In my company we are using custom measurement systems with multimode fiber optic transmitters and receivers for synchronization between different devices. We are thinking of migrating our multimode fiber optic technology to single mode to extend the reach to 20 km. The problem is that I have certain doubts about the single-mode fiber technology.

At the moment, our synchronization system consist of emitting synchronous pulses through the optical line from a base generator, and receiving and replicating said pulses from first equipment on the line to the next ones, cascade connection. The pulse synchronization system has the following characteristics:

  • Type of fiber = Multimode 62.5 / 125 um
  • Wavelength = 850 nm
  • Optical power = 0.17 mW (for 1 m fiber)
  • Front delay < 5 ns
  • Pulse duration = 40 ms
  • Pulse Distortion <1 ns
  • Reach = 2.5 km

Therefore, I want to migrate this multimode system to a single-mode in which to reach distances of optical fiber of synchronization up to 20 km., but I have some questions:

  • Will our synchronism methodology continue to be compatible with this kind of pulses? I need to know if at such distances this kind of sync pulses suffers some distortion or deterioration. I know that the new pulse generated on single-mode fiber will have different characteristics but I am concerned about possible phenomena that may interfere with the operation.

  • In any case, could I implement a system of synchronism using a bit string, for example?

  • What type of optical transmitter and receiver can I use? I have seen some single-mode fiber optic transducers with wavelength of 1310 nm that manage to transmit at 30-40 km. Are there other options? Some kind of single laser emitter/receiver?

  • Do you know some good evaluation kit for this technology?

Would appreciate If someone can give me some help.

  • \$\begingroup\$ What does the spec "pulse distortion < 1 ns" mean? Distortion is normally measured in terms of spectral content added at multiples of a carrier or fundamental frequency. Is this meant to be a spec about pulse width dispersion? Or about pulse timing jitter? \$\endgroup\$
    – The Photon
    Sep 5, 2017 at 15:40
  • \$\begingroup\$ Yes, its pulse width dispersion, sorry for not clarifying it. \$\endgroup\$
    – JohnM
    Sep 6, 2017 at 7:52

1 Answer 1


You do not indicate what devices you are using at the moment, it would give a good idea of what serves your current needs.

Moving from multi to single is doable and often there are matching almost drop in optical devices that will have comparable specifications.

More than 20km will need good design (noise issues in the RX circuitry) and infrastructure techniques (professional fibre terminations, not too hard to arrange these days).

You also need to take the fixed delay between sites into account over those distances.

If your sites can see the sky and have some spare power budget it may be cheaper to provision good GPS disciplined local clocks as opposed to laying and maintaining many tens of kilometres of fibre cable.


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