In this paper, we investigate both static and dynamic traffic grooming problems in a wavelength routing network, so as to minimize the total energy consumption of the core network, with the additional consideration of the holding times of the lightpaths and connection requests. In static case, all connection requests with their setup and tear-down times are known in advance, we formulate an Integer Linear Programming (ILP) to minimize the energy consumption. In dynamic case, we adopt a layered graph model called Grooming Graph and propose a new traffic grooming heuristics called Time-Aware Traffic Grooming (TATG) which takes the holding time of a new arrival connection request and the remaining holding time of existing lightpaths into consideration. We compare the energy efficiency of different traffic grooming policies under various traffic loads, and the results provide implications to choose the most energy-efficient traffic grooming policies under various scenarios.

We propose to make use of optical sub-carriers to realize optical multicast overlay on a WDM passive optical network. By employing optical carrier suppression technique at each downstream optical transmitter at the OLT, two coherent optical sub-carriers are generated to carry the 10-Gb/s downstream unicast DPSK signal and the 10-Gb/s downstream multicast ASK signal, separately without any additional light sources. At the ONU, the 10-Gb/s upstream data is superimposed on the received downstream unicast DPSK signal, to form the upstream ASK signal. System characterization is performed to optimize the performance. In addition, we further demonstrate simultaneous optical overlay of two streams of multicast data in the network.

We propose and demonstrate a single-fiber bidirectional wavelength division multiplexing self-healing ring network for metro-access applications. By incorporating a simple bi-directional optical add-drop multiplexer at each network node as well as employing our proposed alternate-path switching scheme, the bi-directional traffic can be restored promptly under single fiber failure in the ring network. All the protection switching is performed at the hub only, thus the operation, administration and management cost can be easily optimized

We investigate the performance of maximum likelihood sequence estimation (MLSE) receiver in the presence of the impairments from both the pulse carver-data modulator timing misalignment (TM) and polarization mode dispersion (PMD) in optically amplified return-to-zero (RZ) systems. RZ modulation format is commonly used in long-haul wavelengthdivision multiplexing transmission systems and the dominating noise source in those systems is amplified spontaneous emission (ASE) noise, which is signal dependent and requires special study when direct detection is employed. In this paper, based on the bit-to-bit error probability estimation using Karhunen-Loeve (KL) expansion and decorrelation of noise components, we use the steepest descent method to obtain sequence-to-sequence error probability and achieve the performance evaluation of MLSE receiver with arbitrary input signal pulse shape, optical filtering and electrical filtering taken into consideration. Monte Carlo simulations of a 10-Gb/s RZ system are demonstrated and agree with the theory well. The results show that the power penalty induced by TM and PMD can be effectively reduced by MLSE receiver, which thus validates its capability to enhance tolerance to both TM and PMD with shared electrical devices.

This paper proposes and demonstrates a nonlinear distortion reduction scheme for subcarrier multiplexed optical CATV networks based on optical sampling and optical time-division multiplexing (OTDM) techniques. Intermodulation distortion is reduced by about 10 dB for a 40-channel system. The proposed optical sampling and OTDM process is shown to induce negligible additional distortion.

This paper describes the design and the experimental demonstration of a novel fast channel tunable optical transmitter which is suitable for ultrahigh-speed all-optical time-division multiaccess (TDMA) networks. This optical transmitter is capable of performing fast channel tuning and data modulation in a simple and cost-effective way without using the expensive optical modulators and optical switches. By employing this transmitter, together with the proposed destructive writing scheme, ultrahigh-speed channel multiplexing with relaxed synchronization requirements for data access can be achieved. The demonstrated prototype can be arbitrarily tuned to any one of the 16 1-Gb/s channels in a 16-Gb/s all-optical TDMA network with a channel switching time of less than 5 ns. This is suitable for use in most high-speed optical time-division multiplexed (TDM) systems and tunable-channel multiaccess (TCMA) networks.