| 摘要 |
A distributed Bragg reflection pass-band filter in an optical fibre waveguid e (170) is provided by grating elements (172) arranged to provide improved flatness of reflection pass-band, a high rate of roll-off, and reduced amplitude side-bands by the use of nonlinear chirp and apodisation profiles that are related such that the square of the coupli ng coefficient is substantially proportional to the rate of change of chirp.
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