Basic SFP Optical fiber questions

[saravanakumar.s]

I am newbie to this optical fiber networking communication.

Below are clarifications,

#Whether 100 base Fx Implementation, can support any wavelength? (Eg: 1310nm or 850nm)

#In case if we are selecting 1Gbps SFP Transceivers, But, my controller will support only (100Mbps)100 base FX. Will this 1 Gbps SFP Transceiver support for 100 Mbps also?

#In case if we are selecting 125MbPs SFP Transceiver, But, my controller will support only (100Mbps)100 base FX. Will this 125 Mbps SFP Transceiver support for 100 Mbps also?

[Marvin Rhoads]

1. 100Base-FX SFPs generally operate at 1310 nm wavelength. (A few uncommon use ones operate at 1550 nm.) 850 nm is not an option.

2. A given optical transceiver only operates at its rated speed. they do not auto negotiate or step down their speed like a copper 10/.100/100 Mbps link does.

3. I have seen a few European vendors refer to "125 Mbps". I believe this is inexact as in college I learned that bits are abbreviated with small "b" and bytes with capital "B". They are actually talking about IEEE 802.3Z Gigabit Ethernet which is 1000 Megabits per second = 125 Megabytes per second. As with my second answer, the transceiver only operates at its rated speed - no others.

[saravanakumar.s]

Thank you very much for your quick feedback.

My Microcontroller will operate at 100 Base FX(100 Mbps/1310 nm length)

Is there any other options for the below clarifications,

         # How can I convert the 100 Mbps to 1 Gbps? Because. SFP Transceiver will operate at Gbps.

  # Even though, my microcontroller will operate at 100 Base FX, Is there any option to for this   

     option(100 Mbps/850 nm wavelength) ?

[Marvin Rhoads]

You're welcome.

You must match your microcontolller 100 Mbps/1310 nm output with an SFP at the switch operating at the same speed and wavelength.

Tell us what switch model you are using and we can tell you what SFP is compatible.

[saravanakumar.s]

We have selected only the microcontroller.

We are not planning to use any switch. We want to drive the SFP Transceiver directly from the microcontroller.

My microcontroller will support with the below configurations,

Integrated high-performance 100Mbps Ethernet transceivers

- Compliant with IEEE 802.3/802.3u (Fast Ethernet)

- 100BASE-FX support via external fiber transceiver

- Loop-back modes

- Automatic polarity

Could you please recommend the suitable Single mode SFP Transceiver with LC connector with Temperature range -40C to +85C? We want to drive up to 40 km distance.

This is going to be used for Train control applications.

[Marvin Rhoads]

Unfortunately Cisco does not have a 100 Mbps transceiver that operates both at that temperature range ("Industrial") and distance ("EX").

The data sheet below lists currently available models:

https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/fast-ethernet-sfp-modules/product_data_sheet0900aecd801f931c.html

You may be able to find a 3rd party product but that would be outside the Cisco Support Community scope.