Kam-Hon Tse

Generation and Transmission of 10-Gb/s RZ-DPSK Signals Using a Directly Modulated Chirp-Managed Laser

We propose and experimentally demonstrate the generation of a 10-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) signal based on a directly modulated chirp-managed laser (CML), without requiring any differential encoder and optical phase modulator (PM). It shows better fiber chromatic dispersion tolerance and comparable nonlinearity tolerance, compared with a PM-based RZ-DPSK signal using 231 - 1 pseudorandom bit sequence data.

Adaptive Fault Monitoring in All-Optical Networks Utilizing Real-Time Data Traffic

We propose a novel fault detection and localization scheme for all-optical networks with the information of real-time data traffic. Our adaptive fault localization framework is based on combining passive and proactive monitoring solutions, together with adaptive management in two phases. Numerical results indicate that our proposed scheme has good scalability, in terms of the number of fault monitors required. Also, we show that our framework allows more flexible network design, and requires much less monitoring bandwidth when compared with the passive monitoring solutions.

A Pilot-Correlated PMD Monitoring Scheme for Direct Detection Optical OFDM System

A polarization mode dispersion monitoring scheme is proposed and demonstrated for direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems. A pair of data-assisted pilot subcarriers is inserted at two spectral edges of the OFDM signal spectrum. Simple data correlation technique is used to estimate the powers of the pilot subcarriers and thus retrieves the DGD value at the monitoring unit, without the need of demodulation of the pilot subcarriers. Experiments show a DGD monitoring range of 0 to 45 ps in a typical radio-frequency tone-assisted DDO-OFDM system. The robustness of the proposed scheme to optical signal-to-noise ratio and accumulated chromatic dispersion is further experimentally investigated. Besides, simulations and experiments are performed to demonstrate the feasibility of using photodiodes with narrow bandwidth. By inserting one more data-assisted pilot subcarrier, the proposed scheme becomes insensitive to the input angle of the state of polarization. The proposed scheme provides an effective monitoring solution for the optical OFDM signals across intermediate nodes in flexible optical network.

Coded-subcarrier-aided chromatic dispersion monitoring scheme for flexible optical OFDM networks

A simple coded-subcarrier aided scheme is proposed to perform chromatic dispersion monitoring in flexible optical OFDM networks. A pair of coded label subcarriers is added to both edges of the optical OFDM signal spectrum at the edge transmitter node. Upon reception at any intermediate or the receiver node, chromatic dispersion estimation is performed, via simple direct detection, followed by electronic correlation procedures with the designated code sequences. The feasibility and the performance of the proposed scheme have been experimentally characterized. It provides a cost-effective monitoring solution for the optical OFDM signals across intermediate nodes in flexible OFDM networks.

A Novel Fiber-Based Variable All-Optical Packet Buffer Based on Self-Phase-Modulation-Induced Spectral Broadening

We propose a novel optical delay control mechanism to realize variable all-optical packet buffering, in which the amount of optical delay is controlled by the input signal power level. It consists of a passive fiber delay loop followed by an optical power dependent filter, which is realized by means of two stages of self-phase-modulation-induced spectral broadening and offset filtering. The feasibility of the proposed optical packet buffer has been investigated through numerical simulations and experiments. No polarization control and additional laser source are needed.

Optical performance monitoring in elastic optical OFDM networks

Optical performance monitoring (OPM) is a crucial element in network management, in order to assure the quality of the optical signals at various intermediate and destination nodes. In future elastic optical network, the network operation is more adaptive and reconfigurable. The OPM monitoring information retrieved at each intermediate node would be useful for optimal network control. Common OPM parameters in an optical transmission system, include optical signal-to-noise ratio (OSNR), accumulated chromatic dispersion (CD) and polarization mode dispersion (PMD). In this paper, we present our OPM techniques for these three parameters, based on signal correlation procedures on one or a few pilot subcarriers inserted in the spectrum of an optical OFDM signal, which is one of the promising signal format to support the future elastic optical networks.

A Path Tracing Scheme for All-Optical Packet-Switched Networks

A novel optical scheme is proposed to perform path tracing in an all-optical packet-switched network. Prime-number-encoded tag is employed as the distinct network node or network link identifier. As the optical data packet traverses every network node, the path trace is recorded and updated optically, through prime number multiplication via an optical delay circuit encoder. Hence, all traversed network nodes along the path of a received optical data packet can be retrieved and identified at the destination node, via simple prime number factorization. Possible looping of optical data packets in the network can also be detected. The scheme can facilitate the connection management in an optical packet-switched network.