'Roam Like at Home' is a slogan used to express the new roaming regulation applied to the countries within the European Union. Since June 15th, 2017, mobile network subscribers of the network operators within the European Union can use mobile services in other European countries without having extra charges for it. Although almost all mobile subscribers within countries of the European Union benefits from the new roaming rule, many mobile service providers are yet to be adapted to this change. Therefore, those providers bear the burden of the cost for the inter-provider traffic. Moreover, the latency between subscribers and their operator specific content must be reduced in order to provide a roaming service 'like at home'. An emerging virtualization technology such as a Network Function Virtualization (NFV) sheds light on these challenges. This paper describes the concept of the mobile roaming service and our on-going implementation work as a part of 5G-PPP 5GEx project which aims at localizing inter-provider mobile traffic within the virtualized network infrastructure.

In this paper we show an SDN controller implementation named Basebox that listens to Linux Netlink and translates commands into OpenFlow rules to control a domain of OF-DPA based switches in an OpenStack cluster.

The orthogonal frequency division multiple access (OFDMA)-based passive optical network (PON) is a potential candidate to meet the flexibility requirements for next-generation optical access networks. We propose an OFDMA-based PON with a transmission employing intensity modulation/direct detection in the downstream and a remodulation of a remotely seeded carrier provided by the optical line terminal with coherent detection in the upstream, which enables cost-effective colorless optical network units (ONUs). Furthermore, an OFDMA-PON field trial using the proposed scheme over 37.5 km feeder fiber is demonstrated. A power budget supporting 32 ONUs with dynamic bandwidth allocation and trellis coded modulation (TCM) is reported.

Transmission capabilities of a coherent real-time UDWDM PON over deployed fibers in two testbeds (Berlin and Darmstadt, Germany) are demonstrated. Extensive coexistence tests including LTE backhauling and GPON, RF-Video, 100G and OTDR were performed. A silicon photonics-integrated CMOS laser was used for parts of the trial.

OFDM is an interesting candidate to meet the requirements of high flexibility and speed for the next generation optical access networks. We show an OFDM system utilizing a timing advance tracking algorithm to realize a synchronized upstream transmission. Therefore, a dynamic bandwidth allocation can be used in the upstream and an interleaved assignment is made possible. We then demonstrate the feasibility in a field trial with four individual ONUs using a 37.5 km field deployed feeder fiber of the Deutsche Telekom AG. Power loading and the trellis coded modulation was used to achieve a power budget supporting 32 ONUs for up- as well as downstream transmission.

An OFDMA-PON field trial using coherent detection in upstream and direct detection in downstream on 37.5 km feeder fiber is demonstrated. A power budget supporting 32 cost-effective colorless ONUs with dynamic bandwidth allocation is reported.

An open converged metro-access network approach allows for sharing optical layer resources like fibers and optical spectrum among different services and operators. We demonstrated experimentally the feasibility of such a concept by the simultaneous operation of multiple services showing different modulation formats and multiplexing techniques. Flexible access nodes are implemented including semiconductor optical amplifiers to create a transparent and reconfigurable optical ring network. The impact of cascaded optical amplifiers on the signal quality is studied along the ring. In addition, the influence of high power rival signals in the same waveband and in the same fiber is analyzed.

Passive optical network (PON) monitoring with as many as 1024 subscribers encounters difficulties due to high splitting losses and drop fiber differentiation problems. In this work a novel concept for monitoring PONs for fiber to the home (FTTH) access, which is based on concatenated wavelength-selective mirrors, has been investigated in a field trial. At each subscriber a unique mirror combination is installed. Binomial coefficients guarantee that each mirror combination in a given PON is used only once. The field trial has been performed successfully with a PON consisting of 37 km deployed standard single-mode fiber and up to 1:32 passive optical power splitting causing a total one-way attenuation of at least 30.7 dB. Different subscribers located at equal distances from the optical time domain reflectometry could be distinguished and identified individually. For the measurement setup only low-cost components were used.

Field trial results of high resolution optical frequency modulated continuous wave (FMCW) monitoring approaches are presented. The variable chirp rate technique and the phase noise cancellation method show promising results on a deployed fiber PON-infrastructure.

Our novel PON monitoring concept succeeded in a field trial. Subscribers located at equal distances were individually identified across a PON with at least 30.7 dB one-way loss and utilization of low cost components.

This paper discusses necessary steps for the migration from today's residential network model to a converged access/aggregation platform based on software defined networks (SDN).

A method to distinguish single- and equidistant multi-target reflections in optical monitoring is successfully demonstrated. The polarization dependent transmission in field deployed fiber PON-infrastructure was evaluated by combining polarization diversity detection with frequency modulated continuous-wave.

In this article we present a summary of the latest 100 Gbps field trials in the network of Deutsche Telekom AG with industry partners. We cover a brown field approach as alien wavelength on existing systems, a green field high speed overlay network approach and a high speed interface router-router coupling.

Successful 112 Gbit/s PDM-CSRZ-DQPSK transmission with coherent detection and digital electronic DSP post processing is reported over a 1730 km SSMF plus 300 km DCF field installed DWDM-system. A modular network approach with co-propagating 10 Gbit/s WDM-channels is achieved.

In the framework of the BMBF / Celtic funded program 100GET, the OCTET (Open Environment for Advanced Carrier Ethernet Technologies) project provided a test environment for 100 Gbit/s solutions of different partners in the already installed fiber infrastructure of Deutsche Telekom in Germany. The project was well in time with the development of 100 Gbit/s client and transport network interface technologies, standardized at IEEE 802.3ba for 100GE Ethernet, and at ITU-T G.709 for 100G OTN, respectively. Additionally, long haul 100 Gbit/s DWDM transmission technologies have been specified in a multi source agreement of the Optical Internet Forum. However, the goal of the project was to investigate 100 Gbit/s solutions which can be deployed in DWDM channels of field installed packet/optical transport networks, supporting the development of cost efficient and scalable Terabit/s transmissions. Since the project finished in December 2010, in this paper we summarize the work and present the main results and conclusions.

This paper shows the requirements for next generation optical access (NGOA) networks and analyzes the potential of OFDM (orthogonal frequency division multiplexing) for the use in such network scenarios. First, we show the motivation for NGOA systems based on the future requirements on FTTH access systems and list the advantages of OFDM in such scenarios. In the next part, the basics of OFDM and different methods to generate and detect optical OFDM signals are explained and analyzed. At the transmitter side the options include intensity modulation and the more advanced field modulation of the optical OFDM signal. At the receiver there is the choice between direct detection and coherent detection. As the result of this discussion we show our vision of the future use of OFDM in optical access networks.

The accumulated PMD along several fibers in an optical network was measured in order to identify those short fiber portions exhibiting high PMD. By replacing high-PMD-portion(s) in each fiber, the overall-PMD could be reduced significantly. Additionally the PMDaccumulation of different fibers in the same buried cable was investigated and compared to each other.

Fibre links in optical networks generally comprise several relatively short fibre segments which have been spliced together in cables. These fibre segments or “sections” are assembled with optical connectors and have a typical length of some tens of km. The important characteristic parameters of the fibre sections are attenuation, chromatic dispersion (CD) and polarisation mode dispersion (PMD). However, the PMD of the optical fibres can hamper the upgrade of optical backbone networks towards higher data rates of 40 Gbit/s and beyond. The PMD distribution along a buried fibre link is not constant and can also significantly vary between the concatenated fibres of the same optical cable. In the absence of such spatial information, the whole cable with higher PMD-values may have to be replaced in order to transmit 40 Gbit/s transparently over long distances. But investigations have shown that frequently localized pieces within a section are the major contributors to the overall high PMD value of the whole fibre, rendering the link unsuitable for higher data rates. A new random-scrambling polarization optical time domain reflectometry (POTDR) measurement technique is used to investigate the spatial distribution of the cumulative PMD in deployed fibres. Results help to identify high-PMD fibre pieces or sections which need to be replaced to enable 40 Gbit/s transmission and beyond, rather than substitution of a whole fibre link. Techno-economical investigations show the high economic potential of this method leading to significant reduction of expenses for infrastructure improvements. These improvements will enable network operators to transmit high data rates without limitation given by PMD.

The accumulated PMD along several fibres in an optical network was measured in order to identify those short fibre portions exhibiting high PMD. By replacing high-PMD-portion(s) in each fibre, the overall-PMD could be reduced significantly.