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20 Aug 2002
A single laser can now remove the polymer jacket and write fiber Bragg gratings in an optical fiber.
A frequency-doubled copper vapor laser is the ideal source for removing the polymer jacket and writing fiber Bragg gratings (FBGs) in optical fibers, say scientists in Australia. This non-contact approach opens the door to efficient and high-volume manufacturing of FBGs. (Optics Express 10 818)
The team from Australia's Macquarie University use the 289 nm output to strip the fiber's polymer coating and then the 255 nm emission to write the grating. The researchers claim that the 289 nm wavelength can remove the polymer coating without interacting with the fiber's photosensitive core. At this wavelength, the fiber's core is only weakly photosensitive but its polymer jacket absorbs strongly.
The technique means it is no longer necessary to remove a fiber's polymer jacket by either mechanical or chemical methods, which both involve direct contact with the fiber and can potentially weaken it.
The team used a beta barium borate crystal (BBO) to frequency double both the 511 or 578 nm fundamental of the copper vapor laser, producing a 255 and 289 nm pulsed output. This generates an output of approximately 500 mW at both wavelengths.
The researchers mounted the fiber on a positioning stage and focussed the laser to a 10-micron diameter spot to remove the jacket.
"The best results were achieved using output powers from 100 to 150 mW, and several translations using speeds of 12.5 mm/s, rather than a single pass at a slow translation speed," report the authors in their paper. "The photosensitivity of the fiber to 289 nm light is a factor of 20 smaller than that of the 255 nm light at the same power densities."
The team says strong gratings could be fabricated after the stripping process.
Author
Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.
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