For transmitting video or financial transaction information, communication interruption must be short, so hitless redundancy switching (HRS) technology is a useful solution. However, when this technology is used in multiple sites, a large amount of resources is required for HRS devices to communicate. In this paper, we propose an efficient resource allocation method and demonstrate that it can reduce resource usage by 97% in a numerical simulation.
Amplitude and phase characteristics in an alkali metal vapor magnetometer of self-oscillating type have been studied experimentally. Dependence of these characteristics on D1 radiation alone or D1+D2 radiation, rf field intensity H1, light intensity and orientation of the oscillator are observed. Bell-Bloom's representation Sx of light modulation is modified to apply to the experiments using D1+D2 radiation as well as D1 radiation alone. The observed characteristics are well described by the modified representation taking the hyperfine interaction into account. Convenient method to observe the transverse relaxation of the atoms in the self-oscillator is demonstrated.
Various applications and services have been provided over broadband optical access networks such as passive optical networks (PONs). The data communication among optical network units (ONUs) in the same PON, i.e. inter-ONU communication, is expected to be one of the most attractive communication architectures in the future, since it can provide low-latency peer-to-peer (P2P) communication services. However, the current PON systems cannot provide the services which require precise time synchronization among ONUs, e.g. smart grid services. This paper proposes an inter-ONU time synchronization technique using jitter buffer in the optical line terminal (OLT) to make inter-arrival time of control messages for time synchronization a constant value. The practical effectiveness of the jitter compensation technique is verified by a numerical simulation. The simulation results show that the proposed technique provides small packet delay variation (PDV) of the control messages, and improves the synchronization accuracy.
The spot size has been measured by chopping the beam spot with a knife edge on an optical disk. Tangential and radial spot sizes are measured with different two angled knife edges: θ 1 -edge and θ 2 -edge. In this paper, the errors in the measurement of spot sizes caused by the error in the scanning angle and the scanning velocity are described. The result of the theoretical analysis gives the best combinations of the scanning angles which are θ 1 =0°, θ 2 =±45° with the radial direction. For example, if the angle error of θ 1 and θ 2 obtained experimentally 0.64°, then the calculated error of the radial spot size is 2.2%. The analyzed error shows a good agreement with the experimental results. It was analytically observed that the influence of the scanning velocity error on the error of the measured spot sizes can be practically ignored using this method.
We propose a downlink transmission timing shift in the centralized radio access network architecture that advances the downlink transmission timing in order to improve the frame efficiency for time-division duplex radio access network with the optical transmission line. We evaluate the frame efficiency of the proposed downlink transmission timing shift with numerical simulation.
A fronthaul bridged network has attracted attention as a means of efficiently constructing the centralized radio access network (C-RAN) architecture. If we change the functional split of C-RAN and employ time-division duplex (TDD), the data rate in fronthaul will become variable, and the global synchronization of fronthaul streams will occur. This feature results in an increase in the queuing delay in fronthaul bridges among fronthaul flows. To address this problem, this paper proposes a novel low-latency routing scheme designed to minimize the worst-case delay in fronthaul networks with path-control protocols. The proposed scheme formulates the worst-case delay of each fronthaul stream based on the distribution of nodes, the propagation delay, and metric of the links. It selects the set of paths that minimizes the maximum value of the worst-case delay from the candidate path sets for fronthaul flows generated with the k-th shortest path algorithm. We confirmed with computer simulations that the proposed scheme can adequately minimize the worst-case delay, irrespective of the network topology. The maximum queuing delay is minimized by considering the time synchronization between fronthaul flows and the burst size determined by the TDD subframe length.
Under the ISO/IEC 10090 specification for magneto-optical disks, write conditions including write laser power should be appropriately written on control tracks. However, the definition and measurement method of the write power are not necessarily clear. Satisfactory normalization schemes for the write power should be developed. In this paper we describe the possibility of normalizing the write power of optical disk drives using a typical laser power. The main findings obtained were as follows. (1) Saturation curves normalized by a typical laser power were correlated well in shape in the laser power range in which jitter and error rate are minimum. (2) Our results show the possibility of normalizing the write power of drives using a typical laser power of a calibration disk and the feasibility of a relative value method for facilitating optical disk interchangeability.
We propose an in-line monitoring technique that uses 650 nm visible light for performing maintenance work on Fiber-to-the-home (FTTH) network quickly without the need for measuring skills or external devices. This technique is characterized by visible light (650 nm) generated by an SHG module from the 1.3 microm-band line signal. We fabricate a 1.3 microm-band quasi phase matched LiNbO(3) (QPM-LN) module, and the measure the 650 nm second harmonic (SH) power to test the proposed short-pulse modulation method. The results confirm the feasibility of the short-pulse modulation method with different peak factors (PFs) (1.0-7.3). We also examine the effect of short-pulse modulation on system performance at the optical receiver by measuring the bit error rate (BER) of received data (1.25 Gb/s). The BER is basically unaffected by the PF (1.0-5.5). This means that the proposed technique has little influence on data reception as regards PF (1.0-5.5).
This paper proposes a joint routing and scheduling scheme for achieving low latency in a fronthaul bridged network. We confirmed with computer simulations the proposed scheme improves the accommodation efficiency of bridged networks.
