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Advanced phase modulation formats, such as differential binary phase-shift keying (DPSK), differential
quadrature phase-shift keying (DQPSK), and differential eight-ary phase-shift keying (D8PSK), and so on,
have attracted considerable research attention as promising candidates for future optical communication
systems. To accommodate different requirements such as nonlinear and dispersion tolerance, implementation
complexity or spectral efficiency in different regions of networks, several different modulation formats are
expected to coexist in the future optical network. For example, low-speed binary modulation formats may be
deployed in the edge networks such as metro or access networks, whereas high-speed or multi-level
modulation formats are preferred to be employed at the core networks to support high-speed long-haul
transmission. To support the transparent cross-connection among various networks, and the traffic grooming
from low-speed edge networks to high-speed core networks, optical phase transmultiplexing technology is
highly desirable.
In this paper, we report an all-optical phase interleaving technology to phase-multiplex 3x10-Gb/s
differential phase-shift keying (DPSK) wavelength-division multiplexing (WDM) signals to a single 30-Gb/s
DPSK, and an optical phase-modulated format conversion scheme to convert 2x10-Gb/s DPSK WDM to a
single quadrature 20-Gb/s differential quadrature phase-shift keying (DQPSK). The proposed schemes are
based on four-wave mixing effect in highly-nonlinear fiber. Different from conventional optical signal
processing schemes, the proposed schemes are achieved in optical phase domain directly. Experiments were
performed to verify the feasibility of the proposed schemes. Both of them could be applied in transparent
optical networks to act as an optical phase transmultiplexer enabling traffic grooming and cross-connection
among different networks.
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