Real-Time Monitoeing Technology Of Physical Impairments In Elastic Optical Networks

In order to meet the growing demand for bandwidth, next generation optical network will be designed to challenge higher-order modulation formats and high bit rate. With the development of optical communication technology, more and more mature technology of tunable optical transceiver and reconfigurable all-optical devices (such as ROADM) have been widely used in the network. Optical network connection is changing from point to point connection to a mesh network connection which is more flexible. The International Telecommunication Union (ITU) regulations50GHz grid will not be suitable for fixed bit rate of more than100Gb/s in transmission links. Even if there is sufficient bandwidth, it is difficult to achieve efficient use of the spectrum in the long distance transmission of high rate signal. In order to achieve efficient use of spectrum resource, elastic optical network (EON, Elastic Optical Network) emerges. The flexible spectrum allocation, as well as the transmission of multi-rate traffic can be achieved by EON. Since the appearance of resilient optical network, not only can use any modulation format, but also enabling multiple variable bandwidth business needs are met simultaneously. So it is possible to use spectrum resources more efficient. However, the higher the spectral efficiency of the optical signal, more sensitive to physical impairments in the transmission links. To ensure reliable, robust, high-speed data link, future optical networks will require advanced optical performance monitoring (OPM) to dynamically measure the degradation of optical signals in real time, so it is possible to rapid assess optical transmission quality (QoT). Optical performance monitoring of several parameters, including the optical signal noise ratio (OSNR), the power of the optical signal, chromatic dispersion (CD) and polarization mode dispersion (PMD) and so on, can provide a means of feedback informance in the data plane to higher network layer or control plane, and optimize global routing and network performance.The focus of this paper is based on the SDN (Software Defined Network) control plane, the design and implementation of flexible optical network software platform considering physical impairments. The main content of the work we are:(1) Optical Performance monitoringFirstly, the establishment of physical impairments model considering the Amplified Spontaneous Emission, crosstalk caused by non ideal optical switches, and Four Wave Mixing;Secondly, we design an OSNR detection based on M-Z delay line interferometer (DLI) to achieve real-time monitoring of physical impairments in hardware platform of the high order modulation format (such as QAM, QPSK), RZ-DQPSK, OOK/DPSK signal;Finally, we use the VPI software to simulated the OSNR threshold for different modulation formats, such as QPSK, DQPSK and16QAM in optical transmission systems.(2) Design and implementation of flexible optical network software platformThe mainly extensions to the OpenFlow protocol based on SDN adaptive control plane is the most important.In order to adapt to the flexible optical network, we also make deal with the controller NOX and PCE.