Chun-Kit Chan

An optical network unit for WDM access networks with downstream DPSK and upstream remodulated OOK data using injection-locked FP laser

We investigate the use of optical differential phase-shift keying (DPSK) as the downstream modulation format in a low-cost upstream data remodulation scheme for a wavelength-division multiplexing (WDM)-based passive optical network. A 2.5-Gb/s upstream data transmitter is realized by directly modulating a Fabry-Perot (FP) laser, injection-locked with a 10-Gb/s downstream optical DPSK signal. A simple polarization-offset technique is proposed to largely minimize the induced power penalty.

A self-protected architecture for wavelength-division-multiplexed passive optical networks

We propose a novel network architecture for wavelength-division-multiplexed passive optical networks which can provide bidirectional 1:1 protection against any fiber cut between the remote node and the optical network units (ONUs). In case of such fiber cut, the affected ONU can still communicate with the optical line terminal by rerouting the wavelength channels via the adjacent ONU.

Demonstration of 20-Gb/s all-optical XOR gate by four-wave mixing in semiconductor optical amplifier with RZ-DPSK modulated inputs

We propose and demonstrate an all-optical XOR gate at 20 Gb/s using four-wave mixing in a semiconductor optical amplifier (SOA), with return-to-zero differential phase-shifted keying modulated input signals. With such constant intensity modulation format, the patterning-induced degradation in SOA is also alleviated. The proposed scheme is robust and feasible for optical logic operation at ultrahigh speeds.

An all-optical XOR logic gate for high-speed RZ-DPSK signals by FWM in semiconductor optical amplifier

All-optical exclusive-OR (XOR) logic gate is a basic and crucial element for optical signal processing. We propose and demonstrate a novel high-speed all-optical XOR gate based on four-wave mixing (FWM) in a semiconductor optical amplifier, with optical return-to-zero differential phase-shift keying (RZ-DPSK) input signals. With this constant-envelope modulation format, the patterning effect-induced signal degradation in semiconductor optical amplifier (SOA) is alleviated. The proposed XOR gate can accommodate both two-input and three-input logic operations, which offer better flexibility for cascaded all-optical processing. Experimental demonstrations at 10- and 20-Gb/s verified the logic integrity of the proposed XOR gate. In addition, the XOR output tolerance against temporal misalignment among the data inputs is also experimentally investigated

A novel centrally controlled protection scheme for traffic restoration in WDM passive optical networks

We propose and experimentally demonstrate a novel centrally controlled protection scheme for arrayed waveguide grating-based bidirectional wavelength-division-multiplexing passive optical networks which can provide automatic traffic restoration against fiber cut between remote node and optical network unit. Compared with the previous structures, its requirements on the network resources are greatly reduced with negligible protection performance degradation.

A fast 100-channel wavelength-tunable transmitter for optical packet switching

This letter demonstrates a fast wavelength-tunable transmitter, based on a widely tunable grating-assisted co-directional coupler with sampled grating reflector laser diode for optical packet switching application. A high-speed control driver board was built to facilitate the fast wavelength channel selection and control. It supported 100 wavelength channels spaced by 0.4 nm with a side-mode suppression ratio >30 dB. Wavelength channel switching was measured to be within 100 ns.

Fiber-fault identification for branched access networks using a wavelength-sweeping monitoring source

We propose and experimentally demonstrate a new fiber-fault identification scheme for optically amplified branched networks. The scheme makes use of fiber Bragg gratings and an internally generated light source from erbium-doped fiber amplifiers through an optical feedback loop, and no additional dedicated monitoring source is required. The monitoring technique invokes both frequency and time domain by sweeping the wavelength of the monitoring source. By combining with a conventional optical time-domain reflectometer technique, exact location in fiber cut in branched network can be identified readily.

A WDM Passive Optical Network With Centralized Light Sources and Multicast Overlay

We propose a novel wavelength-division-multiplexed passive optical network (WDM-PON) architecture to provide a downstream multicast overlay on the conventional point-to-point data service. The differential-phase-shift-keying multicast data is modulated on the same optical downstream carrier with the inverse return-to-zero point-to-point data signal, thus additional light sources are saved. Broadcast or multicast control is realized at the optical line terminal. For each WDM channel, part of the downstream power is re-used as the upstream data carrier, and thus realizes a colorless optical network unit. We successfully demonstrate the proposed WDM-PON with 10-Gb/s downstream point-to-point signals,10-Gb/s downstream multicast signals, and 2.5-Gb/s upstream signals.

A Multicast WDM-PON Architecture Using DPSK/NRZ Orthogonal Modulation

We propose a novel scheme to overlay multicast data on a wavelength-division-multiplexed passive optical network (WDM-PON) with point-to-point data delivery. The differential phase-shift keying multicast signal is superimposed onto all point-to-point nonreturn-to-zero (NRZ) signals. By adjusting the extinction ratios of the individual NRZ point-to-point signals, multicast can be realized and only the designated optical network units can properly receive the multicast data. We successfully demonstrated the proposed WDM-PON with 10-Gb/s downstream point-to-point signals and 10-Gb/s multicast signals.

A novel star-ring protection architecture scheme for WDM passive optical access networks

We propose and demonstrate a star-ring network architecture and wavelength assignment scheme for multi-wavelength passive optical networks with full path protection capability. Bi-directional traffic can be restored promptly for single/multiple link failure scenarios.