Fiber technology overview

[dane]

We spend a lot of time talking about the technologies used here, and with fiber, there are some new TLAs (three letter acronyms) flying around that may have some folks confused. Here's a primer on some of the basic items that are different than our old DSL world.

OLT -- Optical Line Terminal -- this is the interface or port in the central office or cabinet that the customers connect to. In our case, this is a card in the Adtran TA5000, which we also use as a DSLAM using another card which delivers ADSL2+, or VDSL2, and POTS. Here's Adtran's data sheet, which includes a photo and application diagram: http://j.mp/1zRmdi6

PON -- Passive Optical Network -- there are two types of fiber networks, point to point (PtP) and passive optical. In a PON, splitters are used to share the OLT port between multiple homes. In our case, 32 homes share a PON segment, connecting to a single OLT interface. PONs can be split at a variety of ratios, from 16:1 (sixteen premises connected to a single OLT port) up to 128:1. Diagram and overview of PON here: http://j.mp/17WJj0l

LCP -- Local Convergence Point -- a cabinet in the neighborhood which passively splits the connection from the OLT from one fiber to 32. The LCP cabinet generally hosts from 288 to 432 homes, and houses splitter cartridges that turn a single fiber from the OLT into 32 fibers which are then plugged into jacks which connect to homes. See an LCP cabinet here: http://j.mp/1Eryj7P

Terminal -- the terminal has multiple ports which homes are connected to, and it is located off the nearby utility pole or in a vault near the home. For underground applications such as Brentwood, we are using the Clearfield FieldShield, see one here: http://j.mp/1FghzyI -- and for aerial applications on overhead wire, we are using a FlexNap type solution, an overview is available here: http://j.mp/1wZ2NIb (note, we do not use FlexNap for underground, only aerial.)

Drop -- the drop cable goes from the terminal to the home. We generally use preconnectorized drop cables, which are plugged into the terminal, pulled (in conduit underground) or dropped (from an aerial pole line) to the home. Here's an example image: http://j.mp/1wKdtzR

GPON -- Gigabit PON -- the layer-2 network protocol running over the PON. GPON is the most common type of PON here in the US. (In Asia, EPON is more common.) GPON offers a shared 2.4Gbps/1Gbps connection for the 32 or so customers in the PON segment. In the future, next-generation PON technologies such as XGPON1 and NGPON2 will
replace GPON and provide 10Gbps capabilities. This means an upgrade of the OLT and customer premise equipment, but it runs over the same fiber, a bit like ADSL1, 2+ and VDSL2 have delivered faster speeds over copper.

ONT -- Optical Network Terminal -- the device on the side of the house which converts GPON into Gigabit Ethernet and delivers POTS voice. This customer premise equipment takes in the fiber, speaks GPON with the OLT, and outputs IP Ethernet, plus phone service. The solution we are using is the Adtran 411, a small "micro" ONT (or μONT) that outputs "one plus one", one Gigabit Ethernet plus one POTS phone jack. Datasheet with photo here: http://j.mp/1DZ2y4T

RG - Residential Gateway -- the router/WiFi access point. Today we use a combined modem/RG to deliver xDSL technologies, as well as to provide routing and WiFi. The residential gateway can also be used with fiber, it's simply fed the Ethernet from the ONT, and the RG takes care of delivering DHCP and NAT, multiple Ethernet ports, and premise WiFi. Today in we are using the Pace 5168, which is our standard VDSL2/bonding modem, which also supports an upstream interface of Gigabit Ethernet instead of xDSL. As with DSL, the RG is managed, and data for troubleshooting is available for support.

I hope this jargon overview helps with the basic outline.

Corning, one of the leading manufacturers of fiber, has a good "Fiber 101" website. It's here: http://j.mp/1X4ilrP - in particular, check out the videos. Their 101 video is here, it's a good intro to fiber itself: http://j.mp/1CDYpVZ -- the Corning YouTube channel is pretty cool too, their vision for the connected, glass-rich future is pretty wild, view it here: http://j.mp/Day-of-glass

Finally, if you'd would like to even learn more about fiber optic networks, the Fiber Optic Association has a "Fiber U" website which provides a lot of tutorial reading material and videos. Some of the material is dated, as technology marches on, but it is a good foundation. You can find it here: http://j.mp/Fiber-U

[cdrayson]

Thanks for this overview, it's very helpful! A couple of questions - Can the ONT be located in our apartment? There would be no other way to get power to it, and there is an existing access hole (formerly for cable TV) going directly into our unit. Also, Can we forgo your RG in favor our our router?

Thanks Dane!

[mfeemster]

Hi Dane, thanks for the technical explanation. Brand new gigabit fiber customer here in the Sunset as of 1/28. I am very happy with what I've got so thanks for providing such a great service at a low price! I am also very impressed with how accessible you and the rest of the staff seem to be on here. I'm sure that will change as you scale, but it's nice to have now.

One suggestion on the subject of what you wrote:

I think you should make information available about what exactly a new gigabit connection means to a potential new customer. When doing research, I was unable to find information on exactly how it would work. Would it come off the pole, then go into a phone box? A cable box? Would it be converted to copper, then a Cat5 line run into my apartment? Despite poking around sonic.net, I was unable to find much in the way of installation details. Much to my surprise and delight, the term "fiber to the home" was no joke, as there is literally a fiber optic cable coming out of my wall =)

Having this information available would help potential customers know more about what the service entails.

PS: I only hope you can run your lines to the rest of San Francisco as well.

PPS: Your first link to http://j.mp/Fiber-101 is broken.

[dane]

Thanks for this overview, it's very helpful! A couple of questions - Can the ONT be located in our apartment? There would be no other way to get power to it, and there is an existing access hole (formerly for cable TV) going directly into our unit. Also, Can we forgo your RG in favor our our router?

Thanks Dane!

The ONT is generally located indoors, and must be adjacent to a power outlet. In some cases however it's placed in a box on the outside of the home, if one exists. Most homes in Brentwood for example have an exterior box, with a power outlet inside, which houses network termination equipment for cable, telco and optical.

In SF, we're generally placing it in the garage, adjacent to the other telecom NIDs and power panel board.

[mzhaozhao]

Hi Dane,

If we are unable to locate any power outlet in the garage(there is one, but its in the ceiling and its occupied by the garage door opener), can the fiber line come through the house(into the garage) and up the living room and be terminated there rather then in the garage? I currently have a hole in the floor where my coaxial cables comes up to the living room, where I would like to have the fiber line come up through. Do you think this is something the installer/tech can do easily? Basically to terminate the line in the living room(where there is power etc) rather then in the garage.

Much appreciated!

[dane]

Hi Dane,

If we are unable to locate any power outlet in the garage(there is one, but its in the ceiling and its occupied by the garage door opener), can the fiber line come through the house(into the garage) and up the living room and be terminated there rather then in the garage? I currently have a hole in the floor where my coaxial cables comes up to the living room, where I would like to have the fiber line come up through. Do you think this is something the installer/tech can do easily? Basically to terminate the line in the living room(where there is power etc) rather then in the garage.

Much appreciated!

Yes, that seems likely. Every situation is unique though, and the installer will work with you on the day of installation to find the simplest solution.

[Duncan]

Thank you so much for laying this out, including links to photos of the equipment.

While it will probably be another decade before our neighborhood (Bernal Heights) sees fiber the way these things go, it's good to know what's involved in terms of future planning. I'm glad to see that the ONT includes the POTS interface, as opposed to the separate ATA wart hanging off a short Ethernet cable next to the unused telephone jack of the Pace router. That thing annoys me.

[cdrayson]

Thank you so much for laying this out, including links to photos of the equipment.

While it will probably be another decade before our neighborhood (Bernal Heights) sees fiber the way these things go, it's good to know what's involved in terms of future planning. I'm glad to see that the ONT includes the POTS interface, as opposed to the separate ATA wart hanging off a short Ethernet cable next to the unused telephone jack of the Pace router. That thing annoys me.

I don't think you'll have to wait that long. They're adding fiber where subscriber density justifies the expense, and the high housing density of most parts of SF will help to drive that.

[shihonage]

Hello,

I received a generic letter from Sonic saying I'm qualified for Gigabit Fiber. I am an existing Fusion customer. During the sign-up process it makes me select a NEW Fusion phone number, with no regard to the one already being used.

Is there an actual way to migrate existing Sonic customers? Preferably... ahead of non-Sonic customers?

Thank you.

[dane]

Hello,

I received a generic letter from Sonic saying I'm qualified for Gigabit Fiber. I am an existing Fusion customer. During the sign-up process it makes me select a NEW Fusion phone number, with no regard to the one already being used.

Is there an actual way to migrate existing Sonic customers? Preferably... ahead of non-Sonic customers?

Thank you.

Yes, we sent a letter to many addresses in SF, some of whom were customers.

But the website on the signup page should have asked if you were an existing customer, and accepted your login. Did that not occur, or was it not obvious enough?