Industry`s First Standards-compliant OBI-free

Defining the Evolution
Industry’s First Standards-compliant
OBI-free RFoG Solution
OBI is an issue in RFoG Deployments
The Radio Frequency over Glass (RFoG) solution enables cable operators to offer
a Fiber-to-the-Home (FTTH) architecture without changes to standard equipment in
the headend or home.
Since its first deployment in 2006, RFoG has grown in popularity with cable
operators looking to service new subscribers in both rural and MDU deployments.
Here, it is a particularly cost-effective deployment when compared to traditional
HFC networks.
RFoG Deployment success introduces a service-affecting issue
With the success of RFoG deployments comes an issue, Optical Beat Interference
(OBI). With Optical Network Units (ONUs) at the home all designed to transmit
back to the headend on the same wavelength, subject to design tolerances, this
phenomenon is inherent to RFoG deployments. Specifically, OBI occurs when two
RFoG ONUs both transmit at the same time, on the same optical wavelengths,
into the same optical receiver. It causes a sharp increase in the noise floor across
the entire return spectrum and increased codeword errors. Its occurrence is a
statistical probability which increases with the number of customers connected and
the amount of traffic being transmitted.
In RFoG systems, there are multiple optical sources communicating with a single
receiver (multipoint-to-point system). With a single TDMA MAC domain within a
RFoG group served by a single receiver, only one optical source transmits at any
particular time. However many networks have return signals utilizing disparate
protocols or multiple MAC domains, such as settop return, separate DOCSIS
non-synchronized channels for VoIP and data, non-TDMA MAC protocols (e.g.,
SCDMA and OFDMA), which presents the opportunity to have multiple ONUs
transmit at the same time within the RFoG PON group.
OBI is inherent to
RFoG and driven by:
Multiple protocols or
MAC domains
Growing number of
subscribers
Growing upstream
traffic usage
MDU environments, in
particular
This phenomenon does not occur in HFC networks. HFC networks are capable
of supporting multiple MAC domains within the area served by a single reverse
receiver due to the fact that different MAC domain services are assigned different
non-interfering frequencies in the FDM RF reverse network. From the node
upstream, a point-to-point optical link introduces a simple frequency up (into the
optical spectrum) and down (back into the RF spectrum) conversion.
Unfortunately, OBI is more prevalent with a growing number of subscribers all
driving more upstream traffic with multiple upstream channels and the increasing
requirements to deploy DOCSIS 3.0 upstream channel bonding. This applies in
particular to users in an MDU environment where we have multiple cable modems
serviced by a single ONU, resulting in an ONU which is almost continuously being
driven to transmit back to the headend, ultimately increasing the probability of OBI.
Standards-compliant OBI-free Solution
OBI-avoidance
With our extensive experience in RFoG, Aurora was quick to recognize and respond to the OBI issue. Aurora has
introduced products which eliminate the occurrence probability of OBI by managing the upstream wavelength. Our
new standards-compliant OBI-freeTM solution is cost effective, increases total throughput, supports DOCSIS 3.0 and
beyond and, therefore, supports higher subscriber penetrations, thus generating more revenue potential. Moreover, our
approach does not compromise the RFoG SCTE standard; Aurora’s solution is fully standard-compliant, enabling an
operator to enjoy all the associated benefits of a standards-based approach, including a future migration path to a full
PON deployment, if required.
OBI-mitigation
All Aurora’s RFoG ONUs are designed to reduce the probability of OBI – incorporating only DFB lasers. Laser
technology has a direct impact on the probability of experiencing OBI when multiple MAC domains are present within
the RFoG PON group. It is common for vendors to utilize FP (Fabry-Perot) lasers for their lower cost. FP lasers,
however, produce multiple side lasing modes along with the main mode. The probability of optical beating interference
to the RF signals caused by optical beating between FP lasers communicating with the same receiver at the same
time is much higher due to the fact that the interference can be caused not only by optical beating between the main
lasing modes of the FP lasers but also between the main mode of one and several side modes of another laser.
We also strongly recommend smaller RFoG service area sizes with one RFoG upstream receiver serving a reduced
number of ONUs. With a smaller number of ONUs able to transmit simultaneously, the probability of OBI is reduced
significantly.
Industry’s only standards-compliant OBI-free solution
www.aurora.com
Complete End-to-end RFoG Solution
5400 Betsy Ross Drive
Santa Clara, CA 95054
Voice: +1-408-235-7000
Fax: +1-408-845-9043
Chassis
Aurora Networks’ 3RU chassis supports a
broad portfolio of modules with the latest
technological advances, including:
16-port EDFAs with 21 dBm output
High-density, low-noise optical receiver
Octal PON filter
VHub™
OP3168P OR3144H
FA3533M
16x21 dBm
Aurora Networks’ VHub provides a fully
operational hub in a standard, weatherproof
node housing. In RFPON applications, it serves
up to 256 subscribers with one transport fiber.
The VHub solution:
Future-proof Networks
Enables long-distance route redundancy
Because Aurora’s RFPON
solution adheres to the
widely deployed PON
standard, cable operators
are well positioned for the
future.
Solves fiber limitations
Traditional RFoG
implementations use the
1310 nm wavelength to
carry upstream traffic from
subscribers. However,
PON standards require this
wavelength for upstream
data communications.
To solve this potential
conflict, Aurora’s RFPON
solution transports
traditional cable TV
services over 1550 nm
(downstream) and 1610
nm (upstream). This
wavelength selection
results in a future-proof
solution. The wavelengths
1490 nm and 1310 nm
are standard for EPON
implementation.
Solves distance limitations
Supports RFoG and EPON
Supports AUROS™ DOCSIS® provisioning
Mounts on strand or pedestal
ONU
Aurora’s RFoG ONUs enable cable operators
to extend service offerings over fiber into new
residential, business park and multiple-dwelling
unit (MDU) markets. This family of ONU
devices supports RFoG and standard PONbased applications. Features include:
Indoor or outdoor mounting
RFoG-only configuration
EPON-only configuration
RFoG + PON configuration
High-output power versions supporting
32 units in MDUs
All units can be OBI-free
© 2013 Aurora Networks. In an effort to continue improving product reliability and features, Aurora Networks reserves the right to change specifications without notice.
Please contact Aurora Networks for the most current product information.
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