Dispersion compensation apparatus and method utilising sampled Bragg gratings
AssigneeNortel Networks Limited
InventorsAlan Robinson, Terry V Clapp
Life of this patent
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Abstract
Dispersion compensation devices are described which comprise waveguides including sampled Bragg gratings which exhibit comb-like reflectance characteristics. The profile of effective refractive index along the length of the grating is controlled to adjust the position of the teeth and/or to control the dispersion exhibited by the device (i.e. to control the chirp of the grating). The devices can thus be used to provide dispersion compensation to any one of a number of wavelength channels in a WDM system. In preferred arrangements, the effective refractive index distribution is set by a applying a temperature distribution along the length of the grating, or by setting an applied electric field.
Claims61
Dispersion compensation apparatus comprising:
- a waveguide comprising a sampled Bragg grating extending along a length of the waveguide, the sampled Bragg grating exhibiting a comb-like reflectance versus wavelength spectrum comprising a plurality of teeth, the waveguide comprising a core and a plurality of slots interrupting the core, said slots being spaced apart along said length of the waveguide;
- and
- being filled with a material having a variable refractive index and
- adjustment apparatus arranged to adjust an effective refractive index of the waveguide along at least a portion of said length.
Dispersion compensation apparatus comprising:
- a waveguide comprising a sampled Bragg grating extending along a length of the waveguide, the sampled Bragg grating exhibiting a comb-like reflectance versus wavelength spectrum comprising a plurality of teeth, the waveguide comprising a core and a plurality of slots interrupting the core, said slots being spaced apart along said length of the waveguide and bring filled with a material having a variable refractive index;
- and
- adjustment apparatus for controlling and adjusting an effective refractive index profile of the waveguide along said length.
A waveguide comprising:
- a core formed from a first material;
- a sampled Bragg grating comprising a sequence of grating samples spaced apart along said core;
- and
- a plurality of waveguide sections comprising slots filled with a second material, each section at least partially interrupting the core and being arranged in the optical path between a respective pair of adjacent grating samples,
- the second material having a higher thermal coefficient of refractive index than the first, whereby the optical path lengths between the samples, and hence the reflectance characteristics of the grating, pay be adjusted by controlling the temperature of the sections.
A waveguide comprising:
- a core formed from a first material;
- a sampled Bragg grating comprising a sequence of grating samples spaced apart along said core;
- and
- a plurality of waveguide sections comprising slots filled with a second material, each section at least partially interrupting the core and being arranged in the optical path between a respective pair of adjacent grating samples,
- the second material having a refractive index which is dependent on applied electric field, whereby the optical path lengths between the samples, and hence the reflectance characteristics of the grating, may be adjusted by applying electric fields to the sections.
A method of compensating for dispersion in an optical signal having a bandwidth, the method comprising the steps of:
- inputting the signal to a waveguide comprising a chirped sampled Bragg grating extending along a length of the waveguide, the chirped sampled Bragg grating exhibiting a comb-like reflectance versus wavelength spectrum comprising a plurality of teeth, the waveguide comprising a core and a plurality of slots interrupting the core, said slots being spaced apart along said length of the waveguide and being filled with a material having a variable refractive index;
- shifting the position of said teeth in the reflectance spectrum by adjusting the effective refractive index of the waveguide along at least a portion of said length, such that one of said teeth spans said bandwidth;
- and
- reflecting the optical signal from the chirped sampled Bragg grating.
A method of compensating for dispersion in an optical signal having a bandwidth, the method comprising the steps of:
- inputting the signal to waveguide comprising a sampled Bragg grating extending along a length of the waveguide, the sampled Bragg grating exhibiting a comb-like reflectance versus wavelength spectrum comprising a plurality of teeth, the waveguide comprising a core and a plurality of slots interrupting the core, said slots being spaced apart along said length of the waveguide and being filled with a material having a variable refractive index;
- chirping the sampled Bragg grating by adjusting the effective refractive index of the waveguide at a plurality of positions along said length to set a variation in effective refractive index along said length;
- shifting the positions of raid teeth in the reflectance spectrum by further adjusting the effective refractive index at said plurality of positions, such that one of said teeth spans said bandwidth;
- and
- reflecting the optical signal from the chirped, sampled Bragg grating.
A method of compensating for dispersion in an optical signal, the method comprising the steps of:
- inputting the signal to a waveguide comprising a sampled Bragg grating extending along a length of the waveguide, the waveguide comprising a core and a plurality of slots interrupting the core, said slots being spaced apart along said length of the waveguide and being filled with a material having a variable refractive index;
- reflecting the signal from the sampled Bragg grating;
- and
- adjusting the profile of the waveguide effective refractive index along said length to adjust the dispersion imparted to the signal by said reflection.
Dispersion compensation apparatus comprising waveguide comprising an optical reflector extending along a length of the
- a waveguide, the reflector exhibiting a comb-like reflectance versus wavelength spectrum comprising a plurality of teeth, the waveguide comprising a core and a plurality of slots interrupting the core, said slot being spaced apart along said length of the waveguide and being filled with a material having a variable refractive index;
- and
- adjustment apparatus arranged to adjust an effective refractive index profile of the waveguide along said length of adjust at least one of:
- 1) the dispersion imparted to a signal on reflection by the reflector and
- 2) the position of the teeth in the spectrum.
Dependencies are inferred from the claim text.