Sang-Min Jung

AMO-FBMC for Asynchronous Heterogeneous Signal Integrated Optical Transmission

Orthogonal frequency-division multiplexing (OFDM) is susceptible to multiple access interference and synchronization errors due to sidelobes, which hinder the integration of various applications and multiple access in OFDM-based optical transmission. In this letter, an adaptively modulated optical filter bank multicarrier with offset quadrature amplitude modulation-based sidelobe suppression is proposed in a wired/wireless converged optical network. We experimentally verified both the improvements in signal performance and spectral efficiency compared with OFDM in a multisender-supported optical network after a 50-km transmission.

Mitigation of timing offset effect in IM/DD based OFDMA-PON uplink multiple access.

In orthogonal frequency division multiple access based passive optical network (OFDMA-PON) uplink, synchronization between optical network units (ONUs) is very important to maintain orthogonality. The synchronization among uplink signals is considered as one of the main challenges in OFDMA-PON due to optical path difference. In this paper, the performance degradation according to timing offset between ONUs is experimentally analyzed. And we propose and demonstrate timing offset effect reduction in asynchronous multiple access by using CP extension and filter bank based multicarrier (FBMC) system in intensity modulation/direct detection (IM/DD) based OFDMA-PON uplink transmission.

Optical beat interference noise reduction by using out-of-band RF clipping tone signal in remotely fed OFDMA-PON link.

A novel technique for mitigating the optical beat interference (OBI) noise in an optical orthogonal frequency division multiple access passive optical network (OFDMA-PON) uplink transmission is presented. By using an out of signal band RF clipping tone to the optical seed carrier, the OBI noise has been reduced and the resulting throughput and spectral efficiency has been improved. As an experimental verification, we demonstrate that the spectral efficiency of 23 km and 50 km have been doubled in the OFDMA-PON uplink transmission.

I/Q Channel Separated Baseband OFDM Optical Transmission Using Orthogonal Polarizations in IM/DD System

We have proposed baseband orthogonal frequency division multiplexing (OFDM) optical transmission technique using I/Q channel separation based on dual polarization with intensity modulation/direct detection (IM/DD). We experimentally verified performance of a proposed system in compare with intermediate frequency (IF)-upconverted OFDM system. In order to obtain better performance, adaptively modulated optical OFDM signal was used in this study. As a result, experimentally achieved maximum throughput after 50 km single mode fiber transmission was 28 Gbps with only using 4 GHz signal bandwidth. The proposed technique has relatively simple hardware structure and reduces computational complexity compared to other methods (IF upconversion or Hermitian symmetry) in IM/DD-based polarization multiplexed OFDM system.

Optical pulse division multiplexing-based OBI reduction for single wavelength uplink multiple access in IM/DD OFDMA-PON.

Orthogonal frequency division multiple access-based passive optical network (OFDMA-PON) is considered as a strong candidate for next-generation optical access network. In intensity modulation/direct detection system, OFDMA-PON downlink transmission is relatively stable, but critical issues exist in uplink multiple access. Because of different optical paths, optical beat interference (OBI) and timing offset effect are generated, which seriously disturb signal detection. We propose optical pulse division multiplexing-based OBI reduction. By considering both the spectrum broadening effect and the time domain near orthogonality, OBI could be reduced. We demonstrate that the spectral efficiency can be improved from 0.37 to 3.8 bit/s/Hz in 1-GHz signal bandwidth.

Timing-offset-tolerant universal- filtered multicarrier passive optical network for asynchronous multiservices-over-fiber

We propose a universal filtered multicarrier (UFMC) passive optical network for asynchronous multiservices- over-fiber to overcome the limitations of a conventional discrete multitone (DMT). The channel performance in terms of error vector magnitude was compared by adding a timing offset to conventional DMTand UFMC signals. In addition, both signals were adaptively modulated at the most asynchronous timing-offset case. Our experimental results demonstrated improvement in UFMC performance, which was 32% and 32.5% higher in terms of bit rate and spectral efficiency, respectively, compared with conventional DMT in the most asynchronous case.

All-Optical Virtual Private Network in OFDM-PON Using Microwave Photonic Filter

We propose and demonstrate a novel all-optical virtual private network (VPN) using a microwave photonic filter, which enables inter-communications among optical network units in a passive optical network system. In our scheme, an optical coupler based recirculating delay line is used at optical line terminal as an optical subsystem to implement a microwave photonic-bandpass filter (MP-BPF). The periodic passbands of an MP-BPF are used to transmit VPN signal, whereas stopbands are used for conventional upstream transmission. The proposed system has two critical issues, optical phase-induced intensity noise in the MP-BPF and Rayleigh back-scattering interference by a single-fiber loop back link. To overcome the issues, an RF clipping tone based spectrum-broadening technique is applied to uplink transmitter. The proposed all-optical VPN system is tolerant to wavelength of VPN optical carrier, and enables multi-VPN data transmission using multi-passbands of MP-BPF.

Optical-Beat-Induced Multi-User-Interference Reduction in Single Wavelength OFDMA PON Upstream Multiple Access Systems With Self-Homodyne Coherent Detection

We propose a novel technique for mitigating the optical-beat-induced multi-user-interference (MUI) between the upstream multiple access signals in an orthogonal frequency division multiple access (OFDMA) passive optical network (PON). To provide upstream multiple access on a single-wavelength orthogonal frequency division multiplexing optical access network, optical beating interference and polarization diverseness are critical issues that severely degrade system performance. By using the proposed total intensity aggregation with self-homodyne coherent detection, we experimentally demonstrated stable transmission performance by reducing MUI in OFDMA PON upstream multiple access transmission.

All-optical virtual private network based on microwave photonic bandpass filter in OFDM-PON system

We propose all optical virtual private network (VPN) using microwave photonic filter for the first time in orthogonal frequency-division multiple based passive optical network (OFDM-PON). In our scheme, optical resonator is used at optical line terminal (OLT) as a subsystem to design photonic bandpass filter (P-BPF). This filter has free spectral range (FSR) corresponding to resonator length. Using this property, VPN data modulated on passbands of P-BPF could be extracted among upstream data at OLT, and transmitted to optical network units (ONUs) without electrical processes. To overcome coherent interference problem in the resonator, spectrum broadening technique using clipping RF tone is applied. The proposed system enables dynamic bandwidth allocation between VPN and conventional upstream by adjusting tunable delay line in the resonator. Also it supports VPN communication regardless of optical wavelength.

Mitigation of the polarization sensitivity in OFDMA PON uplink transmission

A novel detection technique to eliminate the polarization mismatch for the stable OFDMA PON uplink multiple access transmission was proposed and experimentally demonstrated a stable transmission performance with 2 ONU uplink multiple access.