T. Wuth

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.

11

We demonstrate the generation and transmission of 11 channels with 224-Gb/s polarization-multiplexed return-to-zero 16-level quadrature amplitude modulation over 670 km of standard single-mode fiber (SSMF) with 50-GHz channel spacing and a spectral efficiency of 4.2 b/s/Hz. We report a penalty of around 4.3 dB in the performance at back-to-back in comparison to the theoretical limits, and a margin of 1 dB in Q-factor below the forward-error correction limit (assumed to be at a bit-error rate of 3.8 × 10-3) after transmission over 670 km of SSMF.

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We investigate, by means of simulations, polarization-multiplexed (PolMux) quadrature duobinary (QDB) as a modulation format for transmitting 111-Gb/s signals with high spectral efficiency (SE) and acceptable system complexity. We show that PolMux-QDB can be used to transmit 111-Gb/s signals with an SE of 4-b/s/Hz, but at the same time has a higher tolerance to nonlinear transmission effects and local oscillator laser linewidth compared to PolMux-16QAM at the same data rate and SE.

224-Gb/s POLMUX-RZ-16QAM Transmission Over 670 km of SSMF With 50-GHz Channel Spacing

We demonstrate transmission of 11 × 224-Gb/s POLMUX-RZ-16QAM over 1500 km with a channel spacing of 50 GHz. A hybrid configuration of LongLine and pure silica fiber is used to optimize both nonlinear tolerance and Raman gain.

111-Gb/s PolMux-Quadrature Duobinary for Robust and Bandwidth Efficient Transmission

The authors demonstrate the successful transmission of 10 channels with 224-Gb/s POLMUX-16QAM modulation (28 GBaud) on a 37.5-GHz wavelength grid. Using large-Aeff pure-silica-core fibers they show a 656-km transmission distance with a spectral efficiency of 5.6 b/s/Hz. They report a back-to-back performance penalty of 3.5 dB compared to theoretical limits at the forward-error correction (FEC) limit (bit-error rate of 3.8·10-3), and a margin of 0.5 dB in Q-factor with respect to the FEC limit after 656 km of transmission.

Transmission of 11 × 224-Gb/s POLMUX-RZ-16QAM over 1500 km of LongLine and pure-silica SMF

We study the tolerance of 111-Gb/s POLMUX-RZ-DQPSK to nonlinear impairments and show the advantage of using non-dispersion managed links and large effective area fibers in ultra long-haul transmission.

10

The rise of coherent detection and digital signal processing is drastically changing the design of optical transmission systems. In this paper we review the challenges and opportunities offered by such receivers in the design of long-haul 40G/100G systems.

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We investigate the performance and implementation complexity of different equalization techniques combined with phase modulation. We demonstrate that for data rates ges40-Gb/s, FFE allows for the most efficient equalization of linear transmission impairments.

224-Gb/s POLMUX-16QAM Transmission Over 656 km of Large-

We discuss the long haul-transmission of 50 GHz wavelength division multiplexed (WDM) 111-Gb/s POLMUX-RZ-QPSK and 224-Gb/s POLMUX-RZ-16QAM channels. Furthermore, we demonstrate that using non-dispersion managed (NDM) links and super large effective area (SLA) fiber can considerably enhance the transmission performance of 111-Gb/s and 224-Gb/s channels.