where [[omega].sub.f] is the central angle frequency of the OBPF. The filter is implemented in the frequency domain using a fast Fourier transform (FFT) algorithm.
Figure 3 shows the optical spectra obtained at the input of the PCF, output of the PCF, and after OBPF (corresponding to points A, B, and C, respectively, shown in Figure 1).
In our test, the RZ signal with different wavelength is obtained by a HNLF based wavelength converter, which consists of a HP-EDFA (Amonics: AEDFA-33-B-FA), a 700 m HNLF, and a 1.5 nm bandwidth OBPF (Santec: OTF-950).
The OBPF bandwidth is maintained at 0.38 nm as before.