FORM 2
THE PATENTS ACT  1970
(39 of 1970)
&
THE PATENTS RULES  2003

COMPLETE SPECIFICATION
(See section 10  rule 13)

“A distributed Optical Line Terminal (OLT) network architecture”

Tejas Networks Limited
2nd floor  GNR Tech Park  46/4  Garbebhavi Palya 
Kudlu Gate  Hosur main road 
Bangalore 560 068  Karnataka  India

The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the Invention
The present invention relates to a field of passive optical network (PON)  and in particular  the passive optical networks to have a distributed network.

Background of the Invention
Presently  the system for a passive optical network (PON) constitutes central office equipment called OLT and the customer premises equipment called ONT or ONU. In the present network design  single OLT is used only in a 20 km radius as the GPON standard specifies the physical length of the GPON connection to be within 20Kms. Hence  multiple OLTs need to be placed in various locations to get the 20 km proximity to customer premises or dwelling units. Because of this design  most of the time the service provider’s are forced to use many OLTs in different locations  with very few ports actively used. Also  this adds to the cost of network design as the OLTs needs to be equipped with full-capacity power. Further  another issue is that even though each OLT port is capable of supporting 128 ports  in most cases few ports will be used  hence the efficiency of OLT ports i.e. number of active subscriber per OLT port comes down.
Therefore  it would be desirable to have an OLT architecture which overcomes the restriction of 20 km and reach beyond that.
Summary of the Invention
An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below.
Accordingly  an aspect of the present invention is to provide a distributed Optical Line Terminal (OLT) network architecture  wherein the OLT includes OLT-Server and OLT-Client  the network architecture comprising: a plurality of optical line terminal server (OLT-S) associated over Optical Transport Network (OTN) backhaul interface  a plurality of OTN aggregation elements allied to at least one OLT-S and a plurality of optical line terminal client (OLT-C) configured to receive traffic from OLT- S via at least one OTN aggregation element  wherein the logical OLT port is processed by OLT-S and multiple OLT-C distributed via OTN network.

Other aspects  advantages  and salient features of the invention will become apparent to those skilled in the art from the following detailed description  which  taken in conjunction with the annexed drawings  discloses exemplary embodiments of the invention.
Brief description of the drawings
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example  the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Figure 1 shows a typical Passive Optical Network (PON) Architecture.
Figure 2 shows a distributed Optical Line Terminal (OLT) network architecture  in accordance with one embodiment of the present invention.
Throughout the drawings  it should be noted that like reference numbers are used to depict the same or similar elements  features  and structures.
Detail description of the invention
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly  those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition  descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings  but  are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly  it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a ” “an ” and “the” include plural referents unless the context clearly dictates otherwise. Thus  for example  reference to “a component surface” includes reference to one or more of such surfaces.
By the term “substantially” it is meant that the recited characteristic  parameter  or value need not be achieved exactly  but that deviations or variations  including for example  tolerances  measurement error  measurement accuracy limitations and other factors known to those of skill in the art  may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Figs. 1 through 2  discussed below  and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communications system. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description  and that their use and definitions in no way limit the scope of the invention. Terms first  second  and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order  unless where explicitly stated otherwise. A set is defined as a non-empty set including at least one element.
Figure 1 shows a general Passive Optical Network (PON) Architecture (100). The elements of a PON are (i) Optical Line Terminal (OLT) 110 (ii) Passive Optical Splitter 120 and (iii) Optical Network Unit (ONU) 130. The Optical Line Terminal 110 is the main element of the network and is usually placed in the Local Exchange. It is a network element with PON line card  basically a aggregation switch. It works as an interface between core network and PON network.
Optical Splitter 120 is a passive device with single input and multiple outputs. Optical power at input is split evenly between outputs. Not only signal travels from input to the outputs  signal can also travel from the output to the input. Splitters can be placed anywhere in between Central Office (CO) and Subscriber premises. It is used to connect an optical port of OLT with multiple subscribers.
Optical Network units (ONUs) 130 serve as an interface to the network and are deployed at customer premises 140. It provides several interfaces for accessing triple play services and in the upper side it connects with the OLT via optical splitter.
Although PONs can exist in three basic configuration (tree  bus and ring)  the tree topology is favored due to smaller variation in the signal power from different end station. PON uses 1490 nm for the downstream wavelength and 1310 nm for the upstream wavelength. Signals are inserted or extracted from the fibre using a coarse wavelength division multiplexer (CWDM) filter at the CO and subscriber premises.
Figure 2 shows a distributed Optical Line Terminal (OLT) network architecture  in accordance with one embodiment of the present invention. In an exemplary embodiment  figure 2 shows a distributed xPON network design with OLT-Server (OLT-S) and OLT-Client (OLT-C). As shown in figure  a distributed Optical Line Terminal (OLT) network architecture  wherein the OLT split into two halves one as OLT-Server and the other as OLT-Client. Marked as label ‘A’ shows the OLT-S with OTN backhaul interfaces  where a plurality of optical line terminal server (OLT-S) associated over Optical Transport Network (OTN) backhaul interface. Further  the OTN ring which carries one or multiple GPON over ODUx over the ring as marked as label ‘B’  where one or more OTN aggregation elements allied to one of the OLT-S. Label ‘C’ as shown in figure illustrates the further distribution of GPON over ODUx in OTU ring  where one or more optical line terminal client (OLT-C) is configured to receive traffic from OLT- S via at least one OTN aggregation element.
The aggregation equipments are provided with GPON-C port card  where the GPON port is distributed over regular GPON fiber infrastructure. The logical OLT port is processed by OLT-S and multiple OLT-C distributed via OTN network. The OLT-C further distribute the traffic locally to a plurality of ONUs with at least one OLT-S thereby achieving the effective utilization of OLT ports. The OLT-C includes SDH ports which are used for dual use of OTL-C Ports  the OTL-C port and a transport backhaul equipment port.
The OTN aggregation element of the centralized OLT network includes OTN-C port card  where the port is distributed over GPON fiber infrastructure. Further  the OTN-S and OTN-C includes at least one GPON ports  where GPON-C card is a STM16 card.
The present centralized OLT architecture with single OLT with much higher densities in a central location can be used to serve diverse customer localities as if it is served within the specified 20Kms optical distribution network without changing any parameters of the ODN and ONT elements. By solving the problem of local distribution length limitation of 20 Kms and efficient utilization of OLT ports which thereby reducing the cost by implementing the OLT as two distributed units. The logical OLT port is processed by a central OLT-S unit and multiple OLT-C elements distributed over a vast geographical location through an OTN network caters to the physical connectivity of GPON ODN.
The present OLT network architecture brings together two technologies from two different type of network areas  namely OTN technology of the core networks is seamlessly used to transport the xPON from the access area to get a much longer customer coverage and better efficiency of the OLT system usage. Also the network architecture where OLT is centrally located and GPON is transported over similar metro network (Carrying GPON over OTN Mapping) builds using DWDM or any future technology. The design of converting the xPON OLT-Server on remote side to the OLT-Client on a distributed way using OTN technology as the transport mechanism. The protocols used to get the proper management of the system as an integrated solution.
FIGS. 1-2 are merely representational and are not drawn to scale. Certain portions thereof may be exaggerated  while others may be minimized. FIGS. 1-2 illustrate various embodiments of the invention that can be understood and appropriately carried out by those of ordinary skill in the art.
In the foregoing detailed description of embodiments of the invention  various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather  as the following claims reflect  inventive subject matter lies in less than all features of a single disclosed embodiment. Thus  the following claims are hereby incorporated into the detailed description of embodiments of the invention  with each claim standing on its own as a separate embodiment.
It is understood that the above description is intended to be illustrative  and not restrictive. It is intended to cover all alternatives  modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should  therefore  be determined with reference to the appended claims  along with the full scope of equivalents to which such claims are entitled. In the appended claims  the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein ” respectively.

We Claim:

1. A distributed Optical Line Terminal (OLT) network architecture  wherein the OLT includes OLT-Server and OLT-Client  the network architecture comprising:
a plurality of optical line terminal server (OLT-S) associated over Optical Transport Network (OTN) backhaul interface;
a plurality of OTN aggregation elements allied to at least one OLT-S; and
a plurality of optical line terminal client (OLT-C) configured to receive traffic from OLT- S via at least one OTN aggregation element  wherein the logical OLT port is processed by OLT-S and multiple OLT-C distributed via OTN network.

2. The OLT network of claim 1  wherein the OLT-C further distribute the traffic locally to a plurality of ONUs with at least one OLT-S thereby achieving the effective utilization of OLT ports.

3. The OLT network of claim 1  wherein the OTN aggregation element includes OTN-C port card  wherein the port is distributed over GPON fiber infrastructure.

4. The OLT network of claim 1  wherein the OTN-S and OTN-C includes a at least one GPON ports  wherein GPON-C card is a STM16 card.

5. The OLT network of claim 1  wherein OLT-C includes SDH ports which are used for dual use of OTL-C Ports  the OTL-C port and a transport backhaul equipment port.

6. The OLT network substantially as herein with reference to the above mentioned description and accompanying drawings.
Dated this the 30th day of March  2012
S Afsar
Agent for the Applicant
Of Krishna & Saurastri Associates
Registration No. IN/PA-1073

Abstract
A distributed Optical Line Terminal (OLT) network architecture
The present invention relates to a field of passive optical network (PON)  and in particular  the passive optical networks to have a distributed network. In one embodiment the network includes a plurality of optical line terminal server (OLT-S) associated over Optical Transport Network (OTN) backhaul interface  a plurality of OTN aggregation elements allied to at least one OLT-S and a plurality of optical line terminal client (OLT-C) configured to receive traffic from OLT- S via at least one OTN aggregation element  wherein the logical OLT port is processed by OLT-S and multiple OLT-C distributed via OTN network.