Channel estimation and interference suppression in frequency-selective fading channels - Electronics Letters

substrate by a specially-designed drawbridge structure developed in our previous work [4]. The mounting plate is designed to have a large area (612 x 300 pm), therefore the required driving voltage can be low. Two fibres are aligned using translation stages and then fixed to the substrate by use of a strong adhesive. The distances between the fibre terminals and the micromirror are both 10 pm. Initially, the micromirror is kept away from the light path, and the light beam from the input fibre passes to the output fibre with a small attenuation, corresponding to the insertion loss of the VOA. It is measured to be 1.5 dB at 1.55 pm wavelength. When the driving voltage applied to the actuator increases from 0 to 8 V, the mirror gradually moves down so that it cuts into the light path and blocks a portion of the light energy. As a result, the light intensity is attenuated. The attenuation can continuously increase to 45 dB as shown in Fig. 2. Further increase of the driving voltage does not produce higher attenuation as the signal power becomes too weak to be detected in our experiment.