Blind adaptive equalization of polarization-switched QPSK modulation

Coherent detection in combination with digital signal processing has recently enabled significant progress in the capacity of optical communications systems. This improvement has enabled detection of optimum constellations for optical signals in four dimensions. In this paper, we propose and investigate an algorithm for the blind adaptive equalization of one such modulation format: polarization-switched quaternary phase shift keying (PS-QPSK). The proposed algorithm, which includes both blind initialization and adaptation of the equalizer, is found to be insensitive to the input polarization state and demonstrates highly robust convergence in the presence of PDL, DGD and polarization rotation. (C)2011 Optical Society of Americ

Estimating network throughput with an adaptive routing and wavelength assignment algorithm

We propose an adaptive sequential loading algorithm that approaches the ILP throughput. Of 2,000 network realizations tested, shortest path routing achieves >90% of the maximum throughput in 341 cases c.f. 1,904 with the proposed algorithm

Designing adaptive coded modulation for optical networks via achievable information rates

© 2017 IEEE. Achievable information rates are discussed as a tool to analyse and design optical networks. It is shown that the maximum throughput of the network and its dependency of different network parameters can be predicted with such a tool

Congestion Aware Routing in Nonlinear Elastic Optical Networks

In elastic optical networks, digital coherent transceivers modify their symbol rate, modulation format, and forward error correction to best serve the network demands. In a nonlinear elastic optical network, these parameters are inherently coupled with the routing algorithm. We propose to use congestion aware routing in a nonlinear elastic optical network and demonstrate its efficacy for the NSFNET reference network (14 nodes, 22 links). The network is sequentially loaded with 100 GbE demands until a demand becomes blocked, this procedure being repeated 10000 times to estimate the network blocking probability (NBP). Three routing algorithms are considered: 1) shortest path routing; 2) simple congestion aware algorithm; and 3) weighted congestion aware routing algorithm with 50, 25, 12.5, and 6.25 GHz resolution flexgrids. For NBP = 1% using a 50 GHz grid, congestion aware routing doubles the network capacity compared with the shortest path routing. When congestion aware routing is combined with a 6.25 GHz resolution flexgrid, a fivefold increase in network capacity is afforded

Remote abstraction of an installed dark fiber network using noise to signal ratio

© 2018 OSA. A dark fiber network was partially abstracted utilizing network monitors, prior information and a single probe channel. Validation employed 13×200Gb·s-1 DWDM signals transmitted at the optimum launch power, with measured performance 0.2dB better than abstracted

Physical layer transmitter and routing optimization to maximize the traffic throughput of a nonlinear optical mesh network

This paper investigates the physical layer optimization as a means of improving the utilization of limited network resources. A transparent optical network operating in the nonlinear transmission regime using coherent optical technology is considered. A physical layer model is described that allows the transmission signal quality to be included in the optimization process. Initially a fixed power, route-adapted modulation format approach is taken using integer linear programming to solve the static route allocation problem. It is shown that for the 14-node, 21-link NSF mesh network adaptation of the modulation formats leads to increases in data throughput of 17%. Optimization of the individual transmitter launch powers and spectral channel allocation results in a SNR margin of 2.3 dB, which is used to further increase the overall network traffic throughput exceeding the fixed PM-QPSK modulation format by as much as 50%. Compared to other work this paper highlights that increased gains in network throughput can be achieved if nonlinear interference is included in the routing and spectral assignment algorithm and individual transmitter spectral assignment and launch power is optimized to minimize nonlinear interference

Technology Requirements for an Alamouti-Coded 100 Gb/s Digital Coherent Receiver Using 3 × 3 Couplers for Passive Optical Networks

Digital coherent receivers employing Alamouti-coding are a promising solution for passive optical networks (PON) with downstream rates of 100Gb/s/λ. To reduce cost by utilizing high-volume photodiodes designed for 25Gb/s data-center applications, we consider 28-Gbaud 16-QAM modulation format detected with a single-polarization coherent receiver based on a 3×3 coupler with single-ended detection. We investigate two alternative configurations: first, a receiver with a symmetric 3×3 coupler and subsequently an IQ coupler (asymmetric 3×3 coupler) with Alamouti-coding based polarization diversity. In this paper, we present a detailed investigation as to the feasibility of both the receivers for a wide range of parameters including quantization noise, relative intensity noise (RIN), I/Q mismatch etc. It is found that such receivers can be realized with commercially available components. We also quantify the penalty associated with non-ideal components to allow for lower cost designs with reduced specifications suitable for access applications. In addition, we present the adaptive DSP algorithms required to recover data for single-carrier Alamouti-coded signal. Considering both linear and nonlinear impairments, a power budget of 36.4dB and 33.1dB is found at BER of 3.8×10−3 for receiver with symmetric 3×3 coupler and IQ coupler, respectively and thereby proving their applicability as receivers for 100Gb/s/λ PON

Single Channel Probe Utilizing the EGN Model to Estimate Link Parameters for Network Abstraction

© 2017 IEEE. We experimentally demonstrate multi-span link parameter abstraction using a single channel 11.5GBd probe. EGN based abstraction gave γ=1.14W 1 km -1 c.f. 0.72W 1 km 1 for a GN based abstraction. The GN model overestimates the abstracted SNR by 0.4dB c.f. the EGN model at 1000km

DSP algorithms for recovering single-carrier Alamouti coded signals for PON applications

Alamouti space-time block code (STBC) combined with a simple heterodyne coherent receiver enables phase diverse coherent detection without any optical polarization tracking. While such a system consisting of only a 3-dB coupler and a single balanced photodiode has been recently demonstrated using orthogonal frequency-division multiplexed (OFDM) signals, herein we report the first application to single-carrier systems. Applicability of such technique for single-carrier systems is not straightforward since specialized digital signal processing (DSP) algorithms are required for data recovery. In this paper, we address the implementing issues and DSP algorithms applicable for single-carrier (SC) Alamouti STBC based simplified heterodyne receivers. Polarization-insensitive operation of the proposed scheme and its performance are verified by means of simulation for a 12-Gbits/s quadrature phase-shift keying (QPSK) transmission system.European Union (Project ICONE (Grant ID: 608099)), Engineering and Physical Sciences Research Council (UNLOC (Grant ID: EP/J017582/1)