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We demonstrate three novel all-optical signal processing methods for RZ-DPSK signals using a saturated SOA. The two logically opposite pulse streams from a demodulated noisy RZ-DPSK signal counter-propagate in the SOA. This configuration decreases the fluctuations in the demodulated marks while preventing the spaces from getting amplified. Photonic balancing provides functionality analogous to electrical balanced detection by reducing the required OSNR, and saturated asymmetric filtering removes the in-band ASE noise before detection. These methods are demonstrated experimentally by observing eye diagrams and BER measurements at 10.7 Gb/s and 22.3 Gb/s.

The performance of various modulation schemes for 100 Gbit/s single-channel serial transmission is investigated by means of numerical simulations. Different ASK and PSK modulation formats are compared in terms of total system reach for a 10 −9 BER requirement. RZ-DQPSK format with a 1920 km reach, without FEC and without the support of additional Raman amplification, outperforms all the other schemes including 10 × 10 Gbit/s NRZ DWDM inverse multiplexing.

An operator's view on a flexible and future proof network design and operation is described. Scalability and standardised interfaces are key to achieve an efficient and manageable network operation guaranteeing a seamless and cost efficient interoperability of network elements and layers.

Tbit/s transmission capacities are demonstrated in a 1,000 km field trial, provided by Deutsche Telekom, between high performance computing centers of the Universities Dresden and Stuttgart. Brocade and Intel Security Technologies are used to perform Tbit/s generation and processing including software defined networking and network virtualization functionalities. Increased 3 bit/s/Hz spectral efficiency of ADVA Optical Networking 100-Gbit/s transponders, passive wavelength routing, and multi-vendor optical interworking are demonstrated.

Optical systems and technologies have been radically changing the telecommunication networks for past 15 years; today wavelength division multiplexing (WDM) technology, optical amplifiers, and simple optical switching elements like optical add-drop multiplexers (OADMs) are used in the backbone networks of all operators worldwide. Optical systems nowadays provide the basis for cost-effective transmission of large amounts of bandwidth over the Internet, and will enable its future growth and the spreading of new applications and services. This paper summarizes the main trends in optical networking and investigates potential future application areas. Optical system technology has become so pervasive in network design that it needs to be considered in the context of provisioning new applications and services. Therefore, the analysis is not limited to the aspects of physical transmission, but also takes into account recent developments in integrated network design as well as network control and management. The following sections describe the key functionalities of future optical network architectures, and the key findings of the theoretical analysis are supported by the results of a field trial of advanced transmission technology

Saturated Collision Amplifier (SCA) is a novel amplification scheme that uses SOA saturation in order to maximize the output power and minimize the ASE noise and the polarization sensitivity. We demonstrate the SCA reach extension in a commercial single-wavelength XGPON1 prototype system where bidirectional optical budget of up to 50 dB is obtained. The traffic performances are compared between the SCA and the conventional SOA extender. The novel extension scheme is demonstrated also for two- and four-wavelength 10 Gbit/s unidirectional downstream configurations with 45 km and 100 km transmission distances with 58-dB maximum total optical budget for each wavelength.

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.

Photonic balancing - a scheme where logically opposite pulses derived from the two outputs of a delay-line demodulator for phase shift keyed (PSK) signals counter-propagate in the saturated regime of a semiconductor optical amplifier (SOA) - has been proven to enhance the receiver performance, e.g. in terms of decreased optical signal-to-noise-ratio (OSNR) requirements for a given target bit error ratio (BER). Here, we extend the photonic balancing scheme towards a new concept for a regenerative amplifier targeted at extending the reach and/or the number of subscribers in passive optical networks (PON) in order to support major operators' plans to reduce the number of central offices and access areas by approximately 90%. For a given target BER, we demonstrate experimentally (a) an 8-dB higher post-amplifier loss tolerance, (b) an extended feeder line length (75 km) combined with high splitting ratio (10 layers) for a preamplified version, and (c) high input power variation tolerance (> 30 dB burst-to-burst) in upstream direction as needed for highly asymmetric tree structures.

This paper presents for the first time the network architecture and the multiple-wavelength operation of a novel SOA-based PON extender. In 10-Gbit/s four-wavelength 100-km configuration, the total optical budget for each wavelength is 58 dB.

Publisher Summary In recent years, the distinction between the system reach of metro and long-haul systems has diminished. Today's metro systems can be easily extended to cover distances longer than 500 km. This development has profound impact on the architecture of the European national networks, where the size of networks is closer to that of current metro/regional networks. Moreover, since signal wavelengths can be extended to distances nearing 100 km without re-amplification, the requirement of a large number of central offices in the legacy national networks in countries like Germany has also diminished. It is therefore more cost effective to consider network architectures with fewer central offices, potentially eliminating up to 90% of the existing ones. Cost benefits will also be derived from the implementation of new technologies such as new modulation formats and coherent detection, particularly for high-data-rate channels. In this chapter, network architecture issues and physical impairments due to chromatic dispersion, polarization mode dispersion (PMD), and related mitigation techniques for these networks are described from the point of view of a European network operator. Simulation results are also presented to show a comparison of the system reach over different types of fiber for signals with return to zero (RZ) and carrier suppressed RZ (CSRZ) modulation formats and the use of Raman and EDFA hybrid amplifiers to optimize the network design.

Due to the vast increase of internet and data traffic and upgrading existing optical metro-, regio- and long haul transport networks, the migration from existing networks toward high speed optical networks with channel data rates up to 100 Gb/s/λ is one of the most important questions today and in the near future. Researchers, system vendors and -operators focus on investigations, targeting the relaxation of constraints for 100 Gb/s transmission to find the most efficient upgrade strategies. This presentation describes the requirements and realization scenarios for 100 Gb/s networks from an incumbent network operator point of view. The field trials with channel rates of 100 Gb/s, carried out in the network of Deutsche Telekom AG, in cooperation with system vendors are summarized.

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.

We present an optical receiver for RZ-DPSK signals that use photonic balancing. Photonic balancing is achieved through pulse counter-propagation and collision in a saturated SOA. We explain the principles of photonic balancing and show how it can lead to an improvement in RZ-DPSK detection by 3 dB, similar to electrical balancing. We also show how this scheme can be used as a Mamyshev-type regenerator.

Due to the doubling of the internet traffic every twelve month and upgrading existing optical metro-, regio- and long haul transport networks, the migration from existing networks toward high speed optical networks with channel data rates up to 100 Gbit/s/λ is one of the most important questions today and in the near future. Current WDM Systems in photonic networks are commonly operated at linerates of 2.5 and 10 Gbit/s/λ and major carriers already started the deployment of 40 Gbit/s/λ services. Due to the inherent increase of the bandwidth per channel, limitations due to linear and non-linear transmission impairments become stronger resulting in a highly increased complexity of link engineering, potentially increasing the operational expenditures (OPEX). Researchers, system vendors and -operators focus on investigations, targeting the relaxation of constraints for 100 Gbit/s transmission to find the most efficient upgrade strategies. The approaches towards increased robustness against signal distortions are the transmission of the 100 Gbit/s data signals via multiple fibers, wavelength, subcarriers or the introduction of more advanced modulation formats. Different modulation schemes and reduced baud rates show strongly different optical WDM transmission characteristics. The choice of the appropriate format does not only depend on the technical requirements, but also on economical considerations as an increased transmitter- and receiver-complexity will drive the transponder price. This article presents investigations on different approaches for the upgrade of existing metro-/ regio and long haul transport networks. The robustness against the main degrading physical effects and economy of scale are considered for different mitigation strategies.

We demonstrate a 6.3 dB improvement in Q‐factor for RZ‐DPSK signals using a shifted filter after a highly saturated SOA working in a contra‐propagating colliding pulse scheme. We show first, both theoretically and by means of simulations, how the phase noise is transformed after demodulation. Then, we demonstrate experimentally, for the first time, that this configuration induces a spectral asymmetry in addition to self phase modulation that if associated with a shifted filter, removes significantly the noise present in both the demodulated marks and spaces. The Asymmetric Saturated Regeneration (ASR) is an enhanced version of the fiber based Mamyshev regenerator.

Due to the increasing demand for higher transmission capacity, originated from upcoming Triple-Play services, network operators are forced to increase the transmission capacity in the backbone and aggregation networks and drive down the costs per bit/s. Many concepts have been presented, optimizing backbone network and increasing the network capacity by introducing higher data rates or channel count. In this paper we focus on aggregation network architectures investigating appropriate architectures for the aggregation of broadband services for an incumbent European network operator. These architectures have to be cost effective and ensure high service availability. These requirements can be met by either aggregating via star topology, using several stages of Ethernet aggregation nodes, by a ring topology using cost effective optical add/drop multiplexers (OADM), or furthermore a mixture of star and ring topologies. The right choice depends on the traffic load, the traffic forecast, distribution of the traffic matrix and underlying fiber graph.

Data rates generated in the access network by new services and customer demand on triple play influence on the transmission capacity and flexibility of the transport network. A field trial to upgrade an existing DWDM link with 10 Gbit/s RZ- and NRZ-channels by 40 Gbit/s RZ-DQPSK-channels was performed on a link consisting of legacy G.652 fibre with two ROADM and EDFA amplification only. The field link had a length of 1047 km. To obtain a high spectral efficiency of the 40 Gbit/s transport the channel spacing was reduced from 100 GHz to 50 GHz. We investigated channel crosstalk for 50 GHz and 100 GHz channel spacing, mixed types of neighbour channels, PMD and chromatic dispersion tolerance which influence on maximum transparent transmission length and signal quality of the 40 Gbit/s signal in a field experiment.

We present a 8×170 Gbit/s DWDM/OTDM (1.28 Tbit/s) field transmission experiment over 421 km in commercially operated network of Deutsche Telekom. Stable transmission performance was achieved for all channels with BER  2.8*10-4 using adaptive PMD compensation. (3 pages)

40-Gbit/s OTDM transmission over a field-installed dispersion-compensated 130-km single mode fibre (SMF) link was demonstrated successfully (BER < 10/sup -12/). The impact of high PMD (7.8 ps) in the order of the RZ pulse width (7 ps) was studied in detail.

Manufacturing of long chirped fiber gratings can lead to slight phase jumps inside the structure resulting in additional ripples in the spectrum. Simulation and high-resolution measurement results are demonstrated using a novel evaluation procedure.

A polarization-mode dispersion (PMD) transient recorder setup was realized enabling for the first time to our knowledge the monitoring of fast PMD fluctuation with a bandwidth of up to 1 MHz. Thirty-six hours of observation of an installed field fiber exhibits significant PMD variation within 10 ms.

A novel two-output PON amplifier is demonstrated to provide over 8-dB output power budget improvement over a conventional SOA, with negligible ASE noise. With an additional preamplifier it can accommodate up to 30 dB burst-to-burst power variation.