Fiber sensing scientists from Shenzhen University have developed an encrypted fiber optic tag that can be used for all-optical labeling and recognition of optical transmission channels such as access networks. The team led by researchers based at the Guangdong and Hong Kong Joint Research Centre for Optical Fibre Sensors proposed an all-optical labeling method with encryption property, which uses the feature information and spatial distri­bution of fiber Bragg grating arrays to flexibly store different coding sequences.

Unlike traditional optical link labeling methods, the all-fiber tag proposed by the team fully utilizes the charac­teristics of the optical link to achieve all-optical reading, recognition, and restoration of link information. The findings could have a signi­ficant impact on the maintenance of optical distribution networks. The fiber optic tag is based on a fiber Bragg grating array prepared by femtosecond laser direct writing. By cleverly utilizing the spatial distri­bution, reflec­tivity, and reflection wavelength of the gratings, the tag can carry rich information. When using an optical time-domain reflectometer for reading, a specific adminis­trator can perform complete and error-free infor­mation recovery.

One of the lead researchers, Changrui Liao, commented, “This study developed a method for all-optical link encryption labeling and recognition. Faced with the increasing number of optical trans­mission links, traditional physical labels have high labor costs and are prone to waste port resources, making it difficult to meet efficient and stable link labeling requirements. All of these indicate that this fiber optic tag will have broad market appli­cation prospects.” 

One-off printed physical labels or handwritten symbols can be used to number and distinguish links, however, these highly manual methods face significant challenges in the information age. Zhihao Cai explained, “Our work provides a reliable and efficient encryp­tion labeling method for optical signal transmission link labeling. The use of femto­second laser direct writing can achieve rapid mass production of tags, which are very helpful for obtaining dumb information for optical network users.”

The team prepared a fiber Bragg grating array using femtosecond laser multi-pulse exposure, which can control the charac­teristics of different grating fragments, such as reflectivity. Cleverly utilizing the reflected signal of the grating to increase the number of switch states that the fiber optic tag can represent, thereby improving the storage capacity of the fiber tag. Because of the distribution and reflection charac­teristics of the grating, there are many possibilities for fiber optic tags to read and recover information. Therefore, only specific manage­ment personnel can obtain correct optical link information to prove that fiber optic tags have sufficient security.

Yiping Wang said, “This work fully demonstrates the flexi­bility of the femtosecond laser direct writing technology, by adjusting the number of femtosecond laser pulse exposures to achieve regulation of the reflection charac­teristics of each encoded grating fragment, ultimately giving the proposed fiber tag greater capacity and appli­cation potential. It is a fascinating and practical task for maintaining existing optical networks.” (Source: IJEM)

Reference: Z. Cai et al.: Encrypted optical fiber tag based on encoded fiber Bragg grating array, Int. J. Extr. Manufac. 5 035502 (2023); DOI: 10.1088/2631-7990/acd825

Link: Shenzhen Key Laboratory of Photonic Devices and Sensing Systems for Internet of Things, Shenzhen University, Shenzhen, China