Overview
This topic explains how Raman tuning operates in coordination with OTDR lock and OSRI to prevent interference between tuning and OTDR scanning, ensure optical safety, and protect personnel during high-power Raman tuning operations across a fiber span.
Raman tuning with OTDR lock and OSRI is a coordinated operating mechanism that prevents interference between Raman tuning and OTDR scanning while maintaining optical safety during tuning.
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Prevents OTDR scans and Raman tuning from running concurrently on the same fiber.
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Coordinates OTDR lock acquisition between peer nodes.
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Uses OSRI to protect personnel from high-power laser exposure.
| Feature Name | Release Information | Description |
|---|---|---|
| Raman Tuning with OTDR Lock |
Cisco IOS XR Release 7.10.1 |
If the OTDR scan and Raman tuning are performed on the same fiber simultaneously, the OTDR reports unexpected results. In this release, a check is being implemented to prevent both operations from running simultaneously. The Raman tuning application imposes an OTDR lock at both ends of the fiber before the process starts and releases the same after the tuning is completed. |
Concurrent operation of OTDR and Raman tuning
OTDR lock prevents OTDR scanning and Raman tuning from running concurrently on a single fiber. This avoids interference from Raman pump lasers that could introduce noise and reduce OTDR measurement accuracy.
Before Raman tuning begins, the system acquires OTDR lock at both ends of the fiber span. The lock is released after tuning completes. If Raman tuning is active, the system rejects any request to start an OTDR scan.
When an OTDR scan is already in progress:
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Raman tuning lock requests are rejected, and the system retries every minute.
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Raman tuning starts only after OTDR lock is acquired at both ends of the fiber.
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The system acquires OTDR lock at both ends of the fiber span, performs Raman tuning, and releases the lock after tuning completes.
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If an OTDR scan request occurs while Raman tuning is active, the system rejects the request to prevent interference.
For more information, see Optical Time Domain Reflectometer.
Raman tuning with OSRI
Raman tuning uses the Optical Safety Remote Interlock (OSRI) feature to safely disable the amplifier on the peer node during tuning. This reduces the risk of accidental exposure to high-power laser light.
While Raman tuning is in progress and traffic is blocked, only the OSC remains active.
At the transmit end of the span, the system combines a dedicated Raman probe laser—typically a Distributed Feedback (DFB) laser operating at a defined frequency such as 191.1 THz—with the outgoing optical channels. This probe laser provides a continuity check to support optical safety.
At the receive end, the system injects multiple wavelengths in the 1424 nm to 1495 nm range opposite to signal propagation. These wavelengths provide Raman amplification for both C-band and L-band channels.