Electrical and optical equalization strategies in direct detected high-speed transmission systems

Using duobinary with first‐ and second‐order optical equalisers for extending transmission distance of optical access networks

“…The devices have 0° phase shifters, 0.5 coupling coefficients and insertion loss of ∼2 and 4 dB for the first-and second-order OEQ, respectively. A detailed description of the OEQs can be found in [9,23]. The signal is subsequently passed to an optical receiver which including a variable optical attenuator that adjusts the received optical power into a photodetector having a responsivity of 0.8 A/W, followed by a fourthorder Bessel low-pass filter with the bandwidth of ∼70% of the bit rate.…”

Optical Equalization of PMD-Induced Penalties in 112 Gbit/s Metro Networks

“…(left). In order to mitigate PMD-related distortions, a very simple approach would be to implement two parallel filter structures: Each equalizer structure has its own set of coefficients and can be adjusted independently while the input and output signals are split and, respectively, combined using a polarization beam splitter (PBS) [5]. In this contribution we also implemented a socalled "butterfly" structure as depicted in Fig.…”

“…They can also be used to equalize group delay ripples (GDR) due to deviations from an ideal dispersion compensation scheme as has been shown in [3]. In contrast to electrical equalization, which has been intensively studied [4], optical equalization has received comparatively little attention [5]. We have carried out extensive numerical simulations to compare two alternative strategies to realize an optical PMD equalizer and we found that the occurring maximum and mean penalties can be significantly reduced, when optical equalization is implemented.…”

Multilevel Manchester (2 bits/symbol) coding with optical equaliser for increasing the transmission distance of high‐speed fibre optic links

“…The chromatic dispersion (CD) is a significant linear impairment, while the key non-linear distortion is due to the Kerr effect of the transmission fibre. Non-mitigation of these distortions caused deterioration of signal quality that could lead to substantial power penalties in the optical links [7,8]. Generally, there are several digital techniques of mitigating the distortion penalty which has attracted exhaustive studies such as using digital filters in a coherent optical receiver and the application of digital signal processing [1].…”