Holographically generated gratings in optical fibers
ZAP, ZAP, ZAP...two beams from a pulsed UV laser collide on the side of an optical fiber and a wavelength filter or out-coupling tap is produced. With this" method, we have developed a new way for generating periodic modulations of the refractive index, or gratings, in the core of a germania-doped optical fiber. When the wavelength of a guided optical signal in the fiber is twice the grating periodicity (the Bragg condition), a fraction of the signal will be reflected into a counter propagating mode. That is, the grating produces a band rejection filter in the fiber.
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