The EML-Based Coherent Receiver With High Sensitivity for Data Center Interconnection

The necessity for high carrier-to-signal power ratio (CSPR) in the single-sideband direct-detection transmission system results in a low receiver sensitivity. To address this problem, we propose a coherent reception scheme based on an electro-absorption modulated laser (EML) to amplify the optical carrier at the receiver in virtue of optical injection locking (OIL) technique, thereby mitigating the impact of the signal-signal beat interference. Specifically, the local oscillator yielded by an injection-locked distributed feedback (DFB) laser is coupled with the optical signal, and coherently detected by an electro-absorption modulator (EAM). We experimentally investigate the feasibility and performance of the 8-Gbaud Nyquist-shaped quadrature phase shift keying (QPSK) signal transmission system employing an EML-based coherent receiver without the Kramers-Kronig (KK) algorithm. As a result, 9- and 7-dB sensitivity improvements are achieved in comparison with the standard KK receiver while the CSPR is reduced by 10 dB in the optical back-to-back and after 80-km fiber transmission cases, respectively. The experimental results indicate that the proposed approach owns the potential to improve receiver sensitivity for power and cost-efficient data center interconnection.