Ze Dong

Direct-Detection Optical OFDM Transmission System Without Frequency Guard Band

Interleaver and turbo code techniques are used in high spectral-efficient direct-detection optical orthogonal frequency-division-multiplexing (OFDM) transmission systems allowing significant improvement of optical receiver sensitivity by mitigating the unbalanced noise distribution in subcarrier signals. The optical signal-to-noise ratio of 5.18 Gb/s, 7.77-Gb/s coded OFDM (5.18 Gb/s after decoding), and 7.77-Gb/s coded OFDM with interleaver (5.18 Gb/s after decoding) over 200-km single-mode fiber at a bit-error rate of 10-4 are 23.7, 18.0, and 17.1 dB, respectively.

A Novel Scheme for Seamless Integration of ROF With Centralized Lightwave OFDM-WDM-PON System

We have experimentally demonstrated a novel transmission system for seamless integration of ROF with centralized lightwave OFDM-WDM-PON based on an integrated external modulator. At the one of two arms of the integrated external modulator, the optical carrier suppression (OCS) is realized to generate 40-GHz optical millimeter-wave (mm-wave) and up-converted baseband data signal as wireless signal. In another arm of the integrated external modulator, 16 quadrature amplitude modulation intensity-modulated OFDM signals at 10 Gbit/s are used for downstream transmission as wired signal based on double sideband modulation. By using one intensity modulator (IM), the downstream RF OFDM signal is remodulated for upstream on-off keying (OOK) data at 2.5 Gbit/s because of its downstream RZ shape waveform. The 10-Gbit/s wired signal, 2.5-Gbit/s wireless signal, and 2.5-Gbit/s upstream signal have been transmitted over 20-km single mode fiber (SMF) successfully.

1.96 Tb/s (21

A novel scheme to generate coherent 21 optical subcarriers with fixed frequency of 25 GHz is proposed and experimentally demonstrated. Using these optical subcarriers, we have successfully generated 1.96 Tb/s (21 × 100 Gb/s) polarization-multiplexing optical orthogonal frequency multiplexed (PM-OFDM) polarization multiplexed quadrature phase-shift keying (QPSK) optical superchannel signal with optical signal-noise ratio of each subchannel larger than 30 dB (0.1-nm bandwidth). We have transmitted this 1.96-Tb/s optical OFDM superchannel over 3200-km SMF-28 with amplification span of 80 km with erbium-doped fiber amplifier-only.

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We have theoretically and experimentally investigated polarization insensitive all-optical wavelength conversion for polarization multiplexing signal based on orthogonal pump four-wave mixing in nonlinear optical fiber. After wavelength conversion based on 1 km high-nonlinear optical fiber with polarization insensitivity, the power penalties of 2.5 Gbit/s optical OOK intensity and 10 Gbit/s differential phase-shift keying orthogonal signals are less than 0.5 and 0.8 dB, respectively.

100 Gb/s) OFDM Optical Signal Generation and Transmission Over 3200-km Fiber

We have proposed and experimentally investigated polarization insensitive all-optical up-conversion for ROF system based on FWM in a semiconductor optical amplifier (SOA). The parallel pump is generated based on odd-order optical sidebands and carrier suppression using an external intensity modulator and a cascaded optical filter. Therefore, the two pumps are always parallel and phase locked, which makes system polarization insensitive. After FWM in a SOA and optical filtering, similar to single sideband (SSB) 40 GHz optical millimeter-wave is generated only using 10 GHz RF as local oscillator (LO). The receiver sensitivity at a BER of 10(-9) for the up-converted signals is -28.4 dBm. The power penalty for the up-converted downstream signals is smaller than 1 dBm after 20 km SSMF-28 transmission.

Polarization Insensitive Wavelength Conversion Based on Orthogonal Pump Four-Wave Mixing for Polarization Multiplexing Signal in High-Nonlinear Fiber

We theoretically and experimentally investigate three different schemes to generate optical millimeter-wave and wavelength reuse for uplink connection in radio-over-fiber (ROF) systems. In these schemes, the optical millimeter waves (mm-waves) are generated via a LiNbO3 Mach-Zehnder modulator with the double-sidebands scheme. Particularly, we experimentally demonstrate what we believe to be a new scheme (scheme III) to genetate optical mm-waves by a multiple double-frequency technique to further reduce the overall cost. We compare the performance of the three different schemes for ROF systems considering the cost and configuration of their architectures.

Polarization insensitive all-optical up-conversion for ROF systems based on parallel pump FWM in a SOA

We demonstrate what we believe to be a novel WDM-PON architecture compatible with radio-over-fiber systems to provide both wired and wireless services. A frequency-quadrupled modulation scheme is employed to generate optical millimeter waves and realize centralized lightwaves in radio-over-fiber systems.

Optical millimeter-wave signal generation and wavelength reuse for upstream connection in radio-over-fiber systems

We demonstrate the generation of full C-band coherent and frequency-lock multi-carriers by using two recirculating frequency shifter (RFS) EDFA loops based on phase modulator with external injection-seeding. In our proposed novel scheme, only one phase modulator is used in each loop and two loops are used to generate long wavelength and short wavelength subcarriers, respectively. Full C-band with totally 178 subcarriers and 26 GHz subcarrier frequency spacing covering nearly 36.66 nm from 1527.54 to 1564.20 nm are obtained. The performance of 178 subcarriers with superior flatness less than 3dB and tone-to-noise ratio (TNR) larger than 20 dB after a wavelength selective switch (WSS) shows that this novel scheme is a potential technique for the future 10Tb/s optical communication.

Low-cost optical line terminal for a WDM-PON compatible with radio-over-fiber systems

We have experimentally demonstrated a wavelength reuse scheme for up-link connection in a radio-over-fiber (ROF) system with photonics generated 2.5Gbit/s 16QAM OFDM signals. In this architecture, 2.5Gbit/s 16QAM OFDM signals carried by the optical millimeter-wave (mm-wave) carriers which are generated with four times frequency of the local oscillator (LO) signal, and both down- and up-stream signal delivery over 20km fiber with 1dB power penalty.

Generation of full C-band coherent and frequency-lock multi-carriers by using recirculating frequency shifter loops based on phase modulator with external injection

A hybrid optical access configuration for simultaneously providing wired and wireless services was proposed. The proposed system can also remote deliver doubled local-oscillator signal, which can be reused in the uplink. At the central station, the signals used for wireless links are subcarrier multiplexing and modulated as PSK format, and the wired baseband signals are directly modulated as NRZ format, then two signals are simultaneously generated by an external integrated modulator and transmitted on the same wavelength. The doubled local-oscillator signal is extracted in the wireless links, then used in the uplinks, the recieved eye diagrams are pretty well.