Bernhard Schrenk

10 Gb/s full-duplex bidirectional transmission with RSOA-based ONU using detuned optical filtering and decision feedback equalization

Full-duplex bidirectional transmission at 10 Gb/s is demonstrated for extended wavelength division multiplexed passive optical network (WDM-PON) applications, achieving transmission distances up to 25 km of standard single mode fiber (SSMF) when using a low-bandwidth (approximately 1.2 GHz) reflective semiconductor optical amplifier (RSOA) for signal re-modulation at the optical network unit (ONU). The system is assisted by optimum offset filtering at the optical line terminal (OLT)-receiver and the performance is further improved with the use of decision-feedback equalization (DFE). Chromatic dispersion (CD) and Rayleigh Backscattering (RB) effects are considered and analyzed.

Direct 10-Gb/s Modulation of a Single-Section RSOA in PONs With High Optical Budget

We experimentally demonstrate 10-Gb/s operation of a reflective semiconductor optical amplifier (RSOA) for data transmission in passive optical networks, with optical power budgets of up to 28 dB. Besides a passive adaptation for the electrooptical response of the semiconductor device, neither active electronic equalization nor optical offset filtering was applied to enhance the modulation bandwidth of the RSOA. Error-free transmission without using error correcting codes can be obtained even for low RSOA input power values of -20 dBm.

10 Gb/s RSOA transmission by direct duobinary modulation

An ultra low-cost electronic solution to achieve 10 Gb/s transmission by means of passive equalization and duobinary encoding using an RSOA with 1.5 GHz electrical bandwidth is demonstrated.

Remotely Pumped Long-Reach Hybrid PON With Wavelength Reuse in RSOA-Based ONUs

Symmetrical full-duplex transmission in a Passive Optical Network (PON) is demonstrated over a 100 km dual-fiber ring with 1:16 split trees. The customer premises equipment is based on a Reflective Semiconductor Optical Amplifier (RSOA), which reuses the wavelength of the intensity modulated downstream signal for upstream data transmission. A commercial RSOA was used together with optical offset filtering at the upstream receiver to operate at data rates of 5 and 10 Gb/s. Margins of >; 8 dB are left at a data rate of 5 Gb/s, proving that the utilized downstream suppression scheme and therefore the intensity modulation format for both, down- and upstream, is suitable for its application in long-reach hybrid access networks. The signal degradation along the PON and the transmitted pump that features means of remote amplification in its conjunction points between the metro ring and the local trees are discussed and further possibilities for an improvement of the transmission performance are proposed.

Demonstration of a Remotely Dual-Pumped Long-Reach PON for Flexible Deployment

We propose and experimentally demonstrate a flexible wavelength division multiplexing/time division multiplexing network architecture for converged metro-access environment. Entire passiveness in the fiber plant is achieved with remote amplification in the signal distribution nodes along the metro ring and in the power splitters of the local access tree. We assist a traditional remote pumping scheme with a distributed pump provided by the optical network units and demonstrate that loss budgets beyond 30 dB can be supported. Data transmission of up to 10 Gb/s is evaluated in different deployment scenarios, reaching from a 78 km long reach rural to a dense 1:128 split/λ urban configuration with field installed fibers, including also worst case resilience configurations.

Energy-Efficient Optical Access Networks Supported by a Noise-Powered Extender Box

A method for energy-efficient amplification by reutilization of optical noise as pumping power in access networks with extended loss budget is presented. The amplified spontaneous emission (ASE) of an optical amplifier at the customer premises is thereby reshaped and reused as a natural pump source for Erbium-doped fibers (EDF) inside the signal distribution elements of an access network. This increases the number of served customers and enables also transmission at no extra cost, by just recycling optical noise. Three scenarios, which differ in the design of the optical network unit (ONU), are evaluated and show that up to 4000 users can be served in passive optical networks with adequate signal quality for certain configurations of the ONU. Typical transmission constraints due to the use of cost-effective reflective ONUs, such as Rayleigh backscattering effects, are reduced due to the introduction of a distributed amplification scheme. Besides, full-duplex 10 Gb/s transmission on a single wavelength with simultaneous EDF pump generation is demonstrated with low-cost ONUs, based on reflective semiconductor optical amplifiers. A comparison with traditional amplification techniques is given, and the relationship between the different power consumption for the pump delivery is discussed.

All-optical carrier recovery with periodic optical filtering for wavelength reuse in RSOA-based colorless optical network units in full-duplex 10Gbps WDM-PONs

Optically assisted downstream cancellation for wavelength reuse in WDM-PONs is demonstrated, allowing downstream extinction ratios up to 9 dB for symmetrical full-duplex data transmission at 10Gbps with RSOA-based ONUs. PON budgets of ~20dB can be reached.

Fully-Passive Optical Switch Introducing Dynamicity and Flexibility to Metro-Access

We experimentally demonstrate a tool for dynamic reconfigurability at the physical layer infrastructure through optically powered switches based on micro-opto-electro-mechanical system technology. Energy scavenging at the optical network layer is exploited to feed this switching element. Up to 13 consecutive switching operations are shown for a full energy reservoir in addition to endless continuous switching operation with a recharge time of 24 s between operations for an optical feed of 6 dBm. A fast switching mode with 120 ms is also supported. Crosstalk robustness, penalty-free switching, and compatibility with reflective networking schemes are achieved and guarantee scalable node technology that is, from a network point-of-view, fully passive.

Quantum key distribution over optical access networks

It is well known that optical access networks are able to provide high data rates over long distances and to a reasonable number of users. Security and privacy are always a challenge for public accessible network infrastructures. Especially in time-division multiplexing passive optical networks (TDM-PONs), in which the downstream signal is broadcasted to all users connected via the same wavelength channel in a shared fiber link, privacy can be a critical concern. Although encryption at the application layer can provide a high level of security, this can be achieved only if the encryption key distribution is perfectly save. On the other hand, encryption on the physical layer such as quantum cryptography or, more precisely, quantum key distribution (QKD) is a very promising approach to achieve secure communication. However, there remain several issues that have to be solved before the quantum cryptography reaches the maturity level needed for a cost effective implementation in practical networks. In this paper, we address quantum key distribution (QKD) over passive optical access networks, which is an enabling technology required to cost efficiently deploy practical quantum encrypted data communication in the access area. We study different methods to integrate QKD systems in conventional optical access networks and quantitatively evaluate their suitability for a potential implementation.

Rayleigh Scattering Tolerant PON Assisted by Four-Wave Mixing in SOA-based ONUs

A scheme for the mitigation of Rayleigh backscattering (RB) in hybrid passive optical networks (PON) is presented. Semiconductor optical amplifiers (SOA) of the optical network units (ONU) are advantageously used as nonlinear elements, exploiting Four-Wave Mixing (FWM) between the downstream signals to create a spectrally displaced optical upstream carrier. The proposed technique is experimentally proven in a long reach and high split PON, and the suppression of the pumps and further FWM products, obtained via a modified filtering scheme inside the PON, is analyzed. Full-duplex transmission at 10/2.5 Gb/s is demonstrated, showing that upstream transmission is possible despite low optical signal-to-RB ratios (OSRR) of ~ 12 dB.