Analytical and experimental performance evaluation of an integrated Si-photonic balanced coherent receiver in a colorless scenario

Mohamed Morsy-Osman,Michel Poulin,Mathieu Chagnon,Carl Paquet,Martin Pelletier,Qunbi Zhuge,Xian Xu,David V Plant,Yves Painchaud

doi:10.1364/oe.22.005693

Abstract

We study analytically and experimentally the performance limits of a Si-photonic (SiP) balanced coherent receiver (CRx) co-packaged with transimpedance amplifiers (TIAs) in a colorless WDM scheme. Firstly, the CRx architecture is depicted and characterization results are presented. Secondly, an analytical expression for the signal-to-noise ratio (SNR) at the CRx output is rigorously developed and various noise sources in the context of colorless reception are outlined. Thirdly, we study experimentally the system-level CRx performance in colorless reception of 16 × 112 Gbps PDM-QPSK WDM channels. Using a 15.5 dBm local oscillator (LO) power, error free transmissions over 4800 and 4160 km at received powers of -3 and -21 dBm per channel, respectively, were achieved in a fully colorless and preamplifierless reception. Next, a set of measurements on one of the center WDM channels is performed where the LO power, received signal power, distance, and number of channels presented to the CRx are swept to evaluate the performance limits of colorless reception. Results reveal that the LO beating with optical noise incoming with the signal is a dominant noise source regardless of received signal power. In the high received signal power regime (~0 dBm/channel), the self-beat noise from out-of-band (OOB) channels is an additional major noise source especially for small LO-to-signal power ratio, short reach and large number of OOB channels. For example, at a received signal power of 0 dBm/channel after 1600 km transmission, the SNR difference between the fully filtered and colorless scenarios, where 1 and 16 channels are passed to the CRx respectively, grows from 0.5 to 3.3 dB as the LO power changes from 12 to 0 dBm. For low received power (~-12 dBm/channel), the effect of OOB channels becomes minor while the receiver shot and thermal noises become more significant. We identify the common mode rejection ratio (CMRR) and sensitivity as the two important CRx specifications that impact the performance at high and low received signal power regimes, respectively. Finally, an excellent match between experimental and analytical SNRs is proven after the derived SNR model is fitted to the experimental data in a least-squares sense. The model is then used to predict that the CRx can operate colorlessly for a fully populated WDM spectrum with 80 channels provided that the LO-to-signal power ratio is properly set.

Highlights

The incessantly growing capacity demand in optical transport has been spurring extensive research efforts in the realm of coherent optical technology [1,2,3,4,5,6,7,8,9,10]
We develop rigorously an analytical expression of the signal-to-noise ratio (SNR) at the CRx output in the case of colorless reception taking into consideration all sources of noise namely, local oscillator (LO)-ON, SIG-SIG, SIG-ON, ON-ON and LO-LO beatings as well as the receiver shot and thermal noises, where SIG stands for signal and ON stands for optical noise incoming with the signal
Results collected from channel 9 include the SNR measured after offline digital signal processing (DSP) while sweeping the aforementioned parameters to evaluate the impact of each parameter on the performance of colorless CRx operation and to identify the dynamic range of the CRx for various number of channels

Summary

Introduction

The incessantly growing capacity demand in optical transport has been spurring extensive research efforts in the realm of coherent optical technology [1,2,3,4,5,6,7,8,9,10]. It still remains a challenge to meet the relentless growing network traffic demand [11] Technological solutions such as space division multiplexing (SDM) that utilizes multiple fiber modes / cores have the potential to multiply the capacity per fiber [8]. In the envisioned agile network, flexible coherent transceivers, that are capable of adapting to dynamic traffic needs and maximizing the network capacity, are key elements that need to be deployed at ingress/egress nodes. There have been some reports on experimental colorless coherent reception by utilizing either a conventional CRx front-end followed by single-ended detection [14], which suffers from limited maximum channel count and poor dynamic range due to the inability to reject the self-beat common mode noise, or a more complicated receiver front-end followed by single-ended detection to enable rejecting the self-beat noise [15]. More recently in [17], the authors demonstrated experimentally the use of an integrated PLC-based balanced coherent receiver for colorless reception of one 100G channel among 80 WDM channels

Methods

Results

Conclusion