Optical Metering; Wavelength Filtering; Gpon/Ethernet Characteristics - Televes 769501 User Manual

GPON ONT

3.4 Optical metering

The equipment measures the downstream received power from the OLT in 1490nm and reports this value through OMCI. The accuracy of the
measurement is +/- 3dBm, maximum. Optionally, Refs. 769501-769502 has also the chance to have an embeded optical reflective component
in order to increase the FTTH probing capabilities in a 50 centimeters resolution factor, which turns to have a single probing system to probe all
GPON network ONTs even when its number increases over Million customers.

3.5 Wavelength filtering

The optical interface has WDM filters that allow GPON coexistence with RF video services (1550-1560nm) and the new generation of NGPON1
technology, according to G.984.5 Recommendation.
ITU-T Rec. G987.1 is also granted for XGPON, (following FSAN NG-PON2).
In order to face the final user´s demands, current GPON networks have to confront the first evolution in terms of terminal equipments and actual
infrastructure. Migration will be available through a new wavelength planning, by allowing the co-existence of two different technologies over
the same fiber. The ITU-T Rec. G987.1 provides a mechanism for GPON to XGPON migration with the possibility to achieve 2.5Gbps upstream path.
Nominally downstream will be 10 Gbps.
The next figure depicts the wavelength planning of ITU-T Rec. G987.1:
In order to accomplish to that plan, the upstream wavelength for GPON must be restricted to ONU (ONT) equipment based on the ordinary DFB
lasers, while the XGPON downstream signal range is defined from 1575 nm to 1580 nm and the XGPON upstream signal from 1260 nm to 1280
nm. For the coexistence of XGPON and GPON over the same fiber, the CO requires a WDM filter that combines the downstream signal (1490 nm,
1555 nm and 1577 nm), isolating the 1310 nm and 1270 nm upstream signal, with the video signal. Also the wavelength of 1650 nm, used for fiber
monitoring, has to be handled.
In addition, ONT devices require the use of a triplexer type transceiver that include an integrated filter or a discrete WDM filter to distinguish the
different signals that may be present on the fiber. The current networks, equipped with ONT in accordance with the current ITU-T Rec. G984.5, will
be easily updated to XGPON.
Class B+ optical budget are the nominal requirement for coexistence of GPON and XGPON over the same optical fiber. Taking this requirement
into account, the fiber network architecture will not limit the future of the service provider business since GPON architectures, respecting B+ class
of the GPON, are easily updated by placing newest terminal equipments, namely XOLT and XONT, and by replacing the current WDM filter by the
new one in order to handle the new XGPON signals.
XGPON must support/emulate all GPON legacy services in case of total migration.
Like GPON, XGPON is required to support triple play services (data, voice and video), as well as mobile backhauling (accurate frequency/phase/
time synchronization) application through its high quality of service and high bit rate feature capabilities. Access to Ethernet services such as
point-to-point, multipoint-to-multipoint and rooted-multipoint Ethernet Virtual Connection services should be provided. Finally, as a global re-
quirement, XG-PON needs to support IPv6.

3.6 GPON/Ethernet characteristics

GPON/Ethernet characteristics supported, both functional level and GTC-OMCI configuration, corresponds with the general mandatory character-
istics defined in ITU-T G.984.3, G.984.4 and G.988 Recommendation:
PON interface: downstream operating rate 2.488 Gbits/s, upstream operating rate 1.244 Gbits/s;
32 T-CONT and 256 simultaneous GEM ports;
Figure 3-1: Wavelength planning
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