Improved optical coding method for orthogonal ASK/DPSK modulation format

Abstract

Orthogonal ASK/DPSK labeling, which encodes label information on optical carriers in a modulation format, is regarded as a competing scheme to sub-carrier multiplexed optical labeling. However, the inherent cross-talk limits the extinction ratio (ER) of the payload and label sensitivity. In this paper, two optical coding methods–Manchester coding and 8B10B coding–which can remarkably improve the system quality to obtain acceptable ER are discussed. A novel optical packet encoding method–mark-insertion coding–is demonstrated to significantly reduce cross-talk between the amplitude shift keying (ASK) payload and the differential phase shift keying (DPSK) label through spectrum shaping. The performance of mark-insertion coding depends on the number of inserted ‘marks’. Finally, the transmission over a 40 km single mode fiber (SMF) is compared with optical label swapping for a 40 Gbit/s ASK payload and 2.5 Gbit/s DPSK label under these coding schemes. The experimental result is consistent with the theoretical analysis.

Keywords

orthogonal modulation / amplitude shift keying (ASK) / differential phase shift keying (DPSK) / mark-insertion coding