Optical Distribution System Research Articles

DISTRIBUTED FIBRE OPTIC TEMPERATURE SENSING

Since the introduction of the fibre optic distributed temperature system by York in 1986, the system has been successfully applied in a number of areas. The monitoring of hot‐spots in large power transformers and electricity cables to the analysis of the curing process in large concrete structures such as dams are some examples of where the technology is being used and is providing temperature data. Other more imaginative but nevertheless potentially feasible applications range from detecting black ice on roads to the monitoring of volcanic eruptions for the purpose of disaster prevention.

Cost‐effective configuration for large‐scale optical distribution system utilizing optical fiber amplifiers

AbstractThis paper investigates the cost‐effective optimum configuration of large‐scale optical distribution systems utilizing optical fiber amplifiers.First, the relation between network topology and the number of equipment is discussed. It is shown that in low‐loss optical fiber distribution systems, the tree configuration is more advantageous than the bus configuration from the viewpoint of required optical fiber amplifiers.Next, the relation between the network topology or distribution scale and the cost of each equipment is investigated. It is shown that when the cost of the fiber amplifier dominates, the tree distribution system with multilayer structure divided properly into subsystems is the optimum one. It is clarified that the structure with a large number of layers and the minimum number of segments in each layer is the economical configuration.

The Institutional Conditions for Technological Change: Fiber to the Home

For the first time in nearly one hundred years, telephone companies are attempting to upgrade the umbilical cord that ties each household to the public switched network. This cord is currently a twisted pair of copper wires. The new cord could be a fiber optic cable. The number and complexity of fiber optic experimental distribution systems is growing every year.' The telephone companies allege they are introducing fiber because it has the potential to carry not only voice and data communications but also video programs and services. In order to bring the alleged benefits of this new technology to the public, the telephone companies are attempting to a secure a release from the legal restrictions that limit their involvement in the video industry. The release will enable the telephone industry to secure the additional revenues that are needed to support the introduction of the new technology. Cable television, the alternative video carriage industry, is also evolving towards a fiber environment. Cable television companies are reinforcing coaxial systems with fiber backbones. This innovation will not only improve the quality of cable television services, but will also enhance the two-way communications abilities of the cable systems. The author is a senior telecommunications economist with the Public Service Commission of the District of Columbia. The views expressed in this article are those of the author and do not necessarily represent the views of the Public Service Commission of the District of Columbia or its Staff

Polarisation-insensitive optical coherent SCM system using mixed lightwave transmission of signal and local laser light

An optical coherent transmission and distribution system using subcarrier multiplexing (SCM) techniques is proposed in which the local LD is set in the transmitter and the signal and local light are mixed before transmission. The feasibility of the system was experimentally confirmed, using three-electrode DFB-LDs, with an optical FM by two-channel 560 Mbit/s ASK-SCM signal and a heterodyne transmission through 25.7 km of single mode fibre. This system was insensitive to the state of polarisation in the transmission fibre. It was shown that more than 1000 subscribers could be served with Er3+-doped fibre amplifiers.

Über die Klirr- und Intermodulationseigenschaften des klassischen Ringmodulators mit Differentialübertragern

The distortion and intermodulation qualities of diode modulators were studied theoretically and numerically, to prove their aptitude as high linear translators in modern fibre optic TV distribution systems. In this paper the classic diode modulator using differential transformers is treated. If parasitic capacities and inductivities are neglectible, the influence of the non-linear diode characteristics can be estimated very exactly under wording conditions even in multichannel systems

Performance evaluation of coherent subcarrier multiplexed optical distribution systems with common local oscillators

Coherent subcarrier multiplexed local distribution systems using a common local oscillator (LO) in which the LO is provided by a distribution centre instead of locally generated at the subscriber premise are described. Both single and multiple optical carrier systems are considered. Because of the low path loss in a local optical network, a common LO system is possible with a LO shared by many subscribers, and indeed provides many advantages. First, a simplified receiver is achievable which eliminates a tunable LO, an automatic frequency control (AFC) circuit, a polarisation controller, and an optical coupler. Secondly, the system cost is decreased due to the reduction of components. Thirdly, laser phase noise and intermediate frequency (IF) drift are expected to be minimised. Fourthly, because no active optical components are placed at the subscriber premises, the system reliability is increased. Fifthly, the common LO system can be expanded with optical amplifiers without increasing the number of LO and simultaneous amplification of the message, and LO signals are achievable. By sharing high power, highly frequency stabilised, and very narrow linewidth LO lasers provided by the centre, it is expected that a simple and reliable coherent optical distributing network can be constructed by using common LO.

Fiber optic distribution systems

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text T. J. B. Swanenburg, "Fiber optic distribution systems," Optics & Photonics News 1(11), 21-24 (1990) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Coherent optical ring using common local oscillator

A coherent optical ring distribution system using a common local oscillator is investigated. The results show that equal IF signal for all the nodes can be easily achieved and there exists an optimum branch coupling ratio to achieve a maximum IF signal. In addition, equal IF signal to noise ratio is achievable when the signal and LO have limited output powers.

Studies on realization of information retrieval service function by fiber optic broadband distribution system

AbstractAs one approach to the realization of post 64 kbit/s ISDN, studies have been made on the optic broadband distribution system, based on the fiber optic transmission by tree (or bus) trunk line and star subscriber line. To realize a more versatile C‐E communication system, however, not only must the service functions such as distribution of multichannel video information, character, still picture and data be provided, but also the information retrieval function with random access such as videotex.This paper discusses theoretically the realizability of the information retrieval service by the optic broadband distribution system from the viewpoint of whether or not a sufficient number of subscribers can be accommodated.

A novel low-loss inline bimodal-fiber tap: wavelength-selective properties

The tap described is a combination of two elementary devices: a low-loss (resonant) mode converter and a special fused-taper coupler. Efficient coupling of light for a narrow wavelength band (<10 nm) is demonstrated. The center-wavelength of the band can be selected by tuning the resonant condition for intermodal coupling in the mode converter. The uncoupled (nonresonant) light passes through the tap, exhibiting low excess loss (<0.2 dB). The tap has application in linearly tapped fiber optic distribution systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Factors affecting the design of optical FDM information distribution systems

Major factors affecting optical frequency division multiplexing (FDM) distribution system design are described. In particular, multiplexing/distribution configuration and channel-selection methods are compared from the viewpoint of the number of channels, the number of subscribers, and the transmission distance. The applicability of optical fiber amplifiers to the optical FDM information-distribution network is also discussed. The experimental results of a 5 GHz spaced 16-channel FDM distribution/transmission at 622 Mb/s, using a waveguide frequency-selection switch (tunable filter) and a multicarrier frequency-stabilization technique, are also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A 16-channel frequency selection switch for optical FDM distribution systems

The performance of a 5-GHz-spaced, 16-channel frequency selection switch (FS-SW) for optical frequency division multiplexing (FDM) distribution systems is described. The silica waveguide-type FS-SW is constructed with four serially connected periodic filters integrated on a silicon chip. The required crosstalk level for each periodic filter of the FS-SW was estimated to be -21.0 dB for a 16-channel FS-SW and 23.6 dB for a 128-channel FS-SW. Crosstalk can be independent of the power coupling ratio of the 3-dB-coupler regions by choosing suitable connecting configurations for the periodic filters. A controller for the switch is also described and the desired channel can be selected successfully from among 16 optical carriers under an average crosstalk level of less than -20 dB. >

Channel selection and stabilization technique for a waveguide-type 16-channel frequency selection switch for optical FDM distribution systems

A channel selection and stabilization technique for a waveguide-type 16-channel frequency selection switch (FS-SW) was examined at the 1.5- mu m wavelength region. The desired channel could be selected from 16 optical channels with a 5-GHz channel separation. The frequency fluctuation width for the observed short period was 65-250 MHz, and the frequency drift during 30 min was 20-100 MHz. An average crosstalk level of less than -20 dB was successfully achieved in the on state of the FS-SW stabilization.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Architecture of fiber optic broadband interactive distribution system

AbstractThe ideal situation in constructing a broadband communication network is that all kinds of services are provided by a single network. Such a structure is not necessarily advantageous at the present state of technology. From such a viewpoint, the best approach would be first to construct an economically‐optimum system, mostly considering the CE type broadband distribution service, which is estimated to have the highest demand, and gradually extend the network for other services. This paper first describes that the configuration combining the star‐type subscriber link and the tree‐type trunk lines is economical and has the functional expandability. Next another configuration is considered, in which the optical fiber is used for the subscriber link and the frequency division switch is used for the channel selections in the conversion of network topology. It is shown that the system is the optimum from the viewpoint of the cost per subscriber. By applying the notion of the cross‐contact switch, it is shown that the proposed system can be extended to the CE type video retrieval service and EE type transmission service. The optical distribution system will be utilized effectively in the future new media, providing the basis for the broadband communication network.

A Conceptional Design on Optical Frequency-Division-Multiplexing Distribution Systems with Optical Tunable Filters

Optical frequency-division-multiplexing distribution systems providing more than ten frequency multiplexed optical signals separated by on the order of gigahertz, distribute signals to plural receivers, where one of the signals is selected by a frequency selection switch (FS-SW). This paper describes the design of an optical frequency-divisionmultiplexing distribution system. Investigation is made of periodic filters for frequency division multiplexers and FS-SW, and the optical source, as well as single-mode fiber polarization mode dispersion. Preliminary transmission experiments using a bit rate of 450 Mbits/s, fiber length of 13 km, and frequency spacing of 11 GHz are also demonstrated at a 1.5 μm wavelength to show the design's suitability.

Optical Clock Distribution To Silicon Chips

Timing constraints for state-of-the-art very large scale integrated circuits (VLSI) in silicon are rapidly approaching communication limits available with layered two-dimensional metal and polysilicon wiring approaches. For such communication-limited systems, reliable clock distribution is a key concern. The range of finite differences in signal delays over clock wires of various lengths for large chips creates a timing skew that is significant when compared to the switching time of transistors in the circuit. The high bandwidth and three-dimensionality of imaging optical systems suggest that optical clock distribution systems have the potential to overcome the timing barriers presented by planar wiring. Clock signals can be holographically mapped to detector sites within small functional cells on a chip surface. Within each functional cell, the clock is distributed with negligible delays via surface wires, reducing skew effects to the variation in reaction times of the photodetectors on the chip. This paper includes the presentation of an optical clock distribution system assuming holographic mapping of beams from an off-chip optical source. Computer simulations of the electronic response of optical clock detection circuits in standard 4 µm CMOS technology have been performed.

Secure Splice Closures for Optical Fiber Systems

The problems of splice closure are discussed briefly and the options available for optical fiber cable systems are reviewed. It is concluded that for long-haul point-to-point cables, absolute security is paramount, and that for these, welded splice closures should be used. For optical fiber cables in local distribution networks, however, closures which can easily be reentered are needed. This requirement can only be met with some kind of mechanical closure. The security of these is considered inadequate for nonpressurized optical fiber networks. It is concluded that the use of mechanical closures must be supported by a satisfactory test method to confirm that they are sealed after each reentry. Conventional pressure testing of complete closures is considered to be too unreliable and slow for the purpose. A new double-seal closure system is described which allows the integrity of closures to be tested in seconds using a purpose-designed test device. The double-seal system is being used for the optical fiber distribution system being installed in the city of London by Mercury Communications Ltd.

Fused conically tapered fibre-optical power divider

We describe a novel, conically tapered fibre-optical power divider which substantially increases the usable power of an LED source and provides highly homogeneous power division among the output fibres. Such devices are of use in optical signal distribution systems such as fibre-optical local computer networks. The performance of a 25-fibre power divider is described.

Proposal for a Hub Controlled Cable Television System Using Optical Fiber

A practical hub oriented optical fiber TV distribution system is described. Pulse Width Modulation is utilized for ease in switching and a simple set-top coverter delivers pictures to a conventional TV set. A low cost connector concept is also discussed.

Conceptual Design of a Switched Television-Distribution System Using Optical-Fiber Waveguides

A conceptual design of a switched television-distribution system based on analogue intensty-modulated (IM) transmission through optical-fiber waveguides is discussed. Transmission of two TV channels and provision of telephone or data service over two optical-fiber waveguides to each subscriber by frequency-division multiplexing is considered first and then other design options such as spatial-division multiplexing, inclusion of copperwire pairsfor the supply of electrical power and telephone or data service is reviewed. Thepresent state ofdevelopment of system components is also discussed and areas requiring further development are pointed out. Theoretical Calculation of the possible transmission distances for analogue IM transmission of baseband and frequency-division multiplexed video signals is described. The results show that if-3 dBm (0.5 mW) of optical power modulated by a baseband video signal to a peak modulationfactor of 80% is launched into an optical-fiber waveguide, a distance of approximately 15 km can be spanned without a repeater. It is concluded that in view ofthe distances that can be covered by low-loss optical-fiber transmission systems, a centrally switched optical television distribution system may well be attractive for applications not only to urban areas, but also to rural areas. It is further suggested that an economic analysis is needed to ascertain the practicality of such a system.