Somayeh Ziaie

Experimental Assessment of the Adaptive Stokes Space-Based Polarization Demultiplexing for Optical Metro and Access Networks

We experimentally analyze an adaptive polarization-demultiplexing (PolDemux) technique based on the representation of the state of polarization of the signal in the Stokes space. The performance and convergence speed of the Stokes PolDemux are compared with the constant modulus algorithm, for dual polarization QPSK and 16QAM modulation formats in a system with a maximum polarization rotation of 6 kHz. Moreover, the applicability of the adaptive Stokes algorithm is tested in an ultradense wavelength-division multiplexing scenario over 80 km of standard single-mode fiber. The BER results show a very small power penalty confirming the suitability of the adaptive Stokes method in systems where the accumulated chromatic and polarization-mode dispersion are small, such as high capacity optical metro and access networks scenarios.

Real-Time Bidirectional Coherent Nyquist UDWDM-PON Coexisting With Multiple Deployed Systems in Field-Trial

We experimentally characterize a bidirectional 2.5 Gb/s UDWDM-PON system based on Nyquist shaped DQPSK with digital signal processing in real time. The optical distribution network power budget of this system is evaluated and in coexistence of UDWDM channels with upstream TWDM-PON and RF video overlay signals, a set of optimum parameters and their impact on the network operation is driven. Additionally, we report the first field-trial of bidirectional coherent Nyquist UDWDM-PON using commercial real-time FPGA-based transceivers, coexisting with the deployed GPON, RF video overlay, and NG-PON2 technologies. A -44.5 dBm receiver sensitivity is achieved for 64 × 2.5 Gb/s DQPSK downstream channels and a 17 dB tolerance in dynamic power range of upstream channels is performed.

Free space optics hybrid PTMP advanced modulation bidirectional PON

We experimentally demonstrate a 12×10Gb/s bi-directional hybrid SSMF and FSO PHY PON recurring to 6.25 GHz grid, Nyquist shaping and frequency-shifting. Performance is evaluated over a 30.5 dB ODN with Hybrid splitting and coexistence with TWDM-PON.

CAPEX model for PON technology using single and cascaded splitter schemes

We present a model to estimate the Capital Expenditure (CAPEX) for passive optical network (PON) technology. We begin by identifying the key components of the PON technology and from that a CAPEX model is obtained. We then present single and cascaded splitter schemes, and their influence on the CAPEX.

Distributive FIR-Based Chromatic Dispersion Equalization for Coherent Receivers

We propose a novel and efficient multiplierless finite-impulse response (FIR)-based filter architecture for chromatic dispersion equalization (CDE) in coherent optical communication systems. After quantizing the FIR coefficients, we take advantage of the high multiplicity of their real and imaginary parts, employing the distributive property of multiplication over addition to sharply reduce the number of multiplication operations, obtaining the distributive FIR-CDE (D-FIR-CDE). Furthermore, the implementation of multiplication operations with shifts and additions allows us to obtain a multiplierless D-FIR-CDE (MD-FIR-CDE). The proposed equalizers are experimentally validated in a 100G polarization-multiplexed (PM)-QPSK long-haul optical link and compared against benchmark FIR-CDE and frequency-domain (FD)-CDE implementations. We demonstrate computational resources savings of over 99% in number of multiplication operations and 40% in number of additions, relatively to the FIR-CDE implementation. In addition, the D-FIR-CDE is also shown to compare favorably relatively to the most widely used FD-CDE, achieving significant gains both in terms of required chip area and latency: more than 99% and 30% fewer multipliers and additions, respectively, and a latency reduction of over 90%. We have also experimentally demonstrated that the performance penalty imposed by the coefficient quantization tends to decrease with increasing propagation length, rendering it as an attractive solution for efficient and high-performance chromatic dispersion compensation in long-haul optical fiber links.

Multiple system configuration for next generation optical access networks with real-time Nyquist UDWDM-PON

We experimentally characterize 2.5-Gb/s bidirectional UDWDM based on Nyquist shaped QPSK with DSP in real-time. A 41 dB ODN is achieved over 80-km SSMF. Additionally, the required guard-bands for a coexisting scenario with TWDM and video overlay are evaluated.

Considerations on performance, cost and power consumption of candidate 100G EPON architectures

An overview of several candidate architectures for 100 Gb/s capable optical access networks is presented. Considerations for their system requirements are outlined in regards to performance, cost and energy efficiency, towards addressing the design issues for the next generation EPON.

Digital equalization of optical nonlinearities in very high-speed optical communication systems

We review recently proposed nonlinear mitigation methods based on a frequency-domain Volterra series expansion for high-speed and long-haul optical transmission systems. Using a symmetric kernel reconstruction we derive a set of parallel frequency-domain filters that constructively add up to rebuild the matrix-based Volterra series nonlinear equalizer (VSNE). It is demonstrated through simulation results that a reduced set of symmetric VSNE (symVSNE) filters is able to achieve a near-optimum performance. In addition, a constant-coefficient approximation is used to obtain a simplified VSNE (simVSNE), achieving several orders of magnitude computational gain. The validity of this approximation is shown to mostly depend on the amount of accumulated chromatic dispersion to be compensated per simVSNE iteration, therefore impacting the spatial resolution requirements of the algorithm.

Clock and carrier recovery in high-speed coherent optical communication systems

In this paper, the implementations of clock and carrier recovery in digital domain are analyzed. Hardware implementation details, resources estimation and real-time results are presented. Analog-to-Digital Converters (ADC), operating at 1.25Gsa/s, and a Virtex-6 Field-Programmable Gate Array (FPGA), have been used, allowing the implementation of a real-time Quadrature Phase Shift Keying (QPSK) system operating at 1.25Gb/s. The real-time mode operation is successfully demonstrated over 80 km of Standard Single Mode Fiber (SSMF).

Advanced digital signal processing techniques based on Stokes space analysis for high-capacity coherent optical systems

Stokes space based digital signal processing (DSP) techniques can improve polarization demultiplexing, polarization dependent losses compensation, and other polarization-related tasks in coherent receivers, particularly in terms of convergence speed and transparency to higher-level M-ary modulated signals. This paper reports recent advances on Stokes space based DSP for coherent optical communications. We study and discuss the performance the polarization demultiplexing algorithm in terms of convergence speed and computational complexity, and present a new space-demultiplexing algorithm based on signal analysis in higher-order Poincaré spheres for spatial division multiplexing transmission systems. Moreover, practical issues regarding the real-time implementation on FPGAs of Stokes space based algorithms for flexible optical communications are also investigated and discussed.