11 Replies Latest reply: Aug 27, 2011 4:20 PM by Mike Gannon RSS

    SingleMode and MultiMode Fiber Distance Lengths


      Hi Guys,


      I need a "cisco answer" here. What's the distance limitations for multimode and singlemode fiber cables? The precise answer seems to vary greatly between the resources I've checked.



        • 1. Re: SingleMode and MultiMode Fiber Distance Lengths


          Please wait for an expert to answer this one, but to my knowledge, multimode fiber is 275 meters to a few miles. Singlemode is 1 mile to many miles



          • 2. Re: SingleMode and MultiMode Fiber Distance Lengths


            Hi Mike,



            The reason that Cisco Anwers vary is because there are several variables that determine distance limitations of both single and multimode fiber.



            The variables to consider are the fiber tranceiver, wavelength, cable type, Core size of fiber (micron), and modal bandwidth of the fiber.



            Now, fiber tranceivers could be 1 gig modules, 10 gig modules or possibly 40 gig & 100 gig. I personally haven't seen the latter, but last I checked, standards were being developed for both. With 10 gig tranceivers, there are several variations of them, each with their own specs.



            Cable type is either multimode or single mode. With multimode, you can have different core sizes. OM1 fiber is usually 62.5 micron, OM2 fiber is usually 50 micron and OM3 is lazer enhanced 50 micon. Depending on the model bandwidth of the fiber and the transciever that will tell you your fiber distance limitation. If you do search on cisco 10gbase xenpak modules, you should find a doc explaining this is much better detail.



            • 3. Re: SingleMode and MultiMode Fiber Distance Lengths
              Scott Morris - CCDE/4xCCIE/2xJNCIE


              I'm not sure there's really a good answer!



              With fiber, the quality of the cable will determine that, but more so it's the optical transmitters you put on there. Very much the same idea as you can have the same piece of glass, but different optics will determine whether it's an OC-3, OC-12, OC-48, OC-192, Gig-E, 10Gig-E or whatever...



              multimode is definitely shorter. I don't know enough about the engineering part of optical networking to give a good reason why. But single mode can work long, long distances depending on the optics used. 20km + isn't unheard of. ( think that's about 13 miles if my math is ok)









              • 4. Re: SingleMode and MultiMode Fiber Distance Lengths


                Hi Mike,



                The guys are right as a number of things depend on the equipment being used. If you go purely on Standards base limitations then the breakdown is as follows



                MultiMode Cable OM1 (50 & 62.5) which is (10Mb) from 300 to 2000m



                OM2 which is gigabit (50 & 62.5) - 500m



                OM3 which is 10gig (300m by standard) but some manufactures go 500m



                OM3+ which 10 - 40 gig - 500m



                SM Cable - 20km at a gigabit



                OS1 (10 gigabit) - 2000m



                I have included an attachment to help you. Unfortunately its not an updated one but the only item mising is OM3 fibre.



                We have found that Transistion is one of the best products on the market for fibre optic convertors, transmitters etc... not cheap though



                Jared, i only know of one manufacturing who is selling their fibre optics as OM4 (40-100Gig ready) is SYSTIMAX. As for actual equipment at that level i'm not sure yet.









                • 5. Re: SingleMode and MultiMode Fiber Distance Lengths
                  Jeff Bankston

                  This a nice Wikipedia article that explains cabling nicely, the footnote references in TIA also provide helpful data.





                  • 6. Re: SingleMode and MultiMode Fiber Distance Lengths

                    very nice answer by the other posters.  Here is a another point of view that is rather basic in nature.


                    Take a look at the following picture.




                    You will notice in the first two, which are multi-mode fiber, the signal "bounces" off the inside of the glass medium.  thus cause signals to disapate over time and therefore not able to travel as far.  The is in contrast to the single mode fiber (bottom picture) where the light travels down the center of the glass medium resulting in much longer distances.  This explains the fact why SM can go further than MM.  The actual distance is determined by such factors as wavelength, the type of glass fibers used, incoherent scattering, absorption, diameter of the fiber, etc, etc, etc.


                    Regarding Cisco's answer, go with the Cisco documentation.  What do they say in Cisco Press books or online articles.  In my opinion these would be the recommended lengths for use with their equipment.  I agree with Scott, finding a "real" answer my be difficult.




                    • 7. Re: SingleMode and MultiMode Fiber Distance Lengths

                      Here is a link to Cisco's Documentation regarding their SFP Gigabit Interface Converters.  SM fiber can be as much as 40x the distance of MM fiber.  very big difference.






                      • 8. Re: SingleMode and MultiMode Fiber Distance Lengths

                        Hi Jeff


                        You do realise that the original post was from 2009. We have not heard from Mike B in years. We always thought it was Scott generating questions himself.


                        Regards Conwyn

                        • 9. Re: SingleMode and MultiMode Fiber Distance Lengths

                          I only just noticed the date of that post, i thought he had come back to the CLN. He certainly kept the CLN busy and all on his own.

                          • 10. Re: SingleMode and MultiMode Fiber Distance Lengths

                            Hey guys, I'm working on a case where the distance between 2 places is 127 kilometers. I have to connect these 2 offices by Single Mode fiber. I understand that the maximum distance supported by Single mode fiber cable is upto 70 Kilometers. Can I just connect a switch (Say Cisco 2960)in between, at 65 kms, so that I can extend the cable length to achive my distance? Any response is greatly appreciated. Thanks,



                            • 11. Re: SingleMode and MultiMode Fiber Distance Lengths
                              Mike Gannon

                              Hi Jay,

                              The ISP you use will have a backhaul network that will use regenerators / multiplexers to handle the problems with signal degredation due to distance. unless you are actually 127km from your local CO or are planning on setting up your own fibre.

                              By installing a switch at the mid point you are carrying out signal regeneration called OEO (optical-->electrical-->optical). The switch generates a whole new optical signal andcleans up the signal taking care of attenuation, dispersion that are the reasons that you have fibre distance limitations.