Configuration Guide for Cisco Optical Site Manager, IOS XR Release 26.x.x

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Configuration Guide for Cisco Optical Site Manager, IOS XR Release 26.x.x

Span loss measurement

Updated: October 14, 2026

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This section explains span loss measurement in Cisco Optical Site Manager. Span loss measurements (in dB) check the span loss and are useful whenever changes to the network occur.

Span loss measurements (in dB) check the span loss and are useful whenever changes to the network occur.

The span loss operational parameters are:

  • Measured By-Displays whether the span loss is measured by the channel or Optical Service Channel (OSC). If a channel is not configured, the span loss is measured by the OSC. An EDFA measures the span loss based on circuits.

  • Measured Span Loss-Displays the measured span loss.

  • Measured Span Loss Accuracy-Displays the accuracy of the span loss measurement. For example, if the measured span loss is 20 dB and the displayed accuracy value is 2.5, the actual span loss could either be 19 or 21 dB.

  • Measured Time-Displays the time and date when the last span loss measured value is changed.

If there is a new network with Cisco Optical Site Manager, the operational parameters list of span loss has two rows. The first row displays the OSC-measured span loss details. After the channel is configured, the second row is added, which displays the channel-measured span loss details. After the channel is configured, only the channel-measured span loss details are updated.

View or modify span loss parameters

Use this task to measure span loss and update the minimum and maximum expected span loss values for an optical span.

Span loss parameters help monitor optical span performance and detect conditions where measured loss exceeds expected thresholds.

If a channel or OSC is not configured, span loss measurement is not reported and the operational parameters list is empty.

Before you begin

Log into Cisco Optical Site Manager

Follow these steps to view or modify span loss parameters.

Procedure

  1. Click Optical Setup in the left panel.

  2. Click the Optical Configuration tab, and then click Span Loss to expand it.

  3. Click the + icon next to a degree to expand it.

  4. Select a row and click Measure Span Loss.

    A message appears.

    Click OK.

  5. Click Retrieve to view updated values.

    The measured span loss, accuracy, and measurement time are updated.

  6. Enter values for Min. Exp. Span Loss or Max. Exp. Span Loss in dB.

    The valid range is from 0 to 99 dB.

  7. Click Apply.

    A confirmation message appears.

  8. Click Yes.

    The span loss range is extended to include the accuracy value.

    A Span Loss Out of Range condition is raised when the measured span loss exceeds the extended range.

  9. (Optional) Click Export to Excel to export the data.

The Span Loss Measured Data section displays the following information:

Field

Description

Degree

Displays the side for which span loss information is shown.

Measured By

Indicates whether the measurement was executed using OSC or channels.

Min. Exp. Span Loss (dB)

Displays the minimum expected span loss value.

Max. Exp. Span Loss (dB)

Displays the maximum expected span loss value.

Measured Span Loss (dB)

Displays the measured span loss value.

Measured Accuracy (dB)

Displays the accuracy of the span loss measurement.

For example, if the measured span loss is 20 dB and the accuracy value shown is 2.5, the actual span loss may range approximately from 19 dB to 21 dB.

Measured Time

Displays the date and time of the last span loss measurement.