Active long-period waveguide grating and its application in Er-Yb co-doped waveguide amplifier

The performance of active long-period waveguide grating based on Er-Yb codoped phosphate glass is studied by using coupled-mode theory. The transmission spectra of the gratings show distinct band-rejection at specific wavelengths, known as the resonance wavelengths. The phase-matching curves of the gratings, which govern the relationship between the resonance wavelength and the grating pitch, is investigated in deatail. As an application in gain equalizer, the effects of the transmission spectra of the gratings on the amplified spontaneous emission (ASE) spectrum of Er-Yb codoped phosphate glass waveguide amplifiers are discussed theoretically. It´s demonstrated that the flatness of about 1 dB is achieved over a bandwidth of about 30 nm.