nanoLAB Roll-to-Roll FBG (r-FBG)

For Scientific Research & Industry Modernisation.

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Industry Challenge

Fiber Bragg gratings (FBGs) manufactured by femtosecond laser technology possess significant advantages over conventional FBGs fabricated by ultraviolet lasers. This is due to the large refractive index difference introduced by a femtosecond laser, which can be up to 10^-3 (Δn ∽ 10^-3). FBGs manufactured by femtosecond laser pulses offer three major advantages:

1. Achieving a high reflectivity with a short grating length.

2. Femtosecond laser manufactured FBGs can work in a high-temperature environment.

3. Capability and high flexibility of processing different types of FBGs, e.g. FBGs with ultra-narrow bandwidth, ultra-wide bandwidth, apodized FBGs, chirped FBGs etc.

However, currently the cost of femtosecond-laser processed FBG products is significantly greater than that of traditional UV laser processed FBG products. Meanwhile, the performance parameters of current femtosecond FBG products cannot be well-controlled with precision and stability. The yield rate is also low. Such issues limit the broad applications of femtosecond FBG.

To elaborate, the problems arise from the following three challenges of femtosecond laser FBG processing :

Conventional method of processing FBG using femtosecond laser is incapable of achieving precise quantitative product standardization (e.g. reflectivity, wavelength, bandwidth etc.)

During femtosecond laser processing, the accurate control of the femtosecond laser power stability as well as the precise synchronization of exposure time and speed of the displacement stage, are the rigorous requirements for precise processing of FBG with fine quantitative measures of identical performance index.

Difficulty of quantitatively fabricating FBG strings with identical performance indexes in large scale on a single long-distance fiber

Low degree of automation hinders the development of high-yield large-scale FBG fabrication