Abstract
Next-generation optical communication networks aim to vastly increase capacity by exploiting a larger optical transmission window covering the S-C-L-band. Simultaneously, the clear market trend is to maximize capacity per wavelength to reduce operational costs. This approach requires an increase in spectral efficiency, resulting in stringent requirements on the transceivers, which may not be satisfied in a multi-band (MB) scenario by current commercial components designed for operation in C-band. Transceiver specifications for MB operation can be relaxed through additional digital signal processing (DSP), at the cost of additional complexity, and by more resource-intensive calibration procedures. In this context, we experimentally characterize the wavelength-dependent frequency-resolved in-phase/quadrature (I/Q) imbalance of a standard C-band IQ-modulator and coherent receiver operating in an S-C-L-band system utilizing receiver-side DSP. This operation allows us to understand the nature of the wavelength-dependency of I/Q imbalance in MB systems. In the considered scenario, we validate the effectiveness of a cost-effective strategy for transceiver impairments mitigation and monitoring based on standard wavelength-independent calibration and reduced-complexity DSP.
Highlights
T HE continuous rise in IP traffic encourages operators to accelerate the deployment of multi-band (MB) wavelength division multiplexing (WDM) systems
We extend the work in [4] by identifying the variation of the frequency-resolved I/Q imbalance inside the signal electrical bandwidth versus wavelength for off-theshelf C-band transceivers working in S-C-L-band systems
The frequency offset (FO) separation results in a fundamental difference in the impact of Tx-side and Rx-side imbalance on system performance: while we can immediately compensate for Rx-side imbalance, Tx-side imbalance lies under the surface until carrier recovery is accomplished, affecting the performance of the whole digital signal processing (DSP) chain
Summary
T HE continuous rise in IP traffic encourages operators to accelerate the deployment of multi-band (MB) wavelength division multiplexing (WDM) systems. With currently available off-the-shelf components and doped fiber amplifiers, an S-C-L-band setup spanning from 1460 nm to 1608.8 nm (≈ 150nm) has been demonstrated for dual-polarization (DP) 64 GBd 32/64-QAM with calibration and digital pre-distortion (DPD) performed through system identification at a single wavelength [5]. In this configuration, we performed the characterization of the wavelengthdependency of the I/Q imbalance considering a flat frequency response inside the signal bandwidth for the impairments [4].
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