB optical attenuation is experimentally measured and agreed well with theoretical simulation. The PDL and WDL are both as low as expectation because of the center symmetric optical design. As a result, the novel MEMS VOA has been successfully designed, fabricated, and tested.