A lens module includes a barrel, a lens and a shielding layer. An adjusting mechanism applies two bending moments to the grating support member on both sides of the selected channel. The local administration server comprises device for communication with the terminal facilities, independent of the cellular network, to supervise the exchanges over the first communication interface. The CCSI is highly accurate due to highly accurate derivative estimates arrived at by repeated Richardson extrapolation. According to an embodiment of the invention, the device for monitoring an optical link fault and the method thereof apply an optical link fault monitoring signal to an optical link and precisely identify a type of the fault using waveforms of a reflected signal returned from the optical link or a wavelength dependence of reflected signal intensity. Materials to be tested include flat panels for computer screens and other applications and semiconductor wafers.