Spectra of dual overwritten fiber Bragg grating

Regenerated Fibre Bragg Gratings

“…Each of the seed gratings was of moderate strength with transmission loss at λ ~ -20 dB (grating with λ 1 being slightly stronger than that at λ 2 ). The superposition of two gratings leads to a compound form of the local index modulation described as [Bao et al 2001 (1) Λ B1 and Λ B2 are the periods of the gratings with Λ B2 = Λ B1 +ΔΛ and ΔΦ is the initial phase difference of the gratings. It is clear from this expression any non-uniformity introduced by the thermal annealing process will result in a spread of ΔΦ and broadening of the peaks.…”

Spectra of dual-overwritten chirped fiber Bragg gratings

“…As Áà ) Áà c , the reflection spectra of the two gratings are separate enough, so the dual-overwritten CFBGs are independent of each other. Since the value Áà c is approximate to à 2 =L for dual-overwritten uniform FBGs [12], we put emphasis on the effect of chirp parameter F on the value of Áà c . As an example, we chose L ¼ 4.0 mm and Figure 3 shows the values of Áà c corresponding to different values of F. It can be seen that Áà c is approximately linear with chirp parameter F. Using Equations (28) and (29), we have the difference of central wavelength b,2 À b,1 ¼ 2ðn eff þ 2Án 10 ÞÁÃ.…”

“…Moreover, a dual-overwritten fiber grating can create interesting devices in optic communications [11]. For dual-overwritten uniform FBGs, some relations between the reflection spectrum and the parameters, such as grating length, period difference, and primary phase difference have been discussed [12]. For dual-overwritten CFBGs, Cong et al only considered the effects of period difference and chirp parameter on the group delay characteristics [13], their results are useful in fiber dispersion compensation.…”

Triple overwritten Bragg gratings based multiwavelength distributed feedback dye laser

“…The major parameters causing multiple wavelength spectra may be period differences, primary phase difference and overall grating interaction length. Overwriting of two gratings in optical fibres has shown to produce spectra of six lines due to creation of degenerate gratings in overlaid gratings [5]. Superposition of three or more gratings may cause even more number of degenerate gratings but the observation of oscillating lines is restricted to satisfaction of Bragg scattering conditions.…”