Natasa B. Pavlovic

Improved remote node configuration for passive ring-tree architectures

In this paper, a set of optically fed passive remote node configurations for a ring-tree extended reach PON which allow increased efficiency and resilience are presented.

Self-Homodyne Detection-Based Fully Coherent Reflective PON Using RSOA and Simplified DSP

We investigate the power budget of a fully coherent reflective passive optical network, based on self-coherent upstream (US) and self-homodyne downstream (DS) detection schemes. We consider, for US, both binary phase-shift keyed (BPSK) and quadrature phase-shift keyed (QPSK) at 1 GBd generated by direct modulation of a low-cost reflective semiconductor optical amplifier having 1-GHz electrical bandwidth and using simplified digital signal processing (DSP). We find that the penalty of increasing the order of US modulation format from BPSK to QPSK for higher capacity can be reduced to 1 dB by means of DS digital spectral shifting and US static postequalization.

Efficient Dynamic Modeling of the Reflective Semiconductor Optical Amplifier

Reflective semiconductor optical amplifier (RSOA) is considered a strong candidate to play an important role in realizing the next generation wavelength division multiplexing passive optical network, based on the wavelength reuse concept. Therefore, an accurate and efficient modeling of RSOA is of significant importance. We present a time-domain wideband model for simulation of spatial and temporal distribution of photons and carriers in a bulk RSOA. We provide a novel approach for efficient amplified spontaneous emission modeling, considering a tradeoff between the accuracy and the computational efficiency. The multiobjective genetic algorithm is utilized for parameter extraction. Experimental validation has been performed for continuous wave input, nonreturn to zero (NRZ) on-off keying, and quadrature phase-shift keying (QPSK) signaling pulses up to 40 Gb/s of bit rate, in both amplification and remodulation regimes. We further present systematic performance evaluation under remodulation scenario. Saturation, noise, chirp, and signal broadening are successfully predicted, while reducing the computational time compared to other wideband models.

Evolution of Optical Access Networks

This chapter reviews the current developments in access network architectures and protocols to communicate dynamically the emerging broadband services to end-users at low cost. Following a summary of Gigabit Ethernet and Passive Optical Network (PON) standards and deployment issues with reference to Ethernet (EPON) and Gigabit-capable PON (GPON) infrastructures, an original transparent network architecture is presented to allow interoperability of time division multiplexing (TDM) and wavelength division multiplexing (WDM) PONs, by means of coarse routing. To provide flexible connectivity at extended service reach hybrid wireless and free space optic technologies have been investigated to terminate mobile end users to high bandwidth PON terminals. To demonstrate independent bandwidth management of the constituent sectors of such architectures developed dynamic bandwidth allocation (DBA) algorithms are summarised followed by an original control plane to coordinate the various mandatory access control (MAC) protocols. Finally, to provide reliable service delivery several protection schemes have been analysed.

Optimized optical filtering for 40 Gb/s/channel enhanced phase-shaped binary transmission in ultra dense WDM systems

The systematic optimization of multiplexing (MUX) and demultiplexing (DMUX) 3 dB filter bandwidths for enhanced phase-shaped binary transmission (EPSBT) coding format is performed. Long-haul 40 Gb/s ultra dense wavelength division multiplexing (UDWDM) system with 0.8 bit/s/Hz spectral efficiency is shown to be achievable with different filter types. By extensive numerical optimization of MUX and DMUX filtering, we show that the optimum EPSBT has an extinction ratio parameter of 0 dB for second-order super Gaussian filters and between 2 and 6 dB for Gaussian filters.

Demonstration of Wavelength-Shared Coherent PON Using RSOA and Simplified DSP

We investigate the role of a reflective semiconductor optical amplifier (RSOA) in a fully coherent wavelength-shared passive optical network architecture, based on self-coherent upstream (US) and self-homodyne downstream (DS) detection schemes. We present a proof of concept experimental study, demonstrating 32-dB loss budget over a 30-km fiber link, operating at 9.4-Gb/s DS and 750-Mb/s US effective rates with 7% forward error correction and 8b/10b US overheads, respectively. This was achieved using simplified digital signal processing and a low-cost, off-the-shelf RSOA with 18-dB gain and 1-GHz modulation bandwidth.

Single-Sideband Differential Phase-Shift Keying Asynchronous Carrier-Suppressed Return-to-Zero – A Novel Signaling Format Optimized for Long-Haul UDWDM Systems

In this paper, a novel single-sideband differential phase-shift keying asynchronous carrier-suppressed return-to-zero (SSB-DPSK-ACS-RZ) format is proposed for long-haul ultradense wavelength-division multiplexing (UDWDM) systems with 43 Gbit/s/channel and 50 GHz of channel spacing. The time delay between the DPSK and clock signals is optimized to achieve higher eye-opening and improved group velocity dispersion tolerance. Furthermore, the tight SSB filtering performed by the multiplexer is used to convert the DPSK-ACS-RZ signal from phase- to amplitude-shift keying, allowing using a lower-cost direct-detection receiver and improving its spectral efficiency. The single-channel and UDWDM transmission performance of the novel format is numerically investigated and compared to the SSB duobinary carrier-suppressed RZ, bandwidth-limited duobinary, phase-modulated duobinary transmission, and bandwidth-limited DPSK formats. The SSB-DPSK-ACS-RZ format shows similar Q-factor and tolerances to pre- and in-line dispersion compensations and fiber nonlinearity to the ones of other investigated direct-detection formats. Significant total residual dispersion tolerance improvement is achieved by the SSB-DPSK-ACS-RZ format relative to the other formats due to the signal chirp. Moreover, the SSB-DPSK-ACS-RZ format shows higher Q-factor than the one of the bandwidth-limited DPSK for long-haul UDWDM transmission systems. In ultra-long-haul UDWDM transmission systems, SSB-DPSK-ACS-RZ and bandwidth-limited DPSK formats show similar performance.

Optimization of Single-Sideband DCS-RZ Format for Long-Haul 43-Gb/s/channel Ultradense WDM Systems

The optimization of the single-sideband (SSB) duobinary carrier-suppressed (DCS) return-to-zero (RZ) format for long-haul ultradense wavelength-division multiplexing (UDWDM) systems with a 43-Gb/s/channel and a channel spacing of 50 GHz is investigated numerically. It is shown that the optimized SSB-DCS-RZ format with an electrical transmitter bandwidth of 0.35 of the bit rate has about 1 dB of Q-factor improvement relative to the conventional SSB-DCS-RZ format (an electrical transmitter bandwidth of 0.25 of the bit rate) due to the reduction of noise bandwidth, smaller linear crosstalk, and better tolerance to the intra-channel fiber nonlinear effects. No substantially different UDWDM system performance is observed when varying the duty cycle of the DCS-RZ signal with optimized SSB filters settings. The UDWDM transmission performance of SSB-DCS-RZ formats is compared with the bandwidth-limited (BL)-duobinary formats. It is shown that generally, the SSB-DCS-RZ formats have poorer Q-factor and tolerance to the total residual dispersion but much higher tolerance to the in-line dispersion compensation and intra-channel nonlinear effects than the BL-duobinary formats

Optimized bandwidth-limited duobinary coding format for ultra dense WDM systems

By varying simultaneously the bandwidths of electrical transmitter filter, multiplexer and demultiplexer, the system performance of several duobinary coding formats is optimized for 40 Gbit/s/channel ultra dense wavelength division multiplexing (UDWDM) system with 50 GHz of channel spacing after 4/spl times/80 km of transmission. It is shown that bandwidth-limited (BL) duobinary generation schemes with optimized electrical transmitter filter bandwidth can achieve a Q-factor improvement of 1.4 dB over BL-conventional duobinary coding schemes. Moreover, the optimized BL-duobinary format achieves a better UDWDM system performance than BL-phase-shaped binary transmission, for which a capacity/spl times/distance record was demonstrated.

SBS induced four-wave mixing in ultra dense WDM systems

We experimentally investigated the efficiency of the Brillouin induced FWM process, using two types of fibers. Even with the pump power levels above the SBS threshold, the power of the FWM signal was found to saturate at low power, inducing low crosstalk in bidirectional WDM transmission.