6 Replies Latest reply: Apr 7, 2012 2:43 AM by Pre21 RSS

    Optical Fibre Basics!!


      Hi All,



                I want to know about Optical fibre basics and their interconnectivity.As i have to work on switches and Datacentre i am new and facing problem for what ,why and how?  My colleagues are unable to answer my queries.Topics like

             1.SFP module

             2.SC LC

             3.Kaplar Switch

             4.Fiber to Ethernet convertor and vice-versa

             5.Multi-mode and single mode

             6.Thin cables colored blue,yellow,orange thak for rack to rack connectivity  and Thick cable of black colored for one location to another location connectivity.


      etc etc......Plz provide relevant documents or links in order to clear my doubts.






        • 1. Re: Optical Fibre Basics!!

          Wow, that's quite a lot to cover.  Understand that what I've listed below only scratches the surface.  Hopefully it will whet your appetite and send you on the path to a little understanding and additional learning. 


          1. SFP (small form factor pluggable) - Modular transceiver that can be used in an SFP port to enable use of different types of media from the port.  In fiber, you don't have just a single distance limitation.  Various distances can be covered by different standards (short-range, long-haul, etc.)  A couple of starter nuggets:




          2. SC and LC are fiber optic connector types.  With copper. you're familiar with the 8P8C (RJ-45) connector.  Different fiber connectors have developed over the years for different reasons. LC is a smaller connector that can be used for higher port densities.  An Internet search for "optical fiber connector" will yield much more info.


          3. Not familiar with this one


          4. Allows conversion between various media types.  Transition Networks, IMC Networks, Omnitron are just a few manufacturers.  Much info available on their sites.


          5. "Mode" refers to the way the light transmission occurs through the fiber.  In general practice, you can think of it much more simply.  Multi-mode fiber "generally" is for shorter runs, and is less expensive cable.  Single-mode fiber is generally for longer runs and is more expensive cable.  Single mode may also be necessary as the link bandwidth increases.  You'll hear terms like "core size" that refer to the diameter of the inner "conductor" (fiber / glass) of the cable.  Typical core size for multimode 62.5 or 50 micron, and 9 micron for single mode.  The Corning web site (www.corning.com) contains quite a bit of info on fiber, and you can also browse their product list to get an idea of the extensive list of fiber configurations and accessories.


          6. In *general* (any color can be had with money) multimode comes in orange.  Yellow is single-mode, and blue (aqua) is multi-mode optimized for certain standards (typically higher data rates, such as 10Gbps).  These cables are typically for indoor use in protected spaces, meaning they are constructed to simply withstand normal handling that would occur in short horizontal pulls and patching.


          Other fiber cables can be made that have multiple strands/pairs and/or are "armored" for use in long pulls, outdoor runs, direct-burial, and other applications for which "harsh" environments are expected.  Again, lots of options here that can range from a simple "tough outer jacket" to cables with metal sheathing and gel-filled to resist water ingress.  You should be able to find more info on the Corning site or an Internet search.


          I hope this helps some.  Again, these are not hard and fast answers, but general, typical information based on the questions.  Good luck!

          • 2. Re: Optical Fibre Basics!!

            Hi E Summers,


                 Thanks Buddy!!  Your answers has helped me lot!! I think you have clear concepts on these terms......Do you have more technical terms realting to optical fibre??  If yes plz share!!    I need documnets or links to clear more becoz many things i see...realting to fibre, even don't know their technical term.....so that i can sahre with you.................!!
            Thanks again!!




            • 3. Re: Optical Fibre Basics!!

              You could do a search for




              You can probably down load the whole spec from IEEE. It is heavy going but I often find if I skim read the spec it gives me pointers to where to look.

              The big advantage is that they cant be wrong!


              Optical is a real pain to order, there are sooooo many types of fiber and modes it is very easy to make $5000 errors.


              because there are so many types cisco do not in general put a fiber port on their switches. They put 2 or 4 SFP ports and then you order the approprate SFP for what you want to do.

              You need to be very specific "I want an sfp for  1000base-LX single mode"

              the same for the NIC but if your SPC, NIC and fiber all match it just works easy as UTP.




              Fiber works because light shined in one end of the glass hits the walls of the glass fiber at such a shallow angle that it reflects instead of going through.

              Look at water or glass at a very shallow angle.

              Make sense - thats multimode.

              The fibers are chunky robust, the outside is usually orange.

              You have to be carefull not to get the ends dirty but they basically just work.


              Now it turns out that if you make the fiber very very thin the light sort of skims down not really reflecting so there is much less loss. It is expensive to make fiber this thin, you need more expensive SFP's to get the light in, but the light goes MUCH further. like 5km 70km with some specs.

              That is single mode and I have never seen any but I believe they are yellow.


              although a single mode fiber is thinner and more fragile usually the whole package is much thicker because there is more protective layers.

              • 4. Re: Optical Fibre Basics!!

                There is such a large amount of information that you could cover.  Try starting at the Corning Technical Resources page by viewing some product videos.  It may help orient you by being able to see the actual devices.  There is also a glossary of terms on the page that may be beneficial as you continue to read and learn.




                Note that I'm not recommending Corning as a specific manufacturer.  I just know that the site contains a lot of useful technical information.  In fact, I would highly recommend reading information from a competing manufacturer or industry organization such as BICSI, as taking only one source may introduce confusion when it comes to proprietary systems and terms.




                • 5. Re: Optical Fibre Basics!!

                  There is an excellent point here.  Fiber, especially multimode has all kinds of different specifications.  With that, you need a fiber transceiver to match the fiber specs you have.  There are a variety of fiber transceivers whose laser operates at different wavelenghts and those different wavelenghts are meant for various phycal fiber specifications.


                  For example it is a general rule that 62.5 MM Fiber (OM1) was meant for 100FX and GigSX transmissions.  If you wanted 10 gig, you needed to update fiber.  Well, that is not entirely true.  I have been able to push 10 gig via 62.5, but I needed an LX4 tranceiver to do it and it cost a pretty penny!


                  For newer fiber like OM3 (50 micron laser enhanced) you can use a SR module and be fine with 10 gig speeds over a certain distance.  If you want to go farther, you may need an LRM tranceiver.  You need to do the homework and match your fiber type with the transceiver on your gear.

                  • 6. Re: Optical Fibre Basics!!

                    Thank Sturat ,E Summers and Jared for your reply...I think i gained lot!!




                    Thanks again!!