10 Gigabit Ethernet over fiber using the DTX-EFM2 fiber adapters

The DTX CableAnalyzers are capable of testing both multimode and singlemode fiber for 10GBASE compliance with the optional fiber modules. Details on patch cord testing are given at the bottom of this article.

Should I use the DTX-GM2 instead of the DTX-EFM2?
The loss limits specified in IEEE 802.3ae are based on an LED source, not a VCSEL, even though the active equipment contains a VCSEL. Technically speaking, you should use the DTX-EFM2 to test multimode 10GBASE-SR. However, there were people who felt this was is incorrect. For that reason, we offered the DTX-GFM2 which contained an 850 nm VCSEL and 1310 nm FP laser source. ANSI/TIA-526-14-B is very clear on this subject, no VCSELs, so the DTX-GFM2 was withdrawn. Please look to your testing specification requirements.

You may asked for 10GBASE-SR or 10GBASE-SW testing, yet the DTX only has the 10GBASE-SR option. The R and W designation have no impact on the physical layer testing. The R implementation is for the LAN, the W implementation is for the WAN which has the capability to transmit and receive IEEE 802.3 MAC frames within the payload envelope of a SONET STS-192c/SDH VC-4-64c frame. Hence, in the DTX CableAnalyzer, you will only see 10GBASE-SR, LX4, L and E.

    S: Short haul
    L: Long haul
    E: Extra long haul

10GBASE comes with severe length restrictions for multimode installations.

10GBASE-SR (Multimode 850 nm)

Most users are not aware of the severe length restrictions for 10GBASE-SR.


62.5/125 µm 160 MHz.km: 26 m

<span "="">62.5/125 µm 200 MHz.km: 33 m

50/125 µm 500 MHz.km: 82 m

50/125 µm 2000 MHz.km: 300 m

50/125 µm 4700 MHz.km: 400 m



Implementation of 10GBASE-SR can be a problem, since most customers look to the overall allowable loss:


62.5/125 µm 200 MHz.km: 2.4 dB

50/125 µm 500 MHz.km: 2.3 dB

50/125 µm 2000 MHz.km: 2.6 dB

50/125 µm 4700 MHz.km: 2.9 dB


and believe that if this is met, the link will support 10GBASE-SR. Not true.


There is another parameter called Modal Bandwidth (MBW) that affects the operation of 10GBASE-SR over multimode cable. MBW cannot be measured in the field. Therefore, this parameter is dealt with by defining a maximum length. Defining a maximum length assures the user that the MBW needed for 10GBASE-SR is met.


Another important aspect is how the IEEE defined the 2.6 dB maximum loss for 50/125 µm 2000 MHz.km. It is based on 300 meters of cable with a maximum  loss of 3.5 dB/km and two mated fiber connectors, each with a maximum loss of 0.75 dB. No splices.


Connector Loss = 0.75 dB

Cable Loss = 1.05 dB  (300 m @ 3.5 dB/km)

Connector Loss = 0.75 dB


Total Loss = 2.55 dB (Round up to 2.6 dB)


If your cable has a better fiber loss and/or you can guarantee a better connector loss, this may allow the use of splices. It does not permit you to extend the distance beyond 300 meters, unless the MBW of the cable is better than 2000 MHz.km. The limits in the DTX CableAnalyzer are taken from IEEE 802.3ae Table 52–10—10GBASE-SR link power budgets.