The DOM problem of AOC in Huawei


The DOM problem of AOC in Huawei 



1. Active Optical Cable introduction

AOC(Active Optical Cable)is used for short-range multi-lane data communicationand interconnect applications. Usually, the wire transmission of opticalcommunication should belong to passive part, but AOC is an exception. AOCconsist of multimode optical fiber, fiber optic transceivers, control chip andmodules. It uses electrical-to-optical conversion on the cable ends to improvespeed and distance performance of the cable without sacrificing compatibilitywith standard electrical interfaces. Since people expect more information to beavailable at their fingertips, communications systems will need to be quicker,and AOC is one of the best solutions to solve this problem. Compared withdirect attach copper cable for data transmission, AOC provides more advantages,such as lighter weight, high performance, low power consumption, lowinterconnection loss, EMI immunity and flexibility. At present, AOC is widelyused in many fields as well as promoting the traditional data center to stepinto optical interconnection.

In fact, AOC are SR module. SFP+ AOC consists ofSFP-10G-SR module and multimode optical fiber, QSFP+ AOC consisting ofQSFP-40G-SR4 and multimode optical fiber, QSFP28 AOC consisting ofQSFP28-100G-SR4 and multimode optical fiber.


2. DOM Problem

As for DOM, there are definitions inSFF-MSA.

For SFP+ 10G AOC, the DDM is defined in SFF-8472:

TheDDM is supported when the 92 Byte is writen “68”. The code is as below:

For QSFP+ AOC,there is noexact definitionin SFF-8436 for QSFP+:

Itonly defines the received power measurements type in Bit 3, no DOM opening andclosing instruction. The 220 Byte is often written “08” for Average Power.

SoSFP+ AOC can show the DOM when the 92 Byte is written “68”, but QSFP AOC showDOM without special definition.


3. Test DOM in Huawei switch

       For Huawei switch, the general code can work well.

       So code the SFP+ AOC and QSFP+ AOC, and then test in Huawei switch.

(1) Huawei 6810 switch:






QSFP+ 40G SR4:



So in Huawei 6810 switch, the QSFP+ 40G AOC can notshow the DOM, but QSFP+ 40G SR4 can.

Then with the same QSFP+ 40G AOC and the same code, testin Cisco 3064:




Itshows DOM in Cisco 3064.And I also test it in other switch such as Huawei S6720、Cisco C93180YC-EX.

It’sspecial of some Huawei switch not showing DOM of QSFP AOC. And it varies withswitch and software.


4. Conclusion

       For QSFP AOC, it may not show DOM in some Huawei switchand software. So for QSFP AOC Compatible Huawei, it should code QSFP SR4 codein case of no DOM in some Huawei switch.

By Faten Fang|Position: FAE


Phone: +86-15271810438

Date: 2018.03.08


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