Data-aided single-carrier coherent receivers

Data-aided algorithms for coherent optic receivers are discussed as an extension of existing non-data aided methods. The concept presents a scalable approach with low implementation complexity and limited overhead for higher-order modulation formats

111-Gb/s POLMUX-RZ-DQPSK Transmission over LEAF: Optical versus Electrical Dispersion Compensation

We investigate the transmission performance of 111-Gb/s POLMUX-RZ-DQPSK modulation using either optical or electrical dispersion compensation. We show that after 2000-km LEAF transmission both link configurations have a comparable nonlinear tolerance

Multilevel modulation formats for robust long-haul high capacity transmission

In the past couple of years we have witnessed a rapid growth in the required bandwidth due to a variation of Internet applications. This has trigged a significant interest in the development of optical transponders with fast data rates and high spectral efficiencies. The recent developments in DSP speeds brought optical coherent detection back into the picture, which has opened a whole new world of robust multilevel optical modulation formats capable of matching the increase in required transmission capacity. Recently, polarization-multiplexed (POLMUX) differential phase shift keying (DPSK) with coherent detection has been proposed for realizing ultra long-halu transmission with a data rate of 43 Gb/s. In the first part of this thesis we compare the suitability of 43 Gb/s POLMUX-RZ-DPSK and POLMUX-RZ differential quadrature phase shift keying (DQPSK) modulation for ultra long-haul optical transmission. We experimentally demonstrate that the higher robustness against nonlinear impairments of 43 Gb/s POLMUX-RZ-DPSK allows for a v 40% increase in feasible transmission distance compared to POLMUX-RZ-DQPSK. This extra reach of 43 Gb/s POLMUX-RZ-DPSK has enabled us to demonstrate a transoceanic transmission over more than 7000 km of field deployed fiber. After the data rate of 40 Gb/s, 100 Gb/s seemed to be the next logical step for the optical communication community. The transmission of 100 Gb/s channels has been successfully demonstrated using several modulation formats such as VSB and DQPSK with direct detection. However, the most cumbersome issues with such solutions were the susceptibility to linear optical effects and the low SE of the signal. In 2007 the first 111 Gb/s long-haul transmission using POLMUX-RZ-DQPSK with a SE of 2 b/s/Hz together with coherent detection has been demonstrated. Due to the high SE of the signal, the ability to compensate almost all kinds of linear effects and the enhanced sensitivity of a coherent detection receiver this solution was considered very favorably. In the second part of this thesis we investigate on the tolerance of the 111 Gb/s POLMUX-RZ-DQPSK signal to the different transmission impairments. The compatibility of the 111 Gb/s channels with existing networks has been investigated both using lab experiments and field trials. We demonstrated transmission of 111 Gb/s channels over field deployed fiber with co-propagating 10.7 Gb/s OOK and 43 Gb/s DPSK channels. We showed that by carefully choosing the launch power levels and the neighboring channels configuration, a 111 Gb/s channel can fit very well in currently existing transmission links. Furthermore, We studied the tolerance of the 111 Gb/s signal to the different nonlinear transmission impairments in different link structures. We analyze the effect of dispersion maps for different fiber types, and derived some rules for the reduction of performance difference between dispersion managed and non-dispersion managed links. Furthermore, we confirm that the super large effective area (SLA) fiber family can provide around 3 dB advantage in the tolerance to nonlinear effects compared to standard single mode fiber (SSMF). Despite of the high OSNR requirements of POLMUX- 16 level quadrature amplitude modulation (16QAM) and its low tolerance to nonlinear transmission effects it can achieve a SE as high as 4 b/s/Hz. Consequently, POLMUX-16QAM can enable the transmission of 200 Gb/s channels on the standard 50 GHz channel grid. In the last part of this thesis we demonstrate the generation and detection of a 224 Gb/s POLMUX-RZ-16QAM signal with around 4 dB of penalty in comparison to the theoretical limits. Furthermore, we report the transmission of eleven 224 Gb/s POLMUX-RZ-16QAM channels over 670 km of SSMF with a channel spacing of 50 GHz and a SE of 4.2 b/s/Hz. A long-haul transmission for the eleven 224 Gb/s channels over 1500 km has also been realized through employing advanced fiber types

Polmux-QPSK modulation and coherent detection : the challenge of long-haul 100G transmission

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 100G systems

Equalization of FBG-induced group-delay ripples penalties using a coherent receiver and digital signal processing

We show the mitigation of fiber Bragg gratings induced group delay ripple penalties through the use of coherent detection and electronic equalizer. For 111-Gb/s POLMUX-RZDQPSK only a negligible penalty is observed after 10 cascaded FBGs

Stereo multiplexing for direct detected optical communication systems

We propose a novel technique that allows simultaneous detection of two modulated optical sub-carriers. A proof-of-principle experiment is described and subsequently the performance at high data rates (111Gb/s) is assessed by simulations

Polmux-QPSK modulation and coherent detection : the challenge of long-haul 100G transmission

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 100G systems

A DPSK receiver with enhanced CD tolerance through optimized demodulation and MLSE

We experimentally demonstrate that a differential phase-shift keying (DPSK) receiver employing a Mach-Zehnder delay interferometer (MZDI) with a bit delay of less than one bit combined with maximum likelihood sequence estimation can considerably enhance the tolerance to chromatic dispersion (CD). Furthermore, we analyze the impact of sampling phase and optimize the MZDI bit delay for 10.7-Gb/s nonreturn-to-zero (NRZ)-DPSK demodulation. Our investigation shows that a 4000-ps/nm CD tolerance at 2-dB penalty is feasible for 10.7-Gb/s NRZ-DPSK

Equalization of FBG-induced group-delay ripples penalties using a coherent receiver and digital signal processing

We show the mitigation of fiber Bragg gratings induced group delay ripple penalties through the use of coherent detection and electronic equalizer. For 111-Gb/s POLMUX-RZDQPSK only a negligible penalty is observed after 10 cascaded FBGs

DSP for coherent single-carrier receivers

In this paper, we outline the design of signal processing (DSP) algorithms with blind estimation for 100-G coherent optical polarization-diversity receivers in single-carrier systems. As main degrading optical propagation effects, we considered chromatic dispersion (CD), polarization-mode dispersion (PMD), polarization-dependent loss (PDL), and cross-phase modulation (XPM). In the context of this work, we developed algorithms to increase the robustness of the single DSP receiver modules against the aforesaid propagation effects. In particular, we first present a new and fast algorithm to perform blind adaptive CD compensation through frequency-domain equalization. This low complexity equalizer component inherits a highly precise estimation of residual dispersion independent from previous or subsequent blocks. Next, we introduce an original dispersion-tolerant timing recovery and illustrate the derivation of blind polarization demultiplexing, capable to operate also in condition of high PDL. At last, we propose an XPM-mitigating carrier phase recovery as an extension of the standard Viterbi-Viterbi algorithm