Study on the Characteristics of All Fiber Comb Interleaver with Unequal Bandwidth

An all-fiber comb interleaver with unequal bandwidth is proposed, which is composed of an asymmetrical Mach–Zehnder interferometer and a cascaded 3 × 3 single-mode fiber coupler. The expression of optical output spectrum is obtained by light transmission theory. And the theoretical analysis is carried out, the theoretical analysis shows that when the length differences of two pairs of optical fiber interference arms are equal, and the value of coupling coefficient of each coupler is proper. The proposed all-fiber comb interleaver can be realized a unequal bandwidth output on even and odd channels, through test and calculation, the passband bandwidths of the even and odd channel are greater than 20 Gb/s and 60 Gb/s respectively, and channel isolations are greater than 25 dB, so, the proposed all-fiber comb interleaver can be used for 10 Gb/s + 40 Gb/s communication system. Compared with other comb interleavers with unequal bandwidth, the proposed all-fiber comb interleaver not only has the advantages of wide passband and simple structure, but also is an all fiber comb interleaver with lower cost.