D. van den Borne

Coherent Equalization and POLMUX-RZ-DQPSK for Robust 100-GE Transmission

We discuss the use of a coherent digital receiver for the compensation of linear transmission impairments and polarization demultiplexing in a transmission system compatible with a future 100-Gb/s Ethernet standard. We present experimental results on the transmission performance of 111 Gbit/s POLMUX-RZ-DQPSK. For a dense WDM setup with channels carrying 111 Gbit/s with a 50 GHz channel spacing (2.0 bits/s/Hz), we show the feasibility of 2375 km transmission. This is enabled through coherent detection which results in excellent noise performance, and subsequent electronic equalization which provides the high tolerance to polarization mode dispersion and chromatic dispersion (CD). Furthermore, we discuss the impact of sampling and digital signal processing with either 1 or 2 samples/bit. We show that when combined with low-pass electrical filtering, 1 sample/bit signal processing is sufficient to obtain a large tolerance towards CD. The proposed modulation and detection techniques enable 111 Gbit/s transmission that is directly compatible with the existing 10 Gbit/s infrastructure.

1.6-b/s/Hz Spectrally Efficient Transmission Over 1700 km of SSMF Using 40

We discuss high spectral efficient long-haul transmission using multilevel modulation formats. In particular, we investigate long-haul transmission with a 1.6-b/s/Hz spectral efficiency using polarization-multiplexed return-to-zero differential quadrature phase-shift keying. In an experimental demonstration, we show 40 times 85.6-Gb/s transmission with a 50-GHz channel spacing over 1700 km (18 times 94.5 km) of standard-single-mode fiber

\times

107-Gb/s full-ETDM transmission is shown over a 160-km field installed fiber link. A high tolerance towards narrowband optical filtering is demonstrated using vestigial sideband modulation to minimize the spectral width.

85.6-Gb/s POLMUX-RZ-DQPSK

We review coherent-optical orthogonal frequency division multiplexing (OFDM) for long-haul optical transmission systems. Two important aspects of such systems are reviewed: RF-aided phase noise compensation and polarization division multiplexing enabled by MIMO processing.

107-Gb/s full-ETDM transmission over field installed fiber using vestigial sideband modulation

A robust in-service estimation of fiber channel parameters from equalizer parameters of a polarization diverse coherent receiver is presented. The equations used for estimation are evolved from a theoretical fiber channel model. The theory is validated based on simulations and data from transmission experiments.

Optical OFDM - A Candidate for Future Long-Haul Optical Transmission Systems

We show that spectral inversion can be employed for regeneration to reduce the effect of phase noise (Gordon-Mollenauer phase noise) in a nonreturn-to-zero differential phase-shift-keying based transmission system. Several locations of the spectral inverter in an eight-span transmission link have been investigated. We show that the best results are obtained when the spectral inverter is placed in the middle of the link. Compared to the transmission system without spectral inverter, an improvement of over four decades in bit-error-rate performance is achieved.

Channel Parameter Estimation for Polarization Diverse Coherent Receivers

In this paper, we investigate for the first time chromatic dispersion and nonlinearity tolerances in the presence of polarization-mode dispersion (PMD) for polarization-multiplexed (POLMUX) 2 /spl times/ 10-Gb/s nonreturn-to-zero (NRZ) transmission. In polarization-multiplexing, the interaction between fiber nonlinearity and PMD can lower the nonlinear tolerance beyond the tolerances evident when considering both transmission penalties separately; the combined penalties are significantly worse than in the case for non-POLMUX transmission. In this paper, we show, through simulations comparing POLMUX with non-POMUX transmission in the presence of nonlinearity, a reduction of about a factor of three in PMD tolerance. In addition, we show that the dispersion tolerance of POLMUX transmission is severely limited in the presence of PMD. For example, a 40-ps differential group delay (DGD) with worst case coupling of the polarization channels into the fiber lowers the dispersion tolerance, resulting in a 1-dB eye-opening penalty (EOP), from 1200 to 450 ps/nm. We conclude that the interaction between PMD, chromatic dispersion, and nonlinearity leads to the worst signal impairments in POLMUX transmission and increases the effort of using polarization-multiplexing as a modulation format.

Reduction of Gordon-Mollenauer phase noise by midlink spectral inversion

We discuss coherent equalization to realize robust 111-Gb/s transmission. For 111-Gb/s POLMUX-RZ-DQPSK we experimentally show the advantage of coherent equalization over direction detection for compensation of both chromatic dispersion and differential group delay.

PMD-induced transmission penalties in polarization-multiplexed transmission

The feasibility of long-haul transmission using differential quadrature phase shift keying (DQPSK) modulation is discussed. We focus in particular on the trade-off between spectral efficiency and reach in optical transmission systems using DQPSK modulation.

Coherent Equalization versus Direct Detection for 111-Gb/s Ethernet Transport

We show, in an 800 km SSMF (standard single mode fiber) transmission experiment, that mid-link spectral inversion can be employed to reduce the effect of phase noise (Gordon-Mollenauer noise) on DPSK (differential phase-shift-keying) by over two decades in BER.