Abstract: A long length continuous phase Bragg reflector and the method and an apparatus for writing the gratings into an optical fiber. The method includes the steps of providing a photosensitive optical fiber and a writing beam. A periodic intensity distribution of period &Lgr; is created from the writing beam and the optical fiber is translated relative to the intensity distribution at a velocity v(t). The intensity of the writing beam is modulated as a function of time at a frequency f(t), where. v(t)/f(t)≈&Lgr;. The intensity of the writing beam is varied further to control the envelope of the refractive index profile to write apodized gratings. The gratings measure at least 2.5 meters in length.

Abstract: A method and an apparatus for stretching an optical pulse and shaping its spectrum. The method includes the step of: providing a an optical fiber element having a first long length fiber Bragg grating having a refractive index perturbation of varying periodicity. The optical pulse is launched into the fiber Bragg grating, wherein the Bragg grating reflects the pulse in a chromatically dispersed output. The reflected output is coupled with an optical modulator programmed to temporally modify the amplitude of the chromatically dispersed output to attenuate selected optical frequencies in a desired pattern. The apparatus for stretching and arbitrarily shaping the spectrum of an optical pulse with a desired wavelength resolution &Dgr;&lgr;res includes a routing optical device and an optical fiber element having a Bragg grating. The routing optical device routs energy between different waveguides, and has an input port to receive the optical pulse.

Abstract: A method and an apparatus for writing arbitrary refractive index perturbations along an optical waveguide. The method includes the steps of providing a waveguide having a photosensitive region and providing a writing beam of actinic radiation having a nominal diameter D, the writing beam defining an optical axis. A waveguide is translated relative to the optical axis of the writing beam at a known velocity v(t). A modulator modulates the radiation intensity I(t) of the writing beam as a function of time t to deliver a fluence of radiation, .PHI.(x), directly to the waveguide, wherein ##EQU1## The refractive index change .DELTA.n.sub.(x) at a position x along the waveguide length is related to the fluence delivered to that position as, .DELTA.n.sub.(x) =C.multidot..PHI..sub.(x), wherein C is a scaling factor that accounts for the photosensitivity of the waveguide.