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Optical connections support virtual links in MPLS-over-optical multilayer networks and therefore, errors in the optical layer impact on the quality of the services deployed on such networks. Monitoring the performance of the physical layer allows verifying the proper operation of optical connections, as well as detecting bit error rate (BER) degradations and anticipating connection disruption. In addition, failure identification facilitates localizing the cause of the failure by providing a short list of potential failed elements and enables self-decision making to keep committed service level. In this paper, we analyze several failure causes affecting the quality of optical connections and propose two different algorithms: one focused on detecting significant BER changes in optical connections, named as BANDO, and the other focused on identifying the most probable failure pattern, named as LUCIDA. BANDO runs inside the network nodes to accelerate degradation detection and sends a notification to the LUCIDA algorithm running on the centralized controller. Experimental measures were carried out on two different setups to obtain values for BER and received power and used to generate synthetic data used in subsequent simulations. Results show significant improvement anticipating maximum BER violation with small failure identification errors. [ABSTRACT FROM PUBLISHER]

Coherent detection is the usual solution to achieve high bit rate transmission over long distance. However, it requires a local oscillator and energy consuming digital signal processing that make it not suitable for cost and energy sensitive interconnections and short haul links. In these applications, direct detection is the preferred solution and the main impairment is the chromatic dispersion of optical fibers. In theory, combined amplitude-phase shift (CAPS) codes are able to defeat any amount of chromatic dispersion. However, while they can be detected with a very simple direct detection receiver, their generation is not trivial. Their complexity grows with the order of the code which, in turn, increases with the chromatic dispersion. In this paper, the IQ-duobinary modulation scheme, a novel technique for approximating an order-3 CAPS code, is presented. Such a modulation scheme allows us to bridge up to 18 km at a bit-rate of 50 Gb/s over a standard single mode fiber using a simple direct-detection receiver without the need of any digital signal processing technique. [ABSTRACT FROM PUBLISHER]

Advances in transmission technologies and control plane solutions are driving the introduction of spectrally-efficient ultrahigh rate superchannel transmissions. Modulation format, forward error correction/coding, and carrier spacing represent the key transmission parameters to configure in order to obtain efficient network resource utilization according to the specific optical path requirements. So far, several studies have mainly addressed the efficient configuration of a single selected transmission parameter. Instead, the topic of the combined configuration of the whole set of parameters still requires significant investigations, particularly in the case of automatic configuration procedures. In this study, we first review the aforementioned transmission parameters in terms of their adaptation capabilities. Then, a novel procedure for effective configuration of the whole set of transmission parameters is presented. The procedure, besides modulation format and coding configuration, includes a novel self-adaptation technique for the carrier spacing in a superchannel transmission. Moreover, the technique relies on a novel software-defined networking control to reoptimize the superchannel frequency slot width. The technique has been successfully validated in a field trial where a 1 Tb/s superchannel of eight subcarriers has been automatically adapted from a frequency slot width of 200 GHz to a more efficient slot width of 175 GHz, without traffic disruption. [ABSTRACT FROM PUBLISHER]

Next generation optical networks will require high levels of flexibility both at the data and control planes, being able to fit rate, bandwidth, and optical reach requirements of different connections. Optical transmission should be able to support very high rates (e.g., 1 Tb/s) and to be distance adaptive while optimizing spectral efficiency (i.e., the information rate transmitted over a given bandwidth). Similarly, the control plane should be capable of performing effective routing and spectrum assignment as well as proper selection of the transmission parameters (e.g., modulation format) depending on the required optical reach. In this paper we present and demonstrate a software-defined super-channel transmission based on time frequency packing and on the proposed differentiated filter configuration (DFC). Time frequency packing is a technique able to achieve high spectral efficiency even with low-order modulation formats (e.g., quadrature phase-shift keying). It consists in sending pulses that overlap in time or frequency or both to achieve high spectral efficiency. Coding and detection are properly designed to account for the introduced inter-symbol and inter-carrier interference. We present a software defined network (SDN) controller that sets transmission parameters (e.g., code rate) both at the transmitter and the receiver side. In particular, at the transmitter side, a programmable encoder adding redundancy to the data is controlled by SDN. At the receiver side, the digital signal processing is set by SDN based on the selected transmission parameters (e.g., code rate). Thus, extensions to the OpenFlow architectures are presented to control super-channel transmission based on time frequency packing. Then, the SDN-based DFC is proposed. According to DFC, the passband of the filters traversed by the same connection can be configured to different values. Experiments including data and control planes are shown to demonstrate the feasibility of optical-reach-adaptive super-channel at 1 Tb/s controlled by extended OpenFlow. Then, the effectiveness of the proposed SDN-based DFC is demonstrated in a testbed with both wavelength selective switches and spectrum selective switches, where filters traversed by a connection requires different passband values. Extended OpenFlow messages for time frequency packing and supporting DFC have been captured and shown in the paper. [ABSTRACT FROM PUBLISHER]

An intra-data center architecture employing a cost-effective multi-level transmission scheme is presented. Unlike related previous works, the proposed scheme enables the optical multiplexing of two asynchronous and independent optical streams into an eight-amplitude phase-shift keying signal. The scheme is particularly suitable for intra-data center scenarios, where cost-effective solutions have to guarantee adequate bandwidth flexibility. The proposed transmitter successfully multiplexes two data streams, namely a 40 Gb/s differential quadrature phase-shift keying signal and a 10 Gb/s on-off keying one, coming from two separate (and not synchronized) apparatus. The experimental implementation, including two non-coherent receivers, reveals satisfactory performance ensuring a correct functionality (bit error rate <;10 -9) for an optical signal-to-noise ratio of about 31 dB. The design of an intra-data center switch architecture encompassing the proposed transmission scheme is then presented. Additionally, the switch includes a specifically defined Open Flow control enabling bandwidth flexibility according to application service requirements. The overall solution has been successfully implemented and demonstrated in an experimental testbed including traffic tributaries provided through off-the-shelf network elements. The overall configuration is successfully completed within a few milliseconds only. [ABSTRACT FROM PUBLISHER]