SIST ETS 300 681 E1:2003
(Main)Transmission and Multiplexing (TM); Optical Distribution Network (ODN) for Optical Access Network (OAN)
Transmission and Multiplexing (TM); Optical Distribution Network (ODN) for Optical Access Network (OAN)
This draft European Telecommunication Standard (ETS) defines the Optical Distribution Network (ODN) which is that part of the Optical Access Network (OAN) between the Optical Network Unit (ONU) and the Optical Line Terminal (OLT). This ETS primarily addresses the optical aspects related to the transmission of the interactive services in an OAN according to the functional requirements specified in ETS 300 463. Optical aspects related to the transmission of signals corresponding to distributive services, which may have impact on the definition of this type of ODN (e.g. the use of Optical Amplification) are also taken into account, even if further studies are required in some cases.
Prenos in multipleksiranje (TM) – Optično razdelilno omrežje (ODN) za optično dostopovno omrežje (OAN)
General Information
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Transmission and Multiplexing (TM); Optical Distribution Network (ODN) for Optical Access Network (OAN)33.040.20Prenosni sistemTransmission systemsICS:Ta slovenski standard je istoveten z:ETS 300 681 Edition 1SIST ETS 300 681 E1:2003en01-december-2003SIST ETS 300 681 E1:2003SLOVENSKI
STANDARD
SIST ETS 300 681 E1:2003
EUROPEANETS 300 681TELECOMMUNICATIONJune 1997STANDARDSource: ETSI TC-TMReference: DE/TM-01009ICS:33.020Key words:Access, optical, SDH, OAN, transmission, networkTransmission and Multiplexing (TM);Optical Distribution Network (ODN) forOptical Access Network (OAN)ETSIEuropean Telecommunications Standards InstituteETSI SecretariatPostal address: F-06921 Sophia Antipolis CEDEX - FRANCEOffice address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCEX.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: secretariat@etsi.frTel.: +33 4 92 94 42 00 - Fax: +33 4 93 65 47 16Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and theforegoing restriction extend to reproduction in all media.© European Telecommunications Standards Institute 1997. All rights reserved.SIST ETS 300 681 E1:2003
Page 2ETS 300 681: June 1997Whilst every care has been taken in the preparation and publication of this document, errors in content,typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to"ETSI Editing and Committee Support Dept." at the address shown on the title page.SIST ETS 300 681 E1:2003
Page 3ETS 300 681: June 1997ContentsForeword.51Scope.72Normative references.73Definitions and abbreviations.83.1Definitions.83.2Abbreviations.94Definition of the ODN in an OAN.94.1Introduction.104.2Definition of ODN architectures.124.3ODN functions.134.4Protection configurations.145Wavelength ranges.145.1Wavelength range for the 1 310 nm region.145.2Wavelength range for the 1 550 nm region.146Specification of the optical path.146.1Definition of the optical path.146.2Loss allowance.166.2.1Loss definition.166.2.2Calculation methodology.166.2.3Optical path loss classes.176.3Passive optical components.186.3.1Fibre.186.3.2Optical branching devices.186.3.3Splices.186.3.4Connectors.186.3.5Attenuators.186.4Reflectance (return loss).186.5Chromatic dispersion.196.6Optical delay.196.7Polarization.196.8Environmental conditions.197Radiation safety requirements.198Introduction of OAs in the OAN.199Influence of upgrade possibilities.20SIST ETS 300 681 E1:2003
Page 4ETS 300 681: June 1997Annex A (informative):The bus architecture.21Annex B (informative):Protection configurations.22Annex C (informative):Example of application of the calculation methodology.24Annex D (informative):Survey of possible wavelength allocation for interactive services.28Annex E (informative):ODN reflectance calculations.29Annex F (informative):Bibliography.31History.32SIST ETS 300 681 E1:2003
Page 5ETS 300 681: June 1997ForewordThis European Telecommunication Standard (ETS) has been produced by the Transmission andMultiplexing (TM) Technical Committee of the European Telecommunications Standards Institute (ETSI).Transposition datesDate of adoption:2 May 1997Date of latest announcement of this ETS (doa):30 September 1997Date of latest publication of new National Standardor endorsement of this ETS (dop/e):31 March 1998Date of withdrawal of any conflicting National Standard (dow):31 March 1998SIST ETS 300 681 E1:2003
Page 6ETS 300 681: June 1997Blank pageSIST ETS 300 681 E1:2003
Page 7ETS 300 681: June 19971ScopeThis European Telecommunication Standard (ETS) defines the Optical Distribution Network (ODN) whichis that part of the Optical Access Network (OAN) between the Optical Network Unit (ONU) and the OpticalLine Termination (OLT).This ETS primarily addresses the optical aspects related to the transmission of the interactive services inan OAN according to the functional requirements specified in ETS 300 463 [11].Optical aspects related to the transmission of signals corresponding to distributive services, which mayhave impact on the definition of this type of ODN (e.g. the use of optical amplification) are also taken intoaccount, even if further studies are required in some cases.2Normative referencesThis ETS incorporates, by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text and the publications are listed below.For dated references, subsequent amendments to or revisions of, these publications apply to this ETSonly when incorporated by amendment or revision. For undated references the latest edition of thepublication referred to applies.[1]ETR 247 (1996): "Transmission and Multiplexing (TM); Technical report onstatistical approach design".[2]ETR 248 (1996): "Transmission and Multiplexing (TM); Use of single-modefibres in the access network".[3]ETR 126 (1994): "Transmission and Multiplexing (TM); Applications of opticalfibre amplifiers in long distance and optical fibre networks".[4]ETS 300 019-1 (1992): "Equipment Engineering (EE); Environmental conditionsand environmental tests for telecommunications equipment Part 1: Classificationof environmental conditions".[5]EN 187101 (1995): "Optical telecommunication cables to be used in ducts andfor direct buried applications".[6]EN 188101 (1995): "Single-mode dispersion-unshifted (B1.1) optical fibre".[7]EN 188102 (1995): "Single-mode dispersion-shifted (B2) optical fibre".[8]EN 187102 (1995): "Optical aerial telecommunication cables".[9]ETS 300 232 (1996): "Transmission and Multiplexing (TM); Optical interfaces forequipments and systems relating to the Synchronous Digital Hierarchy(SDH) [ITU-T Recommendation G.957 (1995) modified]".[10]I-ETS 300 671 (1996): "Transmission and Multiplexing (TM); Passive opticalcomponents; Fibre optical connectors for single-mode optical fibrecommunication systems; Common requirements and conformance testing".[11]ETS 300 463 (1996): "Transmission and Multiplexing (TM); Requirements ofOptical Access Networks (OANs) to provide services up to 2 Mbit/s bearercapacity".[12]EN 60825-1 (1994): "Safety of laser products - Part 1: Equipment classification,requirements and user's guide".[13]EN 60825-2, (1994): "Safety of laser products - Part 2: Safety of optical fibrecommunication systems".SIST ETS 300 681 E1:2003
Page 8ETS 300 681: June 1997[14]ITU-T Recommendation G.662 (1995): "Generic characteristics of optical fibreamplifier devices and sub-systems".[15]ITU-T Recommendation G.955 (1993): "Digital line systems based on the1 544 kbit/s and the 2 048 kbit/s hierarchy on optical fibre cables".3Definitions and abbreviations3.1DefinitionsFor the purposes of this ETS, the following definitions apply:diplex (working): The use of a different wavelength for each direction of transmission over a single fibre.downstream: The transmission direction from OLT to ONUs.duplex (working): The use of the same wavelength for both directions of transmission over a single fibre.Optical Access Network (OAN): The set of access links sharing the same network side interfaces andsupported by optical access transmission systems.NOTE 1:An OAN may include a number of ODNs connected to the same OLT.Optical Amplifier (OA): Optical amplification element without any signal processing.Optical Branching Device (OBD): A passive component (sometimes referred to as splitter/coupler),which has h inputs and n outputs, where h = 1 to H and n = 2 to N; it performs optical powersplitting/combining according to a fixed factor (balanced or unbalanced).optical connector: A passive component allowing removable interconnection between fibres.Optical Distribution Network (ODN): Provides the optical transmission medium from the OLT towardsthe ONUs and vice versa between the S/R and R/S reference points.optical fibre: The medium for the transport of optical signals.optical filter: A device for the selection of optical signals at specific wavelengths.Optical Line Termination (OLT): Provides the network-side interface of the OAN, and is connected toone or more ODNs.Optical Network Unit (ONU): Provides (directly or remotely) the user-side interface of the OAN, and isconnected to the ODN.passive component: A device that does not require external power (e.g. fibre, optical branching device,connector, filter, etc.).point-to-multipoint: A network configuration which has one input/output at one end with multipleinputs/outputs at the other end.point-to-point: A network configuration which has one input/output at one end with one input/output at theother end.reference point: A point at which optical interfaces are defined.reflectance: The ratio of reflected power to incident power for given conditions of spectral composition,polarization and geometrical distribution.NOTE 2:In optics, the reflectance is generally expressed as reflectance density or inpercentage terms; in communication applications it is generally expressed as10 log(Pr / Pi ) in dB, where Pr is the reflected power and Pi is the incident power.SIST ETS 300 681 E1:2003
Page 9ETS 300 681: June 1997simplex (working): The use of a different fibre for each direction of transmission.splice: A passive component allowing permanent interconnection between fibres (usually fusion of fibreends).upstream: The transmission direction from ONUs to (OLT).3.2AbbreviationsFor the purposes of this ETS, the following abbreviations apply:CENComité Européen de NormalisationENEuropean Standard (CEN/CENELEC)E/OElectrical-to-Optical (conversion)FDMFrequency Division MultiplexingO/EOptical-to-Electrical (conversion)OAOptical AmplifierOANOptical Access NetworkOBDOptical Branching DeviceODNOptical Distribution NetworkOlOLT/ODN Optical Interface (local exchange side)OLTOptical Line TerminationOmoptical interface for testing and monitoring equipmentONUOptical Network UnitOrONU/ODN Optical interface (remote side)OTDROptical Time Domain ReflectometerR/Soptical Receive/Send reference pointsS/Roptical Send/Receive reference pointsSDMSpace Division MultiplexingTCMTime Compression MultiplexingWDMWavelength Division Multiplexing4Definition of the ODN in an OANThe ODN specified in this ETS has a passive distribution function. It shall be able to provide:-future proof cable plant;-easily maintainable network;-longitudinal compatibility;-reliable network structure;-high transport capacity;-a means to allow integration of interactive and distributive services; and-high availability.For manufacturing purposes, this ETS caters for ODN elements which can be mass produced, give a costeffective solution and stimulate further development.SIST ETS 300 681 E1:2003
Page 10ETS 300 681: June 19974.1IntroductionIn general, the ODN provides the optical transmission medium for the physical connection of the ONUs tothe OLTs.The ODN consists of passive optical components:-single-mode fibres, in compliance with EN 188101 [6];-single-mode optical fibre cables, in compliance with EN 187101 [5] and EN 187102 [8];-optical fibre ribbons on ribbon cables, (see annex F);-optical connectors, in compliance with I-ETS 300 671 [10];-fibre optic branching devices, (see annex F);-fixed optical attenuators, (see annex F);-fusion splices, (see annex F).NOTE 1:Passive components not included in the above list (e.g. optical filters, WDM devices)are for further study.R, S: reference points
bold solid lines represent one or more fibres;dashed lines represent protection fibres (see annex B)O , O , O
: optical interfacesrlmOlOLTS/RR/SmOrONUONU1nODNR/SOrONOTE:Each line linking any two optical blocks may represent one or more fibres in all subsequentfigures.Figure 1: Generic physical configuration of the ODNSIST ETS 300 681 E1:2003
Page 11ETS 300 681: June 1997The ODN is defined between the reference points S and R (see figure 1). In alignment with the definitionsprovided in ITU-T Recommendation G.955 [15] and ETS 300 232 [9], S and R shall be defined as follows:a)S: point on the optical fibre just after the OLT[a]/ONU[b] optical connection point (i.e. opticalconnector or optical splice);b)R: point on the optical fibre just before the ONU[a]/OLT[b] optical connection point (i.e. opticalconnector or optical splice).NOTE 2:These optical connection points are not part of the ODN.Definition a) holds when considering optical signals travelling from the OLT(s) to the ONUs anddefinition b) holds when considering optical signals travelling from the ONUs to the OLT(s).Depending on the physical realization of the ODN, the points S and R at each end of the ODN may belocated either on the same fibre (i.e. they coincide) or on separate fibres.The ODN offers one or more optical path(s) between one OLT and one or more ONUs. Each optical pathis defined between reference points S and R in a specific wavelength window.The following optical interfaces are defined in figure 1:Or:optical interface at the reference point R/S between the ONU and the ODN;Ol:optical interface at the reference point S/R between the OLT and the ODN;Om:optical interface between testing and monitoring equipment and the ODN.At the physical layer, the interfaces Or and Ol may require more than one fibre, e.g. for separation oftransmission directions or different types of signal (services). The interface Om may be physically locatedat several points in the ODN and may be implemented both with dedicated fibres and with network fibrescarrying traffic.Specification of the optical interfaces defined above is for further study.The optical properties of the ODN shall enable the provision of any presently foreseeable service, withoutthe need of extensive modifications to the ODN itself. This requirement has an impact on the properties ofthe passive optical components which constitute the ODN. A set of essential requirements, which have adirect influence on the optical properties of the ODN, are identified as follows:-optical wavelength transparency: devices, such as optical branching devices, which are notintended to perform any wavelength-selective function, shall be able to support the transmission ofsignals at any wavelength in the 1 310 nm and 1 550 nm regions;-reciprocity: reversal of input and output ports shall not cause significant changes to the optical lossthrough the devices;-fibre compatibility: all optical components shall be compatible with single-mode fibre as specifiedin EN 188101 [6].The two directions for optical transmission in the ODN are identified as follows:-downstream: direction for signals travelling from the OLT to the ONU(s);-upstream: direction for signals travelling from the ONU(s) to the OLT.Transmission in downstream and upstream directions can take place on the same fibre and components(duplex/diplex working) or on separate fibres and components (simplex working). Duplex working refers tothe use of the same wavelengths for both directions of transmission over a single fibre; diplex workingrefers to the use of different wavelengths for each direction of transmission over a single fibre. Simplexworking refers to the use of a different fibre for each direction of transmission.SIST ETS 300 681 E1:2003
Page 12ETS 300 681: June 1997The introduction of Optical Amplifiers (OAs) within the OAN is possible under the rules given in clause 8 ofthis ETS. In this case each OA shall not be considered as a part of the ODN. Instead separate ODNs willbe considered, according to the rules also given in clause 8.If additional connectors or other passive devices are needed for ODN rearrangement, they shall belocated between S and R and their losses shall be taken into account.4.2Definition of ODN architecturesThe physical connection of the OLT and ONUs to the ODN is made via one or two fibres, depending onthe bi-directional transmission scheme adopted (duplex, diplex or simplex). Use of a greater number offibres is allowed for upgrade or protection purposes.The configuration of the ODN shall be point-to-multipoint, where a number of ONUs are connected to theOLT via the ODN. Thus, sharing by ONUs of the optical medium and optoelectronic devices of the OLT isachieved.Two basic point-to-multipoint architectures for the ODN can be defined: tree and bus.An example of a tree architecture is shown in figure 2. It employs cascaded optical branching devices tosplit the downstream signal and to combine the upstream signals. The optical branching devices aregenerally of the 1:n type. To achieve enhanced network performance and reliability (e.g. input of additionalsignals, access points for testing and monitoring, network protection by means of path diversity, etc.)optical branching devices of the h:n type, where 1 < h £ n, may also be used. Typically, the opticalbranching devices used in the tree architecture are balanced devices, i.e. the optical loss from any inputport to any output port is nominally the same for any choice of input and output ports. This requirementstems mainly from the need to have simple and general rules for power budget calculation and overallnetwork design.A description of a bus architecture with the use of unbalanced optical branching devices is given inannex A.NetworksideOBDOLTOBDOBDONUONUONUONUUsersideR/SS/R121splittinglevelsODN321Fibresegmentsn21n11n2nn2n-+1n = n1 x n2.Dashed lines represent protection fibres.1n2Figure 2: An example of a tree architectureSIST ETS 300 681 E1:2003
Page 13ETS 300 681: June 1997In this ETS, the point-to-point configuration, where one ONU is connected to the OLT via the ODN, isconsidered as a specific point-to-multipoint implementation. In this case there are no optical branchingdevices in the ODN and a dedicated optical link, consisting of one or two fibres, connects each ONU tothe OLT (see figure 3). This configuration is called single star architecture, which allows the maximumfibre length between the OLT and the ONU to be greater than that for a point-to-multipoint configuration.NOTE:Several factors can be taken into account when choosing the ODN architecture, themain ones being: topological distribution of customers, distances between OLT andONUs, optical paths for various services to be provided, available technology, opticalpower budget, wavelength allocation, upgrade requirements, reliability and availability,operation and maintenance, ONU powering, security, cable capacity.NetworksideUsersideR/SS/RnOLT1ONUONUODN 1nFigure 3: An example of a single star architecture4.3ODN functionsThe following functions are identified for the ODN:a)Direct optical connection:-The ODN shall provide facilities for the direct exchange of optical signals between the OLTand the ONU. This function does not apply to the point-to-point ODN configuration, as thiscontains no optical branching devices.b)Optical splitting/combining:-Splitting is performed on the downstream signals and combining on the upstream signals, bymeans of optical branching devices.c)Optical multi-wavelength transport capability:-The ODN shall allow the simultaneous transmission on the same fibre of signals havingdifferent wavelengths, both in the downstream and upstream direction.SIST ETS 300 681 E1:2003
Page 14ETS 300 681: June 1997d)Optical monitoring attachments:-The location of the access points for ODN optical testing and monitoring, and themeasurements carried out in the ODN, shall not degrade the operation of the access link.Access points should be provided in the OAN. The access points may be located at the OLT,ONUs and intermediate places in the ODN. At the access points optical testing equipmentsuch as OTDRs (Optical Time Domain Reflectometers) and optical power meters may beconnected. Power measurements may be carried out at fibre terminations or along the fibreusing appropriate measuring equipment.e)Optical interfaces:-The ODN shall provide physical interface functions for optical connection to the OLT andONUs.4.4Protection configurationsExamples of protection configurations are given in annex B.5Wavelength rangesThe operating wavelengths used in the ODN shall be in the 1 310 nm (2nd) window and the 1 550 nm(3rd) window. A survey of some possibilities for wavelength allocation in case of interactive services isgiven in annex D.NOTE:Transmission of testing and monitoring signals at other wavelengths may be used, butthese are considered to be outside the scope of this ETS.5.1Wavelength range for the 1 310 nm regionThe operating wavelength range for the 1 310 nm wavelength region shall be 1 260 nm to 1 360 nm.NOTE:If OAs are used, a narrower wavelength range may be considered.5.2Wavelength range for the 1 550 nm regionThe operating wavelength range for the 1 550 nm wavelength region shall be 1 480 nm to 1 580 nm.NOTE:If OAs are used, a narrower wavelength range may be considered.6Specification of the optical path6.1Definition of the optical pathThe ODN is constituted by P splitting levels, even though one or two splitting levels are typically adopted.Within the ODN, several optical paths can be identified. Each optical path connects a specific ONU to theOLT.The optical path between the OLT and ONU, or more generally, between reference points S/R and R/S, isformed by a cascade of P optical path elements.SIST ETS 300 681 E1:2003
Page 15ETS 300 681: June 1997LPOLTONUR/SS/Roptical pathconnectorspliceoptical branching device:PPkjmjk1m1LjL1::L(j)-thoptical pathelementh
: n11Ph
: nPjh
: njPPPPmP=+PPkP=+k"m"k'k"m"m'k'm'Figure 4: Schematic representation of the optical path between the OLT and the ONUIn figure 4, which gives a schematic representation of the downstream optical path between the OLT anda specific ONU, or more generally between reference points S/R and R/S, the P-th splitting level is shownas a cascade of P optical path elements. The (j)-th optical path element begins at the output port of the(j-1)-th optical branching device and ends at the output port of the (j)-th optical branching device, with thefollowing exceptions:-for j = 1, the optical path element begins at the S/R reference point and ends at the output port ofthe first optical branching device (or, for P = j = 1, at the R/S reference point);-for j = P, the optical path element begins at the output port of the (P-1)-th optical branching device(or, for P = j = 1, the S/R reference point) and ends at the R/S reference point, in order to take intoaccount possible splices and connectors present at the output after the last optical branchingdevice.The (j)-th optical path element consists of optical fibre of length Lj and of the following passive opticalcomponents (the sequence of components in each path element is arbitrary):-the (j)-th optical branching device with splitting ratio hj:nj (hj ³ 1, nj ³ 1);-kj connectors, with kj ³ 0;-mj splices, with:m
=
m
+
mL
+
mjdjrjjajwhere:-mdj is the average number of planned splices per unit length of fibre in the first installation phase;-mrj is the average number of repair splices per unit length of fibre, foreseen in the operationalphase;-maj is the number of additional planned splices, not taken into account in the figure mLdjj, in thefirst installation phase; maj takes into account the splices due to the installation of the opticalbranching device and the extra splices at the termination points of the ODN (e.g. at an opticaldistribution frame inside the central office, at the optical termination point at the ONU side).SIST ETS 300 681 E1:2003
Page 16ETS 300 681: June 1997In conclusion, the whole optical path consists of optical fibre of length L = j=1PLjå and of the followingpassive optical components:-P optical branching devices, with splitting ratio hj:nj (hj ³ 1, nj ³ 1, j = 1, ., P);-k = kj=1Pjå connectors;-m = mj=1Pjå splices.The overall splitting ratio of the optical path is:
n = njj=1PÕ.NOTE:In the case of a point-to-point ODN configuration there is no optical branching devicealong the optical path. Consequently, only one optical path element is considered, andthe previous evaluations are valid simply excluding any reference to the opticalbranching device.6.2Loss allowance6.2.1Loss definitionLoss allowance for the optical power budget is defined as the loss, in dB, between reference points, S/Rand R/S, of the ODN. This includes the loss due to fibre length and passive optical components (e.g.optical branching devices, splices and connectors). The loss allowance has the same value both in thedownstream and upstream direction.The following parameters are important for the overall system performance:-maximum difference of loss between the optical paths of the ODN;-maximum allowable path loss, defined as the difference between minimum transmitter output powerand maximum receiver sensitivity, both under end of life conditions (including variations due totemperature, ageing, etc.);-minimum allowable loss, defined as the difference between maximum transmitter output power andminimum receiver overload, both under end of life conditions.These maximum and minimum losses shall be defined over the required environmental and wavelengthranges and not just measured at a given wavelength, given time and at a given temperature.These definitions are analogous to ETS 300 232 [9], where the attenuation ranges for SDH opticalinterfaces are specified.6.2.2Calculation methodologyUsing the methodology of this subclause, appropriate optical loss ranges can be calculated for differentoptical paths.The optical loss of an optical path of an ODN is calculated by adding the losses of all optical componentsalong the optical path.A statistical approach, based upon the following procedure, shall be used in the summation in order toavoid over specification of the ODN. The statistical distribution of the overall optical path loss shall beobtained by combining the statistical distributions of losses of the various components of the optical path.SIST ETS 300 681 E1:2003
Page 17
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.