Connect ISP Optical Cable into Turris Omnia?

Hi All,

My current home internet flow is follows

ISP Optical Cable → Blue port on PON Device → 2-ended Cat6 RJ45 Cable from its LAN1 port → Netgear WiFi Router → Wired/Wireless devices

Before I purchase a Turris Omnia to augment my home internet, could someone please let me know if I can directly connect the ISP optical cable into it?

This would help me eliminate the PON device and the new network diagram becomes much simpler

ISP Optical Cable → Turris Omnia Router → Wired/Wireless devices

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You would need to get a SFP module that is compatible with the SFP cage in the omnia and will also be provisioned by your ISP.
For GPON there are success reports on the forum, that really depends on the ISP and also is not free of unexpected side effects. E.g. a gpon ONT often is implemented as a full computer running a gpon network stack together with the appropriate optics. And that means after power on it can take that ONT computer longer to boot up than the omnia is willing to wait/probe for it… resulting in a missing interface until the next ‘warm’ reboot. Not sure this is universally true, but seems to apply to at least one example.

Thanks for the response @moeller0. The official Turris SFP+ Copper module (RJ45) has an RJ-45 connector that would not work for me. From your experience could you kindly recommend any modules having an optical cable connector compatible with the Turris Omnia?

Will review them and the GPON ONT module side-effects you mentioned with my ISP before purchasing.

But that only speaks ethernet, if you only need 1 Gbps, why not simply use the already existing sibling rj45 socket port?

My first hand experience is still zero, I have neither optical links at home nor anything else in my omnia’s SFP cage/port, I was just relaying information I learned in the forum. Here is a thread that might be helpful:

there was/is a community wiki, but I can not reach it at the moment, so it might be gone for good:

GPON is unfortunately a very black-boxy technology. Your ISP has to encrypt traffic to your router and the GPON device has to decrypt it. Most ISPs are reluctant to providing the deciphering keys to customers. So I think there’s a high chance you’ll need to use the ISP’s GPON transceiver. But you can still ask them…


Thanks for the replies


But that only speaks ethernet, if you only need 1 Gbps, why not simply use the already existing sibling rj45 socket port?

I meant the official module would probably fit in the SFP port of Turris Omnia but as the other connecting end would be rj45 so my optical cable would not fit in. What exactly do you mean by use the already existing sibling rj45 socket port?

Had already seen the community wiki link you shared but I’m not much aware on the hardware side.

Most ISPs are reluctant to providing the deciphering keys to customers. So I think there’s a high chance you’ll need to use the ISP’s GPON transceiver. But you can still ask them

@peci1 while useful, I agree GPON is complicated indeed. Plus my ISP’s staff does not seem very technically aware of its details as well so would not help much if I goto them with a list of optical modules either. From your personal experience, would you suggest using the GPON device itself with the RJ45 cable connected to a router as is my current setup?

I use it like that. No hassle. If internet goes down, I can exactly tell my ISP whether the problem is in their box or in my Omnia.

There can, however be a difference in what the ISP’s box actually does. It can either be a full-fledged router (which is the worse option in your case), or it can be just a transparent transceiver that “translates” GPON to RJ45 connector and acts as a bridge (that would be the better case).


Well, if you use copper ethernet up to 1 Gbps there is no need to use the SFP cage at all, as there is a WAN port already that offers 1 Gbps copper ethernet (and you can only ever use that copper port or a SFP module, not both at the same time). Sure the official module will work and offer ethernet speeds up to 2.5 Gbps (the module is rated for up to 10 Gbps, but that omnia’s SFP cage/port is limited to 2.5 Gbps).
But a copper port will not allow a glas-fiber cable connector, you need some sort of media converter. If your ISP uses a point to point topology (often also called active optical network or AON) you can buy cheap media converter the convert ethernet over glas-fiber to ethernet over copper, but if your ISP uses a point to multipoint topology (using passive splitter, often called passive optical network, or PON)) then the “media-converter” needs more smarts, these then are often called optical network termination units (or ONT, but some ISPs also call a media converter for AON by the same name). E.g. GPON requires a quite sophisticated ONT and this ONT needs to be accepted by your ISPs GPON system.

What exactly is your hardware question?

If this is GPON they are using, you need to ask the for the list of devices they support, maybe this includes an SFP module (and maybe that is even generally compatible with Linux and specificially with the omnia’s SFP-port).

If your ISP already offers a “dumb” ONT that really has no router functionality then just using that ONT’s “RJ45” port to connect to the omnia’s “RJ45” wan port would be the simplest way forward.

EDIT: typo fix and correctin 2.5 Gbps instead of 25 Gbps


Yes even though it’s an additional device and network hop, it’s easy to pinpoint which device has errors, i.e: PON or the corresponding router (Omnia or otherwise).

I use a regular 100-200 Mbps internet unlikely to reach >1 Gbps but thanks for enlightening me with this limitation.

My question was is there a better way (than asking my ISP) to identify which exact module would be compatible with my above PON device?

This is my current setup so I believe replicating it would be the simplest way to ensure all works correctly. It’d save me the trouble / cost of getting SFP <-> RJ-45 connector modules, try & return if unsuccessful until I find the right one.

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I don’t think this would be possible with GPON. Your ISP has to provide you with decryption keys in the module. So they have to actively support each one. Or at least this is how I understand it.

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Trial and error, if you prefer? Some folks in Germany had success in cloning the ISP ONT’s relevant id numbers into some SFP-ONTs, but that is not guaranteed to work… however if you consider the challenge attractive that might be for you (there is a relevant thread in the OpenWrt forum).

This is not half as involved/sophisticated as in DOCSIS, often ISPs really check for something like a PLOAM password or some id number of an ONT and if that matches the same information in their database will happily provision the ONT (including the required key(s)). But that is not guaranteed to work robustly and reliably (not that using the ISP’s ONT gives much better guarantees either :wink: )

You need to know how authenticates the gpon module itself to the ISP.
There are some SFP gpon compatibles with turris omnia, my recommendation is to use a ma5671a if you want to modify or a ODI DFP-34X-2C2 (aliexpress) this is very configurable sfp ont compatible too with TUrris but its not cheap (90e)

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thanks @moeller0 @peci1 @backon for the detailed insights, very helpful for me to understand the pros / cons of SFP modules before buying a Turris Omnia device for an optical fibre based internet connection.

TL;DR of this thread:

  1. We can use either WAN or SFP port on Turris Omnia however the former is limited to 1 Gbps while the latter to 2.5 Gbps.

  2. Separating GPON Device and Router by connecting them from GPON Source LAN port to Router’s WAN port via RJ-45 cables creates an an additional device and network hop. However its easy to pinpoint which device has errors, i.e: GPON or the corresponding router (Omnia or otherwise).

  3. A SFP module is required to connect optical cable directly into Turris Omnia that’s compatible with any Internet Service Provider (ISP). GPON has a difficult implementation as ISP encrypts traffic to router and decrypted via GPON device.

  4. Trial and error could help determine the right SFP module however they are neither cheap nor is their setup limited to only plug & play.

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The SFP cage is limited to 2.5 Gbps, the ethernet WAN port is limited to 1 Gbps ethernet…

Basically, except that “hop” often is used to denote IP/L3 hops, while a ONT often acts as L2 device, that like a L2 switch will not show up in traceroutes.

GPON is not difficult per se, but most ISPs (I know of) want to know which devices are in use and hence will not provision any ONT by default.

That depends on your ISP, sometimes all your ISP wants is either a specific number from your ONT (so they can register that with their head end equipment) or they want you to enter a specific password into the ONT… this is not as well standardized as cable/DOCSIS (or rather the GPON specifications simply leave the whole provisioning issue to the vendor).

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