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ONF Document Type: Technical Recommendation

ONF Document Name: Core Information Model version 1.4 Draft



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Important note

This Technical Recommendations has been approved by the Project TST, but has not been approved by the ONF board.   This Technical Recommendation is an update to a previously released TR specification, but it has been approved under the ONF publishing guidelines for 'Informational' publications that allow Project technical steering teams (TSTs) to authorize publication of Informational documents.   The designation of '-info' at the end of the document ID also reflects that the project team (not the ONF board) approved this TR.


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Table of Contents


Open Networking Foundation

Document History

1 Introduction

2 References

3 Definitions

4 Conventions

5 Introduction to the Core Network Model

5.1 Understanding the figures

6 Forwarding and Termination model detail LogicalTerminationPoint (LTP) LayerProtocol (LP)

6.1.2 Forwarding ForwardingDomain (FD) ForwardingConstruct (FC) FcPort Link LinkPort

6.1.3 NetworkElement, NetworkControlDomain and SdnController

7 Explanatory Figures

7.1 Forwarding

7.1.1 Basic Forwarding

7.1.2 Forwarding the topology

7.2 Termination

7.3 Directionality

List of Figures

Figure 1-1 Methodology of IM and DS Development

Document History



Description of Change



Appendix material was not published prior to Version 1.3


September 2017

Version 1.3 {{Published via wiki only}}


January 2018

Addition of text related to approval status.


May 2018



1        Introduction [A1]

This document is an appendix of the addendum to the TR-512 ONF Core Information Model and forms part of the description of the ONF-CIM. For general overview material and references to the other parts refer to TR-512.1 .

1.1      References

For a full list of references see TR-512.1 .

1.2      Definitions

For a full list of definition see TR-512.1 .

1.3      Conventions

See TR-512.1 for an explanation of:

  • UML conventions
  • Lifecycle Stereotypes
  • Diagram symbol set

1.4      Viewing UML diagrams

Some of the UML diagrams are very dense. To view them either zoom (sometimes to 400%) or open the associated image file (and zoom appropriately) or open the corresponding UML diagram via Papyrus (for each figure with a UML diagram the UML model diagram name is provided under the figure or within the figure).

1.5      Understanding the figures

Figures showing fragments of the model using standard UML symbols and also figures illustrating application of the model are provided throughout this document. Many of the application-oriented figures also provide UML class diagrams for the corresponding model fragments (see TR-512.1 for diagram symbol sets). All UML diagrams depict a subset of the relationships between the classes, such as inheritance (i.e. specialization), association relationships (such as aggregation and composition), and conditional features or capabilities. Some UML diagrams also show further details of the individual classes, such as their attributes and the data types used by the attributes.

1.6      Appendix Overview

This document is part of the Appendix to TR-512. An overview of the Appendix is provided in TR-512.A.1 .

2        Introduction to this Appendix document [A2]

This document provides various examples of the use of the CIM to model analogue and media structures

The examples in this document are built from descriptions other documents. The media examples are supported by a combination of the FC/LTP (as described in TR-512.2 ), the physical model (as described in TR-512. 6 ) and the specification model (as described in TR-512.7 ).

Each case discussed in this document will be supported by FC specs, LTP specs and scheme specs. Most cases do not explicitly show the scheme spec but have been described using the base classes (FC, LTP etc) from which the scheme spec can be derived.

2.1      Further context


2.2      A physical example [A3]

3        Optical Media

The network model required to support media is discussed in TR-512.2 .

This document provides examples of usage of the network model to represent various photonic media functions and devices. For each example detailed stylized layouts of functions that are used to drive FD, FC, LTP and scheme spec are provided along with the resulting simple compact representation.

It is intended that sufficient stylized cases are covered here to allow a modeler to represent their specific function/device.  It is not intended that all possible cases are covered.

The spec models provide detail to allow interpretation of the properties compacted into the simplified model and hence allow faults to be diagnosed. The figures in this document are essentially pictorial views of specs.

3.1      The basic components of the mode

3.1.1      The basic attenuator and filter

The following figure shows symbols for the basic attenuator and filter. Attenuators and filters are inherently omnidirectional.

Figure 6 - 45 Attenuator and Filter (explaining the symbol set)

The filter models the ability to allow only those photons that are within in a defined portion of spectrum to be passed. The filter is described as a media channel and is represented by an FC.

The portion of the spectrum is called a frequency slot and is described by centre frequency and width. Frequency slot is an administrative concept and is conceptually square. The actual pass-band of the filter is not square. The frequency slot and pass band relationship is challenging and not covered here.

A single port of a filter can support more than one media channels (see later).

As the filter is represented by an FC the characteristics are expressed in an FcSpec (see TR-512.7 ).

Figure 6 - 13 Pictorial view of example spec model for attenuator

The figure shows the two port FC along with three spec forms:

  • Asymmetric: This allows the parameters for both directions of flow to be different. This is the easiest form to read and is recommended even when the device is symmetric
  • Basic Symmetric: Appropriate where the device has exactly the same effect on both flows and there is no independent control of the flows. The current rule for an FcSpec of this form is that there is no flow from a port to itself so this does not readily allow reflection characteristics to be expressed (the FcSpec rule would need to become flexible per flow expression)
  • Asymmetric with reflection: Shows a long hand form of the spec. Note that this is relatively verbose for a two port device. For a multi-port device, explicit expression seems particularly verbose and a more compact form of expression would be beneficial.

The parameter blocks in the spec provide invariant and adjustable values. Any aging characteristics could be stated in the parameter blocks.

For a complex filter with different characteristics per "band" the spec could either code the complexity in an expression or show separate "flows" (green) per "band". It is also possible to have a filter instance per "band".

The model (and symbol set) allows for a variable attenuator.

3.1.2      Coupler-Splitter

The following figure shows basic coupler/splitters. Coupler-splitters are inherently omnidirectional.


Figure 6 - 45 Coupler/Splitter

The Coupler/Splitter provides a set of atomic media channels between one (common) port and two or more other (branch) ports. All of these atomic media channels have the same frequency slot. In the root to leaf direction the "splitter" attenuates the signal, in the leaf to root direction the "coupler" has negligible attenuation.

3.1.3      The circulator

The circulator is a media component that takes advantage of non-linear characteristics to essentially provide a unidirectional flow. A circulator as shown in the figure below.

Figure 6 - 45 The circulator

In the circulator depicted, photons that arrive at FcPort A will emerge from FcPort B, photons that arrive at FcPort B will emerge at FcPort C and photons that arrive at FcPort C will emerge from FcPort A.

3.1.4      The photodiode

The photodiode is a media component that converts a photonic signal (in a frequency slot) to an electrical signal. Both the signal domain and the media change (the domain changes from photonic to electrical and the media from glass to copper (via various intermediate media)) [1] . There is a media channel from the So to the converter (an adaptation) and a different media channel from the converter to the Se, however it is the domain change that is emphasized by the adapter symbol rather than the media change (as the physical layer is only modeled in abstract). The third symbol shows media transition. The assumption is that the FC is essentially electrical and the element that is not is exposed as an embedded FC with some fiber specification.

Figure 6 - 35 Photodiode as an active element (showing media)

The figure below shows the spec model for the Photodiode highlighting:

  • The media specification
  • The LTP spec representing the transformation from optical to electrical
  • A specification of the reflection characteristics.

The bias signal is not supported at this stage.

Figure 6 - 13 Pictorial view of example spec model for Photodiode

The figure below shows a photodiode in the context of an LP. The photodiode may be extract signal or may be used for power measurement. The optical power monitor measures the power of any optical signals that are present in a media channel.

Figure 6 - 35 Photodiode as an active element showing power monitor


3.2      Complex assemblies

3.2.1      The Laser

The laser is a media component that takes advantage of non-linear characteristics to essentially convert an electrical signal to a photonic signal (in one frequency slot).

Figure 6 - 35 Laser as an active elements (showing media)

The lasing medium when stimulated with an electrical signal produces an equivalent photon signal. In the actual implementation the photons emerge at two facets. The "back" facet photon stream is used to measure the output of the laser. The measurement is fed to a control function that adjusts the electrical input to the laser.

The Laser with back diode is shown in the context of the E-O Source LP.

Figure 6 - 35 Laser as an active element (showing media)

The spec for the E-O Source explains the arrangement of functions and provides a mapping to the E-O LP instance and content. From the figure it can be seen that the LP includes two Terminations an adapter, two FCs and a C&SC. The two FCs can be merged and the spec for the LP then looks as in the figure below.

Figure 6 - 35 Spec for Laser

A compact view of the media E-O LP is shown in the diagram below [2] .

Figure 6 - 35 Essential functions of a laser and abstracted symbol for a laser

An alternative construction of a photonic transmitter is shown in the figure below. In this case, rather than an output that is amplitude modulated with the signal, the output is phase modulated or amplitude modulated (or both) by an external device. In this case the electrical signal carrying the information is applied to the external modulator and the laser produces a constant power output.

Figure 6 - 35 Sketch of phase modulated output

3.2.2      The coherent receiver

The figure below shows the simplified view of a coherent receiver with digital signal processing (DSP) [3] . A coherent receiver uses a heterodyne detector to convert the information carried by the photons into a "baseband" electrical signal that is then processed by DSP to correct for impairments introduced by the network domain channel. The abstracted symbol encapsulates the frequency tuning aspects and the DSP in the FC but separates out a termination to deal with the optical to electrical conversion. The symbol is not an accurate depiction of the actual processing but it allows for a more consistent representation from a management-control perspective.

Figure 6 - 35 Coherent receiver assembly with simplified symbol [A4]

3.3      Network considerations

This section provides views of the basic elements described in the previous section combined into network constructs.

3.3.1      The Media Channel and Information Transfer

Figure 6 - 35 Network Domain Channel formed from Media Channels

In this document the Network Domain Channel (the FCs NDCA and NDCB) is considered as being from the point of injection of electrons into the laser medium or external modulator to the point of emergence of electrons from the photodiode [4] . The NDCs shown are formed as a result of the effects of the filters in the coupler C and splitter D which are reflected in the Media Channels MCY and MCZ (both of which are FCs with three FcPorts). It is not until the lasers A and B are applied to the MCY and MCZ that the effective NDCs can be determined. In the figure, Y and Z are wide band receivers. If A and B were tuned such that A D1 (and hence A ∩D2=Ø) and B D2(and hence B ∩D1=Ø) then NDCA would go from A to Y and NDCB from B to Z.

The figure below shows a basic consideration of information transfer. For the broad band receiver the information transfer capability is dictated by the NDC.

Figure 6 - 35 Information Transfer Channel formed from Media Channels for broadband receiver

The figure below shows MCZ and MCY are transparent. The ability to transfer information is dictated by setting of the tunabe laser, the setting of the hetrodyne detector and the capabilities of the receiver DSP. The figure provides a somewhat simplified representation of the information transfer capability.

Figure 6 - 35 Information Transfer Channel formed from Media Channels for coherent receiver


3.3.2      The amplifier

Amplification is achieved using non-linear characteristics of fiber. The optical amplifier acts on a band of frequencies to increase the optical power level .    General considerations

The abstract symbol for an amplifier element is shown in the figure below.

Figure 6 - 35 Abstract symbol for an amplifier

The abstract symbol can be used to represent an amplifier where a detailed consideration is not relevant. In a simplified view the gain parameters are parameters of the FC and the input and output power measures are parameters of the FcPorts. The spec model set provides the mapping from the parameters in the simplified view and the detailed interpretable view.

Where the amplifier provides different amplification for different bands/slots a number of instances of the symbol can be used as shown below. Where control/monitoring is relevant parameters can be offered on a per amplifier FC or FcPort basis as appropriate.

Figure 6 - 35 Abstract Symbol for a multi-band/slot amplifier

For more complex cases a more detailed model will be required. The following sections detail different applification methods.    Erbium Doped Fiber Amplifier (EDFA)

This amplifier uses a short length of fiber doped with Erbium as the non-linear element that is fed at one or more points by pump lasers of specific wavelengths. This combination causes power transfer to a set of signal wavelengths that arrive at the input side of the amplifier. The EDFA is unidirectional.

The following figure shows a stylized view of an EDFA with one forward (co-directional) pump laser and fragment of control (including measurement of one band of incoming/outgoing signal only). In a full form, many bands may be measured, there may be many pumps in an amplifier and there may be two or more amplifiers in parallel amplifying different bands (e.g. L band and C band [5] ).


Figure 6 - 35 A stylized view of a fragment of an EDFA

The essential function of the amplifier is to provide balanced amplification to all relevant incoming signals. To enable interpretation of the measures and adjustment of the controls a suitably detailed spec model should be provided. The spec model should show necessary detail such that the effects of each control and the meaning of each measure can be interpreted. Certain elements of the EDFA (such as the circulators) are not relevant from this perspective. The spec may represent the amplifier as a set of parallel per band amplifiers from this perspective.

Considering fault analysis, it may be necessary to represent the amplifier in more precise detail especially where the amplifier is constructed from a number of separate field replaceable units.

It is likely that several related spec models will be necessary in the most complex case [6] .

The following figure shows a fragment of a model of an EDFA with a backward pump.

Figure 6 - 35 A further fragment of an EDFA with a forward and a backward pump


3.3.3      Amplification using the Raman effect

The following figure shows a stylized view of a Raman amplifier. The amplifier uses the main transmission fiber as the amplification element. Various other filters and monitors may be present in full representation.

As for the EDFA there may be a need for several related spec models to provide views for different purposes.

A simplified view may use the amplifier symbol in the figure above or amplification can be shown on the FC for the transmission fiber (as in the figure below).

Figure 6 - 35 Stylized model view of a Raman amplifier

3.3.4      Optical Time Domain Reflectometer (OTDR) [A5]

The following figure shows a somewhat simplified representation of an OTDR. The laser fires pulses via the circulator (top) into the fiber (right) and reflections are collected from the fiber (right) via the circulator (bottom) and fed to the single photon detector. The single photons are counted over time and the results analyzed to provide a view of the lengthwise characteristics of the fiber.

Figure 6 - 35 Stylized model view of an OTDR

4        Monitoring and Overhead [A6] [A7]

4.1      Overview

This section deals with the monitoring of sections of a photonic network. The model is derived from representations in {{ITU-T G.872}}. The two subsections provide an overview of the basic monitoring capabilities in the context of the ITU-T work and introduce the OMS, OTS and OTSiG-O. Then further subsections explain how the monitoring is factored into the ONF Core model.

4.2      OMS and OTS [A8]

The following figure shows a fragment of topology positioning the OMS and OTS with respect the photonic and electronic components.

The figure includes three diagrams. The detailed view shows a layout of components (each component view is itself simplified). The measures in the detailed view can be projected to the corresponding points in the simplified view. A set of scheme spec would explain the relationship between the simplified view and the detailed view (and clearly further spec would explain the measures on each component in terms of further detail).




Figure 6 - 35 Topology fragment showing OTS in detail and OMS in abstract (assuming EDFA)

The OMS information is conveyed via the OSC. The OSC terminates for each OTS span and hence the OMS information needs to be propagated between OSCs at the points of OTS termination. This detail is not shown but would be explicitly modeled in the relevant specs (essentially simple forwarding). Bidirectional considerations of the OMS, OTS and OSC are not covered here.

Note that the OTS monitors shown in the figure above will probably be the monitors of the amplifier itself and hence the OTS OSME will extend between the output port and the input of the amplifiers as show in the simplified view such that the OTS and OTS OSME become coincident.

The OTS, OTS OSME, OMS and OMS OSME are represented by FCs. OTS FC is between the output of one amplifier and the input of the next. The OMS FC is between a point of aggregation and a point of disaggregation.

The Optical Supervisory Channel is essentially an NDC and is represented by an FC.

4.3      OTSi in context of OTU, OMS-O and OTS-O

The following figure provides a detailed view of the representation of the LTPs and FCs that represent OTU mapping onto media.


Figure 6 - 35 OTSi in context of OTU, OMS and OTS [A9]

An OTU is supported by a set of one or more OTSi ( Optical Tributary Signal)

The set of OTSis that carry a single OTU are considered as a group (OTSiG) from a management-control perspective. The OTSi is characterized by the central frequency and an application identifier. Each OTSi is carried in an independent NDC. The differential delay between members of the OTSiG must be controlled.

If the OTSiG O is used then all members of the OTSiG and the OSC that carries the OTSiG O are carried over the same fiber .

The OSC is an OTSi that is used to carry the OTSiG O and a Data Communications Channel

4.4      Function blocks and network considerations

The basic photonic structures discussed in the earlier sections are blended with the model of the overhead termination to provide a representation of a ROADM node. The model allows for monitoring of the OTSis at intermediate points. Not all the monitoring opportunities will be present in all devices. The model also assumes the opportunity for Tandem monitoring of OTSis which is not currently present in the relevant standards.

The model is first shown with basic photonic parts grouped into LayerProtocol units and then into LTPs. It should be noted that the overhead aspect of the LTPs is layered but the photonic aspect is not layered. The grouping into LTPs is intended to minimize complex coupling between components. It is also designed to simplify the migration from more traditional layered models. It is important to recognize that the photonic aspects of the model are all in one layer, the "photonic media" layer

The discussion starts from the line side of the ROADM.

4.4.1      OTS and amplification

The figure below shows a fragment of a ROADM where the brown background partial rectangle represents the ROADM node boundary. The figure does not show the FRU arrangement.

To the right of the diagram are the two fiber strands (white rectangle in a blue rectangle where the blue rectangle represents the sheath and hence a cable [7] ). The strands are terminated by connectors (blue squares) each of which has one pin (the white circle in the blue square).

The connector on a cable plugs into a compatible connector on the equipment (this is shown at the boundary of the ROADM node). This connector has one pin, highlighted, related to the strand and the relevant signal flow. The connector is depicted as having more pins that are not shown.

As the OTS overhead termination is bidirectional, there are two pins highlighted on the equipment, one for receive (lower) and one for transmit (upper). The two pins are grouped into a bidirectional AccessPort (see [A10] and this is related to a bidirectional port on a StrandSpan. [A11] The StrandSpan is a physical model abstraction that, in this case, aggregates two serial concatenation of strands, one carrying the signal from the ROADM node and the other carrying the signal to the ROADM node, to the AccessPort on the next equipment.

The pins designated transmit and receive both connect to ports on FCs. The upper FC represents a coupler and the lower a splitter. The coupler takes the light from the OTS laser along with the main signal (discussed more in following sections) and the splitter separates out the OTSi carrying the OTS signal from main signal.

The OTS transponder is shown as a photonic transmitter and receiver. The transponder portion of the OTS termination then feeds to the OTS protocol termination (bidirectional) which has two clients. One of the clients (with the red line emerging) will be discussed in the next section. The other client relates to the monitoring detail.

Returning to the lower part of the diagram, the coupler and splitter discussed above each have to their left a splitter. In each case the splitter takes a small sample of the signal and feeds it to a receiver. The upper splitter samples the outgoing signal and the lower splitter samples the incoming signal. Both samples are terminated and the power, and potentially other optical parameters are measured. The two measures feed to the OTS termination to send to the far end. The monitoring is applied to the OTS as client information. The expectation is that all OTS related local and remote information will also be available at this point.

In the case where there are monitors but no overhead, the local measures will be folded back into the optical parameter measurements units.

Figure 6 - 35 OTS showing physical connectors [A12]

Considering the physical layer further, inside the node boundary there are many connectors, strands and other media components. A pair of media components are shown in grey attached to the receive and transmit pins of the connectors. This is a very small fragment of the overall structure. The physical structure is considered more in a following section. [A13]

The figure below groups the various termination and forwarding elements in LayerProtocol units. The photonic elements of the OTS termination are grouped in a single bidirectional LayerProtocol. The elements of the two measurement functions are grouped into two unidirectional LayerProtocols. The electronic elements of the OTS termination are grouped into several unidirectional LayerProtocols and are OTS_O layerProtocol. The measurement client is MEASURE_AND_CONTROL layerProtocol and the other client of the OTS_O is OMS_O layerProtocol.

Figure 6 - 35 OTS showing LayerProtocol groupings

The figure below extends adds the amplifiers, assumed in this case to be both in the receive and transmit direction. It is the position of these amplifiers that defines the boundary of the OTS.

Figure 6 - 35 OTS with two amplifiers

All of the LayerProtodols are PHOTONIC_MEDIA layerProtocol entities other than the:

  • OTS overhead termination which is an OTS_O layerProtocol entity
  • Right-hand client of the OTS overhead termination which is an OMS_O layerProtocol entity
  • Left-hand client of the OTS overhead termination which is a MAINTENANCE layerProtocol entity.

The figure below shows the assembly discussed encapsulated in an LTP.

Figure 6 - 35 OTS encapsulated in an LTP

The LTP shows the encapsulated ports (blue-filled circles, equivalent to the FcPort. See also . A.4 [A14] ). The right port is supported by the LtpSignalUsesPhysicalPort association (via the _accessPort attribute of the LTP).

The left port carries both photonic and electronic signals. In the next subsection the specific association will be identified. From a management-control perspective, this is essentially no different to a port carrying a protocol that has a signal structure with a mix of encodings (e.g. PathTrace protocol in a frame structure), but it is unusual two have a multi-layer propagation from an LTP.

4.4.2      OTS network considerations

The following figure shows an FC between two OTS LTPs where the FC is supported by MultiStrandSpan (MSS). The MSS is essentially the upper-most abstraction of the physical model that bridges to the logical model. The MSS essentially plays the role of a Link although it is unlike a link in that it is an abstraction of physical things rather than functional things. The relationship between the FC and the MSS is covered in TR-512.xx [A15] .

Figure 6 - 35 OTS ForwardingConstruct [A16]

The FC represents the relationship between the and encapsulates FCs representing:

  • Line side of the amplifiers
  • Measurement points
  • Measurement photonic receivers
  • Coupler/Splitters
  • OTS transponder
  • OTS frame termination

Figure 6 - 35 OTS ForwardingConstruct

More precise FCs could be constructed as encapsulated detail in the OTS FC as shown above. Clearly these details can be derived from the LTP, The LtpSpec and the single FC. The FCs in the diagram do not show the dependencies

4.4.3      OMS

The next figure shows the relationship between the OTS and the OMS. The OMS is modelled as if it is a client of the OTS as it is related to the OTS by the LtpHasClientLtps association represented by the _clientLtp attribute in the OTS LTP.

The OMS LTP shows seven LayerProtocol units. The two monitor LayerProtocol units are the same as in the OTS LTP. The OMS overhead termination is an OMS-O layerProtocol entity

The measures are PHOTONIC_MEDIA layerProtocol entities and hence the OMS LTP is essentially PHOTONIC_MEDIA.

The LTP includes a coupler and a splitter. These are abstractions of the actual combiner and splitter in the equipment as the OMS provides OTSiA clients each of which comprises multiple OTSis. The actual coupler will take individual OTSis. The mapping complexity is highlighted via the blue ports in the coupler and splitter.


Figure 6 - 35 Adding OMS encapsulated in an LTP    The layered model, similarities and differences

Traditionally the OMS-OTS hierarchy has been over emphasize in the modeling of photonics. It is clear, however, that the photonic solution is NOT inherently layered. It is also clear, though, that the overhead is layered. The hybridized LTP model discussed in section combines the layering of the overhead with the non-layered (flat) photonic-media model to provide an LTP arrangement that looks remarkably similar to that of a layered model.

The key distinctions are that the LTPs are in the same base layerProtocol of PHOTONIC_MEDIA.

Migration from a layered model to this flat model should be relatively straight forward in terms of structure. However, the interpretation of the LTPs is radically different and more complex. This approach, i.e. use of an LTP for the OTS demarcation and encapsulation of the the amplifier in the OTS termination, was specifically chosen to simplify the migration from the existing (incorrect) layered representations.

The multi-layer aspect of the LTPs follows the approach for non-intrusive monitoring.

More text on

  • Why LTPs in a photonic model?
  • How can the LTP apply, what is the precedence?
  • What about degenerate cases and how can they be justified. [A17]

4.4.4      OMS network considerations

The figure below shows both the OMS and OTS FC. Both are in the Photonic layerProtocol. The interpretation of the OMS FC is similar to that of the OTS FC.

The OMS FC is supported by the OTS FC via FcHasLowerLevelFc represented through the _lowerLevelFc attribute of the FC. The OMS FC is at the PHOTONIC_MEDIA layerProtocol.

Figure 6 - 35 Adding OMS ForwardingConstruct [A18]

4.4.5      Adding the OTSiA

The figure below shows the addition of the OTSiA intermediate LTP (i.e. at a point where the OTSiA is NOT being terminated). The OTSiA is a parallel aggregation of a number of OTSis (the OTSiG) and the monitoring overhead (OTSiG-O). The LTP is depicted with a sophisticated Tandem Monitoring capability. Whilst not currently standard, this has been shown to:

  • Emphasize the multiple OTSis passing through
  • The OTSiA passing through
  • Show a hybrid LTP with both OTSiA information content and photonic signals passing through.
  • Demonstrate the extensibility of the model pattern

It is assumed that as monitoring capability advances and as disaggregation becomes more viable monitoring at various intermediate points to assist in fault location across a mixed vendor and mixed operator environment will become important.

Each OTSi in each direction for each side of the LTP has a monitor and each has an adapter (at the MEASURE_AND_CONTROL layerProtocol) for each side of the LTP


Figure 6 - 35 Adding OTSiA intermediate LTP

If there is no monitoring present the LTP degenerates to a set of pass-throughs.

Figure 6 - 35 The degenerate OTSiA intermediate LTP


These are essentially null functions. The LTP is only present to represent OTSiA granularity for the following FC to connect to (as described in the next section). The following figure shows a usual representation of a low functionality LTP.

Figure 6 - 35 The simplified degenerate OTSiA intermediate LTP

The LTP spec will consist of an LP for each of the through going flows where each LP has only one connection function that states it key properties.

4.4.6      OTSiA FC and dealing with the "coordination"

The following figure is extracted from {{ITU-T G.872}} highlights the need for coordination of the OTSiG-O connection with the connections of the corresponding OTSis in the OTSiA and also coordination of the adaptation and the coupler/splitter characteristics. The latter has been dealt with by encapsulating the OTSiG coupler/splitter function (abstract) and the OMS-O/OTSiG-O overhead within a combination of the OMS and OTSiA LTPs.

Figure 6 - 35 {{ITU-T G.872}} Figure 8-15 showing OTSi and OTSiG-O connection coordination

The main aspect this coordination, i.e. that of the actual connection, is dealt with by simply encapsulating the connections of the OTSis in the OTSiG/A and the OTSiG-O of the OTSiA in a single OTSiA FC. Whilst the FC is mixed layerProtocol, the main layerProtocol is PHOTONIC_MEDIA [A19] and hence that is the layerProtocol of the FC. The underlying spec detail will explain the mix.

Figure 6 - 35 Adding OTSiA FC

Clearly the FC shown will connect to another LTP. For through going traffic this may be an LTP in a chain identical to that shown above on the right. The Termination of the OTSiA is discussed in the next section.

The usual FC capabilities are available so if there is some form of resilience this can be represented with multi-pointed FC and/or multiple overlaid FCs as appropriate (see …) [A20] .

4.4.7      Adding the OTSiA termination

In a simple solution where there is no disaggregation the termination transponder is part of the ROADM. The figure below shows the OTSiA terminations as an LTP. The LTP encapsulates:

  • A set of bidirectional LayerProtocols, one for each OTSi transmitter/receiver pair
  • A bidirectional LTP for the OTSiG-O overhead termination
  • A set of bidirectional LayerProtocol units one per OTSi measurement and parameters related to the OTSiG-O
  • A bidirectional LayerProtocol that deals with the inverse multiplexing of the OUT/ODU to signals to be carried by the OTSis.

The OTSiA termination transponder is

Figure 6 - 35 Adding OTSiA transponder [A21]

4.4.8      A disaggregated node [A22]


Figure 6 - 35 A ROADM with disaggregated transponder



Figure 6 - 35 A disaggregated transponder


4.4.9      Spec model enhancements supporting the composite LTPs and FCs

Reference the spec document. Work through the enhancements in the spec model. [A23]

4.5      Mapping to MEP/MIP pattern

This section will discuss extraction of the essence of monitoring and the results from the actual monitors and the overhead (so the termination stays in the LTP but the interpretation moves out). [A24]

5        The relationship between functional and physical

5.1      Overview

See section xxx for media element background used as a basis for the development of the "Monitored Media Node" (MMN) and relationship to the FRU.

Note that the MMN will utilize the same approach as is used for the NE as per xxx.

Discuss provisioning and maintenance perspective and note the abstraction for provisioning and the detail (down to FRU) for main [A25]

5.2      The Field Replaceable Unit (FRU) and the Media Element (ME)

Each functional component discussed up to this point do not necessarily equate to an FRU. It is often the case that a function will be supported by several FRUs and also that several functions will be supported by a single FRU. From a maintenance perspective, the FRU is the relevant construct. The FRU is modeled as a Replaceable Equipment.

The following figured depict Media Elements (MEs). It is assumed that MEs equate to Field Replaceable Assemblies of one or more FRUs [8] .



Figure 6 - 35 One of the many possible ME arrangements

The Raman amplifier case would have a similar arrangement to the figure above recognizing that again that the receive side monitors will probably be those of the amplifier itself and that in the case of Raman the amplifier is the fiber.

The figure below shows other possible arrangements of MEs (recognizing that the upper diagram is probably unlikely as the monitor is likely to be part of the amplifier as discussed earlier).

Figure 6 - 35 Two other possible ME arrangements

The ME

  • Encompasses one or more media constructs.
  • Can encompass one or more MEs [9] .
  • Has one or more ports
  • Has zero or more interfaces for management
  • May be opaque such that the internal structure is not visible BUT
    • Clearly there are parameters that will be positioned against the inputs, the function or the outputs
    • The spec structure should explain sufficient of the structure to allow suitable interpretation of the reported information and controls.
  • Is described in most cases as one of more FCs [10]

An example media element is a reconfigurable add-drop . [11]



5.3      Relationship to the internal physical structure


  • Exposure if physical detail is driven by the need to carryout repairs/replacement in the field and to determine the impact of any potential field replacement
  • To enable this, FRUs need to be defined and modelled as equipments
  • The connectors between and from FRUs and any exposed flexible cabling that could easily be misconnected or disconnected needs to be exposed.
  • Cabling and connectors inside the FRU boundaries need not be exposed (assuming that any fault in this cabling can be easily isolated to the FRU).
  • The FRU boundaries need to related to the functional model even if the boundary is essentially in the middle of a functional unit (an LTP, LP, photonic/media element etc)
  • The spec model that relates equipment to functionality should be suitably detailed to express the relationship especially where the FRU is shared be several functions


5.4      Relationship between FRUs and Disaggregation

Brief discussion on disaggregation in the industry. [A27]


6        Development of the Model

6.1      Development of the Monitored Media Node from the ITU-T Media Element

This section includes a number of cases from ITU-T G.872.

  Figure 6 - 35 Copy of Figure 8-13 from {{ITU-T G.872}}


Figure 6 - 35 Copy of Figure 8-15 from {{ITU-T G.872}}

It is assumed that the "NE" carries out the coordination identified e.g. for managing an OTU connection. But for some applications e.g. inventory, fault management an "external" system needs to understand the relationships. This needs to be verified.


Figure 6 - 35 Copy of Figure 8-16 from {{ITU-T G.872}} (on left) with basic proposal (on right)


Figure 6 - 35 Copy of Figure 8-16 from {{ITU-T G.872}} (on left) with enhanced proposal (on right)



Figure 6 - 35 Copy of Figure 8-12 from {{ITU-T G.872}}

7        For further study

7.1      Photonic and Media parameters

The normative source of media parameters will be chosen (ITU-T), the model from that source will be Pruned and Refactored as appropriate and the parameters will be assembled in example spec models. The parameters will be mainly represented in LtpSpecs [12] . All parameters will be available and a selection can be made by the vendor etc.

The spec provides interrelationship rules between the parameters.

7.2      Considering G.872

       Media port

        Media construct/element boundary

        Media Port : a logical abstraction that represents the ends of a media channel, the boundary of a media construct or the boundary of a media element              

Comment: This appear to be somewhat jumbled. Coherent places appear to be the FcPort, the LTP and the Pin. It seems that MediaPort blurs this.

       Media channel – represented by the FC

        Media Channel (MC) (see Figure 8-1): represents both the path through the media and the resource (frequency slot) that it occupies.

        "Atomic" MC: It is a MC at bottom of MC-decomposition in the context of a particular view

        Network Media Channel (NMC) – output of a modulator to input of demodulator [13]

       Media Link – represented by the FC

        Pure topological relationship

        One or more media channels [14]

        Media Link : represents path through the media

Comment: An example of a media link is a uni-directional OMS that uses C-band and L-band amplifiers. The C-band and L-band are represented each represented as media channels (with the same end points each with its own frequency slot. There is some "dead" or unusable spectrum between these frequency slots and hence the combination of these two media channels does not result in a single media channel. A bidirectional media link may also be used to represent a pair of (counter directional) unidirectional OMS media links. In the case where the OMS uses both C-band and L-band amplifiers it would represent four unidirectional media channels.

       Media Subnetwork

        Flexible connectivity

        Media Subnetwork : a topological construct that represents a point of flexibility where the associations (represented by media channels) between the media ports of the media subnetwork may be created or deleted

Comment: Provides constraints to indicate which MCs can be created by control action. BUT probably best represented as FC in FC rather than FD for some cases but as FD for the case where, for example a subnetwork or flexible grid capable filter, had no contained FCs i.e. no enabled forwarding. Since media subnetworks typically have some (load dependent) blocking normally a FC spec is used to describe these constraints.

7.3      Other technology considerations

This section lists other relevant considerations that will be accounted for in future releases:

  • Implications of the Media model for Wireless
  • Raman OTS/OMS.
  • The media element
    • The ME is not simply an FD although the FD is useful in grouping aspects of capability.
    • The boundaries do not look coherent (with Raman, there is no hard end to the amplifier). In some cases it is LTP in others it is some multi-LTP construct
    • Question about the Media Element grouping. The groupings do not look useful from a maintenance/control perspective.
    • Why is the electrical monitoring stack and the corresponding media stuff not grouped? This is more like a normal TTP and then LTP
  • FcSpec: frequency (mandatory; m,n 12.5 step, 25 width; SG15 G.694.1), transfer characteristic, etc.
  • G.694.1 uses the (m,n) schema. There may be other standards schema and proprietary schema.
  • Use identifiers to identify the frequency specification schemas.  
  • OMS Media Channel could be shared by multiple Media Channel
  • Picture using FC for network media channel without power but yet have OMS etc. available.


End of Document





[1] It was concluded that it was not helpful to indicate media change. The key information relates to domain change. In detail, there are at least four media here and probably more. Fiber to p-type to n-type to copper. This complexity does not add value.

[2] The structures shown here and throughout this document need to be described in LTP and FC specs (see TR-512.7 ). The actual spec forms will be developed in the next release.

[3] This model will potentially need enhancement when SD FEC (Soft Decision Forward Error Correction) is included.

[4] Network Domain Channel is used in this document to define the “end to end” span of potentially mixed media that can carry a signal of a particular domain. For example it is defined from the point at which electrons are converted to (modulated) photons to the point where the information carried by the photons is converted to electrons. The term Network Media Channel is not used in this document. An NMC is an MC that spans from the output of a laser to the input of a photo diode. It is potentially mixed media. The MCY and MCZ in the diagram are essentially Network Media Channels. This designation is not helpful in understanding the model or the application. 

[6] Sufficient detail is required in the spec of the amplifier to allow interpretation of the detected conditions. The detail will in part depend upon the FRU structure of the amplifier. The model approach is intended to be suitable for use by the controller that interfaces directly to the optical components, i.e. where there is no lower level controller abstraction and/or analyzing/interpreting the detectors.


[7] Each cable is assumed here to have only one fibre.

[8] An ME larger than an FRU is not ideal as the FRU is the key granularity for field replacement. If an ME is deemed to have failed all FRUs that it is built from will need to be replaced. The ME appears to not include the control functionality. This is not a useful management/control construct.

[9] For normal maintenance physical ports must be visible on the FRUs.  The recursive ME not remove the need for full visibility of FRUs.

[10] Back to back FCs can be used were there is no exposed physical boundary. An FD or CD will be necessary to bound MEs where the ME boundary is not coincident with a physical port. BUT if not coincident with a physical port it is not clear how the ME can be useful wrt field replaceability. The opaqueness may also make the ME not useful.

[11] This appears to be too large a unit for useful management/control.

[12] Note that for management purposes some "parasitic" parameters e.g reverse loss in an isolator may not need to be represented.

[13] As noted earlier the NMC is not a useful concept.

[14] A media channel has a contiguous spectrum. A media link can represent a set of one or more media channels where the spectrum is not contiguous. An example of this is a media link that represents a chain of c-band and l-band amplifiers. This would have two media channels and the spectrum “between” the c-band and l-band media channels is not supported by a media channel.

[A1] To the reviewer

-           Hypertext document references “TR-512…” will not work at this point (as they reference the .pdf files that have not yet been generated).

-           There are some comments in some documents please consider the comments as you review.

-           If you have proposals to change text (typos or small rewordings for grammar errors), please modify the text with change tracking enabled.

-           If you have major concerns or questions or general comments please use word comments (like this)


This is a new document.


[A2] Add a black box device and strand view to the intro and explain the flow of the document against that.

[A3] To be added.

[A4] DSP should be outside the FC really!

[A5] Review model and add text.

[A6] Need to advance the LTP Spec model to accommodate the various assembles. This starts to converge with the scheme spec. The LP becomes a system of multiple protocol termination (but note that it is already really!). The LTP spec template becomes a constrainer of the patterns allowed for the LP system and specifies limitation as to what can be in and what not. The constraints are vital to avoid the LTP spilling into an representation of any system.

[A7] This section has glossed over the C&L band splits and other splits. It should be relatively clear how such a split would be dealt with by considering the detail in this section. It may be necessary to give a C/L example for OTS.

[A8] From 1.3.1 but moved from previous section

[A9] The text and figure will be adjusted to indicate that the separation in the simplified view diagram over-decouples the monitoring overhead from the monitored points and this will justify the progression of modeling in the next sections.

[A10] Reference

[A11] New experimental entity to be added to the physical model along with strand.

[A12] Need to show the band splitter symbol.

Need to show the small proportion symbol.

[A13] Reference.

[A14] Proper reference.

[A15] Proper reference. The MSS is new in 1.4.

[A16] To save drawing time the right hand node is a mirror of the left hand node (so several of the symbols are invalid mirrors). This will be corrected in the final version of the document.

[A17] Add text

[A18] Right hand node in the figure needs to be redrawn.

[A19] The justification here is a little weak. It would seem wrong to have an OTSiA layer FC as that starts to suggest layering but this is also clearly not PHOTONIC_MEDIA. It may be necessary to reserve PHOTONIC_MEDIA for the pieces that genuinely are and to have other layerProtocol names for these hybrids.

[A20] Reference

[A21] Add a network diagram with OTSiA and various relevant FCs (as per some of the earlier diagrams in the slide pack).

[A22] Text to be added

[A23] To be added.

[A24] To be added.

[A25] Clean up and also consider whether to develop the term MMN or to remove it.

[A26] Add some detailed examples.

[A27] Add some figures.