Tunable nonlinearly chirped grating

An optical device, comprising:

• a segment of fiber;
• a fiber grating formed in said fiber, said fiber grating having a grating period that changes along said fiber in a nonlinear manner to effect different delays for optical waves of different frequencies that are Bragg phase-matched in said fiber grating;
• and
• a fiber stretcher engaged to said fiber grating and configured to change a length of said fiber grating to produce a change in relative delays of said optical waves at said different frequencies.

An optical system capable of dynamically adjusting dispersion compensation, comprising:

• a dispersion analyzer, operating to receive a portion of an optical signal and determine information about dispersion in said optical signal;
• and
• a dispersion compensating element coupled to receive said information from said dispersion analyzer and configured to receive at least a portion of said optical signal and to produce a reflected signal with a reduced amount of dispersion in response to a control signal from said dispersion analyzer, said dispersion compensating element including:
• a wave-guiding element having an optic axis to transport optical energy and an effective index of refraction which is a function of a position along said optic axis;
• and
• a grating formed in said wave-guiding element and configured to have a variable grating period along said optic axis,
• wherein a product of said variable grating period and said effective index of refraction is a nonlinear function of a position along said optic axis to effect a Bragg phase-matching condition so that a reflected optical wave from said grating has a specified wavelength that has a nonlinear dependence on a position along said optic axis.

An optical device, comprising:

• a semiconductor laser;
• an electrical power supply connected to said semiconductor laser to provide a modulated driving current which causes a modulated laser output from said laser;
• a waveguide grating disposed to receive said modulated laser output and having a variable grating period and an effective index of refraction to effect a Bragg phase-matching condition so that a reflected laser beam of said modulated laser output from said waveguide grating has a specified wavelength that has a nonlinear dependence on a position along said waveguide grating;
• a grating control unit coupled to said power supply and configured to control a dispersion characteristics of said waveguide grating to reduce a frequency chirp in said modulated laser output.

An optical device, comprising:

• a segment of waveguide having an optic axis to transport optical energy;
• an optical perturbation region formed in said waveguide and having a variation in a refractive index along said optic axis to define a nonlinearly chirped grating, said nonlinearly chirped grating having a position-varying period that changes nonlinearly along said optic axis and reflecting an optical wave of a specified wavelength which has a nonlinear dependence on a position along said optic axis;
• and
• a waveguide controller to control a parameter of said optical perturbation region as to vary relative time delays of different spectral components of a reflected optical wave.

A method for operating a fiber system, comprising:

• directing an optical signal that is transmitted through a dispersive signal path into a tunable nonlinearly chirped fiber grating;
• determining a polarity and an amount of dispersion in said optical signal;
• and
• adjusting said tunable nonlinearly chirped fiber grating according to said polarity and amount of dispersion to reduce dispersion in said optical signal.