title: Wavelength switchable flat-top all-fiber comb filter based on a double-loop Mach-Zehnder interferometer.
abstract: A wavelength switchable all-fiber comb filter with flat-top spectral response based on a double-loop Mach-Zehnder (M-Z) interferometer is proposed and demonstrated. The proposed flat-top filter consists of a rotatable polarizer and a double-loop M-Z interferometer composed of two fiber couplers with a polarization controller (PC) in the first loop. In the theoretical analysis, when the second coupler of the M-Z interferometer is a non-3dB one, with proper settings of the polarization state of the input light and the PC, the wavelength switchable comb filter with flat-top passband can be obtained. Theoretical prediction was verified by experimental demonstration. The measured 1 dB bandwidth was 0.51 nm with a channel spacing of 0.98 nm, indicating that the flat-top passband of 1 dB bandwidth extends to about 50% of the comb spacing.
authors.affiliation: Laboratory of Photonic Information Technology, School of information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou, Guangdong 510006, PR China.
authors.forename: Ai-Ping
authors.initials: AP
authors.lastname: Luo
authors.forename: Zhi-Chao
authors.initials: ZC
authors.lastname: Luo
authors.forename: Wen-Cheng
authors.initials: WC
authors.lastname: Xu
authors.forename: Hu
authors.initials: H
authors.lastname: Cui
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D005374:Filtration / Q000295:instrumentation*; D007368:Interferometry / Q000295:instrumentation*; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D013685:Telecommunications / Q000295:instrumentation*