Low-cost femtosecond fibre Bragg gratings for harsh-environment sensors

Highlights

NRC has a suite of intellectual property of next-generation inscription techniques and applications for fibre Bragg grating (FBG) using femtosecond pulse-duration infrared lasers. This new approach has all of the advantages of the original ultraviolet laser-based FBG inscription phase-mask technique that was licensed nationally and internationally in the late 1990s. Bragg gratings inscribed with femtosecond lasers (fs‑FBG) can be applied to any optical waveguide, not just those that are photosensitive to UV light such as telecommunication optical fibre. Furthermore fs‑FBG structures with excellent spectral quality can be made stable up to the glass transition temperature of the waveguide, making them ideally suited for high temperature and strain measurements.

Technology transfer

  • Non-exclusive licensing
  • Further development of FBG technologies through a joint collaboration
  • Flexible partnering possibilities to access expertise and infrastructure for the development of FBG technologies

Market applications

  • Harsh-environment applications including:
    • High pressure
    • High vibration
    • High mechanical stress
  • High-sensitivity applications:
    • Small form factor
    • Haptic applications
  • Fibre-laser applications:
    • Laser cavity mirrors in exotic optical fibres
    • High-power fibre-lasers stable under high optical intensity
  • Laser for remote sensing applications
  • Low-cost devices for optical telecom applications: pump stabilization and switching

How it works

The FBG is an optical filtering device within the core of an optical fibre that reflects light of a specific wavelength that is in resonance with the grating structure. It is an intrinsic optical fibre without complicated bulk optics or electronics.

FBG technology is easy to decode, creates no electrical noise and is immune to electromagnetic interference. Due to its simplicity, FBG technology has been easily integrated into existing optical fibre communication networks to expand network capacity. It is also uniquely suited as a temperature and stress sensor since the grating period can be easily affected by heat and strain.

Next-generation FBG technology can be used in extreme environments of temperature, pressure and radiation.

Technology benefits

Application to any optical material: The technique of fs‑FBG inscription using a phase mask can be applied to any optical material or waveguide that previously were not accessible using the UV-laser approach (polymer, glass, crystal, photonic crystal). Examples include:

  • pure silica optical fibre for downhole oil and gas sensing applications where resistance to Hydrogen darkening is important
  • fluorinated silica fibres for temperature and strain sensing in highly radioactive environments
  • crystalline sapphire optical fibre for high temperature measurements up to 2000 °C
  • active silica, phosphate, ZBLAN and tellurite glass optical fibres for high-power fibre-laser sources that emit at wavelengths needed for biomedical and chemical analysis

Technology for production of low-cost FBGs: fs‑FBG inscription with a phase mask can easily be integrated into manufacturing lines as it is similar to most UV‑laser FBG inscription approaches used by the FBG manufacturing industry. The fs‑FBG approach bypasses two key steps in traditional UV‑FBG manufacturing that reduce device reliability and production yield:

  • photosensitization of telecom fibre with high-pressure H2 gas
  • stripping and recoating of optical fibre

Neither process is required for fs‑FBG inscription. There is the potential to establish a truly automated FBG production line thus enabling the production of low cost devices.

Opportunity

Patents available for non-exclusive licensing:

  • US Patent 6,993,221: Bragg grating and method of producing a Bragg grating using an ultrafast laser
  • US Patent 7,031,571: Bragg grating and method of producing a Bragg grating using an ultrafast laser (CIP)
  • US Patent 7,245,795: Optical device incorporating a tilted Bragg grating
  • US Patent 7,379,643: Optical fiber sensor based on retro-reflective fiber Bragg gratings
  • US Patent 7,483,615: Method of changing the refractive index in a region of a core of a photonic crystal fiber using a laser
  • US Patent 7,515,792: Method of increasing photosensitivity of glasses to ultrafast infrared laser radiation using hydrogen or deuterium
  • US Patent 7,567,734: Ridge waveguide optical sensor incorporating a Bragg grating
  • US Patent 7,606,452: Optical fiber fundamental mode field expander
  • US Patent 7,689,087: Method of changing the birefringence of an optical waveguide by laser modification of the cladding
  • US Patent 8,272,236: High temperature stable fiber grating sensor and method for producing same
  • US Patent 8,402,789: High temperature stable fiber grating sensor and method for producing same (divisional)
  • US Patent 8,727,613: Method and system for measuring a parameter in a high temperature environment using an optical sensor

Contact

To inquire about this technology, please contact:

Dr. Stephen Mihailov, Group Leader, Fibre Photonics
Telephone: 613-998-2721
Email: Stephen.Mihailov@nrc-cnrc.gc.ca