Techniques for providing wireless services to mobile subscribers using existing broadband network infrastructures are described herein. The open-cell layer in the thermal insulating packaging film preferably has an average bore diameter of 150 \u03bcm to 500 \u03bcm. Optical image signals retrieved on the image contacting surface are reflected to the light-splitter, and then an optical axis of the image signals is reflected to a lens by the light-splitter once or more. The one driver is turned off in response to the voltage at the point being outside the predetermined voltage range, thereby detecting that the one driver is operating properly.