Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1999-08-31
2001-08-21
Font, Frank G. (Department: 2877)
Optical waveguides
With optical coupler
Input/output coupler
C385S129000
Reexamination Certificate
active
06278817
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to reflective optical filters, and particularly to an asymmetric low dispersion Bragg grating filter.
2. Technical Background
Wavelength division multiplexing (WDM) is pervasive in optical communication systems. Key optical components in these optical system are those that perform the functions of combining different wavelength channels and splitting wavelength channels.
Bragg grating structures are useful as spectral filters for WDM and other optical signal processing applications. In these types of applications, the Bragg grating filters should have low insertion loss, a flat-top spectral response, steep slopes to minimize crosstalk and a linear phase response to avoid transmission penalties due to signal degradation arising from filter dispersion. Although a reflection filter based on Bragg gratings can be designed to have a near-ideal spectral response, the corresponding phase response becomes increasingly nonlinear (i.e., increased dispersion) as the band edges are approached, thereby reducing the useful filter bandwidth. While the amplitude response of such optical filters has received much attention, the phase response has only recently been investigated in the context of optical communication systems.
Reflective filters based on conventional Bragg gratings have dispersion characteristics which are determined by the transmission spectrum of the grating through a relation which is dictated by causality of such filters. As a consequence of this, a band-pass filter with sharp falling edge in spectrum will suffer a larger in-band dispersion. The in-band dispersion is typically worst towards the edge of the band. In this case, the filter exhibits an effective dispersion-limited filter bandwidth less than the bandwidth of a conventional amplitude-limited filter. However, for a fixed amplitude response in a Bragg grating filter, dispersion of the filter can be improved over the causality-defined dispersion limit. Since reflective filters generally use only reflection from one end of the Bragg grating, dispersion of the reflection can be decreased at one end of the grating at the expense of increased dispersion at the other end of the grating. This unique feature of the Bragg grating is very profound, since it opens a way to make a dispersionless ideal filter which can play a very important role in the field of optical communications.
SUMMARY OF THE INVENTION
One aspect of the present invention is a Bragg grating filter for use in an optical fiber of an optical fiber system, where the optical fiber includes a core and a cladding. A plurality of Bragg grating segments are formed into the core and/or at least part of the cladding of the optical fiber. Each grating element is defined by periodic variations in the refractive index. The periodic variations in the refractive index have a spatially asymmetric index of modulation such that dispersion of the reflection at one end of the grating element can be decreased at the expense of increased dispersion of reflection at the other end of the grating element.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described in the deatiled descriptions which follows, the claims as well as the appended drawings.
It is to be understood that both the foregoing general description and the following deatiled description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various features and embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.
REFERENCES:
patent: 5007705 (1991-04-01), Morey et al.
patent: 5218651 (1993-06-01), Faco et al.
patent: 5351321 (1994-09-01), Snitzer et al.
patent: 5363239 (1994-11-01), Mizrahi et al.
patent: 5602949 (1997-02-01), Epworth
patent: 5636304 (1997-06-01), Mizrahi et al.
patent: 5757487 (1998-05-01), Kersey
patent: 5818987 (1998-10-01), Bakhti et al.
patent: 5852690 (1998-12-01), Haggans et al.
patent: 6067391 (2000-05-01), Land
patent: 6104852 (2000-08-01), Kashyap
Group-delay reconstruction for fiber Bragg gratings in reflection and transmission; Poladian; Oct. 1997; p. 1571-1573.
Dispersive Properties of Optical Filters for WDM Systems; Lenz/Eggleton/Giles/Madsen/Slusher; Aug. 1998; p. 1390-1402.
Fibre Bragg grating transmission filters with near-ideal filter response; Chen/Smith; Sep. 1998.
Dispersion Penalty Measurements of Narrow Fiber Bragg Gratings at 10 Gb/s; Nykolak/Eggleton/Lenz/Strasser; Sep. 1998; p. 1319-1321.
Optimised square passband fibre Bragg grating filter with in-band flat group delay response; Ibsen/Durkin/Cole/Laming; Apr. 1998.
Corning Incorporated
Font Frank G.
Harness & Dickey & Pierce P.L.C.
Lauchman Layla
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