Coriant Integrated OTDR Cost-effective Solutions for Testing Fiber, Locating Cuts, and Spotting Intrusions Optical Time Domain Reflectometer (OTDR) technology, available since the early 1980s, is used as external test devices primarily for fiber characterization before a network is deployed, and more recently, to test fiber quality before the deployment of Raman amplifiers or after a fiber cut. A number of trends, however, are driving OTDR technology to be integrated into DWDM equipment. These trends include the demand for ever higher levels of network availability, increasing concerns about security including intrusion and optical line tapping, and the increased use of Raman amplification to extend the reach of OSNR-sensitive 100G+ modulation including 8QAM and 16QAM. Furthermore, OTDR technology has undergone significant miniaturization and steep cost reductions. These trends are enabling Coriant to provide the option of cost-effective, integrated OTDR technology in DWDM equipment across the Coriant optical transport portfolio, including the Coriant® hiT 7300 Multi-Haul Transport Platform, Coriant® mTera® Universal Transport Platform, and Coriant® 7100 Packet Optical Transport Solutions. WHAT IS AN OTDR? Similar to an acoustic echo, an OTDR transmits pulses of light into the fiber under test and then analyzes the light that is returned through scattering (Rayleigh scattering) or reflected back from points along the fiber. This analysis can be used to determine the length and attenuation of the fiber and the location and severity of reflections including the location of any fiber cut. BENEFITS OF CORIANT INTEGRATED OTDR ■ Enables fast identification of fiber cut locations to speed repair times and minimize network downtime ■ Ensures fiber is safe to use for Raman amplification during commissioning and after fiber cut repairs ■ Validates fiber quality between initial characterization and deployment and offers assurance to meet leased fiber SLAs ■ Detects intrusions such as fiber tapping for enhanced security ■ Performs fiber trending analysis to proactively anticipate problems before they impact services ■ Protects investments in existing Coriant WDM solutions with cost-effective upgrade to integrated OTDR INTEGRATED OTDR Coriant offers integrated OTDR in the hiT 7300, mTera® UTP, and 7100 Series Fiber Under Test OTDR HIGH LEVEL DETECTOR ELECTRONICS Display PULSED LASER Figure 1: High Level OTDR
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Coriant Integrated OTDR Cost-effective Solutions for Testing Fiber, Locating Cuts, and Spotting Intrusions
Optical Time Domain Reflectometer (OTDR) technology, available since the early
1980s, is used as external test devices primarily for fiber characterization before a
network is deployed, and more recently, to test fiber quality before the deployment of
Raman amplifiers or after a fiber cut. A number of trends, however, are driving OTDR
technology to be integrated into DWDM equipment.
These trends include the demand for ever higher levels of network availability,
increasing concerns about security including intrusion and optical line tapping, and
the increased use of Raman amplification to extend the reach of OSNR-sensitive
100G+ modulation including 8QAM and 16QAM. Furthermore, OTDR technology has
undergone significant miniaturization and steep cost reductions. These trends are
enabling Coriant to provide the option of cost-effective, integrated OTDR technology in
DWDM equipment across the Coriant optical transport portfolio, including the Coriant®
hiT 7300 Multi-Haul Transport Platform, Coriant® mTera® Universal Transport Platform,
and Coriant® 7100 Packet Optical Transport Solutions.
WHAT IS AN OTDR?Similar to an acoustic echo, an OTDR transmits pulses of light into the fiber under test
and then analyzes the light that is returned through scattering (Rayleigh scattering) or
reflected back from points along the fiber. This analysis can be used to determine the
length and attenuation of the fiber and the location and severity of reflections including
the location of any fiber cut.
BENEFITS OF CORIANT INTEGRATED OTDR
■ Enables fast identification of fiber cut locations to speed repair times and minimize network downtime
■ Ensures fiber is safe to use for Raman amplification during commissioning and after fiber cut repairs
■ Validates fiber quality between initial characterization and deployment and offers assurance to meet leased fiber SLAs
■ Detects intrusions such as fiber tapping for enhanced security
■ Performs fiber trending analysis to proactively anticipate problems before they impact services
■ Protects investments in existing Coriant WDM solutions with cost-effective upgrade to integrated OTDR
INTEGRATED OTDR
Coriant offers integrated OTDR in the hiT 7300, mTera® UTP, and
7100 Series
Fiber Under Test
OTDR HIGH LEVEL
DETECTOR
ELECTRONICS
Display
PULSED LASER
Figure 1: High Level OTDR
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KEY USE CASES FOR INTEGRATED OTDRFiber Testing: Before Commissioning or After a Fiber CutAn integrated OTDR can be used for out-of-service testing of the fiber both before the span has been commissioned and the amplifiers
turned on as well as after an event such as a fiber cut, which could have had a negative impact on fiber quality. While fiber characterization
is highly recommended before the network is planned to ensure accurate performance modeling, testing again with an integrated OTDR
provides useful insurance against any changes that may have occurred between the pre-deployment characterization and the time of
deployment, including ensuring that the fiber pair is the same and the SLA of any leased fiber is still being met. This is especially important
when Raman amplifiers are used. Raman amplifiers shoot powerful lasers into the fiber, and reflections caused by bad splices can
permanently damage the Raman amplifier, the fiber itself, or both. An integrated OTDR can also be used to check the quality of any repairs
made before the Raman amplifiers are turned back on after a fiber cut.
Identifying the Location of Fiber Cuts for Fast RepairsSpeeding time to repair can have a significant impact on network availability. One of the key functions of an OTDR is to use reflections to
accurately identify the exact distance to the fiber cut. Previously, this required sending engineers with an external OTDR test kit to one
or both of the sites adjacent to the failed span before the location of the cut could be identified. By integrating the OTDR into the DWDM
network element, the location of the cut can be identified immediately after it has occurred, potentially reducing the Mean Time to Repair
(MTTR) by hours or even days.
Coriant Integrated OTDR
Figure 2: Example Fiber Testing Results
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Figure 3: Fast and Accurate Location of Fiber Cuts
In-Service Identification of Increased Fiber AttenuationIntegrated OTDRs can also be used to identify increases in attenuation while the span is in service and more significantly identify the
location of any increase in attenuation. This can provide an important component of a proactive downtime prevention strategy – identifying
and resolving problems before they impact services.
Intrusion DetectionTapping of the DWDM signal by an intruder to snoop or intercept the data passing through represents a worst case scenario and
potentially catastrophic security breach. A key strategy to detect such an intrusion is to spot the change in attenuation that a breach
would incur. An integrated OTDR not only provides the most accurate way of measuring this change in attenuation but can also be used to
pinpoint the location of the intrusion.
Historical Data CollectionA final key application is the manual or scheduled collection of OTDR data for a span (OTS). This enables the comparison of historical
versions of the OTDR data (i.e., at installation, after fiber cut, after second fiber cut) with the support of the network management system or
other software tools to perform fiber trending analysis. For example, this type of analysis could be used to provide more accurate modeling
of end-of-life conditions.
INTEGRATED OTDR IN THE CORIANT OPTICAL PORTFOLIOTwo options for integrated OTDR are available in the Coriant optical portfolio. Raman amplifiers such as the PRC-3 and PRC-4 for the hiT
7300 include an integrated out-of-service OTDR to enable safe and fast commissioning of Raman and fast redeployment after a fiber cut.
The second option is based on the Coriant OTDR16. Using the OFP1 pluggable form factor of the Coriant® Pluggable Optical Layer, the
OTDR16 is supported in the hiT 7300, mTera® UTP, and 7100 Series in carrier cards that support OFP1 pluggables.
The OTDR16 supports both in-service and out-of-service OTDR on up to 16 fibers (i.e., 8 bi-directional degrees) and can be used on EDFA-
only spans as well as hybrid EDFA/Raman spans. It supports measurements with resolution down to as little as 1 meter and distances of
approximately 100 km. In order to support in-service operation, the OTDR16 operates at 1625 nm in the L band and therefore requires a
filter to separate this from the C band, which is used for the DWDM channels. Compact, low-loss filters are available for the hiT 7300 and
7100 Series to perform this function while the ROADM-on-a-blade modules for the mTera® UTP contain an integrated filter.
The OTDR16 can be used to upgrade all existing nodes with OTDR functionality. The mTera® UTP offers integrated filters ready for an in-
service upgrade to OTDR. The hiT 7300 and 7100 Series can be prepared for in-service upgrade to OTDR at a later date by pre-deploying
these filters.
OTDR management is supported in the Coriant® Transport Network Management System (TNMS), including the following functionalities:
■ Graphical displays of the OTDR data with the location of key events highlighted in maps
■ Scheduling of OTDR scans
■ Ability to compare different scans on a screen
■ Ability to automatically start scans after a fiber cut to identify its location
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Figure 4: Coriant OTDR16 with OFP1 Pluggable Form Factor
These trademarks are owned by Coriant or its affiliates: Coriant®, Coriant CloudWave™, Coriant Dynamic
Optical Cloud™, Coriant Groove™, Coriant Transcend™, mTera® , Nano™, and Pico™. Other trademarks are
the property of their respective owners. Statements herein may contain projections regarding future
products, features, or technology and resulting commercial or technical benefits, which may or may not
occur. This publication does not constitute legal obligation to deliver any material, code, or functionality.
