S.L. Jansen

Long-haul DWDM transmission systems employing optical phase conjugation

In this paper, we review the recent progress in transmission experiments by employing optical phase conjugation (OPC) for the compensation of chromatic dispersion and nonlinear impairments. OPC is realized with difference frequency generation (DFG) in a periodically poled lithium-niobate (PPLN) waveguide, for transparent wavelength-division multiplexed (WDM) operation with high conversion efficiency. We discuss extensively the principle behind optical phase conjugation and the realization of a polarization independent OPC subsystem. Using OPC for chromatic dispersion compensation WDM 40-Gb/s long-haul transmission is described. As well, transmission employing both mixed data rates and mixed modulation formats is discussed. No significant nonlinear impairments are observed from the nonperiodic dispersion map used in these experiments. The compensation of intrachannel nonlinear impairments by OPC is described for WDM carrier-suppressed return-to-zero (CSRZ) transmission. In this experiment, a 50% increase in transmission reach is obtained by adding an OPC unit to a transmission line using dispersion compensating fiber (DCF) for dispersion compensation. Furthermore, the compensation of impairments due to nonlinear phase noise is reviewed. An in-depth analysis is conducted on what performance improvement is to be expected for various OPC configurations and a proof-of-principle experiment is described showing over 4-dB improvement in Q-factor due to compensation of nonlinear impairments resulting from nonlinear phase noise. Finally, an ultralong-haul WDM transmission of 22times20-Gb/s return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) is discussed showing that OPC can compensate for chromatic dispersion, as well as self-phase modulation (SPM) induced nonlinear impairments, such as nonlinear phase noise. Compared to a conventional transmission link using DCF for dispersion compensation, a 44% increase in transmission reach is obtained when OPC is employed. In this experiment, we show the feasibility of using only one polarization-independent PPLN subsystem to compensate for an accumulated chromatic dispersion of over 160 000 ps/nm

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

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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

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.

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

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.

Reduction of Gordon-Mollenauer phase noise by midlink spectral inversion

We demonstrate the feasibility of a cost-effective 640 Gb/s (16/spl times/40 Gb/s) wavelength-division-multiplexed (WDM) transmission system over 800 km of conventional standard single-mode fiber (SSMF) without using in-line dispersion management. Instead for chromatic-dispersion compensation, a Magnesium-oxide-doped periodically poled lithium niobate (MgO : PPLN)-based polarization-diverse subsystem is used to phase conjugate all 16 channels. The transmission line uses all erbium-doped fiber amplifiers and has an amplifier spacing of 100 km. All channels launched were copolarized. To the best of our knowledge, this is the first WDM transmission experiment with a channel data rate of 40 Gb/s using a PPLN as chromatic-dispersion compensator.

DQPSK modulation for robust optical transmission

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.

16/spl times/40 gb/s over 800 km of SSMF using mid-link spectral inversion

Using optical phase conjugation with a polarization independent periodically-poled lithium-niobate subsystem, we demonstrate dense WDM 2/spl times/10 Gbit/s RZ-DQPSK transmission over 10,200 km of SSMF with a record accumulated dispersion exceeding 80,000 ps/nm.

Reduction of phase noise by mid-link spectral inversion in a DPSK based transmission system

A polarization-diverse subsystem based on periodically poled lithium niobate waveguides is used as an optical phase conjugator for compensation for linear and nonlinear distortion. We show successful transmission formats of 13 x 40 Gbit/s non-return-to-zero mixed with 6 x 10 Gbit/s non-return-to-zero and 40-Gbit/s duobinary over 8 x 100 km of standard single-mode fiber. A single phase conjugator is used to conjugate all data formats, including the alternative duobinary format, simultaneously.