All-Optical Phase Multiplexing from π/2-Shifted DPSK-WDM to DQPSK Using Four-Wave Mixing in Highly-Nonlinear Fiber

Guo-Wei LU
Kazi Sarwar ABEDIN

IEICE TRANSACTIONS on Electronics   Vol.E91-C    No.7    pp.1121-1128
Publication Date: 2008/07/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e91-c.7.1121
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Joint Special Section on Opto-electronics and Communications toward NGN and beyond)
differential quadrature phase-shift keying (DQPSK),  differential phase-shift keying (DPSK),  phase modulation,  four-wave mixing (FWM),  optical fiber communications,  

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An all-optical phase multiplexing scheme for phase-modulated signals is proposed and experimentally demonstrated using four-wave mixing (FWM) in a highly-nonlinear fiber (HNLF). Two 10-Gb/s π/2-shifted differential phase-shift keying (DPSK) wavelength-division multiplexing (WDM) signals are experimentally demonstrated to be converted and phase-multiplexed into a 20-Gb/s differential quadrature phase-shift keying (DQPSK) signal with non-return-to-zero (NRZ) and return-to-zero (RZ) formats, respectively. Experimental results show that, due to phase-modulation-depth doubling effect and phase multiplexing effect in the FWM process, a DQPSK signal is successfully generated through the proposed all-optical phase multiplexing with improved receiver sensitivity and spectral efficiency.