Stefan Warm

Splice loss requirements in multi-mode fiber mode-division-multiplex transmission links

We investigate numerically the influence of fiber splices and fiber connectors to the statistics of mode dependent loss (MDL) and multiple-input multiple-output (MIMO) outage capacity in mode multiplexed multi-mode fiber links. Our results indicate required splice losses much lower than currently feasible to achieve a reasonable outage capacity in long-haul transmission systems. Splice losses as low as 0.03dB may effectively lead to an outage of MIMO channels after only a few hundred kilometers transmission length. In a first approximation, the relative capacity solely depends on the accumulated splice loss and should be less than ≈ 2dB to ensure a relative capacity of 90%. We also show that discrete mode permutation (mixing) within the transmission line may effectively increase the maximum transmission distance by a factor of 5 for conventional splice losses.

Analytical Description of Cross-Modal Nonlinear Interaction in Mode Multiplexed Multimode Fibers

In this letter, we present a semianalytical approach to calculate the nonlinear interference between mode-multiplexed signals that are transmitted over the eigenmodes of a multimode fiber (MMF). We point out the influence of several fiber parameters on nonlinear mode interaction using four-wave mixing concepts. Finally, we apply the presented theories on a mode-division multiplexed transmission link, which uses a graded index multimode fiber. It is shown, in a configuration, that each of the MMFs 55 modes achieves an optical signal to noise ratio at the receiver at least as high as a standard single-mode fiber, resulting in a higher overall capacity than 55 single-mode fibers.

Perspectives of principal mode transmission in mode-division-multiplex operation

We investigate the concept of principal modes and its application for mode division multiplexing in multimode fibers. We start by generalizing the formalism of the principal modes as to include mode dependent loss and show that principal modes overcome modal dispersion induced by modal coupling in mode division multiplexing operation, even for multi-mode-fibers guiding a large number of modes, if the product of modulation bandwidth, fiber length and differential group delay is equal or less than one in each transmission channel. If this condition is not sustained, modal dispersion and crosstalk at the receiver limit the transmission performance, setting very high constraints towards modal coupling.

Modeling of Mode Coupling in Multimode Fibers With Respect to Bandwidth and Loss

A fast, accurate and simple field coupling model is presented which is capable of describing mode coupling effects due to bends and splices in multimode fibers with parabolic index profile as well as the coupling losses induced by this process. This model is validated numerically by comparing the results to the well-known coupled amplitude theory model yielding the same relative bandwidth increase behavior as long as the coupling losses are the same. It is shown, that the number of discrete segments used in this model can be reduced considerably as long as the coupling losses are kept constant. The effect of mode coupling on the differential group delay, mode dependent loss, bandwidth gain and impulse response width reduction are analyzed. It is shown that the relative bandwidth gain induced in MMF links induced by the coupling process is independent of fiber parameters or number of guided modes; it can be fully characterized by coupling induced losses. The model is compared to well-known results given by power coupling models and a good agreement is observed for high steady state loss values.

Performance Evaluation of DWDM Communication Systems With Fiber Optical Parametric Amplifiers

We derive analytical expressions for the performance of a long-haul DWDM communication system employing in-line phase insensitive fiber optic parametric amplifiers (FOPA). In our analysis the impairments of both transmission fibers and FOPAs are taken into account. The analytical model is verified with simulations. The performance of FOPA is compared with EDFA and it is shown that a broad band long-haul DWDM transmission system based on FOPAs as in-line amplifiers could be feasible.

Electronic Dispersion Precompensation With a 10-Gb/s Directly Modulated Laser

We present 10-Gb/s transmission with a directly modulated laser (DML) avoiding inline dispersion compensating by electronic precompensation. To apply this technique of electronic dispersion precompensation to DMLs, a new approach based on artificial neural networks will be introduced. We realized a transmission of 190-km standard single-mode fiber in a laboratory experiment. Simulations show that compensation of up to 350 km can be achieved.

Influence of Discrete Mode Coupling on the Nonlinear Interaction in Mode-Multiplexed Systems

In this letter, we analyze the impact of discrete mode coupling on mode-multiplexed transmission links that employ few-mode fibers. We show that discrete coupling between spatial modes, as introduced, e.g., by splices, highly degrades the performance of mode-division multiplexed transmission links due to an additional nonlinear penalty. This stands in contrast to the performance improvement that is introduced by frequently appearing random mode coupling.

Nonlinear interaction in differential mode delay managed mode-division multiplexed transmission systems

We analyze the impact of Differential Mode Delay (DMD) Management on the nonlinear impairments in mode-division multiplexed transmission systems. It is found out that DMD Management can lead to a degraded performance, due to enhanced intermodal nonlinear interaction. This can be attributed to an increased correlation of co-propagating channels, similar to the effects that show up in dispersion managed single-mode systems.

Impact of SBS on polarization-insensitive single-pump optical parametric amplifiers based on a diversity loop scheme

We experimentally and numerically show that the Brillouin back scattering can result in signal distortions in diversity loop-based polarization insensitive single-pump fiber-optical parametric amplifiers, limiting the distortion-free gain to 10-15 dB for typical highly nonlinear fibers.

Characterization of a fiber-optical parametric amplifier in a 5 × 28-GBd 16-QAM DWDM system

The performance of a FOPA as inline-amplifier for 28-GBd 16-QAM signals at 20-dB gain in a 50-GHz 5-channel DWDM system is experimentally investigated. Less than 0.7-dB OSNR penalty at a BER of 1×10-3 was measured with 0-dBm per-channel output power.