running CWDM or DWDM SFPs on Cisco ONS 15454 prior version 7.2.0 without triggering off nasty alarms

Cisco’s ONS platform like the 15454, is a quite powerful WDM platform for SDH/PDH and Ethernet environments. These days, the current version of the operating system  also supports  CWDM or DWDM transceivers. Older versions like the 7.2.0  support  grey SFPs only (1310nm and 1550nm).

In addition, Cisco offers a small range of STM-16 CWDM SFPs covering up to 80-90km (equals a powerbudget of 27dB) but CWDMs can do more than today´s 34dB.

I did some tests with high-powerbudget CWDM SFPs in an old 7.2.0 and came to the following conclusion: It is possible to operate Multirate (STM-1, STM-4, 1G Ethernet and STM-16) SFPs  with powerbudgets  over 34dB in an ONS plattform. First of all, the transceiver must be programmed correctly (don’t worry, this task is already done because we already prepared the  templates on your behalf on reconfigure.me ). Secondly, all you are required to do is  to slightly tweak the Alarm Profile of the ONS  via the CTC because when you plug in a 34dB SFP, the laser will fire  up to +5dBm. This is too much for the ONS management system. As a  consequence,TX high power and high bias alarms will pop up.

TX High Alarm and Bias High Alarm messages shown in CTC TX High Alarm and Bias High Alarm messages shown in CTC

If you want to get rid of these alarms follow these useful 5 steps:

Change Alarm Profile

  1. On the chassis´ main view, create a new alarm profile found under the Provisioning Tab
    Provisioning -> Alarm Profiles, you can call it e.g. "CWDM"
  2. Change the attributes
    PPM::HI-LASERBIAS and PPM::HI-TXPOWER from the value inherited to NA/NA
  3. Store the newly created profile on your ONS Node (click “Store”)
  4. From the “Alarm Behaviour” tab, select your linecard and select ´´CWDM´´Profile
    (NOTICE: the profile is connected to all of the ports on this linecard)
  5. Finally click “apply” and the alarms based on  “HI-TXPOWER” and “HI-LASERBIAS” will  immediately  disappear!
You can also assign an alarm profile to a certain port. To do this, you have to select the linecard first and then navigate  via “Provisioning” -> “Alarm profiles” -> Alarm Behaviour -> to your port. Upon selection, assign the  newly created profile to the port (ours is “CWDM” here ).Any alarm messages should now also disappear. (Test with ONS 15454 running 7.2.0 in June 2013: It  does not seem to work in 7.2.0. In other words, you have to apply the Alarm Profile to the entire linecard :-( )

Background

In a nutshell, the above-mentioned steps need to be carried out because the ONS operating system (I could not establish the name for  it, so do  feel  free to comment) does not take the SFPs own Digital Diagnostic Monitoring (DDM) thresholds into consideration. Only the actual A/D value is taken from the SFP. Cisco has hardwired thresholds (mainly TX an RX level, Laser Bias) for different SFP types. So an

ONS-SI-2G-L2 (STM-16, 1550nm, 80km) SFP can have a TX level of -2dBm up to +3dBm compared  to an ONS-SI-2G-S1 (STM-16, 1310nm, 10km) this is way lower – between -3dBm down to -10dBm.

If you look around in the CTC, you will find settings for optic thresholds (“Provisioning” -> “Optics Thresholds”). Changing these parameters´ relative values e.g. the deviation of the transmitting power level during operations compared to the initial power level when you started up this SFP! The following parameters can be changed within a range of 50% to 255%:

  1. LBC-LOW and LBC-HIGH (laser bias deviation)
  2. OPT-LOW and OPT-HIGH (Transmission deviation)
  3. OPR-LOW und OPR-HIGH (receive level deviation).

Nevertheless, having the ability to monitor and trigger alarms based on the deviation of a transceiver is very helpful – this allows you to easily identify changes or upcoming issues in your optical path.

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