Adaptive Polarization Control for Coherent Optical Links with Polarization Multiplexed Carrier

Abstract

Self-homodyne systems with polarization multiplexed carrier offer an LO-less coherent receiver with simplified signal processing requirement that can be a good candidate for high-speed short-reach data center interconnects. The practical implementation of these systems is limited by the requirement of polarization control at the receiver end for separating the carrier and the modulated signal. In this paper, effect of polarization impairments in polarization diversity based systems is studied and modeled. A novel and practical adaptive polarization control technique based on optical power feedback from one polarization is proposed for polarization multiplexed carrier based systems and verified through simulation results. The application of the proposed concept is experimentally demonstrated also for a QPSK system with polarization multiplexed carrier.

Demonstration of a low-power, local-oscillator-less, and DSP-free coherent receiver for data center interconnects

“…An optical amplifier is used for fiber length of 80 km to compensate for the losses in the channel. At the receiver end, an external PC is used to manually control the output polarization to maximize power in one of the polarizations and minimize it in the other one (in a practical system, this can be achieved by using adaptive polarization control [8]). These polarizations are separated by a PBS and sent to the signal and LO ports of an integrated DP-QPSK coherent receiver frontend (CPRVx1222A) for the detection of SH-QPSK signals.…”

“…At the receiver end, adaptive polarization control is required for separating the modulated signal and the carrier [8]. As polarization mode dispersion (PMD) is not significant for short-distance links, by maximizing received power in one of the polarizations (thereby minimizing it in the other one), the signal and the carrier can be separated out easily.…”

High-Capacity Coherent DCIs Using Pol-Muxed Carrier and LO-Less Receiver

“…Simulations were performed in VPItransmissionmaker T M for 50 Gbaud SH-QPSK system with 20 km fiber. Details of the simulations are available in our previous work [23].…”

“…For such SH systems, minimization of power in one polarization is able to achieve linear state of polarization as discussed in [23]. An electrically controlled PC can be used to maintain minimum power in one polarization by changing its angles based on the control inputs.…”

“…The adaptive polarization control for the PMC-SH links can be achieved with an electrically controlled polarization controller (EPC) by minimizing power in one of the polarization at reception [23]. Silicon photonics based polarization controllers (PCs) are also being proposed for other applications that can be implemented for PMC-SH systems further [24].…”