Configure OTDR

This chapter describes how to configure the Optical Time Domain Reflectometer (OTDR) module in NCS 1010.

Overview of OTDR

The NCS 1010 OLT and ILA nodes have an in-built bidirectional Optical Time Domain Reflectometer (OTDR) functionality that can run in line with DWDM channels. The OTDR captures real-time measurements of loss and back reflection of the fiber pair linked to the TX and RX ports.


Note

For the OLT device, the OTDR port can switch between LINE-TX and LINE-RX ports, whereas in the ILA device, the OTDR port can switch among LINE-1-TX, LINE-1-RX, LINE-2-TX, and LINE-2-RX ports.

You can use this feature to check the fiber quality during system installation (before traffic is active), especially in case RAMAN is used. It can also be used to monitor the fiber during the system operation (live traffic) and to check the fiber if cable cut and repair events.

You can view the OTDR measurement result in the SOR file that is exported from NCS 1010.

You can determine the following characteristics using OTDR:

  • The attenuation (dB) of the whole fiber link and the attenuation of separate sections of fiber.

  • The distance and magnitude of insertion loss, reflection loss.

  • Fiber events such as concentrated loss events (with value and position), reflection events (with value and position), events at the end of the fiber, and discontinuities or defects on the fiber including loss events.

OTDR Modes

In NCS 1010, you can configure OTDR in the following two modes:

  • Auto—The device selects the optimal values for OTDR pulse width, scan duration, capture start time, and capture end time parameters.

  • Expert—You must configure all the OTDR scan parameters with valid values required for the OTDR measurement.


    Note

    Automatic adjustments are not performed in the expert mode configuration.

Measurement and Data Processing are the two fully automated internal phases in both auto and expert modes that proceed in sequence.

Configure OTDR

The NCS 1010 device uses the default values for OTDR scan parameters before the OTDR configuration.

You can configure the OTDR on the OTS controller. Use the following commands to configure the various OTDR parameters:

configure

controller ots R/S/I/P

otdr scan-mode expert

otdr rx auto reflectance-threshold value

otdr rx auto splice-loss-threshold value

otdr rx auto excess-reflection-threshold value

otdr rx auto back-scattering value

otdr rx auto refractive-index value

otdr tx auto reflectance-threshold value

otdr tx auto raman-setpoint value

otdr tx auto excess-reflection-threshold value

otdr tx auto splice-loss-threshold value

otdr tx auto back-scattering value

otdr tx auto refractive-index value

otdr rx expert pulse-width value

otdr rx expert capture-end value

otdr rx expert capture-start value

otdr rx expert scan duration value

otdr tx expert pulse-width value

otdr tx expert capture-end value

otdr tx expert capture-start value

otdr tx expert scan duration value

otdr tx expert scan duration value

Example: 

RP/0/RP0/CPU0:ios#config
RP/0/RP0/CPU0:ios(config)#controller ots 0/0/0/0
RP/0/RP0/CPU0:ios(config-Ots)#otdr rx auto reflectance-threshold -50
RP/0/RP0/CPU0:ios(config-Ots)#otdr rx auto splice-loss-threshold 200
RP/0/RP0/CPU0:ios(config-Ots)#otdr rx expert pulse-width 6000
RP/0/RP0/CPU0:ios(config-Ots)#otdr tx auto reflectance-threshold -50
RP/0/RP0/CPU0:ios(config-Ots)#otdr tx auto splice-loss-threshold 200
RP/0/RP0/CPU0:ios(config-Ots)#otdr scan-mode expert
RP/0/RP0/CPU0:ios(config-Ots)#otdr scan-mode expert
RP/0/RP0/CPU0:ios(config-Ots)#commit

RP/0/RP0/CPU0:ios#config
RP/0/RP0/CPU0:ios(config)#controller ots 0/0/0/0
RP/0/RP0/CPU0:ios(config-Ots)#otdr rx auto reflectance-threshold -50
RP/0/RP0/CPU0:ios(config-Ots)#otdr rx auto splice-loss-threshold 200
RP/0/RP0/CPU0:ios(config-Ots)#otdr rx expert pulse-width 6000
RP/0/RP0/CPU0:ios(config-Ots)#otdr tx auto reflectance-threshold -50
RP/0/RP0/CPU0:ios(config-Ots)#otdr tx auto splice-loss-threshold 200
RP/0/RP0/CPU0:ios(config-Ots)#otdr scan-mode expert
RP/0/RP0/CPU0:ios(config-Ots)#otdr scan-mode expert
RP/0/RP0/CPU0:ios(config-Ots)#commit
Table 1. OTDR Configuration Parameters

Parameter

Description

Range

Unit

Default

otdr rx auto reflectance-threshold

Threshold beyond which a reflective anomaly is reported as an event in the RX direction.

–50 to –10

dB

–40

otdr rx auto splice-loss-threshold

Threshold beyond which a loss anomaly is reported as an event in RX direction.

0.2 to 5

dB

0.35

otdr rx auto excess-reflection-threshold

Threshold beyond which a reflective event is reported as an excessive reflection event in the RX direction.

–50 to –10

dB

–20

otdr rx auto back-scattering

The back scattering value in the RX direction.

–90 to –70

dB

–81.87

otdr rx auto refractive-index

The refractive-index value in the RX direction.

1.000 to 2.000

-

1.4682

otdr tx auto reflectance-threshold

Threshold beyond which a reflective anomaly is reported as an event in Tx direction.

-50 to -10

dB

–40

otdr tx auto splice-loss-threshold

Threshold beyond which a loss anomaly is reported as an event in TX direction.

0–2.5

dB

0.35

otdr tx auto excess-reflection-threshold

Threshold beyond which a reflective event is reported as an excessive reflection event in the TX direction.

–50 to –10

dB

–20

otdr tx auto back-scattering

Back-scattering value in the TX direction.

–90 to –70

dB

–81.87

otdr tx auto refractive-index

Refractive-index value in the TX direction.

1.0000 to 2.0000

Unit less

1.4682

otdr rx expert pulse-width

Pulse width to be used during the expert scan in the RX direction.

5 to 2000

nanoseconds

20

otdr rx expert capture-end

OTDR capture endpoint during the expert scan in the RX direction.

15000000

cm

15000000

otdr rx expert capture-start

OTDR capture start point during expert scan in the RX direction

0 to 10000000

cm

0

otdr rx expert scan duration

OTDR scan duration during expert scan in the RX direction.

0 to 180

Seconds

60

otdr tx expert pulse-width

Pulse width to be used during the expert scan in the TX direction.

5 to 20000

ns

20

otdr tx expert capture-end

OTDR capture endpoint during expert scan in the TX direction.

0 to 15000000

cm

15000000

otdr tx expert capture-start

OTDR capture start point during expert scan in the TX direction.

0 to 10000000

cm

0

otdr tx expert scan duration

OTDR scan duration during expert scan in the TX direction.

0 to 180

Seconds

60

Start OTDR

NCS 1010 software does not support automatic start of OTDR scan. You have to start the OTDR scan manually using the otdr-start controller ots R/S/I/P direction command to perform the following procedures:

  1. Identify the defect after the fiber has been cut.

  2. Check the fiber quality after correcting the fiber defect.

  3. Initiate an OTDR scan at the time of installation.

Example:

RP/0/RP0/CPU0:ios#otdr-start controller ots 0/0/0/0 rx 
Wed Feb  9 05:49:39.178 UTC
OTS OTDR Scan Started at RX
RP/0/RP0/CPU0:ios#

Stop OTDR

To stop the OTDR scan function, use the following otdr-stop controller ots R/S/I/P direction command:

Example: 

RP/0/RP0/CPU0:ios#otdr-stop controller ots 0/0/0/0 rx 
Wed Feb  9 06:03:37.406 UTC
OTS OTDR Scan Stopped at RX
RP/0/RP0/CPU0:ios#

Display OTDR Scan Measurements

You can use the show controllers ots R/S/I/P otdr-info direction command to view the OTDR scan events and the location of the SOR file.

The SOR file contains the fiber trace details such as the distance, reflectance, loss, and fiber attenuation measurements. You can export the SOR file.


Note

To transfer the SOR file from the source to the destination, use the following command: scp username@device-ip:filename_with_source_location destination-location

Example:
scp test@192.168.0.1:/harddisk:/otdr/ios_OTDR_Ots0_0_0_0_RX_20230301-101927.sor /users/test/

OTDR can detect typical fiber events such as loss due to fiber splicing, patch panel, and coupler connections, single and multiple loss events, single and multiple reflective events, fiber pinch, and fiber cut.

The following is the sample to display the OTDR scan information in the RX direction.

RP/0/RP0/CPU0:ios#show controllers ots 0/0/0/0 otdr-info rx 
Wed Feb  9 05:55:19.791 UTC
       Scan Direction: RX
       Scan Status: Data Ready 
       SOR file: /harddisk:/otdr/IOS_NCS1010_OTDR_Ots0_0_0_0_RX_20220209-055045.sor
       Total Events detected: 11 
       Scan Timestamp: Wed Feb  9 05:50:45 2022 UTC
       Event Type Legend:  NR:Non-Reflective  R:Reflective  FE:Fiber-End  ER:Excess-Reflection
      Event#  | Detected Event(s) | Location(km) | Accuracy(m) | Magnitude(dB)| Attenuation/km(dB)
      1       | R                 | 50.4709      | 52.47       | -39.87       |  0.18            
      2       | NR                | 50.4709      | 52.47       | 1.17         |  0.18            
      3       | R                 | 100.9261     | 102.92      | -37.73       |  0.21            
      4       | NR                | 100.9261     | 102.92      | 1.01         |  0.21            
      5       | R                 | 105.9500     | 107.94      | -38.52       |  0.24            
      6       | NR                | 105.9500     | 107.94      | 0.85         |  0.24            
      7       | R                 | 112.7458     | 114.74      | -40.56       |  0.00             
      8       | NR                | 112.7458     | 114.74      | 1.48         |  0.00            
      9       | NR                | 117.9873     | 119.98      | 0.66         |  -0.02           
      10      | R FE              | 120.1206     | 122.12      | -35.55       |  0.00            
      11      | NR FE             | 120.1206     | 122.12      | 21.65        |  0.00

Note

After the FPD upgrade of the line card, the results of previous OTDR scans may not be available using the CLI command show controllers ots Rack/Slot/Instance/Port otdr-info direction. However, you can get the results of previous OTDR scans in the form of .SOR files that are stored in the hard disk.