Wai Hung

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.

An all-optical packet header recognition scheme for self-routing packet networks

We proposed a serial-to-parallel conversion scheme for optical packet header processing. All-optical recognition of a three-bit packet header was demonstrated. The obtained parallel optical signal from the converter can be detected by low speed photodetector array, and can be used as switching control signal for the optical packet switch in a self-routing network node.

A bit-serial optical packet label-swapping scheme using DPSK encoded labels

We present a simple and robust bit-serial optical packet label-swapping scheme based on return-to-zero differential phase-shift keying encoded labels. The scheme is demonstrated with a label-swapping experiment for 10-Gb/s packets over two network nodes. Penalty-free label swapping is achievable using semiconductor optical amplifier-based interferometric wavelength converters and phase modulators. In addition, the packet data can be simultaneously 2R regenerated through this process. This will greatly enhance the scalability of the network.

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

We propose and demonstrate an upstream data re-modulation scheme for a WDM access network using downstream optical DPSK traffic. A 2.5-Gb/s upstream data transmitter is realized by directly modulating an FP laser, injection-locked with a 10-Gb/s downstream optical DPSK signal.

Intensity-modulated labeling and all-optical label swapping on angle-modulated optical packets

We proposed and investigated superimposing intensity-modulated labels onto high-speed angle-modulated payloads in optical label-switching packet networks. This can largely simplify the all-optical label swapping, including label extraction, processing, removal, and new label insertion. The transmission performances of 1.244-Gb/s on-off keying labels on 9.953-Gb/s optical frequency-shift keying and differential phase-shift keying payloads were investigated; and the all-optical label swapping was successfully demonstrated with low penalty.

A routing loop control scheme in optical layer for optical packet networks

In future optical label switching (OLS) network, optical layer routing loop control is crucial for maintaining the network stability. In this paper, an optical loop control scheme using optical time to live (TTL) count down is proposed and experimentally demonstrated for the first time. Asynchronous TTL count-down up to 24 bits for 20-Gb/s packets is demonstrated.

Waveform restoration in semiconductor optical amplifier using fiber loop mirror

In this letter, we present a simple and effective interferometric approach for waveform restoration in a semiconductor optical amplifier (SOA) using a fiber loop mirror. Pattern-dependent distortion caused by gain dynamics of the SOA can be compensated. With our scheme, an enhanced input power dynamic range of 7 dB was achieved. For data sequences with different pattern lengths, both significant waveform and extinction ratio improvement were obtained.

A novel wavelength shift keying transmitter based on optical phase Modulation

We propose a novel transmitter structure to generate constant-intensity wavelength shift keying signal based on optical phase modulation and demonstrate its application in a wavelength-division-multiplexed passive optical network to facilitate upstream data remodulation. The feasibility and system performance are experimentally investigated.

A novel optical packet labeling scheme using interleaved low-speed DPSK labels

We report a novel DPSK/ASK optical packet label encoding scheme based on synchronous phase modulation on ASK packets. By employing a simple packet structure, this scheme allows the phase-encoded labels being embedded within the ASK packets while having a high modulation extinction ratio. In addition, it also facilitates low-bit-rate DPSK label encoding and detection. Stable label encoding, demodulation and swapping of low-speed labels on 10-Gb/s packets were experimentally demonstrated.

Novel WDM passive optical network with bidirectional protection

Passive optical networks (PONs) have recently emerged to be a promising approach to enhance the penetration of fiber towards the subscriber side, thus further enables delivery of higher data-rate services to the subscribers. They feature easy network maintenance as there is no active component at the remote node (RN). However, in conventional PONs, both upstream and downstream bandwidths have to be time-shared among all optical network units (ONUs). By applying WDM technique to PONs, the total system capacity can be further enhanced. Each ONU enjoys a dedicated bandwidth and resolves the ranging problem as in PONs. In both conventional PON and WDM-PON, little work has been done to offer protection capability though fiber fault detection methods have been extensively studied. We propose a novel network architecture for WDM-PON which offers 1:1 protection capability. In case of any fiber cut between remote node and ONUs, the affected ONU can re-route the wavelength channels via the adjacent ONU and can still maintain normal bidirectional traffic.