Polarization-multiplexed LDPC-coded QAM robust to I-Q imbalance and polarization offset is proposed. Efficient
mitigation of I-Q imbalance and polarization offset is demonstrated with LDPC-coded turbo equalization by
simultaneous MAP detection of symbols transmitted over two orthogonal polarizations. The proposed scheme is much
more efficient in I-Q imbalance and polarization offset compensation than conventional approaches.
Proc. SPIE. 7988, Optical Transmission Systems, Switching, and Subsystems VIII
KEYWORDS: Signal to noise ratio, Modulation, Polarization, Signal attenuation, Receivers, Computer programming, Monte Carlo methods, Transmittance, Dense wavelength division multiplexing, Forward error correction
Two reduced-complexity (RC) LDPC decoders are proposed, which can be used in combination with large-girth LDPC
codes to enable beyond 400 Gb/s serial optical transmission. We show that optimally attenuated RC min-sum sum
algorithm performs only 0.45 dB worse than conventional sum-product algorithm, while having lower storage memory
requirements and much lower latency. We further evaluate the proposed algorithms for use in beyond 400 Gb/s serial
optical transmission in combination with PolMUX 32-IPQ-based signal constellation and show that low BERs can be
achieved for medium optical SNRs, while achieving the net coding gain above 11.4 dB.
In recent years, we have witnessed an increased demand on optical-networks transmission-capacities due to the growing
popularity of the Internet and multimedia in everyday life. According to industry expert estimates, 1Tb/s-Ethernet should
be standardized by the year 2012-2013. To this end, we propose a non-uniform modulation format that achieves the
channel capacity for SNRs of up to 25dB. The proposed modulation format is optimized for ASE-noise-dominated
channels and can achieve 400Gb/s data rate per polarization utilizing the currently-available components operating at
50-GSymbols/s. One major benefit of the current scheme is that it is an affordable upgrade to the current systems.
We report a new design of differential phase-shift keying (DPSK) receivers which utilize a single demodulator to receive
polarization division multiplexed signals. More than 20 dB extinction-ratio can be achieved by optimizing the phase
detuning with a polarization controller in the receiver. Experimental demonstrations using 20 Gb/s polarization
multiplexed DPSK signals and 2<sup>15</sup>-1 pseudorandom binary sequence are conducted to show the performance of the
proposed receiver. After 60 km of optical fiber transmission, the receiver has less than 3 dB power penalty at bit-error
rate (BER) of 10<sup>-9</sup>.
Proc. SPIE. 7136, Optical Transmission, Switching, and Subsystems VI
KEYWORDS: Optical fibers, Digital signal processing, Modulation, Polarization, Receivers, Multiplexing, Signal processing, Optical communications, Orthogonal frequency division multiplexing, Signal detection
We introduce two important technologies for development of next generation ultra-high-speed optical communications:
(i) polarization multiplexing, phase modulation with digital coherent detection, and (ii) OFDM-based optical fiber
transmission. In both schemes, digital signal processing plays a key role in recovering the signal and mitigating the
detrimental effects from optical signal transmission. We further describe a novel three dimensional low-density parity
check (LDPC) coded modulation scheme, including its principle and system performance.
A testbed for metro wavelength division multiplexing (WDM) network is realized and tested. The testbed contains a reconfigurable optical add/drop multiplexer (ROADM) node, a 2x2 wavelength cross-connect (WXC) node, and two interconnected two-fiber bidirectional path protected switching ring networks (TF-BPSR). Both the ROADM and WXC node are bidirectional nodes, so they can select channels from the working and the protection ring networks simultaneously, and they support both protected and unprotected services. The ROADM node uses a flexible band tunable filter (FBTF) to drop a waveband from the input WDM signals and send the express channels directly to the output port. As a result, the physical impairment accumulated on the express channels can be minimized. It also has a modular structure, so additional modules can be cascaded to expand the capacity and functionality of the node without any interruption to current services. The WXC node is realized with interconnected ROADM modules that are comprised of wavelength selective switches (WSSes). Arbitrary wavelength or wavelength sets can be either dropped in the node or cross-connected in a non-blocking manner. Multiple services, such as OC-48 and OC-192 SONET signals, gigabit Ethernet streams carrying interactive movie signals, and live video broadcasting services, are carried in the network, dropped in the ROADM and WXC node, and switched between the two ring networks. The testbed is controlled by a websever based network management system that facilitates remote control and monitoring. Experiments demonstrate that the performance of the nodes and the testbed meets the requirement of the services.