Field Notice: FN - 63126 - CRS: 1OC768-ITU/C cards may experience High Bit Error Rate (BER) or loss of Transmit power incidents in certain batch of optical module - Workaround Fix on Failure
Revised May 12, 2010
June 5, 2009
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CRS-1 OC768-ITU/C PLIMs that match the list of affected Serial Number may encounter intermittent bursts of High BER events or loss of transmitted optical power after several months of operation. Three different failure mechanisms have been identified in Background section below.
The background for three different failure mechanisms are identified:
Dendrite Growth within Mux/Demux components: A dendrite is a tree-like branching conductive structure, formed by a metal or an alloy of multiple metals. Mux/Demux components are used within the OC768 Optics Module on the CRS1 OC768-ITU/C PLIMs. Contamination resulting from the assembly process and materials used in the packaging of these Mux/Demux components may result in corrosion and dendrite growth over a period of time, on the susceptible PLIMs. Dendrite growth may be accelerated by operational conditions, especially temperature. Failures are seen when the dendrites grow long enough to bridge and short out capacitors within the Mux/Demux components. Failure will first show up as intermittent bursts of high BER (bit-error rate), leading to link-flaps. Eventually dendrite growth will force a hard failure (link down) on the Optics.
Laser Facet Coating: Laser power in the active region is dependent on several factors including current, etching, and facet coating. Laser coating issues on the front facet may lead to optics performance degradation over a period of time, on the susceptible list of OC768-ITU/C PLIMs. This defect will typically manifest itself on a sub-set of wavelengths, and will result in low or zero output power from the OC768 optics module.
L25 Inductor: An inductor coil used at location L25 on the optics module did not provide adequate margin for all extreme conditions. As a result, inductance derating at high temperature may initialize saturation and a cyclic peak current within the coil. This condition may lead to gradual temperature rise until coil insulation is shorted, leading to a loss of optical transmit power on the susceptible OC768-ITU/C PLIMs. This failure may also manifest itself over a period of time, depending on operating conditions including temperature
Dendrite growth will lead to intermittent bursts of high BER. This will lead to link flaps on the OC768 interface. Over time, these link flaps may increase in frequency until eventually a hard (persistent) link failure condition is seen.
Laser facet coating issue will affect optical power degradation on a sub-set of wavelengths. This will also manifest itself as link-flaps.
L25 Inductor failure will lead to loss of power to OC768 Optics module over a period of time. With the Optics module powered down, no transmit optical output will be seen from failed OC768-ITU/C PLIM.
Cisco recommends replacing the affected hardware (1OC768-POS-ITU/C). Refer to Figure 2 for TAN number, serial number.
If your card does not match in above table, no action is required.
How To Identify Hardware Levels
Complete these steps in order to check the hardware level of the boards:
Execute the show diag command as seen below to check the 800 TAN number and deviation number or physically at card (refer to figure):
RP/0/RP0/CPU0:CRS4A#sh diag 0/3/cpu0 Sun Apr 6 09:24:38.258 PST PLIM 0/3/CPU0 : Cisco CRS-1 OC768 (C-band) DWDM PLIM MAIN: board type 600097 800-18052-01 rev 38<------------- TAN # is here dev 098101<----------------- Deviation # is here S/N SAD103304GK <-----Serial number PCA: 73-7218-02 rev 16 PID: 1OC768-ITU/C VID: V01 CLEI: IPUIAXSRAA ECI: 141603 Board State : IOS XR RUN PLD: Motherboard: 0x0025, Processor: 0xda13, Power: N/A MONLIB: QNXFFS Monlib Version 3.1 ROMMON: Version 1.48(20070928:224557) [CRS-1 ROMMON] Interface port config: 1 Ports Optical reach type: N/A Connector type: N/A
Figure 1: Card View
Figure 2: Card Close-up View
If the TAN is 800-18052-04 or higher, the 1OC768-ITU/C is upgraded and does NOT need replacing. No further checks are necessary.
If TAN is 800-18052-03 with deviation D098101 and your card serial number validate as "Affected" in Cisco Serial Number Validation Tool, inspect for L25 inductor date code (location 'A' in figures 3 and 4). If date code is earlier than 0628, Cisco recommends replacement of suspect unit, please follow Cisco RMA guidelines and use Failure code AFN with Field notice number to request replacement.
Refer to Figure 3 for inductor location 'A', figure 4 is L25 inductor with date code 0712 is good inductor. Inductor in location B and C shown for reference only in figure 5 and 6 respectively.
Figure 3: Card view - L25 Location
Figure 4: L25 Inductor Location A
Figure 5: Inductor B
Figure 6: Inductor C
If the TAN is 800-18052-02 or lower and your card serial number validate as "Affected" in Cisco Serial Number Validation Tool,, Cisco recommends replacement of suspect unit, please follow Cisco RMA guidelines and use Failure code AFN with Field notice number to request replacement.
For More Information
If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods: