We propose and experimentally demonstrate the generation of various modulation formats using a directly modulated
chirp-managed laser (CML), including phase-shaped binary transmission (PSBT), inverse-return-to-zero duobinary
(IRZ-duobinary), Manchester-duobinary, return-to-zero differential phase shift keying (RZ-DPSK) and return-to-zero
differential quadrature phase-shift-keying (RZ-DQPSK). The CML-based modulation formats improved dispersion
tolerance and their corresponding transmitters have the features of compactness, low power consumption and costeffectiveness,
which are desired in metro/access networks. System applications of such formats are also studied.
We propose and demonstrate the use of 10-Gb/s inverse-RZ data as downstream signal in WDM-PON to injection-lock a directly modulated Fabry-Perot laser used for the upstream signal at 1Gb/s.
We review some of the recent developments of optical performance monitoring (OPM) in various aspects: (i) the
enhancement of monitoring resolution, (ii) multi-impairment monitoring, and (iii) OPM network optimization. In
particular, some of the studies on the optimization of performance monitoring networks to achieve the optimal
monitoring locations and number of monitoring probes are discussed.
In this paper, different kinds of optical performance monitoring (OPM) techniques, in particular the optical signal-to-noise ratio (OSNR) monitoring and chromatic dispersion (CD) monitoring, are reviewed. Then recent trend of multiple-parameter simultaneous monitoring is examined.
Recently, optical differential phase shift keying (DPSK) has attracted much interest in high-speed optical transmission systems. It features constant intensity and thus is less vulnerable to the fiber nonlinearities. In addition to high-speed data transmission, it is desirable to carry relatively low-speed supervisory information simultaneously to facilitate the system monitoring and network management. In this paper, we propose and investigate an orthogonal modulation scheme for carrying relatively low bit-rate supervisory amplitude shift keying (ASK) data on a high-speed (10-Gb/s) optical DPSK data stream. The supervisory data is amplitude-modulated onto the constant intensity optical DPSK signal, thus no dedicated time slots are needed and this eliminates the bandwidth overhead. We investigate both experimentally and numerically the optimized operation conditions for such orthogonal modulation. The results suggest the design guidelines of the proposed ASK/DPSK orthogonal modulation for supervisory information dissemination.
In this paper, we will discuss the network architectures and the enabling technologies to realize a robust multi-wavelength optical access network. Various network topologies employing the dense WDM or coarse WDM technique; as well as several network enabling technologies such as data re-modulation technique, fiber link protection and traffic restoration, etc. will be described. Besides, some future trends and applications of multi-wavelength optical access networks will also be discussed.
With the recent explosive growth of Internet traffic, optical networks with high
connectivity and large capacity are indispensable. This can be achieved by
multi-dimensional optical routing networks, which can offer fine bandwidth granularity
and a large number of channels. In this paper, a trunk switched model is used to study the performance of multi-dimensional optical routing networks. The
closed-form network utilization is derived and compared to that of one-dimensional
optical routing networks. The network utilization gain is found to be closely
related to the link correlation and be insensitive to the network size. Besides,
based on this analytical model, the closed-form conversion gains are derived for
both partially and fully convertible cases. These results provide crucial
information in performance optimization of multi-dimensional optical routing networks.
In our paper, we present a heuristic method for maximizing the utilization of a survivable multi-ring DWDM network without wavelength conversion. We assume that the network is supporting packet and circuit based services simultaneously. The idea is that we can provide ample bandwidth or even dedicated channels to packet based services by sharing the resources in the protection ring under normal conditions. In case of a ring failure, the packet based channels can be compressed into fewer channels to yield protection bandwidth to circuit based services. Packet ring technologies such as Resilient Packet Ring (RPR) or IEEE 802.17 will ensure that all packet connections are still maintained in a fair manner under such condition. The main contribution in this work is to jointly consider the effect of packet and optical connection services on DWDM rings to enhance wavelength utilization.
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.
The results of an investigation of the performance of a time-division-multiplexed fiber Bragg grating (FBG) sensor array using a tunable laser source are reported. The system performance is found to be limited by the extinction ratio of the optical pulse modulator used for pulse amplitude modulation. Formulas that relate the crosstalk to the extinction ratio of the optical pulse modulator, the modulation parameters of the tunable laser, and the optical path differences among sensing channels are derived. Computer simulation shows that an array of 20 FBG sensors with 3 (mu) (epsilon) resolution can be realized with a commercially available single Mach-Zehnder type optical pulse modulator of -35 dB extinction ratio.
In this paper, we propose and demonstrate a novel and effective wavelength-matching scheme for wavelength grating routers to match their transmission peaks to the wavelength assignment of the data channels without any reference sources. The unused portion of the amplified spontaneous emission (ASE) power of the Erbium doped fiber amplifiers is utilized as the monitoring light source and fiber Bragg gratings of a particular center reflection wavelength is used as the wavelength reference. The scheme supports in- service monitoring and will not degrade the performance of the data channels. It is also insensitive to dynamic ASE power variations arising form channel ad-drop. We have experimentally demonstrated the proposed wavelength-matching scheme for WGR and analyzed the scheme numerically for design optimization.
KEYWORDS: Modulation, Data modeling, Switching, Switches, Linear filtering, Transmittance, Optical switching, Modulators, Receivers, Signal attenuation
We propose and experimentally demonstrate a novel variable bit-rate limiter (BRL) for ASK optical transmission systems. The BRL operates on the sampling principle with an optical switch inserted anywhere between the terminals in the fiber link. To facilitate the design of the BRL, a theoretical model of bit-error-rate for the proposed BRL is developed, and shows good agreement with the experimental data.
KEYWORDS: Homodyne detection, Signal to noise ratio, Optical networks, Interference (communication), Receivers, Information operations, Modulation, Lead, Telecommunications, Signal attenuation
Homodyne crosstalk causes severe system performance degradation in optical networks by beating with the desire signal. While Gaussian approximation overestimates the performance degradation, for a single dominant crosstalk source, the exact noise probability distribution and closed- form error probability is derived in this paper.
In this paper, a new 2D split and merge algorithm (2DSM) for image coding is devised. An image is modelled as a 2.5-dimensional surface and approximated by a surface formed by triangular patches. The algorithm iteratively improves the approximated image by splitting the merging of the triangles in order to drive the error under a specified bound. In addition, a new optimal triangulation for image data approximation is proposed. The algorithm is successfully applied for coding monochrome images using Interpolative Vector Quantization (IVQ) technique. Simulation results show that the proposed method can achieve 2.8 dB improvement on the approximated image and 0.68 dB improvement on the decoded image at a bit rate lower than the current schemes. Besides, excellent reconstruction visual quality is observed.
Z-cut proton-exchanged LiTaO3 optical waveguides have been fabricated using cinnamic acid and characterized optically. The diffusion constant (Do) and the activation energy (EA) were found to be 152.4 micrometers 2/h and 0.34 eV, respectively. The diffusion rate is lower than published data for other proton sources. The effect of annealing on waveguide depth increase could be accurately modeled by a power-law relationship, and the surface index change increases initially before decreasing. The maximum surface index increase for a particular exchange temperature was found to be dependent on the exchange temperature, and the higher the exchange temperature the lower the index increase.
The demanding computational requirement of a vector quantization (VQ) encoder has hindered the application to real-time video coding. The complexity of the VQ encoder can be greatly reduced by using a multiplicationless image vector quantization (MLIVQ) technique. A real- time vector quantizer architecture implementing this novel algorithm on a single ASIC chip is presented in this paper. Running at a clock rate of 33 MHz and through the use of a three- stage pipeline architecture, the proposed hardware implementation is capable of real-time compression of motion video with 512 X 512 pixels per frame at a refreshing rate of 30 frames per second. As compared with traditional full-search VQ, the MLIVQ technique shows a big reduction in hardware complexity while introducing an insignificant degradation in picture quality.
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