Optical fiber tag based on ultra-low-loss encoded fiber cladding grating arrays

Optical fibers are commonly employed in telecommunications for transmitting data. However, it is difficult to distinguish optical conduits from one another when servicing data transmission cables due to the large number of optical fibers and optical cables. Conventional methods of physically marking fibers are cumbersome, and the label information is accessible to any potential user. In this work, we propose and demonstrate an encrypted optical fiber tag based on an ultra-low-loss encoded cladding-type fiber Bragg grating (cladding-FBG) array. Using the femtosecond laser point-by-point (PBP) technique, binary data sequences are successfully embedded into the different positions of the optical fiber cladding in the form of Bragg gratings. The cladding-FBGs redistribute light within the cladding, enabling information retrieval via backscattered signals while having minimal impact on the core light transmission. Consequently, the insertion loss of a single encoded cladding grating is suppressed to an exceptionally low level of just 0.00155 dB, which is favorable for optical communication. The data capacity and security of the tag can be enhanced by optimizing the parameters of cladding-FBGs, such as grating periods and spatial distributions. Therefore, the proposed low-loss optical fiber tag presents significant potential for integration into network systems for optical network link identification and data storage.