A novel fiber ring laser technique, which covers both C- and L-bands, with the function of wavelength tunability and single-longitudinal-mode oscillation, is proposed and demonstrated experimentally. We propose a two-stage hybrid amplifier, which consists of a semiconductor optical amplifier (SOA) and an erbium-doped fiber amplifier (EDFA) with cascade configuration, for the gain profile to achieve C- to L-band (1540 to 1610 nm). A saturated-absorber-based autotracking filter, which composes of an unpumped erbium-doped fiber (EDF) and an optical reflected mirror (ORM), is employed to provide fine mode restriction and guarantee the single-frequency operation. The unpumped EDF must use shorter length to retrieve the stabilized single-frequency operation while the EDF length is between 0.5 to 1 m long. The effectively operation range is from 1542 to 1618 nm. The maximal output power of 5.7 dBm is retrieved at near 1577 nm, and the output power will drop to 3.7 and -0.32 dBm at 1604 and 1616 nm, respectively. The SMSR can be up to 53.2 dB/ 0.05 nm at around 1577 nm. The performance of output power of > 2.1 dBm, power stability of ≤ 0.02 dB, wavelength variation of ≤ 0.01 nm and side-mode suppression ratio (SMSR) of > 31 dB / 0.05 nm has been demonstrated for this single-frequency fiber laser over the wavelength range of 1550 to 1608 nm. The linewidth (RF) spectrum of the proposed structure has also been studied.
KEYWORDS: Telecommunications, Control systems, Networks, Switches, Wireless communications, Mobile communications, Network architectures, Databases, Analog electronics, Global system for mobile communications
Recently, it becomes more and more popular that an enterprise builds up a private mobile network. With this wireless network, the enterprise can increase its communication efficiency and productivity. In this paper, we present a private mobile communication system using DECT as the wireless radio technology. The system consists of radio system, Enterprise Service Control Node (ESCN), and PBX. ESCN is the service center of the whole system. It provides functions such as mobility management, call control, and supplementary services. Besides, ESCN is a wireless adjunct to PBX. It integrates the wireless and wired telephone system into one system. In addition, ESCN can connect multiple RE (Radio Exchange) to provide a large number of handsets. The interfaces between ESCN and PBX are T/R and R2/E1. Thus, both line interface and trunk interface are supported. Instead of voice service, it is also important to provide low rate data service in wireless system. In this paper, we describe how to provide short message service in the ESCN. Three different types of short message are supported. They are (1) point-to-point (2) group notification and (3) broadcast. Besides, we also consider how to deliver short message when the short message targets located in multiple campuses. The whole mobile system has been developed, and currently it is under field trial.
IP-based Virtual Private Network becomes more and more popular. It can not only reduce the enterprise communication cost but also increase the revenue of the service provider. The common IP-VPN application types include Intranet VPN, Extranet VPN, and remote access VPN. For the large IP-VPN market, some vendors develop dedicated IP-VPN devices; while some vendors add the VPN functions into their existing network equipment such as router, access gateway, etc. The functions in the IP-VPN device include security, QoS, and management. The common security functions supported are IPSec (IP Security), IKE (Internet Key Exchange), and Firewall. The QoS functions include bandwidth control and packet scheduling. In the management component, policy-based network management is under standardization in IETF. In this paper, we discuss issues on how to integrate the QoS and security functions in an IP-VPN Gateway. We propose three approaches to do this. They are (1) perform Qos first (2) perform IPSec first and (3) reserve fixed bandwidth for IPSec. We also compare the advantages and disadvantages of the three proposed approaches.
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