Anlin Yi

All-Optical Signal Processing for UltraHigh Speed Optical Systems and Networks

With high-bandwidth and on-demand applications continuing to emerge, next-generation core optical networks will likely require significant improvements in reconfigurability and ultra-fast operations. Optical signal processing overcomes the electronic bandwidth limitations with the advantages in terms of transparency and scalability. We review recent progresses in all-optical signal processing potentially for ultrahigh speed systems and networks. Starting from a brief overview of optical signal processing in high-speed optical systems and networks, we highlight a few key network functionalities, including optical logic operations, reconfigurable add/drop multiplexing, optical regeneration, wavelength conversion, format conversion, and phase-sensitive amplification. Different techniques are investigated and discussed, employing a wide range of devices and various nonlinearities. Some of experimental results are presented in both single polarization systems and polarization-division multiplexing systems.

All-Optical Signal Regeneration in Polarization-Division-Multiplexing Systems

Schemes of all-optical regeneration in polarization-division-multiplexing (PDM) systems are proposed and demonstrated with 2 × 10-Gb/s return-to-zero on-off-keying (RZ-OOK) transmission. Regeneration is achieved based on self-phase-modulation (SPM) effect and detuned filtering in highly nonlinear fiber (HNLF) with a polarization-diversified loop configuration. Furthermore, the ability of mitigating polarization-mode-dispersion (PMD) effects in PDM systems is evaluated. More than 3.7-dB eye-diagram-based signal-to-noise-ratio (SNR) improvement is achieved in the presence of 6.3-ps PMD as the pulsewidth of the PDM signal is about 18 ps.

Demonstration of 4-band millimeter-wave radio-over-fiber system for multi-service wireless access networks

A novel all-band 60-GHz RoF system with 4 sub-bands has been proposed to offer converged legacy wireless services and multi-gigabit data access. Successful transmission of 0.4-Gb/s QPSK-OFDM and three independent 0.5-Gb/s OOK data is achieved.

A Photonic Comb Filter With Independently and Digitally Tunable Bandwidth and Frequency Spacing

A photonic comb filter with digitally tunable bandwidth and frequency spacing is proposed. Using cascaded differential-group-delay (DGD) element and polarization switch based filters, we demonstrate independent tunability of both parameters with >; 12-dB first-sidelobe reduction for a 6-bit configuration. Limitations of such an approach are also discussed.

Wavelength Conversion of RZ-OOK PDM Signals Based on XPM in Highly Nonlinear Fiber

Wavelength conversion of return-to-zero on-off keying (RZ-OOK) signals in polarization-division-multiplexing (PDM) systems based on cross-phase modulation (XPM) in highly nonlinear fiber (HNLF) using a polarization-diversified loop configuration is experimentally demonstrated. Eye-diagram-based signal-to-noise-ratio (SNR) results indicate that successful wavelength conversion can be achieved over the whole C -band.

Investigation of intra/inter-band cross-modulation in multi-band radio-over-fiber systems

We theoretically and experimentally investigated the intra/inter-band cross-modulation (XM) induced by the nonlinearity of Mach-Zehnder modulator (MZM) in a multiband radio-over-fiber (RoF) system. A closed-form theoretical analysis was proposed to model and predict the nonlinear XM behaviors, for both single-band vector signals and multiband combination of scalar and vector signals. To verify the feasibility of the theoretical model, both simulation and experimental investigations were carried out, and according to the theoretical analysis, scalar signals only suffer from inter-band XM; whereas vector signals suffer from both intra- and inter-band XM. The signal quality degradation induced by MZM nonlinearity for a single-band 16QAM, QPSK, and two bands of OOK signals are investigated and characterized, and good agreement between theory and experiments was achieved. It was observed that QPSK shows superior performances compared with higher order QAM formats due to its intrinsic resistance to intra-band XM.

A novel direct-modulation envelope-detection Pol-Mux MIMO RoF system based on blind equalization techniques

We demonstrate for the first time a polarization-multiplexed multiple-input multiple-output radio-over-fiber system with direct-modulation and envelope-detection architectures. Based on blind equalization techniques, cross-channel interferences in both optical fiber and wireless channels are cancelled simultaneously without incurring additional overhead.

Closed-form analysis of intra/inter-band cross-modulation in multiband radio-over-fiber systems

A theoretical and experimental investigation of the nonlinear behaviors of intra- and inter-band cross-modulation (XM) in a multiband radio-over-fiber (RoF) system is presented for the first time. A closed-form theoretical analysis is proposed to characterize and validate the data XM induced by the nonlinearity of optical Mach-Zehnder modulator (MZM). Nonlinear behaviors of the intra-band XM between the in-phase and quadrature (I/Q) components of a single-band vector signal, as well as the inter-band XM between multiband combinations of scalar and vector signals are investigated, and consistent agreement has been verified between the theory and experiments. It was confirmed that scalar signals only suffer from inter-band XM; whereas vector signals suffer from both intra- and inter-band XMs. Intra-band XM induces constellation compression to vector signals; while inter-band XM induces eye diagram degradation to scalar signals, as well as nonlinear constellation scaling to vector signals. Moreover, QPSK shows superior tolerance to MZM nonlinearity than higher order QAM formats due to it intrinsic resistance to intra-band XM.

A bidirectional multi-band 60-GHz wireless-over-fiber transmission system with compacted base station and mobile terminal using a robust mm-Wave LO free technique

For the first time, bidirectional multi-band multi-gigabit wireless-over-fiber transmission at 60-GHz mm-wave band has been accomplished with centrally supplied LO service. It does not require mm-wave LO devices in each base stations and mobile terminals.

Simultaneous multilevel RZ-to-NRZ format conversion for two tributaries of a PDM signal

An all-optical multi-level RZ-to-NRZ format converter for two tributaries of a PDM signal is proposed using a polarization-maintaining-fiber inside a polarization-diversified-loop. A three-level format conversion in a 2×15.85-Gbit/s PDM system is experimentally demonstrated.