Abstract
Flexible optical networks require reconfigurable devices with operation on a wavelength range of several tens of nanometers, hitless tuneability (i.e. transparency to other channels during reconfiguration), and polarization independence. All these requirements have not been achieved yet in a single photonic integrated device and this is the reason why the potential of integrated photonics is still largely unexploited in the nodes of optical communication networks. Here we report on a fully-reconfigurable add-drop silicon photonic filter, which can be tuned well beyond the extended C-band (almost 100 nm) in a complete hitless (>35 dB channel isolation) and polarization transparent (1.2 dB polarization dependent loss) way. This achievement is the result of blended strategies applied to the design, calibration, tuning and control of the device. Transmission quality assessment on dual polarization 100 Gbit/s (QPSK) and 200 Gbit/s (16-QAM) signals demonstrates the suitability for dynamic bandwidth allocation in core networks, backhaul networks, intra- and inter-datacenter interconnects.
Highlights
Flexible optical networks require reconfigurable devices with operation on a wavelength range of several tens of nanometers, hitless tuneability, and polarization independence
These filters can fulfill three main requirements which are fundamental to bring them from lab experiments to real applications: (i) operation and tuneability across a wavelength range of several tens of nanometers, matching for instance the gain bandwidth of semiconductor and fiber amplifiers; (ii) possibility of dynamically re-routing selected subsets of channels, while keeping full transparency for all the other channels transmitted through the device, this feature being typically referred to as “hitless” tuneability; and (iii) insensitivity to the polarization state of the input light signals, that translates into a low polarization dependent loss (PDL) and low polarization dependent crosstalk
The radii Ri and the coupling coefficients Ki of the microring resonator (MRR) are optimized starting from the nominal design according to a numerical procedure described in Supplementary Sec. 1 in order to achieve free spectral ranges (FSRs)-free frequency response, while keeping the spectral shape of the main passband over the broadest wavelength range
Summary
Flexible optical networks require reconfigurable devices with operation on a wavelength range of several tens of nanometers, hitless tuneability (i.e. transparency to other channels during reconfiguration), and polarization independence. Coupled microring resonator (MRR) architectures fabricated on high-index-contrast platforms, such as silicon photonics, can provide good spectral performances in terms of wide passbands (several tens of GHz), steep roll-offs, and high extinction ratios (> 50 dB)[8,9,10] On paper, these filters can fulfill three main requirements which are fundamental to bring them from lab experiments to real applications: (i) operation and tuneability across a wavelength range of several tens of nanometers, matching for instance the gain bandwidth of semiconductor and fiber amplifiers; (ii) possibility of dynamically re-routing selected subsets of channels (i.e., wavelengths), while keeping full transparency for all the other channels transmitted through the device, this feature being typically referred to as “hitless” tuneability; and (iii) insensitivity to the polarization state of the input light signals, that translates into a low polarization dependent loss (PDL) and low polarization dependent crosstalk. The proposed filter concept is embedded in a polarization diversity scheme demonstrating polarization-insensitive single passband filter with hitless tunability across a wavelength range of about 100 nm (1520–1610 nm, limited by experimental equipment)
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