Frank Tong

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.

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 practical passive surveillance scheme for optically amplified passive branched optical networks

We propose and experimentally demonstrate a novel and practical surveillance scheme for in-service fault identification in passive optically amplified branched networks. This scheme does not require any wavelength-tunable light source as used in multiwavelength optical time-domain reflectometer (OTDR). Fiber-Bragg gratings are placed at some strategic positions on different fiber branches to slice and reflect the optical amplifiers residual amplified spontaneous emission (ASE) power at some wavelengths other than the signal wavelengths. The conditions of the fiber link and optical amplifier at each branch can be monitored by constantly checking the reflected power level of the corresponding wavelength without suspending the in-service channels.

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 novel optical-path supervisory scheme for optical cross connects in all-optical transport networks

We propose and demonstrate a novel and effective supervisory scheme to monitor the optical-path routing at the optical cross connects in all-optical transport networks. Any error in optical-path routing due to failure in the cross connect can be detected without tapping off the power at the data wavelengths, and no dedicated monitoring light source is required. The scheme supports in-service surveillance. It can facilitate the network management in the optical layer of all-optical and reconfigurable transport networks.

Exact analysis of homodyne crosstalk induced penalty in WDM networks

We present an exact analytical probability density function and a closed-form bit-error-rate (BER) formula for wavelength-division multiplexing (WDM) networks with homodyne crosstalk from a single dominant channel. The derived crosstalk penalties are in excellent agreement with that obtained from experiments.

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.