Thang M. Hoang

400-G Single Carrier 500-km Transmission With an InP Dual Polarization IQ Modulator

In this letter, we demonstrate experimentally 400-G transmission over 500 km using an InP-based dual-polarization IQ modulator on a single wavelength. The results show that a 56-Gbaud polarization division multiplexed (PDM)-16-quadratic-amplitude modulation (QAM) modulated signal can be transmitted over 500 km at a bit error rate (BER) below the hard decision forward error correcting threshold of 3.8 ×10-3. A 43-Gbaud PDM-64-QAM modulated signal can be transmitted over 320 km with a BER below the soft decision forward error correcting threshold of 2×10-2.

100G and 200G single carrier transmission over 2880 and 320 km using an InP IQ modulator and Stokes vector receiver.

We demonstrate experimentally the transmission of single carrier 56 Gbaud 16-QAM, 8-QAM and QPSK optically modulated signals over 320, 960 and 2,880 km, respectively, using a fully packaged InP IQ modulator and a Stokes vector direct detection (SV-DD) receiver realized using discrete optics. Results show that by optimizing the carrier-to-signal-power ratio, the total throughput-times-distance product for 16 QAM and QPSK are 71,680 Gbps.km and 322,560 Gbps.km, respectively, at bit error rate (BER) below the hard decision forward error correcting threshold (HD-FEC) of 4.5 × 10-3.

770-Gb/s PDM-32QAM Coherent Transmission Using InP Dual Polarization IQ Modulator

We experimentally demonstrate 770-Gb/s (77-Gbd PDM-32QAM) transmission on a single wavelength using an indium phosphide dual polarization IQ modulator over 320 km of standard single mode fiber, which is suitable for low-cost metro networks and datacenter interconnects. Moreover with the same setup, we also demonstrate transmissions of 84-Gbd polarization division multiplexed (PDM)-16QAM and 84-Gbd PDM-8QAM signals over 960 and 1980 km distances, respectively, for regional and long-haul networks.

Single wavelength 480 Gb/s direct detection over 80km SSMF enabled by Stokes vector Kramers Kronig transceiver

We propose 4D modulation with directed detection employing a novel Stokes-Vector Kramers-Kronig transceiver. It shows that employing Stokes vector receiver, transmitted digital carrier and Kramers-Kronig detection offers an effective way to de-rotate polarization multiplexed complex double side band signal without using a local oscillator at receiver. The impact of system parameters and configurations including carrier-to-signal-power ratio, guard band of the digital carrier, oversampling ratio and real MIMO is experimentally investigated. Finally, a record 480 Gb/s data rate over 80 km SSMF is achieved in a 60 Gbaud PDM-16QAM single carrier experiment with a BER below the threshold of 2.0x10-2

Transmission of 344 Gb/s 16-QAM Using a Simplified Coherent Receiver Based on Single-Ended Detection

We demonstrate a single-wavelength, 344-Gb/s, 43-Gb 16-quadrature amplitude modulation (QAM) polarization division multiplexed signal transmission over 800 km operating below the hard-decision forward error correction (FEC) BER threshold of 3.8 × 10-3 using an InP dual-polarization in-phase/quadrature modulator. At the receiver, a simplified single-ended coherent receiver with novel digital signal processing (DSP) for self-beating noise removal is employed. Compared with the conventional single-ended detection, this signal processing method doubles the propagation distance and increases the SNR by more than 1 dB. In addition, this DSP method provides 10 dB of the received optical power dynamic range while operating below the hard-FEC BER threshold of 3.8 × 10-3, compared with the no dynamic range for a single-ended receiver without the proposed DSP.

Equalization-Enhanced Phase Noise in Stokes-Vector Direct Detection Systems

In this work, we provide both numerical and experimental investigations of equalization-enhanced phase noise (EEPN) in Stokes-vector direct detection (SV-DD) systems. We show that the influence of EEPN cannot be neglected in high symbol rate SV-DD systems after transmission over several hundred kilometers of fibers when electronic chromatic dispersion compensation and lasers with linewidths of the order of Megahertz are employed. Simulation results are presented to evaluate the dependence of EEPN effects on laser linewidth, transmission distance, and symbol rate. Experiments are then conducted in a 56-Gbaud 16-quadrature amplitude modulation (QAM) SV-DD system to demonstrate the EEPN-induced performance degradation after 320-km transmission over standard single mode fiber (SSMF).

Phase diversity methods for optical coherent receiver

We present the first phase-diversity coherent receiver for an arbitrary hybrid. Colorless reception of 10×132-Gb/s PDM-QPSK is experimentally demonstrated with reduced components and with less than 0.5 dB in OSNR penalty compared to traditional coherent receivers.

Self-homodyne system for next generation intra-datacenter optical interconnects

We propose a self-homodyne system for next generation intra-datacenter networking. The proposed system has a higher spectral efficiency for the modulated signal compared to the intensity-modulation/direct-detection (IM/DD) systems and uses digital signal processing of reduced complexity compared to a conventional coherent system. The concept of the proposed system is to send the modulated signal and a tone originating from the same laser over the full-duplex fiber with the aid of circulators to be used remotely at the receiver for coherent detection. The overall system physical complexity approaches the equivalent IM/DD system giving the same target data rate for 400G systems and beyond. We experimentally demonstrate emulation of the proposed system and report data rates of 530 Gb/s, 448 Gb/s and 320 Gb/s on a single wavelength below the KP4 forward error correcting threshold over 500 m, 2 km and 10 km of single mode fiber, respectively.

Low-Complexity One-Step Digital Back-Propagation for Single Span High-Capacity Coherent Transmissions

A low-complexity one-step digital back-propagation (DBP) scheme is proposed to mitigate intrachannel and interchannel fiber nonlinearities in high-capacity single span transmissions. Compared with conventional coherent receivers, the only additional calculation is a low-complexity nonlinear phase noise compensation stage operated between bulk chromatic dispersion (CD) compensation and adaptive equalizer. The required number of real additions and multiplications per sample are only (6N + 2) and (2N + 6), respectively, where N is the number of compensated wavelength-division-multiplexing (WDM) channels. With the proposed one-step DBP, we demonstrate that the nonlinear noise can be suppressed by >60% in single channel experiments and >40% in seven-channel WDM simulations.