224-Gbps single-photodiode PAM-4 transmission with extended transmitter bandwidth based on optical time-and-polarization interleaving.

Xiaoling Zhang,Longsheng Li,Deming Kong,Chongfu Zhang,Hao Hu,Kun Qiu,Shi Jia,Jin Wei,Yan Fu,Chen Chen

doi:10.1364/oe.397130

Abstract

We have proposed and demonstrated the optical time-and-polarization interleaving (OTPI) technique, which can effectively extend the transmitter bandwidth for an intensity modulation and direct detection (IM/DD) optical system. The 224-Gbit/s line-rate OTPI-PAM-4 signal is successfully transmitted over a 500-m standard single-mode fiber (SSMF) in the C band, using the transmitter with a bandwidth of 25 GHz and the receiver with a single photodiode. By using a 33%-return-to-zero (RZ) pulse train, a bit-error ratio (BER) below 7% hard-decision forward error correction (HD-FEC) threshold is achieved. BER below 20% soft-decision forward error correction (SD-FEC) threshold is also realized using a carrier suppressed return-to-zero (CSRZ) pulse train. The OTPI technique can also be used for more higher-order pulse amplitude modulation (PAM) formats, making it a promising technique for next-generation high-speed optical interconnects.

Highlights

Spurred by the dramatically increasing demand on data traffic in data-center interconnections, the next-generation networks are expected to support ubiquitous availability, ultra-low latency, high rate and high reliability services [1]
We have proposed and demonstrated the optical time-and-polarization interleaving (OTPI) technique, which can effectively extend the transmitter bandwidth for an intensity modulation and direct detection (IM/DD) optical system
We experimentally demonstrated 224-Gbps OTPI-pulse amplitude modulation (PAM)-4 signal transmission over a 500-m standard single-mode fiber (SSMF) using 33%-RZ pulses with a bit-error ratio (BER) below 7% hard-decision forward error correction (HD-FEC) threshold of 3.8×10−3 and using carrier suppressed return-to-zero (CSRZ) pulses with a bit error ratio (BER) below 20% soft-decision forward error correction (SD-FEC) threshold of 2.7 ×10−2, respectively

Summary

Introduction

Spurred by the dramatically increasing demand on data traffic in data-center interconnections, the next-generation networks are expected to support ubiquitous availability, ultra-low latency, high rate and high reliability services [1]. [14], and carrier-less amplitude phase (CAP) [15] These advanced modulation formats require high-resolution DAC and ADC, as well as complex digital signal processing (DSP). Xin et al reported a photonic-aided DAC based 120-Gbaud PAM-4/PAM-6 signal generation scheme using a 40-GHz mode-locked laser diode (MLLD) Most of these schemes apply large-bandwidth transmitters in order to fully utilize the available receiver bandwidth for a large overall capacity. Based on the OTPI technique, 56-GHz analog bandwidth is achieved to generate 112-Gbaud PAM-4 signal using two 25-GHz DACs and two 25-GHz MZMs in the transmitter. Compared to the scheme using a single high-bandwidth DAC and a high-bandwidth MZM, the strict bandwidth requirement in the transmitter can be relieved and device nonlinearity can be effectively mitigated, resulting in much simplified DSP and reduced latency at receiver side. The OTPI technique has potential for advanced IM/DD modulation with higher-order PAM formats to achieve higher capacity, and it’s compatible with advanced coding scheme, such as trellis-coded modulation (TCM) coding [28]

Proposed OTPI technique

Experimental setup

Experimental results

Findings

Conclusions