Abstract
We numerically demonstrate colorless reception of dense wavelength division multiplexed channels in the C-band for high-order QAM (16-64 QAM) signals on a 120° monolithically integrated downconverter, based on a 2x3 MMI with calibrated analog IQ recovery. It is shown that the proposed calibrated 120° downconverter can increase up to 80 the number of coincident channels in an efficient way, exhibiting good signal dynamic range and high fabrication yield. As this downconverter makes use of the minimum number of power outputs required for perfect recovery of IQ signals, it becomes an interesting alternative to conventional 90° based downconverters.
Highlights
The deployment of reconfigurable optical add-drop multiplexers (ROADM) in transport optical networks has provided flexibility and configurability capabilities to network operators
The introduction in the near future of colorless ROADM will allow any wavelength to be added/dropped to any port. In this situation colorless receivers can be used in the drop ports to increase the efficiency and reduce the cost of reconfigurable optical networks
Balanced 90° hybrid based coherent receiver with high CMRR and high local oscillator (LO)-to-signal power ratio can be used as colorless receiver
Summary
The deployment of reconfigurable optical add-drop multiplexers (ROADM) in transport optical networks has provided flexibility and configurability capabilities to network operators. A promising alternative to overcome the above problems is the 120° phase diversity receiver which, if properly calibrated, has shown to be highly tolerant to hardware impairments at microwave frequencies [8] This is an interesting solution because, as it is known from multiport theory [9, 10], three is the minimum number of power outputs to perfectly recover IQ signals from power readings by linear means, and the 120° based downconverter is the simplest multiport receiver. From Eq (5), the self-beating interference contribution from each adjacent channel will be weighted by the signal power and the CMRR at its respective wavelength In this way, colorless reception will require a low Ps/PLO ratio and a high CMRR over the complete received multichannel frequency band. Output electrical signals are linearly combined with a calibrated analog circuit prior to be digitized in two ADCs and digitally processed
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