Re: SFP Optical Receive Power lower than Alarm Threshold

117222400 · ‎12-28-2023

Hi, Experts

Recently we received the alert about the Optical Receive Power -40dBm, it occurred after physical migration.

IOS is: isr4400v2-universalk9.17.03.04a.SPA.bin

cisco#show interfaces g0/0/0 transceiver detail
IDPROM for transceiver Gigabitethernet0/0/0:
Description = SFP or SFP+ optics (type 3)
Transceiver Type: = GE LX (20)
Product Identifier (PID) = GLC-LH-SMD
Vendor Revision = 1.0
Serial Number (SN) = ACW24#####R
Vendor Name = CISCO
Vendor OUI (IEEE company ID) = 00.1C.AD (7341)
CLEI code = WOTRB9YBAA
Cisco part number = 10-2625-01
Device State = Enabled.
Date code (yy/mm/dd) = 20/03/19
Connector type = LC.
Encoding = 8B10B (1)
Nominal bitrate = GE (1300 Mbits/s)
Minimum bit rate as % of nominal bit rate = not specified
Maximum bit rate as % of nominal bit rate = not specified

Socket Verification

SFP IDPROM Page 0xA0:
000: 03 04 07 02 00 00 00 00 00 00
010: 00 01 0D 00 0A 64 37 37 00 00
020: 43 49 53 43 4F 20 20 20 20 20
030: 20 20 20 20 20 20 00 00 1C AD
040: 52 54 58 4D 31 39 31 2D 34 30
050: 34 2D 43 38 38 20 31 2E 30 20
060: 05 1E 00 11 00 1A 00 00 41 43
070: 57 32 34 31 32 30 33 36 52 20
080: 20 20 20 20 32 30 30 33 31 39
090: 20 20 68 F0 04 14 00 00 1F F7
100: 27 A3 59 7D C2 7D 7B 31 DF 15
110: F8 6B 4D 0E DC 00 00 00 00 00
120: 00 00 00 00 5C B8 C2 C3 00 00
130: 00 00 00 00 00 00 00 00 00 00
140: 00 00 00 00 00 00 00 00 00 00
150: 00 00 00 00 00 00 00 00 00 00
160: 00 00 00 00 00 00 00 00 00 00
170: 00 00 00 00 00 00 00 00 00 00
180: 00 00 00 00 00 00 00 00 00 00
190: 00 00 00 00 00 00 00 00 00 00
200: 00 00 00 00 00 00 00 00 00 00
210: 00 00 00 00 00 00 00 00 00 00
220: 00 00 00 00

SFP IDPROM Page 0xA2:
000: 59 00 F7 00 55 00 FB 00 8C A0
010: 75 30 88 B8 79 18 75 30 00 FA
020: 61 A8 01 F4 31 2D 01 BE 13 93
030: 04 62 31 2D 00 32 13 93 00 7D
040: 00 00 00 00 00 00 00 00 00 00
050: 00 00 00 00 00 00 00 00 00 00
060: 00 00 00 00 00 00 00 00 3F 80
070: 00 00 00 00 00 00 01 00 00 00
080: 01 00 00 00 01 00 00 00 01 00
090: 00 00 00 00 00 7E 1D 1D 80 FA
100: 26 46 0A DF 00 01 00 00 00 00
110: 02 00 05 40 00 00 25 40 00 00
120: 00 00 00 00 00 00 00 01 57 4F
130: 54 52 42 39 59 42 41 41 31 30
140: 2D 32 36 32 35 2D 30 31 56 30
150: 31 20 A9 FB 55 00 00 00 00 9F
160: 00 00 00 00 00 00 00 00 00 00
170: 51 7B 64 00 7B 73 A4 31 C8 00
180: 18 E3 0E FA 0A 83 0F 5A 00 00
190: AA AA 47 4C 43 2D 4C 48 2D 53
200: 4D 44 20 20 20 20 20 20 20 20
210: 20 20 00 00 00 00 00 00 00 00
220: 00 00 00 E8 00 00 00 00 00 00
230: 00 00 00 00 00 00 00 00 00 00
240: 00 00 00 00 00 00 00 00 FF FF
250: FF FF 00 00 00 00
Link reach for 9u fiber (m) = 1xFC, 2xFC-SM(10km) (100)
Link reach for 50u fiber (m) = SX(550/270m) (55)
LX(5km/550m) (55)
LX(10km/550m) (55)
Link reach for 62.5u fiber (m) = LX(5km/550m) (55)
LX(10km/550m) (55)
Nominal laser wavelength = 1310 nm.
DWDM wavelength fraction = 1310.0 nm.
Supported options = Tx disable
Tx fault signal
Loss of signal (standard implementation)
Supported enhanced options = Alarms for monitored parameters
Software Tx disable
Software Tx fault monitoring
Software Rx LOS monitoring
Diagnostic monitoring = Digital diagnostics supported
Diagnostics are internally calibrated
Rx power measured is "Average power"ITU Channel not available (Wavelength not available),
Transceiver is internally calibrated.
mA: milliamperes, dBm: decibels (milliwatts), NA or N/A: not applicable.
++ : high alarm, + : high warning, - : low warning, -- : low alarm.
A2D readouts (if they differ), are reported in parentheses.
The threshold values are calibrated.

High Alarm High Warn Low Warn Low Alarm
Temperature Threshold Threshold Threshold Threshold
Port (Celsius) (Celsius) (Celsius) (Celsius) (Celsius)
--------- ----------------- ---------- --------- --------- ---------
Gi0/0/0 31.3 89.0 85.0 -5.0 -9.0

High Alarm High Warn Low Warn Low Alarm
Voltage Threshold Threshold Threshold Threshold
Port (Volts) (Volts) (Volts) (Volts) (Volts)
--------- ----------------- ---------- --------- --------- ---------
Gi0/0/0 3.30 3.60 3.50 3.10 3.00

High Alarm High Warn Low Warn Low Alarm
Current Threshold Threshold Threshold Threshold
Port Lane (milliamperes) (mA) (mA) (mA) (mA)
--------- ---- --------------- ---------- --------- --------- ---------
Gi0/0/0 N/A 19.5 60.0 50.0 1.0 0.5

Optical High Alarm High Warn Low Warn Low Alarm
Transmit Power Threshold Threshold Threshold Threshold
Port Lane (dBm) (dBm) (dBm) (dBm) (dBm)
--------- ---- --------------- ---------- --------- --------- ---------
Gi0/0/0 N/A -5.5 1.0 -3.0 -9.5 -13.5

Optical High Alarm High Warn Low Warn Low Alarm
Receive Power Threshold Threshold Threshold Threshold
Port Lane (dBm) (dBm) (dBm) (dBm) (dBm)
--------- ---- --------------- ---------- --------- --------- ---------
Gi0/0/0 N/A -40.0 1.0 -3.0 -19.0 -23.0

I read the link https://community.cisco.com/t5/optics-and-optical-networking/understanding-tx-rx-light-level/td-p/2794532

It seems no actual signal received if the power is below -30dBm. Does it mean that no data packets were received or incomplete packets on the interface (G0/0/0) ? Is there any actual impact for the network routing and switching?

The interface is in a eBGP zone and the peer should send BGP route entries to it. I run show bgp summary command twice:

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.1.1.69 4 65322 30505 30668 109794 0 0 2w5d 0

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.1.1.69 4 65322 31711 31875 113516 0 0 2w6d 0

It seems the interface can still receive Msg but the PfxRcd is 0. Also I compared the bgp route table before migration, there is bgp route entries received for this interface, but now there isn't. Is it caused by the extreme low optical receive power?

Thanks in advance

Ruben Cocheno · ‎12-28-2023

@117222400

Make sure on the other side you have single-mode SFP and use a single-mode patch fiber cable as well for the Low Optical Tx/Rx

Now the links seem to be up as per your BGP neighbor since their establish connectivity under TCP, check on the other side if prefixes are getting advertised.

Tag me to follow up.
Please mark it as Helpful and/or Solution Accepted if that is the case. Thanks for making Engineering easy again.
Connect with me for more on Linkedin https://www.linkedin.com/in/rubencocheno/

117222400 · ‎12-28-2023

Hi Ruben,

Thanks very much for your reply.

I just checked the connection for the port, the receiver port 0&1 is not connected, as below photo:

As my understanding, slot 0 subslot 0 port 0 is upper one, and port 1 is lower one.

Before migration, the indicator for port 0 is on and no alerts, but after migration(reboot) the indicator is off and the alert is coming. Port 1 is always off.

From below show command, it seems both port 0 and port 1 are -40dBm in Rx power, does it cause the alerts? but before migration no any alerts.

cisco#show interfaces transceiver
The Transceiver in slot 0 subslot 0 port 0 is enabled.
Module temperature = +31.355 C [Range: -5 C to 85 C (extended)]
Transceiver Tx supply voltage = 3301.8 mVolts [Range: 3100.0 to 3500.0 mVolts]
Transceiver Tx bias current = 19596 uAmps [Range: 1000 to 50000 uAmps]
Transceiver Tx power = -5.5 dBm [Range: -9.5 to -3.0 dBm]
Transceiver Rx optical power = -40.0 dBm [Range: -19.0 to -3.0 dBm]
IDPROM for transceiver Gigabitethernet0/0/0:
Description = SFP or SFP+ optics (type 3)
Transceiver Type: = GE LX (20)
Product Identifier (PID) = GLC-LH-SMD
Vendor Revision = 1.0
Serial Number (SN) = ACW2412036R
Vendor Name = CISCO
Vendor OUI (IEEE company ID) = 00.1C.AD (7341)
CLEI code = WOTRB9YBAA
Cisco part number = 10-2625-01
Device State = Enabled.
Date code (yy/mm/dd) = 20/03/19
Connector type = LC.
Encoding = 8B10B (1)
Nominal bitrate = GE (1300 Mbits/s)
Minimum bit rate as % of nominal bit rate = not specified
Maximum bit rate as % of nominal bit rate = not specified

The Transceiver in slot 0 subslot 0 port 1 is enabled.
Module temperature = +30.917 C [Range: -5 C to 85 C (extended)]
Transceiver Tx supply voltage = 3306.5 mVolts [Range: 3100.0 to 3500.0 mVolts]
Transceiver Tx bias current = 18176 uAmps [Range: 1000 to 50000 uAmps]
Transceiver Tx power = -5.7 dBm [Range: -9.5 to -3.0 dBm]
Transceiver Rx optical power = -40.0 dBm [Range: -19.0 to -3.0 dBm]
IDPROM for transceiver Gigabitethernet0/0/1:
Description = SFP or SFP+ optics (type 3)
Transceiver Type: = GE LX (20)
Product Identifier (PID) = GLC-LH-SMD
Vendor Revision = 1.0
Serial Number (SN) = ACW2412036F
Vendor Name = CISCO
Vendor OUI (IEEE company ID) = 00.1C.AD (7341)
CLEI code = WOTRB9YBAA
Cisco part number = 10-2625-01
Device State = Enabled.
Date code (yy/mm/dd) = 20/03/19
Connector type = LC.
Encoding = 8B10B (1)
Nominal bitrate = GE (1300 Mbits/s)
Minimum bit rate as % of nominal bit rate = not specified
Maximum bit rate as % of nominal bit rate = not specified