Solved: distance for 10GB SFP-10G-LRM

q-le · ‎01-27-2016

We have an access switch 3750x connect to our Core by dual -single fiber mode links.

The distance according to our electrician is 528.65m and he said our SFP can only work upto 300m

We use 2 x SFPs 10GB SFP-10G-LRM and one link is working and one link is having issues.

the message on our core is LinkFlap and keep flapping up and down for the second not working link

if the distance is the issues then why one link is up and the switch is connected to the core fine.

Any suggestions are much appreciated

Thanks

Peter

Marvin Rhoads · ‎01-27-2016

Peter,

When you use fiber other than the type the transceiver is deigned to work over, your results may vary widely. The physical cores from the singlemode fiber may not align perfectly or even well to the light coming from the LED or VCSEL on the transceiver. That can cause significant loss and result in no link established (or a very "touchy" link that is prone to losing signal from very small perturbations like someone or a piece of equipment even touching the fiber jumper).

As we see from your output, the non-working link is seeing a Rx optical power of -34 dBm at the access switch despite a strong signal being sent from the Nexus core transceiver.

You may be able to establish link by going through the patch cables and cleaning and reseating them

However, your would bet be served by using the type of (more expensive) transceivers that are designed for singlemode fiber. In your case, that would be the SFP-10G-LR-S.

View solution in original post

Marvin Rhoads · ‎01-27-2016

The SFP-10G-LRM is designed for use with multimode fiber and is capable to connect over distance ranging from 100m to 300m (depending on the type of multimode fiber used and the quality of the interconnects).

See this data sheet:

http://www.cisco.com/c/en/us/products/collateral/interfaces-modules/transceiver-modules/data_sheet_c78-455693.html

Any fiber link is dependent on several factors to operate successfully, most notable and the one that most often causes problems is the actual link loss, measured in dBm.

Cisco has built into most current generation SFPs (including that one) Digital Optical Monitoring (DOM). DOM allows us to get a reading of the actual transmit and receive optical power via the command:

show interface <interface number> transceiver details

Please run that command for your two interfaces and share the results.

q-le · ‎01-27-2016

Hi Marvin,

We use single mode so does it mean it can work for distance > 300 m ie not multimode.

Please the results for both:

sh interfaces ten1/1/1 transceiver detail
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)
--------- ------------------ ---------- --------- --------- ---------
Te1/1/1 45.5 75.0 70.0 0.0 -5.0

High Alarm High Warn Low Warn Low Alarm
Voltage Threshold Threshold Threshold Threshold
Port (Volts) (Volts) (Volts) (Volts) (Volts)
--------- --------------- ---------- --------- --------- ---------
Te1/1/1 3.26 3.63 3.46 3.13 2.97

Optical High Alarm High Warn Low Warn Low Alarm
Transmit Power Threshold Threshold Threshold Threshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
--------- ----------------- ---------- --------- --------- ---------
Te1/1/1 -1.8 3.5 0.5 -6.5 -10.5

Optical High Alarm High Warn Low Warn Low Alarm
Receive Power Threshold Threshold Threshold Threshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
------- ----------------- ---------- --------- --------- ---------
Te1/1/1 -8.1 3.5 0.5 -8.0 -12.4

for the one not working is :

sh interfaces ten1/1/2 transceiver detail
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)
--------- ------------------ ---------- --------- --------- ---------
Te1/1/2 41.1 75.0 70.0 0.0 -5.0

High Alarm High Warn Low Warn Low Alarm
Voltage Threshold Threshold Threshold Threshold
Port (Volts) (Volts) (Volts) (Volts) (Volts)
--------- --------------- ---------- --------- --------- ---------
Te1/1/2 3.19 3.63 3.46 3.13 2.97

Optical High Alarm High Warn Low Warn Low Alarm
Transmit Power Threshold Threshold Threshold Threshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
--------- ----------------- ---------- --------- --------- ---------
Te1/1/2 N/A 3.5 0.5 -6.5 -10.5

Optical High Alarm High Warn Low Warn Low Alarm
Receive Power Threshold Threshold Threshold Threshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
------- ----------------- ---------- --------- --------- ---------
Te1/1/2 -34.0 3.5 0.5 -8.0 -12.4

on the Nexus core:

sh interface eth2/6 transceiver details
Ethernet2/6
transceiver is present
type is 10Gbase-LRM
name is CISCO-AVAGO
part number is SFBR-7600SDZ-CS3
revision is 1.4
serial number is AGD1905V12T
nominal bitrate is 10300 MBit/sec
Link length supported for 50/125um OM2 fiber is 220 m
Link length supported for 62.5/125um fiber is 220 m
Link length supported for 50/125um OM3 fiber is 220 m
cisco id is --
cisco extended id number is 4

SFP Detail Diagnostics Information (internal calibration)
----------------------------------------------------------------------------
Current Alarms Warnings
Measurement High Low High Low
----------------------------------------------------------------------------
Temperature 51.35 C 75.00 C -5.00 C 70.00 C 0.00 C
Voltage 3.28 V 3.63 V 2.97 V 3.46 V 3.13 V
Current 39.52 mA 80.00 mA 10.00 mA 74.00 mA 12.00 mA
Tx Power -2.22 dBm 3.49 dBm -10.50 dBm 0.49 dBm -6.51 dBm
Rx Power -4.42 dBm 3.49 dBm -12.44 dBm 0.49 dBm -8.41 dBm
----------------------------------------------------------------------------
Note: ++ high-alarm; + high-warning; -- low-alarm; - low-warning

not working core:

sh interface eth2/6 transceiver details
Ethernet2/6
transceiver is present
type is 10Gbase-LRM
name is CISCO-AVAGO
part number is SFBR-7600SDZ-CS3
revision is 1.4
serial number is AGD1905V2MB
nominal bitrate is 10300 MBit/sec
Link length supported for 50/125um OM2 fiber is 220 m
Link length supported for 62.5/125um fiber is 220 m
Link length supported for 50/125um OM3 fiber is 220 m
cisco id is --
cisco extended id number is 4

SFP Detail Diagnostics Information (internal calibration)
----------------------------------------------------------------------------
Current Alarms Warnings
Measurement High Low High Low
----------------------------------------------------------------------------
Temperature 43.43 C 75.00 C -5.00 C 70.00 C 0.00 C
Voltage 3.20 V 3.63 V 2.97 V 3.46 V 3.13 V
Current 0.00 mA 80.00 mA 10.00 mA 74.00 mA 12.00 mA
Tx Power N/A 3.49 dBm -10.50 dBm 0.49 dBm -6.51 dBm
Rx Power N/A -- 3.49 dBm -12.44 dBm 0.49 dBm -8.41 dBm
----------------------------------------------------------------------------
Note: ++ high-alarm; + high-warning; -- low-alarm; - low-warning

Thanks

Peter

Marvin Rhoads · ‎01-27-2016

Peter,

When you use fiber other than the type the transceiver is deigned to work over, your results may vary widely. The physical cores from the singlemode fiber may not align perfectly or even well to the light coming from the LED or VCSEL on the transceiver. That can cause significant loss and result in no link established (or a very "touchy" link that is prone to losing signal from very small perturbations like someone or a piece of equipment even touching the fiber jumper).

As we see from your output, the non-working link is seeing a Rx optical power of -34 dBm at the access switch despite a strong signal being sent from the Nexus core transceiver.

You may be able to establish link by going through the patch cables and cleaning and reseating them

However, your would bet be served by using the type of (more expensive) transceivers that are designed for singlemode fiber. In your case, that would be the SFP-10G-LR-S.

q-le · ‎01-27-2016

Thank you Marvin for your insight.

We have several of these SFP-10G-LRM sfps over single mode but at a shorter distance of under 200m and they are working perfectly so distance is the issues here.

Peter

q-le · ‎01-27-2016

Hi Marvin,

is there a command to run to find out the distance of the fiber ?

thanks

Peter

Marvin Rhoads · ‎01-28-2016

Peter,

You cannot determine fiber span length from any switch or router command.

To do that, you need a type of fiber testing equipment known as an Optical Time Domain Reflectometer (OTDR).

Most companies who specialize in fiber optic installation have such equipment. They run from US$5000 and up depending on the capabilities.

http://www.fiberinstrumentsales.com/test-equipment/otdrs.html

http://www.amazon.com/Fluke-Networks-OFP-100-QI-OptiFiber-Inspection/dp/B007IUK21W