Thomas Duthel

Impact of Polarisation Dependent Loss on Coherent POLMUX-NRZ-DQPSK

We present simulations and measurements on the effect of PDL on a POLMUX-NRZ- DQPSK signal. We show that the orientation between the POLMUX signal and PDL element has a major impact on the OSNR performance.

Laser Linewidth Estimation by Means of Coherent Detection

In this letter, we present a novel approach to measure the Lorentzian linewidth of a laser source. The approach is based on a heterodyne detection scheme, such as may be implemented in a coherent optical receiver for data communications, using both in-phase and quadrature information of the optical field. In contrast to previously published works, this approach does not suffer from modulation effects on the laser output.

Optical Performance Monitoring using a 43Gb/s realtime coherent receiver

We present Optical Performance Monitoring from the equalizer filter setting of an FPGA-based Realtime 43Gb/s Polarization Diverse Coherent Receiver. Chromatic Dispersion and Polarization Mode Dispersion of the optical transmission link are independently estimated from the blindly adapted equalizer filter. The accuracy of the estimates is demonstrated based on measurements.

Towards Robust 100G Ethernet Transmission

We discuss transmission requirements for commercially deployable, robust 100 G Ethernet transport. Coherently equalised POLMUX-RZ-DQPSK is shown to be both compatible with 10 G infrastructure and suitable for long-haul transmission.

General Design Rules for the Synthesis of Dispersion and Dispersion Slope Compensation FIR and IIR Filters With Reduced Complexity

Chromatic dispersion is one of the main transmission impairments in optical systems with high bit rates, because the dispersion limit scales with the square of the data rate. Optical delay-line filters can be used to compensate dispersion and dispersion slope. They can be designed as feedforward finite-impulse response filters or as all-pass infinite-impulse response filters. Due to the time-variant property of the dispersion, those filters have to be adaptive, which requires fast and reliable calculation of the filter coefficients. In this paper, a new approach to calculate filter coefficients by applying analytical methods is presented. Design examples are given, and the filter performance is discussed.

Quasi-Analytic Synthesis of Nonrecursive Optical Delay Line Filters for Reliable Compensation of Dispersion Effects

A quasi-analytic synthesis algorithm is presented to determine the coefficients of nonrecursive optical delay line filters with approximately constant or linear dispersion. These filters can be used to compensate the dispersion and dispersion slope effects in high-speed optical transmission systems. The synthesis of the coefficients is based on a rigorous analysis of the impact of transfer function on the filters dispersion behavior. The advantages of this algorithm are that filters of arbitrary order have similar dispersion shapes and that the dispersion values of the filters can be adjusted by controlling a single parameter instead of optimizing all the filter coefficients independently. The realized dispersion shapes are reproducible, and no iterative algorithms are needed for the calculation. The abilities of the synthesized filters are proven in system simulations at 40 Gb/s. Therefore, filters of different orders were investigated in the static case (i.e., with a fixed dispersion) and the dynamic case, where the dispersion of the filter is adapted to the requirements of the simulated optical transmission channel. In addition, the influences of the filters free spectral range and of the utilized bandwidth inside a filter period were investigated. To the best of our knowledge, both the analytical synthesis approach and the investigation of the optimal filter configuration are presented for the first time

Simple tunable all-fiber delay line filter for dispersion compensation

A delay line filter with tunable group delay for residual dispersion compensation is presented. The device is suitable for channel bit rates of 40 Gb/s and consists mainly of two 3 /spl times/ 3 fiber couplers connected in series. Due to the all-fiber implementation, it has low polarization sensitivity and can be directly inserted in the transmission line. Its dispersion value can be tuned by simply changing the optical phase in one filter path. Thereby, a tuning range of /spl plusmn/50 ps/nm is realized with a very good agreement between simulation and measurement.

Simple automatic nonlinear compensation with low complexity for implementation in coherent receivers

We analyze digital nonlinearity compensation. Due to complexity restrictions in real-time applications we propose a simplified compensator with an automatic control scheme and evaluate its performance with simulations on two different dispersion maps.

Fiber optical structure for tunable dispersion compensation using cascaded long-period gratings

A structure that utilizes the mode conversion of long-period gratings to compensate the residual dispersion in high bit rate transmissions is presented. Due to the propagation of the used modes in the same fiber the device is inherent stable and has a low insertion loss.

Flexible manufacturing method for long-period fibre gratings with arbitrary index modulation profiles

Special long-period fibre gratings (LPGs) are needed in multiple applications. For example, LPGs are employed as mode converters in the forward direction to utilise the waveguide dispersion of higher order modes. Other applications are gain flattening of optical amplifiers or filtering in general. In this paper, we propose a flexible manufacturing method for LPGs, which enables the generation of tailored arbitrary index modulation profiles. The results of apodized and chirped gratings are presented, which show the flexibility and reliability of the writing set-up.