I have this multimode transceiver product: http://www8.hp.com/h20195/v2/gethtml.aspx?docname=c04168409&search=J4858C

I am going to use it on the following switch: http://www8.hp.com/h20195/v2/gethtml.aspx?docname=c04111401&search=J9727A

I was wondering if I could use the following fiber optic cable to connect to a same configuration at 200 meter distance (which has been cabled by an electrician and it is a multimode type but I don't know about the OM number) : LC-LC 0200 50/125µ OM3 Duplex 2m

What are the limitations in terms of bandwidth/distance? I really don't understand the MHz*km bandwidth thing.

3 Answers 3


EDIT: Fixing answer now that I'm on a real laptop.

Yes, OM3 is just "laser optimized" multimode, it will work with both your optic and distance.

What are the limitations in terms of bandwidth/distance?

Max Distance @ 1Gbit/s (per the product page): 550m

This also lines up with the OM3 specification http://en.m.wikipedia.org/wiki/Multi-mode_optical_fiber#Types

I really don't understand the MHz*km bandwidth thing.

This is called modal dispersion, it's an inherent property of multimode fiber - it's basically the relationship between distance and bandwidth.

So first you need to understand that multimode fiber is named that way for a reason. There are multiple modes of light that are sent over the cable, so when light is transmitted it looks something like this:

enter image description here

All of those lines are the "modes".

Because they're using the entire width of the fiber, they "bounce" from "top to bottom" as you see in the picture. Modes traveling at the boundaries of the fiber travel faster, and modes traveling at the center travel a little bit slower. If you look at the picture where it says "Dispersion" you see that they don't quite arrive at the same time, this is a very very minute amount of time, however its enough to reduce bandwidth.

So for something like 1GB, because it doesn't need to carry as much data, it has much more tolerance for distance (550m). If you want it to carry 10GB, you need to compensate by shortening the distance because of this dispersion. I hope this helps.

  • Thanks for the link. I just want to be sure that my transceiver will be compatible wizh OM3 because its specifications say: 50 µm core diameter, 500 MHzkm bandwidth but the OM3 says 1500 / 2000 MHzkm. What does that mean?
    – Truefalse
    May 19, 2015 at 12:19
  • 1
    This is directly from the transceivers product page: 62.5/125 µm or 50/125 µm (core/cladding) diameter, graded-index, low metal content, multimode fiber optic, complying with ITU-T G.651 and ISO/IEC 793-2 Type A1b or A1a, respectively; May 19, 2015 at 12:21
  • 1
    The first number in the 50/125, relates to the core size, 50 µm. This will work with your cable. May 19, 2015 at 12:23
  • Thanks @jordan-head, I was just scared that OM3 would only be compatible starting from 1500 MHz*km <- this may be nonsense XD
    – Truefalse
    May 19, 2015 at 12:27

yes, you could use OM3 cable with J4858C, in fact, J4858C can be used with OM1, OM2 or OM3 but with a differenct distance.


The J4858C is a 1000BASE-SX transceiver. 1000BASE-SX is specified for 550 m reach over 500 MHz*km fiber (OM2). OM3 (1500 MHz*km) will probably go quite a bit further.

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