Single fiber bragg grating as delay line interferometer

A method of fabricating a phase-modulated fibre Bragg grating (FBG) for a delay line interferometer, the method comprising:

• obtaining an objective spectral response |HT,obj(ω)| that is a Fourier transform of an objective impulse response hT,obj(t) of the phase-modulated FBG, where the objective impulse response corresponds to a minimum phase system;
• selecting a coupling strength |κ(z)| to be exhibited by the phase-modulated FBG along its length z;
• calculating a grating period variation Λ(z) for the phase-modulated FBG using the objective spectral response |HT,obj(ω)| and the coupling strength |κ(z)|;
• and
• inscribing a refractive index modulation having the grating period variation Λ(z) in an optical fibre,
• whereby the phase-modulated FBG is operable in transmission to output an output optical signal fout(t) in response to an input optical pulse fin(t).

A method of fabricating a phase mask for inscribing a phase-modulated fibre Bragg grating (FBG) in an optical fibre, the method comprising:

• obtaining an objective spectral response |HT,obj(ω)| that is a Fourier transform of an objective impulse response hT,obj(t) of the phase-modulated FBG, where the objective impulse response corresponds to a minimum phase system;
• selecting a coupling strength |κ(z)| to be exhibited by the phase-modulated FBG along its length z;
• calculating a grating period variation Λ(z) for the phase-modulated FBG using the objective spectral response |HT,obj(ω)| and the coupling strength |κ(z)|;
• and
• fabricating a phase mask, whereby the grating period variation Λ(z) is encoded across the phase mask.