This section describes the amplifier APC behavior that enables control loops to regulate amplifier output using a configured expected span-loss value when the OSC is unavailable.
A link turnup without OSC signal is an amplifier APC regulation mode that
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uses the configured expected span-loss value as the span-loss estimate when the OSC is not available,
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activates regulation only when amplifier control loops have never run using the calculated RX signal span loss, and
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transitions to real-span-loss regulation as soon as the calculated span loss becomes available, without reverting to expected span-loss mode even if OSC fails later.
The rx-expected-span-loss is a user-configured parameter that serves as an estimated span loss value for APC regulation when real-time optical measurements are not yet available.
When the Rx expected span loss is configured but signal span loss is unavailable (N/A), or when it is configured and APC leverages the latest available RX-Signal Span Loss value from a previous evaluation.
| Feature name |
Release information |
Feature description |
|---|---|---|
| Link turnup without OSC signal on NCS1K14-EDFA2 line card |
Cisco IOS XR Release 26.2.1 |
The NCS1K14-EDFA2 line card amplifier APC control loop can now regulate amplifier output using the configured rx-expected-span-loss value when the Optical Supervisory Channel (OSC) is unavailable. This helps amplifier output track the expected loss profile during initial link turnup before real span-loss measurement is possible. |
Checkpoint values
To ensure consistent regulation across system events, the APC application stores these checkpointed values when the rx-expected-span-loss is in use:
Last Correction Span-Loss
Last Correction Span-Loss Timestamp
Last Span-Loss Input
Last Span-Loss Input Timestamp
These values are maintained during warm boots, cold boots, and rack power cycles. Once the system calculates the first real span loss through the OSC, the rx-expected-span-loss value is no longer used, even if the OSC communication fails subsequently.
When the system uses the
rx-expected-span-lossfor regulation, the Amplifiers Control Loops Internal Status is set to BLOCKED. No span-loss correction thresholds are applied in this state.