GPON stands for gigabit passive optical network and is standardised under the ITU-T as G.984. It is the technology which is going to make your network deployment environmentally friendly, more economical and easier to maintain.
“A passive optical network (PON) is a telecommunications technology used to provide fibre to the end consumer, both domestic and commercial. A PON’s distinguishing feature is that it implements a point-to-multipoint architecture, in which unpowered fiber optic splitters are used to enable a single optical fiber to serve multiple end-points. The end-points are often individual customers, rather than commercial. A PON does not have to provision individual fibers between the hub and customer. Passive optical networks are often referred to as the ‘last mile’ between an ISP and customer.”
The following section explains GPON technology in further detail, but should you prefer, we are available to meet and show you the solution which is set to trigger a technological revolution. |
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In a typical scenario one would have a router connected to multiple aggregation (core) switches, these would form the fibre backbone which, in a campus LAN would be connected to further aggregation sites or directly to each end user communications closet backbone switch. Attention would to be given to avoid Ethernet loops and much patching and cable management must be performed.
The OLT is a telecom operator grade piece of equipment and they come in various shapes and sizes. The smallest OLT available has 2x PSU and 8x PON ports, larger OLTs may achieve whatever the user requires; multiple PSU, multiple OLT management cards, Multiple Ethernet fibre SFP cards, Multiple GPON cards.
The OLT provides all the aggregation in one location, the user does not require to design other aggregation points and does not have to concern himself of equipment end user communications closets with backbone grade fibre switches. All this is performed in one location in an easy and seamless way.
In a campus network such as a university or resort hotel one would require further aggregation points just for the backbone. These would be connected to the server room via multimode fibre limiting the distance to 550m, one could end up with a mix of singlemode and multimode fibre, perhaps copper trunks. Network complexity is high with a large amount of patching, cross connections for redundancy and special attention to Ethernet looping.
There is no requirement to design for the backbone.
In any network topology one will have a cabinet with switches providing Ethernet cable drops to the final RJ-45 wallplates. These closets have to be within the 100m limit of the wallplates and in the case of delivering POE these must be closer, this may sometimes result in requiring an additional fibre connections and closets to service areas outside of the 100m limit. In the case of smaller networks the backbone switch may be installed in the same cabinet, which is then patched to the distribution switches. Again careful consideration of patching and management of the Ethernet loops is critical.
There is no end communication closet, you can save the space, heating and money and spend it elsewhere!
For each RJ-45 port you will have a cable coming from the end communication closet switch. Each cable must be certified.
Here the ONT/ONU (optical network terminal/unit) makes an appearance; this is a modem like device which converts from fibre to electrical RJ-45 ports. In our case we have 57 different models available covering from 1 port to 24, indoor and outdoor IP ratings and other features.
These can be installed in the soffit or directly on the users desk. All one requires are short copper drops towards the faceplates which can come pre-terminated and pretested further reducing cost and complexity of the installation.
The beauty of GPON networks is that the network topology is passive, each GPON SFP output may be split into 64 different fibres, connecting up to 64 ONTs, over a distance of 20KM. Splitters come in different shapes and sizes and effectively eliminate the telecoms closets which we have become accustomed to.
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On the downstream 1490nm wavelength, the OLT broadcasts the same packet to all ONT on the splitters, the ONT which requires the data reads it, and the rest discard the packet. Download speeds are 2.488Gbps per GPON SFP |
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On the upstream 1310nm wavelength, the OLT arranges time slices dynamically using TDMA algorithm, ONTs which require additional data are able to do so according to the profiles set on commissioning. Upload speeds are 1.244Gbps per GPON SFP |
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The RF 1550nm wavelength is used in a broadcast way as is the case for any coax based cable service, all ONT are able to access the RF service. |
The available bandwidth is dynamically allocated via the OLT software and may be defined per ONT, per VLAN and per Port.
G.987 GPON is on the way which will be 10G Symmetrical and will use the same cable plant as G.984
GPON G.984 is an ITU-T standard and a full technical explanation may be found here.
For the security conscious, Tektraco can go one step further. Developed by EXFO the fibreguardian is an OTDR based remote fibre test system typically used for the monitoring of mission critical fibres in Metro/Core networks. The video below shows what it can do in a typical scenario:
EXFO has a model suitable for GPON deployments; the fibreguardian will be able to characterise the GPON network including the splitters and up until the ONT. It uses an additional out of band wavelength of 1625nm, EXFO’s Node iOLM software and high demarcation patch cords to monitor all your fibres on a 24/7 basis.
